1

1. INTRODUCTION

Rose (Rosa hybrida L.) belongs to kingdom Plantae, division Magnoliophyta, class

Magnoliopsida, order Rosales, family Rosaceae and genus Rosa but the exact species

involved in the development of the present day rose is not well known (Dole and Wilkins,

2005). According to Dole and Wilkins (2005), most rose species are found in the temperate

parts of the Northern hemisphere, especially Southern China and the Far East, the Indian

Himalayas and Bengal to Ethiopia and West to North America from the Arctic Circle to New

Mexico. The chromosome number of rose varies from 2n=2x=14 to 2n=8x=56, with most

species being diploid or tetraploids. Commercial rose cultivars (Rosa x hybrida) tend to be

either triploid or tetraploids (Rout et al., 1999). All species in the genus Rosa are woody, with

thorns and spines prickly stems. Plants can be upright, forming a shrub, or can be trailing and

climbing, with leaves alternate and may be deciduous or persistent. Flowers may be solitary,

corymbose or panicled. The ovary is inferior, and develops into a fleshy fruit (hip) which can

become a colorful yellow to red when ripe. Five part sepals (calyx) are leaf like, cover flower

bud, and reflexed at flowering to expose the petals. Petal colors range from white to pink,

yellow, orange, or red with variety of shades and color combinations (Dole and Wilkins,

2005).

Rose is the most popular ornamental plant in the world, as well as the most important cut

flower (Arene et al., 1993; Canli and Kazaz, 2009). Through out history, no other plants have

such wide appeal and been the centre of so much attention than the rose. It is also beautiful

flower of immense horticultural importance (Campos and Salome, 1990) having an economic

value in ornamental, pharmaceutical and cosmetic trade (Canli and Kazaz, 2009).

Ethiopia’s favorable climate (Bizuayehu, 2006), availability of dependable water and land

resources combined, has made the country an incredible hub for investment. Located in the

Horn of Africa and within easy reach of the Horn’s major ports, Ethiopia is close to its

traditional markets, the Middle East and Europe that provides the major exporters in the world

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unparalleled access to the Ethiopian floricultural market (Economy and Business Section of

Ethiopian Embassy in America, 2009).

A modern, export oriented and private sector based floriculture industry began to emerge in

Ethiopia in the late 1990s. The pioneer, Golden Rose, was established in 1999 and between

2000 and 2001 other two farms (Summit Agro Industry and Enyi Ethio Rose) followed it.

Until 2003 only five farms were involved in export. In 2005, the flower industry continued to

grow. Flower exports as a share of total exports grew from 0.15 % in 2001 to 1.59 % in 2005.

Ethiopian flower export value increased from $660,000 in 2001 to $12,645,000 in 2005

(Economy and Business Section of Ethiopian Embassy in America, 2009). By 2007, the

number of firms involved in flower production and export reached 67. The total hectares of

land held by floriculture investors reached almost 2000 of which about 700 hectares covered

by greenhouses. The sector created above 50,000 employment opportunities and had became

among the five top foreign exchange earning commodities with above $120,000,000 in 2007.

In not more than 7 years, Ethiopia became the second largest flower exporter in Africa (next

to Kenya) to the EU market. This remarkable growth was due to initiatives taken by the

government to promote the sector (Mulu and Tetsushi, 2009).

A substantial number of investors have started operating in Ethiopia due to the Government’s

focus on this sector and the supreme advantages of the country in floricultural crops

production compared to other producers (Economy and Business Section of Ethiopian

Embassy in America, 2009). In 2008 global market, Ethiopian flower exports have increased

five fold and in the first nine months of 2009, the country earned $90,000,000 (EHPEA,

2009). Ethiopia, being in the primary stage in its floriculture industry, needs to take concrete

steps to claim a permanent seat in the investment and exporting hub in floriculture. Poor road

infrastructure beyond capital, cargo bottlenecks and lack of airport facilities, inability to

satisfy foreign market demand, shortage of agronomists and post harvest quality issues are the

prime factors that hinder the country (Belwal and Meseret, 2008).

Keeping quality of cut flowers is one of the major concerns for growers to repeat their

businesses. Many cut flower growers and a large number of consumers use preservatives in

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order to prolong the lasting life of cut flowers. Preservative solutions are generally required to

supply energy source, reduce microbial build up and vascular blockage, increase water uptake

of the stem, and arrest the negative effect of ethylene (Nigussie, 2005) but, a great variation

exists in the ingredient included in the preservatives. Sucrose with or without certain additive

such as aluminum sulfate could be of practical significance for prolonging the life of many

cultivars of cut roses. Such preservatives to extend the vase life of cut roses might be used

effectively at all levels of handling the crop that would be beneficial both for producers and

consumers (Butt, 2005). However, many cut flower growers in our country rarely put energy

source, such as sucrose in the solutions being prepared for post harvest treatment (Nigussie,

2005). Apparently, post harvest quality deteriorations are known to occur repeatedly at

destination markets, because of which many growers frequently receive complaints from their

clients (Mesfin M., personal communication). Prolonged vase life is one of the most

important factors for quality of cut flowers. Senescence of cut flowers is induced by several

factors e.g., water stress (Sankat and Mujaffar, 1994), carbohydrate depletion (Ketsa, 1989),

microorganisms (van Doorn and Witte, 1991) and ethylene effects (Wu et al., 1991). A major

cause of deterioration in cut flowers is blockage of xylem vessels by microorganisms that

accumulate in the vase solution or in the vessels themselves.

In Ethiopia, in recent years production of flowers in general and cut roses in particular is

increasing, and Holeta area is the largest cluster that accounts for 31.3% of the total number

of flower farms in the country (Mulu and Tetsushi, 2009). Ethio-Agri CEFT PLC at Holeta is

one of the flower farms producing and exporting cut rose cultivars Essendre and Utopia. The

company is receiving complaints from its clients that these cultivars are having shorter vase

life (Mesfin M., personal communication). Experiences elsewhere indicate that the vase life of

cut roses could be extended using various preservative solutions such as aluminum sulfate and

sucrose (Capdeville et al., 2003; Regan, 2008). Aluminum sulfate is used as a bactericide

(Regan, 2008), while sucrose is used as a food for the flowers (Capdeville et al., 2003). In

Ethiopia, the use of appropriate preservatives to extend vase life of cut flowers has not yet

been materialized in most flower farms and in Ethio-Agri CEFT PLC in particular (Dogra

S.R., personal communication). The present investigation therefore, was initiated to assess the

effect of different combinations of aluminum sulfate and sucrose solutions on the vase life of

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the two export standard cut rose cultivars (Essendre and Utopia) produced by Ethio-Agri

CEFT PLC. The general and specific objectives of this study were as follows.

General objective

To evaluate the effect of different concentrations of aluminum sulphate and sucrose

combinations on the vase life of two cut rose cultivars.

Specific objectives

To identify the best combination of aluminum sulfate and sucrose concentration that

can extend the vase life of cut rose cultivars, Essendre and Utopia.

To identify a rose cultivar with better keeping quality as a result of treatment of

combination of aluminum sulphate and sucrose.

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2. LITERATURE REVIEW

2.1. Factors Affecting Vase Life

The length of vase life is one of the most important post harvest factors for quality of cut

flowers. It is influenced by a number of factors, some of which are presented here under.

2.1.1. Pre harvest conditions

Pre harvest conditions contribute to the postharvest keeping quality of the flowering shoots.

Among other factors light, relative humidity, temperature, carbon dioxide enrichment and

fertigation (Sarkka, 2005) are pre-harvest conditions affecting shelf life of cut flowers.

2.1.1.1. Light

Light intensity is the most important climatic factor affecting rose plant growth and flowering.

It has been generally accepted that brighter light, during the time of flower development, will

produce a cut flower that has an optimal carbohydrate level and will therefore be of high

quality with a longer vase life (Cross, 2000). Light can also influence post harvest

performance of roses. Cut roses exposed to constant light or 12 hours of light per day lost 5

times more water than roses kept in darkness (Halevy and Mayak, 1981). This is thought to be

due to stomatal opening caused by the light.

2.1.1.2. Relative humidity (RH)

Relative humidity (RH) affects the stomatal conductance, which controls transpiration and

photosynthesis. Plant growth is usually normal in water vapour pressure deficit of 1.0-0.2 kPa,

corresponding to relative humidity of 55-90 % at 20 ºC (Grange and Hand, 1987). High RH

encourages diseases. In low RH, transpiration increases and can even lead to water stress in

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leaves, inducing stomatal closure and leading to the subsequent reduction of transpiration and

photosynthesis (Jarvis and Morison, 1981).

Cultivation of cut roses under high RH (90 %) commonly stimulates bud break, while low RH

(<60 %) delays it. Raising the RH may increase leaf size and shoot weight and length in one

rose cultivar, but has a minor effect in another cultivar (Mortensen and Gislerod, 2000)

indicating that RH has an impact on the vase life of cut roses (Torre and Fjeld, 2001). Cyclic

control of day-night RH is an effective means to achieve both high yield and long vase life of

cut roses (Chun et al., 2006).

2.1.1.3. Temperature

According to De Vries et al. (1982) increased diurnal mean temperature speeds up bud break,

decreases the time to harvest, and shortens the stem length. The number of leaf primordia in

an auxiliary bud before the bud break is unaffected by temperature, but the total number of

leaves preceding the flower decreased in elevated air temperature (Marcelis-van, 1995).

Relatively high night temperatures, in comparison with day temperatures, promote bud break

(Zieslin and Halevy, 1975). Van den Berg (1987) reported a faster bud break in higher night

than day temperature. But according to the report of Vogelezang et al. (2000) temperature rise

for four hours at sunset didn’t show any effect on bud break or flower quality. The

temperature treatment had no effect of temperature treatment on the carbohydrate levels in

plants. However, a higher night than day temperature reduced blindness (Van den Berg,

1987). Low temperature (12-15 ºC) increases shoot blindness until stamen and pistil

primordia have been formed in the developing flower bud (Moe, 1971). Decreasing the

temperature after the flower bud was visible generally increased leaf area, stem length, stem

diameter and flower dry weight (Shin et al., 2001).

In commercial production of cut flowers, the prevalent method for maintaining vase is the use

of moderately low temperatures (Butt, 2005). Both increasing and decreasing the temperature

may reduce the vase life of roses (Moe, 1975). Low temperature close to the harvest may also

affect pigmentation of red roses seen as “blacking” or blueing of petals (Halevy and Zieslin,

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1969). But an alternative method is the use of a sucrose solution that can affect vase life,

ethylene production, and regulation of sugar accumulation in floral organs (Butt, 2005).

2.1.1.4. Carbon dioxide (CO2) enrichment

High carbon dioxide (CO2) enrichment during cultivation has extended the vase life of some

rose cultivars compared to ambient CO2 level. High CO2

concentration lowered cuticular

transpiration and improved leaf water potential at complete stomatal closure, indicating a

higher capacity of leaves to protect themselves against water losses through transpiration

(Urban et al., 2002).

2.1.1.5. Fertigation

Control of fertigation involves the determination of both timing and quantity of fertilizer and

water application. A better understanding of the effects of fertigation frequency on growth,

production and quality of cut roses can help to propose optimal fertigation scheduling since

cut roses have gained great economic importance due to their high market value and great

export potential (Yusuf and Dennis, 1999).

Inadequate plant nutrition causes serious disorders in cut roses cultivation and may eventually

lead to decline of plant vigor and ultimately reduction of yield (Umma and Gowda, 1986).

Unlike most other crops, cut roses are being constantly harvested and thereby exhibiting large

fluctuation of the transpiring area, it must be taken into consideration when attempting to

formulate fertigation schedule for cut roses (Qasim et al., 2008). Therefore, optimal

fertigation scheduling is very important to save water and nutrients, while efficient use of

water by drip irrigation is becoming increasingly important. Accurate supply of nutrients and

water result in better water use efficiency, avoid stress situations and control production

(Raviv and Blom, 2001).

Drought stress is very damaging to cut roses, reducing production (up to 70%) and quality (in

terms of stem length and fresh weight) of the flowering shoots (Chimonidou-Pavlidou, 1996,

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1999). On the other hand, excessive water in the substrate can be injurious to cut roses by

reducing substrate aeration and causing abnormal development of plants. Fertigation

combines the two main inputs, water and nutrients, therefore accurate supply of nutrients and

water is required for optimum plant growth and development (Jaynes et al., 1992). In turn, cut

roses with optimum plant growth and development and with quality flower shoots (Raviv and

Blom, 2001) store enough food reserve for their extended vase life.

2.1.2. Cultivars

Different cultivars of roses show variation in their vase life due to their genetic variability

(Butt, 2005). Because of the variability among rose cultivars in response to post harvest

processing procedures, more work is needed to examine how different cultivars perform under

common post harvest practices. Accordingly the increase in vase life due to sucrose and

commercial preservatives containing sucrose on cut roses is dependent on the cultivar and on

the concentration of sucrose used. Possiel (2008) reported that in cut rose cultivar ‘First Red’,

increasing the concentration of sucrose in a vase solution containing 300 mg aluminum sulfate

up to 15 g sucrose increased the vase life; however, vase life declined with higher

concentration of sucrose up to 30 g.

2.1.3. Development stage

The commercial development stage at picking varies greatly in different flowers and also

influenced by the season, environmental conditions, and the distance to the market and

customers preferences (Halevy and Mayak, 1998). Flowers should be harvested at the proper

stage of development for maximum vase life. Some species may be harvested at a less mature

stage during the summer, when warmer temperatures may induce rapid development (Dole

and Schnelle, 1990). In general, flowers are cut at the earliest stage to assure full opening and

development with good quality in the vase (Halevy and Mayak, 1998). Cutting flowers in the

bud stage is preferable, when possible, since they are easier to handle and are less susceptible

to detrimental environmental conditions like high temperature and ethylene (Halevy and

Mayak, 1998). Due to this fact flowers are usually harvested at the bud stage (Ichimura et al.,

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2002). However, some flowers, if cut at an early stage, either will not open or wilt, that is why

bent neck in roses and gerberas is much more frequent when the flowers are cut too early

(Halevy and Mayak, 1998). Parupas and Voisey (1976) stated that bent neck occurred when

flowers were harvested too immature since at this stage the neck region had insufficient

lignifications of the vascular tissue.

2.1.4. Harvesting time

Morning harvest is often advantageous over afternoon harvests, because the temperature is

lowest during the morning, plant water content is high, and the rest of the day is available for

packing and flower distribution (Dole and Schnelle, 1990).

2.1.5. Post harvest conditions

Storage, transport conditions and the conditions at the consumer’s home are essential for vase

life. Storage in cold slows down transpiration and the growth of bacteria (Sarkka, 2005). The

vase life of cut roses is often very short. The cut flowers wilt and the floral axis becomes bent

just below the flower head (bent neck). The development of such symptoms is considered to

be caused by vascular occlusion, which inhibits water supply to the flowers (Hassan, 2005).

To extend the vase life of cut roses, many preservatives have been developed. Basically there

are three types of preservatives: those designed for growers, for wet transport, and for

consumers. Preservatives for growers are applied to the cut flowers for the short period before

shipment. Owing to the expansion of wet transport, appropriate preservatives have been

developed. Their main components are antimicrobial compounds. Preservatives for consumers

include sugars and antimicrobial compounds that inhibit vascular occlusion (Ichimura and

Shimizu, 2007).

A major cause of quality deterioration in cut flowers is the blockage of xylem vessels by

microorganisms that accumulate in the vase solution or in the vessels themselves. When the

stem is blocked, continuing transpiration by the leaves results in net loss of water from

flowers and stem tissues. For many years, floral preservatives have been acidified and have

10

usually included biocides to inhibit bacterial proliferation. Due to this reason the addition of

antibacterial agents in the storming solution has been recommended (Hassan, 2005).

2.1.5.1. Post harvest retail handling

A serious reduction in quality can occur on florist crops in retail outlets. Major causes of

flower quality reduction during marketing include wilting, undesirable long period storage,

mechanical damage, poor transportation, disease development and the like. Brushing and

breaking destroys the aesthetic and economic value of flowers (Nigussie, 2005).

A retailer can take several steps to ensure that the plant materials have maximum longevity in

the store and in the customer’s home. Unpacking all plant materials as soon as possible

inspecting for insects, diseases and damage and watering all portal materials immediately, if

needed re-cutting the stems of cut materials under water and placing them in water or

preservative solutions and putting them in cooler places immediately are all important

practices to extend vase life of cut flowers (Nigussie, 2005).

2.1.5.2. Excessive water loss

The movement of water through the stem to the leaves and flowers is very important in

prolonging the life of flowers. If turgidity is not maintained, the plant wilts and dies regardless

of the amount of food reserves present. Any wilting of cut materials will result in a vase life

reduction (Van Meeteren, 2009).

2.1.5.3. Ethylene

Ethylene is an odorless, colorless gas produced naturally by plant materials or by incomplete

combustion of heating fuels and engine exhaust. Ethylene can also produced by plant

pathogen which can be especially detrimental during shipping when plant materials are

enclosed and air circulation is limited. Many floriculture crops are sensitive to ethylene and

this gas has various undesirable effects such as abscission of leaves and flower buds and rapid

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flower senescence. Concentration as low as 1ppm and exposure time of as little as 2hrs can

lead to damage and higher concentration of ethylene can cause quality deterioration of flowers

in a shorter period (Chamani et al., 2005).

In general, the extent and type of damage will vary with the plant species, duration of

exposure, ethylene concentration and temperature plant ethylene sensitivity varies from high

for such species as carnation, orchids, Fressia, Hibiscus, to low for such species as Rosa

cultivar, Gerbera and etc (Dole and Wilikins, 2005).

Excess temperature enhances the effect of ethylene as it increases the rate of respiration and

other metabolic activities. Plant tissue wounds also increase the production of ethylene.

Ethylene damage can be prevented by avoiding exposure to engine or other sources of smoke,

removing senescing plant materials from production areas, avoiding storing of flowers with

ripening fruits and vegetables, lowering storage temperature and using anti ethylene agents

(Chamani et al., 2005).

2.1.5.4. Food reserves

Shortage in supply of carbohydrate to support respiratory activities and other biochemical and

physiological processes are one of the factors that cause a short vase life. When the flower is

removed from the plant it losses its life support system. The roots of the plant can no longer

supply water and nutrients to the leaves and flowers. However, the life process such as

respiration, transpiration and other metabolic activities in the harvested bloom take place

continuously. The lasting life of cut flowers is generally influenced as a result of food reserve

depletion (Mayers et al., 1997).

2.1.5.5. Water quality

The vase life of cut flowers depends on many variables. One of those variables is the quality

of water in which the flowers are placed. Historically tap water was used in experiments as

the control solution. However, quality of tap water varies among locations. In some studies,

12

tap water produced the shortest vase life, but in others it produced a longer vase life than

deionized water. Due to the variability of quality of tap water, researchers at the Second

International Symposium on Postharvest Physiology of Cut Flowers determined that distilled

water should be used to obtain more consistent results (Regan, 2008).

2.1.5.6. Sugar (sucrose)

The post harvest life of flowers is strongly dependent on the carbohydrate status and the

acceptable amounts of metabolic sugars. The vase life of cut chrysanthemum and rose flowers

has been often extended when they have been held in vase solutions containing sucrose

(Yakimova et al., 1996).

In post harvest physiology, it is often assumed that a high concentration of carbohydrates in

the harvested cut flowers is a prerequisite for a long vase life. For roses it is known that a

sugar supply in the vase solution increases vase life, probably because the sugars are used as

substrate for respiration, maintenance, synthesis and osmoregulation, and thus senescence is

delayed. Sugars from the vase solution are transported via the leaves into the flower bud. In

roses, the leaves can act as a storage pool for carbohydrates, which are transported to the

flower bud during vase life (Marissen, 2001) but in shortage of water, the petal sugar content

of roses increased (Mayak et al., 2001). According to Van Doorn (2001) low sugar level in

cytoplasm may decrease vase life although the concentration in vacuole is high. Preventing

water stress, sugars in vacuole may become unavailable for respiration because they are

needed for osmotic adjustment.

The role of exogenous sugars for extending the vase life is well known (Van Doorn, 2001).

Sugar from vase solution accumulates in petal tissues, improving the osmotic potential and

enhancing the carbohydrate pool for growth and respiration, which promotes flower opening

and retards senescence. Exogenous sucrose reduces the age-induced increase in membrane

lipid micro viscosity. Sugars in the vase solution accelerate the bacterial growth, which may

lead to stomatal closure as a result of water deficit. Another reason for reduced transpiration

may be a decline in water uptake due to slower flow rate of sucrose solution. Therefore, an

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antimicrobial compound is usually added to sugar solutions. Antimicrobial compounds

prevent and slow down the bacterial growth, ensure proper water uptake and delay

senescence. These compounds are, for example, metal salts, quinoline, ammonium and

chlorine compounds. For instance, silver ion (AgNO3) has a bactericidal character, promotes

water uptake and has an inhibitory effect on ethylene action. Treatment with an antimicrobial

compound shortly after harvest is beneficial for several flower species (Sarkka, 2005).

2.1.5.7. Composition of holding solutions

Preservative solutions are used to lengthen the vase life of cut roses. Some of the compounds

slow down physiological processes, thus delaying senescence, while others enhance water

uptake, reduce transpiration and/or diminish bacterial growth (Sarkka, 2005).

To extend the vase life of cut roses, many preservatives have been developed. There are

basically three types of preservatives: those designed for growers, for wet transport, and for

consumers. Preservatives for consumers are the most effective of the three types in extending

the vase life of cut roses. Indeed, continuous treatment with sucrose plus 8-hydroxyquinoline

citrate extends the vase life of cut roses. Furthermore, continuous treatment with a

formulation known as GLCA, which is composed of glucose, CMI/MI (a mixture of

isothiazolinonic germicides), citric acid and aluminum sulphate, markedly extended the vase

life of cut roses. Similarly, pulse treatment with GLCA only slightly extended the vase life of

cut ‘Rote Rose’ flowers. Since applied sugars are rapidly consumed in cut flowers, their slight

effectiveness can be attributed to insufficient uptake. The uptake of sugars by cut flowers can

be increased by treatment at high concentrations. However, sucrose or glucose at high

concentration damages the leaves of cut roses. Since water uptake by cut flowers is

suppressed in the dark, the use of sugar solution in the dark may thus avoid leaf damage

(Ichimura and Shimizu, 2007). Also, pulse treatment of sucrose and/or silver thiosulfate (STS)

was effective in maintaining the vase life of cut sweet pea flowers. Generally pulsing, offered

potential advantages of extending the vase life and maintaining flower quality (Liao et al.,

2000). Han (1998) also reported that the post harvest quality of cut Heuchera sanguinea was

significantly improved and its vase life also significantly increased by pulsing the

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inflorescence with STS for four hours followed by placing the stems in a sucrose solution

containing 8-hydroxyquinoline citrate (8 HQC). However, relatively few studies have

reported on the effects of the pulse treatment of sucrose and/or STS on improving the vase life

of cut rose flowers (Liao et al., 2000).

Effect of aluminum sulfate (A12(SO4)3) at 50, 100 and 150 mg L-1and cobalt chloride (CoC12)

at 100, 200 and 300 mg L-1 in the holding solution containing 225 mg L-1 8-hydroxyquinoline

sulfate (8 HQS) and 40 g L-1 glucose on vase life of Dendrobium 'Sonia Bom Joe' in

comparison with the conventional holding solution containing 225 mg L-1 8 HQS, 30 mg L-1

AgNO3 and 40 g L-1 glucose was studied at ambient conditions (30.2°C and 62% RH). All

concentrations of A12 (SO4)3 and 200 mg L-1 CoC12 in the holding solutions increased vase

life and bud opening of orchid flowers as effectively as the standard holding solution. The

holding solution containing 225 mg L-1 8 HQS, 50 mg L-1 A12(SO4)3 and 40 g L-1 glucose also

increased significantly vase life and bud opening of Dendrobium 'Sonia Red Joe' and

Dendrobium 'Walter Oumae Taba 4N' flowers (Ketsa and Kosonmethakul, 2009).

The solution of sodium dichloro-s-friazins trione (SDT) combined with 15 to 30 g L-1 sucrose

extended the vase life of a wide range of cut flowers including roses, carnations and

chrysanthemum. Pulsing of cut roses for 10 and 20 minutes with AgNO3 improved the vase

life up to 6.0 and 5.3 days, respectively. Similarly pulsing with AgNO3 and sucrose plus citric

acid solution for 16 hours at pre cooling prior to shipment, not only extended the longevity,

but also prevented bent neck of flower stems of ‘Cara Mia’ rose cultivar. The solution of

silver nitrate (2.5 mg L-1) plus 8-hydroxyquinoline citrate (8 HQC) (130 mg L-1) plus citric

acid (200 mg L-1) plus sucrose (30 g L-1) extended the vase life of cut roses from seven days

to 17 days. The flowers remained open completely and addition of bactericides and fungicides

in solution of AgNO3 and sucrose improved the flower size and the vase life was four days

greater than the control treatment (Butt, 2005).

Maintenance of the vase life of cut roses held in 30 mg L-1 DICA with 50 g L-1 sucrose had the

longest vase life of 7.7 days and no bent neck, while the control cut roses held in tap water

had a vase life of only 3.4 days and 58.3% bent neck. Cut roses held in the solution containing

15

DICA and sucrose had greater solution uptake, fresh weight and water conductivity and less

vascular blockages and browning of stem end underneath the solution. This holding solution

also extended effectively the vase life of other rose cultivars, namely Camelot, King Ransom

and Yankee (Ketsa and Dadaung, 2007).

Complete flower bud opening is characterized by an increase in the petal area and by

enhanced dry and fresh weights of the petals. The import of dry matter into the petals is used

for osmotic, biosynthetic and respiratory demands. An aqueous solution containing 45

millimoles (mM) sucrose induced proper flower bud opening, even when the cut roses have

been exposed initially to a sucrose free solution for 48 hours. This indicates that there is a

requirement for a supply of organic matter from source tissue to the flower as main sink. This

conclusion is confirmed by the observation that complete flower bud opening can also be

achieved without any addition of sucrose by a reduction in the number of participating petals.

Replacing two third part of the 45 millimoles (mM) sucrose by an isomolalic (similar) amount

of KNO3 does not affect the flower opening process, implying that a considerable amount of

the added sucrose is claimed for osmoregulation. The role of added sucrose and the

contribution of the endogenous storage pool in the process of flower bud opening were

reported by Kuiper et al. (2000). Accordingly some vase solutions including sucrose extend

the vase life of cut flowers. Floral preservative solutions containing 150 mg L-1 aluminum

sulfate at 25°C extended cut Eustoma vase life. The effect of other chemical treatments in

increasing vase life of some cut flowers has been suggested by many authors and the vase life

varied among various cultivars in carnation and Gerbera (Hojjati et al., 2007).

Pulsing with gibberellic acid followed by continuous sucrose treatment enhanced flower

longevity and flower bud opening in cut Polianthes tuberosa L. cultivar Double. Pulsing with

gibberellic acid at 10 or 20 mg L-1plus 8 HQS at 200 mg L-1for 24 hours followed by

continuous sucrose treatments at 40 or 80 g L-1 plus 8 HQS extended the vase life and

significantly promoted flower bud opening as compared with the 8 HQS controls. A pulse

with a higher concentration of gibberellic acid, 50 mg L-1, followed by sucrose solutions did

not increase vase life or enhance flower bud opening greater than those pulsed with

gibberellic acid at 10 or 20 mg L-1 followed by 8 HQS. Gibberellic acid at 10, 20 or 50 mg L-1

16

pulse followed by 8 HQS holding solution had little effect on the longevity and flower bud

opening in comparison to 8 HQS controls. Similarly, continuous sucrose treatment at 40 or 80

g L-1 without gibberellic acid pulse treatment also showed little effect on vase life and flower

bud opening. Cut Polianthes tuberosa treated with gibberellic acid pulse followed by 8 HQS

produced more ethylene than those treated with 8 HQS alone. Ethylene production from

flowers pulsed with gibberellic acid followed by sucrose was low when compared with

controls or those pulsed with gibberellic acid alone. Cut stems continuously placed in

solutions containing sucrose produced less ethylene than those without sucrose. It is suggested

that gibberellic acid pulse at 10 mg L-1 followed by continuous sucrose treatment at 40 g L-1

could be used by growers for extending the vase life and enhancing flower bud opening in cut

Polianthes tuberosa (Wei et al., 2001).

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3. MATERIALS AND METHODS

3.1. Description of the Study Site

The study was conducted from October 2009 to May 2010 at Holeta. Holeta is located in

West Showa, Welmera woreda at about 28 km away from Addis Ababa. The area is situated

at 9° 4' N latitude, 38° 30' E longitude and at an altitude of 2380 masl. The soil type of the

area is classified as Vertisoils. The area receives an annual rainfall of 1017 mm and mean

annual temperature of 14°C (Zewdu and Hogberg, 2000). The experiment was carried out in

the grading hall of Ethio Agri CEFT PLC farm. During the execution of the study the grading

hall was with the temperature of 14-24 °C and relative humidity of 70%.

3.2. Experimental Material

3.2.1. Cultivars

Rose (Rosa hybrida L.) cultivars, Essendre and Utopia, were used for this experiment.

Cultivar Essendre is an intermediate rose with yellow flower color, average stem length of 40-

70 cm. It has an average of three cm flower diameter and petal number of 70 at an average.

This cultivar has a production of 120-130 stems per m2 (Schreurs, 2010). Cultivar Utopia is

hybrid tea rose with bicolor (red and white) flower and with an average stem length of 50-80

cm. It has an average of four cm flower diameter, petal number of 40-50 and a production of

130-150 stems per m2 (Terra, 2009).

3.2.2. Preservatives

Aluminum sulfate [A12 (SO4)3] at three concentration levels (150, 250 and 350 mg L-1) (Gast,

1997) and three sucrose (C12H22O11) concentration levels (20, 25 and 30 g L-1) (Butt, 2005)

were used.

18

(A) (B)

Plate 1. Cut rose cultivars Essendre (A) and Utopia (B) at harvest.

3.3. Experimental Design and Treatments

The experiment was laid out in completely randomized design (CRD) with three replications.

The treatments were combinations of three concentration levels of aluminum sulfate [A12

(SO4)3] (150, 250 and 350 mg L-1) and sucrose (C12H22O11) (20, 25 and 30 g L-1). Each level

of aluminum sulfate was combined with the levels of sucrose resulting in nine treatment

combinations and distilled water was used as a control treatment resulting in a total of 10

treatments as indicated below:

Treatment 1= Control (distilled water),

Treatment 2 = 150 mg A12 (SO4)3 plus 20 g C12H22O11 L-1,

Treatment 3 = 250 mg A12 (SO4)3 plus 20 g C12H22O11 L-1,

Treatment 4 = 350 mg A12 (SO4)3 plus 20 g C12H22O11 L-1,

Treatment 5 = 150 mg A12 (SO4)3 plus 25 g C12H22O11 L-1,

Treatment 6 = 250 mg A12 (SO4)3 plus 25 g C12H22O11 L-1,

Treatment 7 = 350 mg A12 (SO4)3 plus 25 g C12H22O11 L-1,

Treatment 8 = 150 mg A12 (SO4)3 plus 30 g C12H22O11 L-1,

Treatment 9 = 250 mg A12 (SO4)3 plus 30 g C12H22O11 L-1 and

Treatment 10 = 350 mg A12 (SO4)3 plus 30 g C12H22O11 L-1.

3.4. Experimental Procedure

19

The flowers were harvested in the morning at stage 1, that is, when petal color of flower buds

is visible and sepals are at vertical position of development (Reid et al., 1989). In order to

remove field heat, the harvested flowers were immediately put in buckets containing distilled

water and transported to pre- cooling room at 2 0C for 2 hrs (Plate 2). After precooling,

leaves were removed up to 20 cm from the bottom by leaving only the upper three leaves

(Ichimura et al., 2002). Following leaf removal, the flowers were graded in terms of stem

length, freedom of damage, disease and insect pests (Ketsa and Chinprayoon, 2007) and cut at

50 cm length (Ichimura and Shimizu, 2007) measuring from the peak of the terminal bud to

the bottom end. This was employed to ensure uniformity among the evaluated stems.

Plate 2. Flower at pre cooling room.

Plate 3. Deleafing of the flowers.

20

The prepared flower stems were cut diagonally (slant cut of 2 cm) using a sharp knife

disinfected with 96 % ethanol before each cut. The slant cut was made prior to treatment

application to facilitate absorption of the preservative solution, aluminum sulfate plus sucrose

(Jules, 1979). Then after, both cut rose cultivars were washed with distilled water before

immersing into the prepared solutions to reduce contamination. The required quantity of test

solution was calculated for all treatments and every possible sanitation procedures were used

during preparation. The plastic buckets used for preparing the solutions were thoroughly

washed with calcium hypo chloride and detergent and again cleaned with distilled water. The

stirring rods used for mixing the solutions were also disinfected with 96% ethanol. Then, test

solution of 100 ml was poured in glass jars with 250 ml capacity previously washed with

calcium hypo chloride and detergent and again cleaned with distilled water. The prepared cut

rose cultivars were placed in each glass jar (Ketsa and Chinprayoon, 2007) keeping the

bottom of the flower stem completely immersed in each treatment. The test solution was

changed every three days and flower stem was put back in to the new solution after re cutting

(Mortazavi et al., 2009) at 2.5 cm from the bottom to remove possible microbial infections.

Plate 4. Cut rose cultivars Essendre and Utopia in aluminum sulfate plus sucrose treatments.

3.4. Data Collected

After putting the cut rose cultivars, Essendre and Utopia, in different levels of the

combinations of aluminum sulfate and sucrose solution, the flowers were observed daily until

21

complete senescence of petals and accordingly data were recorded in number of days on the

following parameters.

3.4.1. Flower parameters

Parameters including complete opening period of flowers (COP), petal edge drying (PED),

longevity of the flowers (LF), emergence of petal drop (EPD) and complete petal drop (CPD)

were recorded.

3.4.1.1. Complete opening period of the flowers (COP)

Complete opening period is the time required for complete blooming of the flowers (Younis

et al., 2006). It was recorded in days when the flowers showed complete blooming.

(A) (B)

Plate 5. Cut rose cultivars Essendre and Utopia at complete opening period (COP).

3.4.1.2. Petal edge drying (PED)

Petal edge drying is the number of days in which the peripheral part of petals starts to show

brownish color (Eason, 2002 and van Doorn and Vojinovic, 1996). It was recorded in days

when the outer four petals developed the above mentioned symptom.

22

Plate 6. Cut rose cultivar Essendre showing petal edge drying (PED).

3.4.1.3. Longevity of the flowers (LF)

The length of time for which the flowers were stayed in their attractive appearance was

recorded in days as the longevity of cut roses (Younis et al., 2006).

23

3.4.1.4. Emergence of petal drop (EPD)

Petal drop is when the petal is detached from the stem (Eason, 2002). Days in which petals

had started to drop was recorded as days for emergence of petal drop.

3.4.1.5. Complete petal drop/complete senescence (CPD)

Vase life of cut flowers ends when petals had dropped (Ichimura and Ueyama, 1998). The

number of total petals per each test flower was recorded before the onset of petal drop. After

the onset of petal drop the number of detached petals was recorded daily. The date on which

50% (Eason, 2002) of total petal had dropped was recorded as complete petal drop date.

3.4.2. Leaf parameters

Parameters such as leaf wilting date (LWD) and leaf drop date (LDD) were measured in days

to assess the effect of preservative solutions on the vase life of cut rose cultivars.

3.4.2.1. Leaf wilting date (LWD)

The date on which 50 % of the leaves were wilted (Eason, 2002; Elgimabi and Ahmed, 2009)

and showed yellowish color (Zieslin, 1989) was recorded in days as leaf wilting date.

Plate 7. Cut rose cultivars showing leaf wilting (LWD).

24

3.4.2.2. Leaf drop date (LDD)

Leaf drop is when the leaf is detached from the stem. The date on which 50% (van Doorn and

Vojinovic, 1996) of total leaves had dropped was recorded as leaf drop date.

3.4.3. Stem parameter

In this experiment the only stem parameter, bent neck occurrence (BNO) was daily followed

and recorded in number of days upon its occurrence (van Doorn and Vojinovic, 1996;

Ichimura and Ueyama, 1998).

Plate 8. Cut rose cultivars showing bent neck occurrences (BNO).

3.5. Statistical Analysis

Analysis of variance (Montgomery, 2005) of the GLM procedure for completely randomized

design (CRD) of SAS Version 9.2 statistical software (SAS Institute, 2002) was used to

analyze the data recorded on flower, leaf and stem parameters in order to assess the effect of

aluminum sulfate plus sucrose and cultivars on the vase life of cut roses after the data were

checked for meeting the various ANOVA assumptions. The means for treatments, cultivars

and interaction effects were compared by using least square means (LSMEANS) and LSD

25

value at 5% significance level (Montgomery, 2005) and the correlation between the respective

parameters were determined using the same procedures.

The following model for CRD was used:

i=1, 2…cultivars

yijk = µ + αi + βj + (αβ)ij + ϵijk j=1, 2…level of aluminum sulfate plus sucrose

k=1, 2…number of replication

Where, µ= overall mean effect,

α i = the effect of the ith level of cultivars

βj = the effect of the jth level of aluminum sulfate plus sucrose,

(αβ)ij =the effect of interaction between αi and βj,

ϵijk= random error,

k= number of replications

26

4. RESULTS AND DISCUSSION

The results of effect of different combinations of aluminum sulfate [Al2 (SO4)3] and sucrose

(C12H22O11) concentrations on vase life of the two cut rose cultivars (Essendre and Utopia) in

terms of complete opening period of flowers (COP), petal edge drying (PED), longevity of the

flowers (LF), emergence of petal drop (EPD) and complete petal drop (CPD), leaf wilting

date (LWD) and leaf drop date (LDD) and bent neck occurrence (BNO) are presented and

accordingly discussed in light of the available literature as follows.

Table 1. Table of P values for COP, PED, LF, EPD, CPD, LWD, LDD and BNO

Source of variation

DF

P values COP PED LF EPD CPD LWD LDD BNO

Treatment 9 0.008 <.001 <.001 0.008 0.001 <.001 <.001 0.250Cultivar 1 0.001 0.806 0.380 0.979 0.657 <.001 <.001 <.001Trt x Cult. 9 0.188 0.567 0.039 0.747 0.632 0.581 0.236 0.373Error 40 1.5 2.5 1.78 6.1 4.7 4.9 5.4 68.4 CV 12.2 7.3 5.3 8.2 5.7 9.9 8.1 22.8 DF = degrees of freedom, Trt = treatments, Cul = cultivar, COP = complete opening period of flowers, PED = petal edge drying, LF = longevity of flowers, EPD = emergence of petal drop, CPD = complete petal drop, LWD = leaf wilting date, LDD = leaf drop date, and BNO = bent neck occurrence.

4.1. Flower Parameters

4.1.1. Complete opening period of flowers (COP)

Complete opening period of flowers/petals was significantly (P < 0.05) affected by the

different combinations of aluminum sulfate [Al2 (SO4)3] and sucrose (C12H22O11)

concentrations. This flower parameter was also highly significantly (P < 0.001) affected by

the cultivars (Table 1). Significantly the longest complete flower opening period (11.25 days)

was observed in T8 (150 mg L–1 A12 (SO4)3 + 30 g L–1 C12H22O11) (Table 2). However, it was

not significantly different from T6 (250 mg L–1 A12 (SO4)3 + 25 g L–1 C12H22O11), T9 (250 mg

L–1 A12 (SO4)3 + 30 g L–1 C12H22O11) and T10 (350 mg L–1 A12 (SO4)3 + 30 g L–1 C12H22O11).

27

Significantly the lowest complete flower opening period (9 days) was recorded in the control

(distilled water alone), though it was not significantly different from T2 (150 mg L–1 A12

(SO4)3 + 20 g L–1 C12H22O11), T3 (250 mg L–1 A12 (SO4)3 + 20 g L–1 C12H22O11), T4 (350 mg

L–1 A12 (SO4)3 + 20 g L–1 C12H22O11) and T5 (150 mg L–1 A12 (SO4)3 + 25 g L–1 C12H22O11).

Combination of 150 mg L–1 aluminum sulfate and 30 g L–1 sucrose (T8) achieved the longest

flower opening period for both cultivars. This treatment extended the complete opening

period of flowers by 2.5 days over the control. This explains the effect of high concentration

of sucrose (in vase solution) in extending the complete opening period of flowers. The result

is consistent with that of Ichimura and Shimizu (2007) who reported that the uptake of

sucrose by cut flower is increased with its concentration in vase solution and subsequently the

content of soluble carbohydrates in cut flowers is related to the length of vase life (Ichimura et

al., 2002).

Table 2. Effect of aluminum sulfate plus sucrose and cultivars on complete opening period (COP) of cut roses in number of days at Holeta, Ethiopia during 2009/2010

Effects and levels N COP + SE Treatments T1 (Control, distilled water alone) 6 9.00 + 0.49 c T2 (150 mg L–1 A12 (SO4)3 + 20 g L–1 C12H22O11) 6 9.33 + 0.49 c T3 (250 mg L–1 A12 (SO4)3 + 20 g L–1 C12H22O11) 6 9.08 + 0.49 c T4 (350 mg L–1 A12 (SO4)3 + 20 g L–1 C12H22O11) 6 9.16 + 0.49 c T5 (150 mg L–1 A12 (SO4)3 + 25 g L–1 C12H22O11) 6 9.50 + 0.49 bc T6 (250 mg L–1 A12 (SO4)3 + 25 g L–1 C12H22O11) 6 10.75 + 0.49 ab T7 (350 mg L–1 A12 (SO4)3 + 25 g L–1 C12H22O11) 6 9.50 + 0.49 bc T8 (150 mg L–1 A12 (SO4)3 + 30 g L–1 C12H22O11) 6 11.25 + 0.49 a T9 (250 mg L–1 A12 (SO4)3 + 30 g L–1 C12H22O11) 6 11.00 + 0.49 a T10 (350 mg L–1 A12 (SO4)3 + 30 g L–1 C12H22O11) 6 10.25 + 0.49 abc LSD 1.405 Cultivars Essendre 30 10.43 + 0.21 a Utopia 30 9.33 + 0.21 b LSD 0.628 CV 12.2 Means followed by different letters per column differ significantly (P < 5 %) as established by LSD test.

28

The current finding is also in agreement with the work of Cho and Lee (1980) who found that

the vase life of cut rose cultivar, Marry Devor was doubled in 30 g L–1 sucrose and Liao et al.

(2001) who reported significant increase of vase life of Eustoma grandiflorum from 8 days

under control treatment to 15 days when aluminum sulfate at 150 mg L-1 was used. Similarly,

Cho and Lee (1979), working on cut rose cultivar Mary Devor, stated that sucrose and

aluminum sulphate when used alone were not very effective in extending the vase life but

when combined (30 to 50 g L–1 sucrose and 300 mg L–1 aluminum sulphate), the vase life was

extended from 6 to 9 days.

In case of cultivars, Essendre showed significantly (P < 0.001) the longest flower opening

period (10.43 days) over the cultivar Utopia which recorded the least (9.33 days) (Table 2).

The observed differences among the two cultivars could be due to their genetic variation

(Butt, 2005). Comparing 25 cultivars of cut roses, Ichimura et al. (2002) also reported the

existence of variation among the cultivars with regard to their vase life.

4.1.2. Petal edge drying (PED)

Petal edge drying (days) was highly significantly (P < 0.001) affected by the different

combinations of aluminum sulfate [Al2 (SO4)3] and sucrose (C12H22O11) concentrations (Table

1). Significantly the longest petal edge drying (23.33 days) was observed in T4 (350 mg L–1

A12 (SO4)3 + 20 g L–1 C12H22O11). However, it was not significantly different from T3 (250

mg L–1 A12 (SO4)3 + 20 g L–1 C12H22O11), T5 (150 mg L–1 A12 (SO4)3 + 25 g L–1 C12H22O11),

T6 (250 mg L–1 A12 (SO4)3 + 25 g L–1 C12H22O11), T8 (150 mg L–1 A12 (SO4)3 + 30 g L–1

C12H22O11) and T10 (350 mg L–1 A12 (SO4)3 + 30 g L–1 C12H22O11) (Table 3). While the least

petal edge drying (17.75 days) was recorded in the control.

Combination of 350 mg L–1 aluminum sulfate and 20 g L–1 sucrose (T4) extended petal edge

drying period by 5.58 days compared to the control. In the vase solution, aluminum sulfate

has the capacity to reduce transpiration by inducing stomatal closure, reduce bent neck and

wilting, stabilize anthocyanins, and improves water uptake (Regan, 2008) while sucrose

29

naturally provide energy for fundamental cellular processes, such as maintenance of the

structure, of mitochondria and other organelles of cut roses (Capdeville et al., 2003)

Table 3. Effect of aluminum sulfate plus sucrose and cultivars on petal edge drying (PED) of cut roses in number of days at Holeta, Ethiopia during 2009/2010

Effects and levels N PED + SE Treatments T1 (Control, distilled water alone) 6 17.75 + 0.63 d T2 (150 mg L–1 A12 (SO4)3 + 20 g L–1 C12H22O11) 6 21.50 + 0.63 bc T3 (250 mg L–1 A12 (SO4)3 + 20 g L–1 C12H22O11) 6 22.41 + 0.63 abc T4 (350 mg L–1 A12 (SO4)3 + 20 g L–1 C12H22O11) 6 23.33 + 0.63 a T5 (150 mg L–1 A12 (SO4)3 + 25 g L–1 C12H22O11) 6 21.83 + 0.63 abc T6 (250 mg L–1 A12 (SO4)3 + 25 g L–1 C12H22O11) 6 21.58 + 0.63 abc T7 (350 mg L–1 A12 (SO4)3 + 25 g L–1 C12H22O11) 6 21.00 + 0.63 c T8 (150 mg L–1 A12 (SO4)3 + 30 g L–1 C12H22O11) 6 22.08 + 0.63 abc T9 (250 mg L–1 A12 (SO4)3 + 30 g L–1 C12H22O11) 6 21.16 + 0.63 bc T10 (350 mg L–1 A12 (SO4)3 + 30 g L–1 C12H22O11) 6 22.83 + 0.63 ab LSD 1.828 Cultivars Essendre 30 21.5 + 0.28 Utopia 30 21.6 + 0.28 LSD NS CV 7.3 Means followed by different letters per column differ significantly (P < 5 %) as established by LSD test

The result of the current study is in line with Gowda (1990) who reported the longest vase life

of 12 days in the combination of 200 mg L–1 aluminum sulphate with 10 g L–1 sucrose and

400 mg L–1 aluminum sulphate combined with 20 g L–1 sucrose. Ichimura et al. (2002) stated

the antibacterial role of aluminum sulfate, and its subsequent effect on absorption of sucrose

by cut roses, which in turn, results extending petal edge drying (longest vase life).

30

4.1.3. Longevity of flowers (LF)

Longevity of flowers was significantly (P < 0.05) affected by the interaction effect of the

different combinations of aluminum sulfate [Al2 (SO4)3] and sucrose (C12H22O11)

concentrations, and the cultivars (Table 1).

Table 4. Effect of aluminum sulfate plus sucrose and cultivars on longevity of flowers (LF) of cut roses in number of days at Holeta, Ethiopia during 2009/2010

Effects and levels N LF + SE Treatments T1 (Control, distilled water alone) 6 20.00 + 0.54 e T2 (150 mg L–1 A12 (SO4)3 + 20 g L–1 C12H22O11) 6 25.00 + 0.54 d T3 (250 mg L–1 A12 (SO4)3 + 20 g L–1 C12H22O11) 6 25.83 + 0.54 bcd T4 (350 mg L–1 A12 (SO4)3 + 20 g L–1 C12H22O11) 6 26.50 + 0.54 abc T5 (150 mg L–1 A12 (SO4)3 + 25 g L–1 C12H22O11) 6 26.66 + 0.54 ab T6 (250 mg L–1 A12 (SO4)3 + 25 g L–1 C12H22O11) 6 24.58 + 0.54 d T7 (350 mg L–1 A12 (SO4)3 + 25 g L–1 C12H22O11) 6 24.75 + 0.54 d T8 (150 mg L–1 A12 (SO4)3 + 30 g L–1 C12H22O11) 6 25.16 + 0.54 bcd T9 (250 mg L–1 A12 (SO4)3 + 30 g L–1 C12H22O11) 6 25.25 + 0.54 bcd T10 (350 mg L–1 A12 (SO4)3 + 30 g L–1 C12H22O11) 6 27.41 + 0.54 a LSD 1.552 Cultivars Essendre 30 24.95 + 0.28 Utopia 30 25.28 + 0.28 LSD NS CV 5.3 Means followed by different letters per column differ significantly (P < 5 %) as established by LSD test.

Accordingly, application of 350 mg L–1 aluminum sulfate plus 30 g L–1 sucrose (T10) resulted

in the longest longevity of flowers (LF) of 27.41 days for both cultivars compared to the other

treatments.

31

Fig. 1. Interaction effects of treatments and cultivars on longevity of flowers (LF) of cut roses at Holeta, Ethiopia during 2009/2010 (SE + 0.76). Means followed by different letters per column differ significantly (P < 5 %) as established by LSD test.

Cultivars Essendre and Utopia showed differences in longevity of flowers under the same

treatments (Fig. 1) indicating that the effect of combinations of aluminum sulfate and sucrose

is cultivar dependent. Young and Jong (2001) reported existence of interaction between vase

solution and cultivars, both of which affect longevity of flower.

4.1.4. Emergence of petal drop (EPD)

Days to emergence of petal drop was significantly (P < 0.05) affected by the different

combinations of aluminum sulfate [Al2 (SO4)3] and sucrose (C12H22O11) concentrations (Table

1). Significantly the maximum number of days (32.5) to emergence of petal drop was

recorded in T10 (350 mg L–1 A12 (SO4)3 + 30 g L–1 C12H22O11) (Table 5). However, it was not

significantly different from T2 (150 mg L–1 A12 (SO4)3 + 20 g L–1 C12H22O11), T3 (250 mg L–1

A12 (SO4)3 + 20 g L–1 C12H22O11), T4 (350 mg L–1 A12 (SO4)3 + 20 g L–1 C12H22O11), T5 (150

a

bcdefg

defgefg

fg

abcdef

abcdefg

abc

g

h

abcd

cdefg

abcd

bcdefg

efg

abcdab

efg

abcde

h

1818.5

1919.5

2020.5

2121.5

2222.5

2323.5

2424.5

2525.5

2626.5

2727.5

2828.5

T1 T2 T3 T4 T5 T6 T7 T8 T9 T10

Treatment

Day

s to

Long

evity

EssendreUtopia

32

mg L–1 A12 (SO4)3 + 25 g L–1 C12H22O11), T6 (250 mg L–1 A12 (SO4)3 + 25 g L–1 C12H22O11),

T7 (350 mg L–1 A12 (SO4)3 + 25 g L–1 C12H22O11) and T8 (150 mg L–1 A12 (SO4)3 + 30 g L–1

C12H22O11). The lowest number of days (26.08) to the emergence of petal drop was observed

in the control.

Table 5. Effect of aluminum sulfate plus sucrose and cultivars on emergence of petal drop (EPD) of cut roses in number of days at Holeta, Ethiopia during 2009/2010

Effects and levels N EPD + SE Treatments T1 (Control, distilled water alone) 6 26.08 + 1 c T2 (150 mg L–1 A12 (SO4)3 + 20 g L–1 C12H22O11) 6 31.25 + 1 ab T3 (250 mg L–1 A12 (SO4)3 + 20 g L–1 C12H22O11) 6 29.75 + 1 ab T4 (350 mg L–1 A12 (SO4)3 + 20 g L–1 C12H22O11) 6 30.00 + 1 ab T5 (150 mg L–1 A12 (SO4)3 + 25 g L–1 C12H22O11) 6 30.41 + 1 ab T6 (250 mg L–1 A12 (SO4)3 + 25 g L–1 C12H22O11) 6 31.66 + 1 ab T7 (350 mg L–1 A12 (SO4)3 + 25 g L–1 C12H22O11) 6 30.58 + 1 ab T8 (150 mg L–1 A12 (SO4)3 + 30 g L–1 C12H22O11) 6 31.25 + 1 ab T9 (250 mg L–1 A12 (SO4)3 + 30 g L–1 C12H22O11) 6 29.41 + 1 b T10 (350 mg L–1 A12 (SO4)3 + 30 g L–1 C12H22O11) 6 32.50 + 1 a LSD 2.884 Cultivars Essendre 30 30.30 + 0.45 Utopia 30 30.28 + 0.45 LSD NS CV 8.2 Means followed by different letters per column differ significantly (P < 5 %) as established by LSD test.

The use of 350 mg L–1 aluminum sulfate plus 30 g L–1 sucrose (T10) extended days to

emergence of petal drop by 6.42 days compared to the control.

Elgimabi and Ahmed (2009) stated that preservative solutions, containing sucrose plus 8-

HQS, extended the vase life by inhibiting senescence, which lead to improving the post

harvest quality of the flowers. The authors further explained that sugar supply, increases the

longevity of many cut flowers. Sucrose may also act as osmotically active molecule, leading

to the promotion of subsequent water relations as the dissolved sugars in cells of petals are

33

osmotically active substances that are drawn into the corolla cells making the cells turgid with

hydrolyzed sugars ready for respiration.

4.1.5. Complete petal drop (CPD)

Complete petal drop was highly significantly (P < 0.001) affected by the different

combinations of aluminum sulfate [Al2 (SO4)3] and sucrose (C12H22O11) concentrations (Table

1). Significantly the maximum number of days (40.25) to complete petal drop was observed

in (Fig. 2). However, it was not significantly different from T2 (150 mg L–1 A12 (SO4)3 + 20 g

L–1 C12H22O11), T3 (250 mg L–1 A12 (SO4)3 + 20 g L–1 C12H22O11), T4 (350 mg L–1 A12 (SO4)3

+ 20 g L–1 C12H22O11), T6 (250 mg L–1 A12 (SO4)3 + 25 g L–1 C12H22O11), T7 (350 mg L–1 A12

(SO4)3 + 25 g L–1 C12H22O11), T8 (150 mg L–1 A12 (SO4)3 + 30 g L–1 C12H22O11) and T9 (250

mg L–1 A12 (SO4)3 + 30 g L–1 C12H22O11). The lowest number of days (26.08) to the

emergence of petal drop was observed in the control.

Treatment 10 extended the days to complete petal drop by 6.25 days compared to the control.

This is in line with finding of Ahn and Um (1991) who reported extension of vase life of cut

roses, when fresh tap water was supplemented with 300 mg L–1 aluminum sulfate and the

highest concentration of sucrose 50 g L–1. Amiri et al. (2009) also stated effectiveness the use

of combination of aluminum sulfate and sucrose on inhibition of vascular blockage and

increasing water retention of cut gerbera flowers than the other treatments.

34

Fig. 2. Effect of treatments on complete petal drop (CPD) of cut roses at Holeta, Ethiopia during 2009/2010 (SE + 0.88). Means followed by different letters per column differ significantly (P < 5 %) as established by LSD test.

4.2. Leaf Parameters

4.2.1. Leaf wilting date (LWD)

Days to leaf wilting date was highly significantly (P < 0.001) affected by the different

combinations of aluminum sulfate [Al2 (SO4)3] and sucrose (C12H22O11) concentrations. This

parameter was also highly significantly affected by the cultivars (Table 1). Significantly the

maximum days (24.83) to leaf wilting date was observed in T10 (350 mg L–1 A12 (SO4)3 + 30

g L–1 C12H22O11) (Table 6). However, it was not significantly different from T3 (250 mg L–1

A12 (SO4)3 + 20 g L–1 C12H22O11), T4 (350 mg L–1 A12 (SO4)3 + 20 g L–1 C12H22O11), T6 (250

mg L–1 A12 (SO4)3 + 25 g L–1 C12H22O11), and T7 (350 mg L–1 A12 (SO4)3 + 25 g L–1

C12H22O11).

aab

abababbabab

ab

c

20

23

26

29

32

35

38

41

44

T1 T2 T3 T4 T5 T6 T7 T8 T9 T10

Treatments (aluminum sulfate plus sucrose)

CPD

in d

ays

35

Table 6. Effect of aluminum sulfate plus sucrose and cultivars on leaf wilting date (LWD) of cut roses in number of days at Holeta, Ethiopia during 2009/2010

Effects and levels N LWD + SE Treatments T1 (Control, distilled water alone) 6 19.58 + 0.9 c T2 (150 mg L–1 A12 (SO4)3 + 20 g L–1 C12H22O11) 6 22.00 + 0.9 bc T3 (250 mg L–1 A12 (SO4)3 + 20 g L–1 C12H22O11) 6 24.08 + 0.9 ab T4 (350 mg L–1 A12 (SO4)3 + 20 g L–1 C12H22O11) 6 24.41 + 0.9 ab T5 (150 mg L–1 A12 (SO4)3 + 25 g L–1 C12H22O11) 6 22.25 + 0.9 b T6 (250 mg L–1 A12 (SO4)3 + 25 g L–1 C12H22O11) 6 22.41 + 0.9 ab T7 (350 mg L–1 A12 (SO4)3 + 25 g L–1 C12H22O11) 6 23.16 + 0.9 ab T8 (150 mg L–1 A12 (SO4)3 + 30 g L–1 C12H22O11) 6 19.66 + 0.9 c T9 (250 mg L–1 A12 (SO4)3 + 30 g L–1 C12H22O11) 6 19.50 + 0.9 c T10 (350 mg L–1 A12 (SO4)3 + 30 g L–1 C12H22O11) 6 24.83 + 0.9 a LSD 2.576 Cultivars Essendre 30 20.83 + 0.4 b Utopia 30 23.55 + 0.4 a LSD 1.152 CV 9.9 Means followed by different letters per column differ significantly (P < 5 %) as established by LSD test

The use of 350 mg L–1 aluminum sulfate in combination with 30 g L–1 sucrose (T10) extended

days to leaf wilting by 5.25 days compared to the control treatment. This could be due to a

microbial inhibiting effect of aluminum sulphate commonly used in commercial

preservatives. Ichimura et al. (2006) reported extension of vase life of cut flowers as a result

of continuous treatment of cut roses with aluminum sulphate because of its antimicrobial

action.

In addition to the treatment effects, the two cut rose cultivars also showed different

performances (Table 6). Cultivar Utopia showed longer period of days to leaf wilting (LWD)

over Essendre by advancing with 2.72 more days (Table 6). This finding is in agreement with

that of Hojjati et al. (2007) who reported the existence of variation in the vase life of cultivars.

The authors further explained that this is attributed to the varietal difference in the uptake of

different solution, ethylene production, carbohydrate, and transpiration rate.

36

4.2.2. Leaf drop date (LDD)

Leaf drop date (LDD) was highly significantly (P < 0.001) affected by the different

combinations of aluminum sulfate [Al2 (SO4)3] and sucrose (C12H22O11) concentrations. This

parameter was also highly significantly affected by the cultivars (Table 1). Significantly

maximum days to leaf drop date (33.23) was observed in T10 (350 mg L–1 A12 (SO4)3 + 30 g

L–1 C12H22O11) (Table 7). However, it was not significantly different from T3 (250 mg L–1

A12 (SO4)3 + 20 g L–1 C12H22O11), T4 (350 mg L–1 A12 (SO4)3 + 20 g L–1 C12H22O11), T5 (150

mg L–1 A12 (SO4)3 + 25 g L–1 C12H22O11), T6 (250 mg L–1 A12 (SO4)3 + 25 g L–1 C12H22O11),

and T7 (350 mg L–1 A12 (SO4)3 + 25 g L–1 C12H22O11). Significantly the least days to leaf drop

date (24.41) was recorded in the control.

Treatment 10, the combination of 350 mg L–1 aluminum sulfate and 30 g L–1 sucrose extended

the days to leaf drop by 7.92 days compared to the control treatment.

Table 7. Effect of aluminum sulfate plus sucrose and cultivars on leaf drop date (LDD) of cut roses in number of days at Holeta, Ethiopia during 2009/2010

Effects and levels N LDD + SE Treatments T1 (Control, distilled water alone) 6 24.41 + 0.94 e T2 (150 mg L–1 A12 (SO4)3 + 20 g L–1 C12H22O11) 6 28.58 + 0.94 bcd T3 (250 mg L–1 A12 (SO4)3 + 20 g L–1 C12H22O11) 6 30.58 + 0.94 ab T4 (350 mg L–1 A12 (SO4)3 + 20 g L–1 C12H22O11) 6 30.75 + 0.94 ab T5 (150 mg L–1 A12 (SO4)3 + 25 g L–1 C12H22O11) 6 28.91 + 0.94 abcd T6 (250 mg L–1 A12 (SO4)3 + 25 g L–1 C12H22O11) 6 29.00 + 0.94 abc T7 (350 mg L–1 A12 (SO4)3 + 25 g L–1 C12H22O11) 6 30.50 + 0.94 ab T8 (150 mg L–1 A12 (SO4)3 + 30 g L–1 C12H22O11) 6 26.33 + 0.94 cde T9 (250 mg L–1 A12 (SO4)3 + 30 g L–1 C12H22O11) 6 26.25 + 0.94 de T10 (350 mg L–1 A12 (SO4)3 + 30 g L–1 C12H22O11) 6 32.33 + 0.94 a LSD 2.7 Cultivars Essendre 30 27.45 + 0.42 b Utopia 30 29.88 + 0.42 a LSD 1.207 CV 8.1 Means followed by different letters per column differ significantly (P < 5 %) as

37

established by LSD test

This could be due to the role of aluminum sulfate in reducing transpiration, inducing stomata

closure and improving water uptake (Regan, 2008) which in turn extend the vase life of cut

flowers. This finding is also in conformity with Hojjati et al. (2007) who stated that

treatments with sucrose in combination with chemical treatments extended the vase life of cut

Eustoma flowers. The authors further explained that the effect could be due to the supply of

carbohydrates as well as inhibition of vascular occlusion by the chemical treatments.

In addition to the effect of treatments, cultivars showed variations in days to occurrence of

leaf drop. Cultivar Utopia showed longer period of days to leaf drop (2.43 days) over cultivar

Essendre (Table 7). Hojjati et al. (2007) reported variation in the vase life of cultivars which

is suggested to be attributed to their difference in the uptake of different solution, ethylene

production, carbohydrate, and transpiration rate.

4.3. Stem Parameter

For the stem parameter, bent neck occurrence (BNO) was highly significantly (P < 0.001)

affected by the cultivars (Table 1). Days to bent neck occurrence (BNO) was 32.28 for

Essendre and 40.37 for Utopia (Table 8).

Table 8. Effect of aluminum sulfate plus sucrose and cultivars on bent neck occurrence (BNO) of cut roses in number of days at Holeta, Ethiopia during 2009/2010

Effects and levels N BNO + SE Treatments T1 (Control, distilled water alone) 6 40.83 + 4.77 T2 (150 mg L–1 A12 (SO4)3 + 20 g L–1 C12H22O11) 6 33.16 + 4.77 T3 (250 mg L–1 A12 (SO4)3 + 20 g L–1 C12H22O11) 6 38.00 + 4.77 T4 (350 mg L–1 A12 (SO4)3 + 20 g L–1 C12H22O11) 6 42.50 + 4.77 T5 (150 mg L–1 A12 (SO4)3 + 25 g L–1 C12H22O11) 6 36.41 + 4.77 T6 (250 mg L–1 A12 (SO4)3 + 25 g L–1 C12H22O11) 6 32.91 + 4.77 T7 (350 mg L–1 A12 (SO4)3 + 25 g L–1 C12H22O11) 6 33.50 + 4.77 T8 (150 mg L–1 A12 (SO4)3 + 30 g L–1 C12H22O11) 6 36.58 + 4.77 T9 (250 mg L–1 A12 (SO4)3 + 30 g L–1 C12H22O11) 6 30.16 + 4.77 T10 (350 mg L–1 A12 (SO4)3 + 30 g L–1 C12H22O11) 6 39.16 + 4.77

38

LSD NS Cultivars Essendre 30 32.28 + 1.51 b Utopia 30 40.37 + 1.51 a LSD 4.315 CV 22.8 Means followed by different letters per column differ significantly (P < 5 %) as established by LSD test

Cultivar Utopia showed longer period of days (8.07) to bent neck occurrence (BNO) over

cultivar Essendre. The difference observed in bent neck occurrence (BNO) is attributed to the

difference in neck strength of cultivars. Neck strength was weak in cultivars which showed a

bent neck symptom, whereas it was strong in cultivars which did not show a bent neck

symptom. Cultivars with no bent neck symptom maintained a positive water balance as

compared to cultivars with bent neck symptom indicating that the vase life of cut rose flowers

was closely related with the water balance of the flower stems. Therefore it can be concluded

that cultivar Utopia has better neck strength since it maintained a positive water balance than

Essendre. Similar results were reported by Young and Jong (2001) who found significant

differences in the vase life of cut roses among cultivars.

4.4. Correlation Analysis among Flower, Leaf and Stem Parameters

The correlation among various flower, leaf and stem parameters is presented in Table 9.

Complete opening period of flowers (COP) of cut roses was significantly and positively

correlated with days to petal edge drying (PED) (r = 0.058*), longevity of flowers (LF) (r =

0.045*), emergence of petal drop (EPD) (r = 0.11*) and complete petal drop (CPD) (r = 0.13*).

On the other hand, complete opening period of flowers (COP) showed none significant

association with leaf wilting date (LWD) (r = -0.25), leaf drop date (LDD) (r = -0.16) and

days to bent neck occurrence (BNO) (r = -0.37). This showed that as complete opening period

of flowers (COP) extended, the number of days to emergence of petal edge drying (PED),

longevity of flowers (LF), emergence of petal drop (EPD) and complete petal drop (CPD) was

extended.

39

Days to petal edge drying (PED) showed highly significant positive correlation with longevity

of flowers (LF) (r = 0.63**), emergence of petal drop (EPD) (r = 0.45**), complete petal drop

(CPD) (r = 0.48**) and also significant positive correlation with days to bent neck occurrence

(BNO) (r = 0.1*). However, the correlation of days to petal edge drying (PED) with leaf

wilting date (LWD) (r = 0.28) and leaf drop date (LDD) (r = 0.38) was none significant. This

showed that as days to petal edge drying (PED) of cut flowers increased, longevity of flowers

(LF), and days to emergence of petal drop (EPD), complete petal drop (CPD) and bent neck

occurrence (BNO) was also increased since delayed petal edge drying progressively leads to

delayed petal drop of flowers and bent neck of the flower steam.

Table 8. Correlation coefficients among parameters in cut rose cultivars Holeta, Ethiopia during 2009/2010

COP PED LF EPD CPD LWD LDD BNO COP - PED 0.058* - LF 0.045* 0.63** - EPD 0.11* 0.45** 0.35** - CPD 0.13* 0.48** 0.36** 0.90* - LWD -0.25 0.28 0.44** 0.10 0.15 - LDD -0.16 0.38 0.48** 0.14 0.23 0.89** - BNO -0.37 0.10* 0.09* -0.08 -0.03 0.38** 0.29** -

**, * = indicate that significant correlation at 0.01 and 0.05 probability level, respectively. COP = complete opening period of flowers, PED = petal edge drying, LF = longevity of

flowers, EPD = emergence of petal drop, CPD = complete petal drop, LWD = leaf wilting

date, LDD = leaf drop date, and BNO = bent neck occurrence.

Similarly, longevity of flowers (LF) showed highly significant and positive correlation with

emergence of petal drop (EPD) (r = 0.35**), complete petal drop (CPD) (r = 0.36**), leaf

wilting date (LWD) (r = 0.44**), leaf drop date (LDD) (r = 0.48**) and also significant

positive correlation with days to bent neck occurrence (BNO) (r = 0.09*).

Emergence of petal drop (EPD) showed significant and positive correlation with complete

petal drop (CPD) (r = 0.09*). Whereas, days to emergence of petal drop (EPD) showed none

40

significant correlation with leaf wilting date (LWD) (r = 0.10), leaf drop date (LDD) (r =

0.14) and bent neck occurrence (BNO) (r = -0.08). In addition, the association of complete

petal drop (CPD) with leaf wilting date (LWD) (r = 0.15), leaf drop date (LDD) (r = 0.23) and

bent neck occurrence (BNO) (r = -0.03) was also none significant.

Leaf wilting date (LWD) showed highly significant and positive correlation with leaf drop

date (LDD) (r = 0.89**) and bent neck occurrence (BNO) (r = 0.38*). Similarly, highly

significant and positive correlation occurred between leaf drop date (LDD) and bent neck

occurrence (BNO) (r = 0.29**). This showed that the delay in leaf drop resulted in delaying

the occurrence of bent neck.

41

5. SUMMARY AND CONCLUSIONS

Roses (Rosa hybrida) belonging to the Rosaceae family are recognized highly valuable for

economical benefits being the best source of raw material to be used in agro-based industry

especially in the cosmetics and perfumery. However, a very peculiar aspect of rose production

is to get the cut flowers, which greatly deals with the floricultural business.

In Ethiopia, roses occupy the largest share of flower production. Like in other cut flowers, one

of the major problems associated with cut roses production is short vase life. Different ways

have been reported by several researchers to increase the vase life of roses keeping their

freshness for a longer period.

The present investigation was carried out to assess the effect of various concentration levels

of combinations aluminum sulfate and sucrose on vase life of two rose cultivars () produced

by Ethio-Agri CEFT PLC at Holetta area. The results revealed that treatment combinations of

aluminum sulfate and sucrose showed significant effect on the vase life of cut rose cultivars,

Essendre and Utopia. The highest concentration of aluminum sulfate and sucrose combination

(350 mg/l Al2 (SO4)3 and 30 gm/l sucrose) was found to significantly increase the vase life of

both cut rose cultivars in terms of the majority of flower and leaf parameters evaluated. Cut

rose cultivars, Essendre and Utopia responded positively to vase solution treatment and the

cultivar Utopia showed longer vase life over cultivar Essendre in terms of flower, leaf and

stem parameters.

In conclusion, results of the present work indicated that the highest concentration of

aluminum sulfate and sucrose combination (350 mg/l Al2 (SO4)3 and 30 gm/l sucrose) can be

used by Ethio-Agri CEFT PLC to extend the vase life of both cut rose cultivars currently

being produced and exported by the farm. Furthermore, it can be suggested that the farm can

use cultivar Utopia which was found to have better vase life than Essendre. These findings

suggest that the use of aluminum sulfate and sucrose in combination could be useful for

preserving cut roses.

42

As it can be observed from the results of the present work, vase life of cut roses was extended

as a result of the use of high concentration of the vase solution. Further study can therefore be

suggested to test the effect of elevated levels of aluminum sulfate and sucrose combination

(beyond 350 mg/l Al2 (SO4)3 and 30 gm/l sucrose). Assessment of benefit cost may also be

considered.

43

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