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A THESIS FOR THE DEGREE OF MASTER OF SCIENCE
Flowering Response of Eremogone
juncea (M.Bieb.) Fenzl to Photoperiod,
Chilling Treatment, and Cold Storage
일장과 저온 처리 및 저온 저장에 따른
벼룩이울타리의 개화 반응
BY
HYEONJEONG KANG
FEBRUARY, 2020
MAJOR IN HORTICULTURAL SCIENCE AND BIOTECHNOLOGY
DEPARTMENT OF PLANT SCIENCE
THE GRADUATE SCHOOL OF SEOUL NATIONAL UNIVERSITY
i
Flowering Response of Eremogone
juncea (M.Bieb.) Fenzl to Photoperiod,
Chilling Treatment, and Cold Storage
HYEONJEONG KANG
DEPARTMENT OF PLANT SCIENCE
THE GRADUATE SCHOOL OF SEOUL NATIONAL
UNIVERSITY
ABSTRACT
Eremogone juncea (M.Bieb.) Fenzl is a Korean native plant which has attractive
characteristics as a potential new ornamental crop with white flowers and summer
flowering. For the commercialization of E. juncea, manipulation techniques to
control flowering time are required. This study was carried out to examine the
flowering response of E. juncea to photoperiod and chilling treatment to induce
flowering (experiments 1 and 2) and cold storage to extend flowering (experiment
ii
3). In experiment 1, naturally chilled one-year-old E. juncea was acclimated under 9
h photoperiod in a greenhouse for a month. After acclimation, the plants were forced
under five different photoperiod conditions of 9, 12, 14, 16, and 24 h. There was no
difference in percent flowering among photoperiod treatments, showing 57-85%.
Furthermore, these plants did not show any significant difference in flowering
parameters, such as days to visible bud, days to the first open flower, and flower stalk
length, among photoperiod treatments. These results indicated that E. juncea can be
classified as day-neutral plants. In experiment 2, the one-year-old plants were
exposed to natural chilling or artificial chilling at 5°C for 0, 4, 8, or 12 weeks and 0,
4, or 8 weeks, respectively, and then moved into a walk-in chamber. Percent
flowering was less than 30% in the non-chilling treatment. Percent flowering
increased with increasing chilling duration at both natural and artificial chilling
conditions. Days to visible bud and days to the first open flower also decreased as
the chilling duration increased. These results indicated that chilling treatment is
necessary for the flowering of E. juncea. To quantify the chilling requirement, the
chill unit was calculated using modified chilling hours model (MCHM) and modified
Utah model (MUM). Irrespective of chilling methods, the flowering characteristics
were highly correlated with the chill unit (CU). For more than 80% flowering, at
least 1,854 CU in MCHM or 1,889 CU in MUM were required in this experiment.
In experiment 3, the plants which were already exposed to natural chilling during
winter season were stored for 0, 4, 8, or 12 weeks at 0°C. Days to visible bud and
days to the first open flower significantly decreased under cold storage treatment
iii
regardless of durations. Percent flowering also significantly decreased in all cold
storage treatments. These results indicated that although flowering could be delayed
by storing the plants at cold temperature, further studies on the storage timing or
temperature are needed to overcome the decrease in percent flowering by cold
storage. In conclusion, chilling treatment and cold storage can be used to control the
flowering time of E. juncea for year-round cultivation.
Additional key words: chill unit, herbaceous perennials, native plants, vernalization
Student number: 2018-28033
iv
CONTENTS
ABSTRACT‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧ⅰ
CONTENTS‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧ⅳ
LIST OF TABLES‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧ⅴ
LIST OF FIGURES‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧ⅵ
GENERAL INTRODUCTION‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧1
LITERATURE REVIEW
Flowering Response to Photoperiod in Caryophyllaceae‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧4
Flowering Response to Chilling in Caryophyllaceae‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧4
Chill Unit Models for Calculating Chilling Hours in Horticultural Crops‧‧‧‧‧‧‧‧‧‧‧‧5
Cold Storage for Delaying Flowering‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧7
MATERIALS AND METHODS
Flowering Response to Photoperiod (Experiment 1)‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧8
Flowering Response to Chilling (Experiment 2)‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧11
Cold Storage for Delaying Flowering (Experiment 3)‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧16
RESULTS AND DISCUSSION
Flowering Response to Photoperiod (Experiment 1)‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧19
Flowering Response to Chilling (Experiment 2)‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧22
Cold Storage for Delaying Flowering (Experiment 3)‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧29
LITERATURE CITED‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧33
ABSTRACT IN KOREAN‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧38
v
LIST OF TABLES
Table 1. Temperature ranges for calculating chill unit (CU) in chilling hours model
(CHM), Utah model (UM), modified chilling hours model (MCHM), and
modified Utah model (MUM).‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧15
Table 2. Flowering characteristics of E. juncea under different photoperiod
conditions.‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧20
Table 3. Flowering characteristics of E. juncea after 0, 4, 8, or 12 weeks of natural
chilling and 0, 4, or 8 weeks of artificial chilling treatments.‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧24
Table 4. Chill units calculated by modified chilling hours model (MCHM) and
modified Utah model (MUM) under 0, 4, 8, or 12 weeks of natural chilling and
0, 4, or 8 weeks of artificial chilling treatments.‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧26
Table 5. Flowering characteristics of E. juncea after 0, 4, 8, or 12 of cold storage
treatment.‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧30
vi
LIST OF FIGURES
Fig. 1. Daily average, maximum, and minimum air temperatures in a greenhouse
located at the Experimental Farm of Seoul National University during
photoperiod treatment (from 6 May 2018 to 29 June 2018).‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧10
Fig. 2. Changes in daily average soil temperature under natural and artificial chilling
treatments from 30 November 2018 to 22 February 2019 and 30 November 2018
to 25 January 2019, respectively.‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧12
Fig. 3. Changes in daily average soil temperature before cold storage treatment from
17 November 2018 to 11 April 2019.‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧17
Fig. 4. Growth and flowering of E. juncea as affected by different photoperiod
conditions.‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧21
Fig. 5. Growth and flowering of E. juncea at 12 weeks after 0, 4, 8, or 12 weeks of
natural chilling and 0, 4, or 8 weeks of artificial chilling treatments.‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧23
Fig. 6. Correlation between chill units calculated by modified chilling hours model
(MCHM) and modified Utah model (MUM) and percent flowering.‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧28
Fig. 7. Growth and flowering of E. juncea at 12 weeks after 0, 4, 8, or 12 weeks of
cold storage treatment.‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧‧31
1
GENERAL INTRODUCTION
With increasing interest and demand for Korean native plants, flowering control
methods for year-round cultivation of new ornamental crops are needed. Eremogone
juncea (M.Bieb.) Fenzl (벼룩이울타리, rush sandwort) is a herbaceous perennial
plant, growing naturally in mountains, slopes, and arid grasslands of Korea, China,
Mongolia, Japan, and far east Russia (Korea Biodiversity Information System). E.
juncea is regarded as a potential ornamental plant because it blooms in the summer
time with white flowers. It is commonly used for the flower garden, ground cover,
and pot plant. However, flowering is limited to a season between July and August.
Therefore, forcing or retarding methods for flowering season control of E. juncea
are needed for introducing E. juncea as a new ornamental crops.
Environmental factors such as photoperiod and temperature affect flowering in
many herbaceous perennial species (Foley et al., 2009; Runkle et al., 1999; Whitman
et al., 1996). The responses to photoperiod and vernalization can be variable among
species or cultivars and the grower needs to recognize the flowering response of
individual cultivars (Seaton et al., 2014).
Eremogone is a genus of Caryophyllaceae and contains about 71 species
(Rabeler and Wagner, 2015). No previous study for determining flowering response
has been reported on E. juncea. Researches have been conducted to examine the
flowering responses of various Caryophyllaceae plants under different photoperiods
2
and temperatures. Krekule and Hájková (1972) identified that Arenaria serphyllifolia
L. is a vernalization required and quantitative long-day plant. Baskin and Baskin
(1987) found that Arenaria fontinalis is a day-neutral plant and required 2,479 h of
vernalization at 0.5-10°C for 100% flowering. Dianthus gratianopolitanus Vill.
‘Bath's Pink’, a day-neutral plant, required three weeks at 5°C for complete
flowering and no plants flowered after eight weeks at 15°C (Padhye and Cameron,
2008). Dall'Agnese et al. (2014) found that cold treatment did not influence flower
opening time of Dianthus barbatus L, a short-day plant.
Determination of chilling requirements for flowering is difficult. Therefore,
many studies have identified the precise chilling requirements by calculating chill
units to quantify low temperatures. Jung and Kim (2009) found that at least 1,200 h
natural cumulative chilling or 1,008 h cumulative chilling below 10°C are
recommended for dormancy breaking of Adonis amurensis Regel et Radde. At least
492 h natural cumulative chill unit or 672 h cumulative chill unit might be required
for dormancy release of Polygonatum odoratum Druce var. pluriflorum Ohwi for.
variegatum Y.N.Lee (Yun et al., 2011).
Finding ways to delay flowering time allows the flowering season control for
year-round cultivation of E. juncea as a new ornamental crop. Cold storage can
extend the flowering season by delaying growth and development. Seo et al. (2009)
and Lee and Park (2015) found that cold temperature by storing delays the flowering
time of Arabidopsis thaliana. The flowering of saffron (Crocus sativus L.) could be
delayed by storing corms before flower initiation (Molina et al., 2005). Li et al. (2005)
3
identified that the cold storage extended the dormant condition of live black willow
(Salix nigra) cuttings for later planting.
The objectives of this study were to observe flowering responses of E. juncea to
photoperiod (Experiment 1), to verify the chilling requirement for flowering of E.
juncea (Experiment 2), and to investigate flowering responses of E. juncea to cold
storage to extend the flowering season (Experiment 3).
4
LITERATURE REVIEW
Flowering Response to Photoperiod in Caryophyllaceae
Photoperiod is an environmental factor to affect flower induction and
development of many plants (Hopkins and Huner, 2004). Flowering responses to
photoperiod are divided into five groups: short-day plants (SDP), long-day plants
(LDP), day-neutral plants (DNP), intermediate-day plants, and ambiphotoperiodic
plants (Thomas and Vince-Prue, 1997). Many studies have been carried out on the
photoperiodic flowering response of plants belonging to Caryophyllaceae. Krekule
and Hájková (1972) found Arenaria serphyllifolia L., a biennial plant, to be a
facultative LDP. Arenaria fontinalis, a winter annual plant, and Dianthus
gratianopolitanus Vill. ‘Bath's Pink’, a herbaceous perennial plant, were classified
to DNP (Baskin and Baskin, 1987; Padhye and Cameron, 2008). Dall'Agnese et al.
(2014) identified that Dianthus barbatus L., a biennial or short-lived perennial plant,
is a SDP. Plants belonging to Caryophyllaceae were classified differently as long-
day plants, day-neutral plants, and short-day plants.
Flowering Response to Chilling in Caryophyllaceae
The flowering of many plants species is either dependent on or promoted by prior
exposure to the prolonged winter cold (Sung and Amasino, 2005). The process by
which exposure to cold promotes flowering is known as vernalization. The effective
5
temperature range for vernalization of many plant species is 1-7°C, however,
vernalization temperature may vary depending on species (Ha TM, 2014). Many
studies have been conducted on the vernalization requirements of plants belonging
to Caryophyllaceae. Krekule and Hájková (1972) identified that Arenaria
serphyllifolia L. is a vernalization requiring plants. Although Arenaria fontinalis
flowered without vernalization, vernalized plants survive better and are healthier
than non-vernalized plants (Baskin and Baskin, 1987). Dianthus gratianopolitanus
Vill. ‘Bath's Pink’ exhibited a quantitative vernalization requiring response (Padhye
and Cameron, 2008). Dianthus barbatus L. did not show significant differences in
days to the first open flower and days to full bloom under vernalization condition,
and longer vernalization duration reduced the inflorescence size but increased the
stem height (Dall'Agnese et al., 2014).
Chill Unit Models for Calculating Chilling Hours in
Horticultural Crops
Chill unit models have been developed for predicting the chilling requirement of
temperate woody perennial plants and quantifying cold temperature (Darbyshire et
al., 2016). Many models have been proposed with varying rages of temperature for
calculating the chill unit. For example, chilling hours model (CHM) is the oldest
method considering one hour at temperature between 0 and 7°C calculated as 1 chill
unit (CU) (Weinberger, 1950). Utah model (UM) calculated the temperature between
6
2.5 and 9.1°C as the most effective temperature for dormancy breaking, taking into
account the negative effects of high winter temperature (Richardson et al., 1974).
Modified chilling hours model (CHM) is the method considering one hour at
temperature between 5 and 7°C calculated as one chill unit (Yun et al., 2011).
Modified Utah model (UM) calculated the temperature between 1.5 and 9.1°C as the
most effective temperature for dormancy breaking.
At least 1,200 h natural cumulative chilling calculated by modified chilling hour
model or 1,008 h cumulative chilling (= six weeks of cold storage) below 10°C might
satisfy the chilling requirement for dormancy breaking, flower bud development, and
subsequent growth of Adonis amurensis Regel et Radde (Jung and Kim, 2009). Yun
et al. (2011) found that at least 492 h natural cumulative chill unit calculated by
modified chilling hours model in the field or 672 h cumulative chill unit (= four
weeks of cold storage at 0°C) is recommended for dormancy release and normal
growth of Polygonatum odoratum Druce var. pluriflorum Ohwi for. variegatum
Y.N.Lee. At least 1,222 h natural cumulative chill unit calculated by modified
chilling hour model of Fulton et al. (2001) could be recommended as a forcing
method for dormancy release, normal growth, and subsequent flowering of Paeonia
lactiflora ‘Taebaek’ (Yeo et al., 2012). Rhie et al. (2012) reported that 1,008 h chill
unit (= chilling for six weeks at 0°C) or 1,058 h chill unit (= nine weeks at 5°C)
calculated by modified chilling hour model of Fulton et al. were necessary to break
dormancy and to induce flowering in P. lactiflora ‘Taebaek’ and ‘Mulsurae’,
respectively. At least 1,483-1,794 cumulative chill unit calculated as the number of
7
hours when the temperatures was below 5°C might satisfy the chilling requirement
for dormancy breaking of Erythronium japonicum Decne. (Liliaceae) (Kim et al.,
2014).
Cold Storage for Delaying Flowering
In Arabidopsis, 10 d of cold at 4°C slightly delays flowering and 20 d of cold at
4°C delays flowering further, indicating that the flowering is delayed in proportion
to the days of cold treatment (Seo et al., 2009). Seo et al. (2009) explain that short-
term cold delays flowering through FLOWERING LOCUS C (FLC) activity. Lee
and Park (2015) identified that flowering is delayed by intermittent cold temperature
that frequently occurs during early spring in the temperate zones in Arabidopsis.
Exposure to cold temperatures triggers the binding of INDUCER OF CBF
EXPRESSION 1 (ICE1) to FLC gene promoter to induce its expression. Lee and
Park (2015) also described that delayed flowering by short-term cold conditions is
mediated primarily by the floral repressor FLC in Arabidopsis. Molina et al. (2005)
found that the flowering of saffron (Crocus sativus L.) could be delayed by extending
the duration of cold storage. In black willow (Salix nigra) cuttings, a dormancy
extension technique can be possible by cold storing at 4.4°C (Li et al., 2005).
8
MATERIALS AND METHODS
Flowering Response to Photoperiod (Experiment 1)
Plant materials
These experiments were conducted in a greenhouse located at the Experimental
Farm of Seoul National University, Suwon, Korea. Naturally chilled one-year-old E.
juncea were purchased from a commercial farm (Gangwon Plant, Hoengseong,
Korea) on 2 April 2018. The plants have been planted into 7 cm (179 mL) plastic
pots filled with saprolite and then were cut with the above-ground part 1.0-1.5 cm
remaining. These plants were acclimated under 9 h photoperiod condition in the
greenhouse for a month. The plants were irrigated when the surface of the potting
medium showed dryness.
Photoperiod treatments
Twenty plants were randomly selected and placed in each greenhouse bench in a
completely randomized design on 6 May 2018. The photoperiods were 9, 12, 14, 16,
and 24 h of continuous light. A truncated 9 h short-day photoperiod was controlled
by black film. The black plastic film on every bench was rolled up at 09:00 HR and
closed at 18:00 HR. Photoperiods were extended by supplemental lighting with white
LEDs (12V SMD 5050 LED, CamFree Co., Ltd., Seoul, Korea). The light intensity
of the white LED was 3 mol∙m2∙s1 at plant canopy to avoid the effects of daily
9
light integral (DLI). The plants were irrigated as necessary with tap water using a
sprinkler. Once every two weeks each pot received 50 mL of water soluble fertilizer
(EC 0.8 mS∙cm1; HYPONeX professional 20N-20P-20K, HYPONeX Japan Co.,
Ltd., Osaka, Japan). Air temperature within the bench was monitored at 30 min
intervals using a data logger (Watch Dog Model 1000, Spectrum Technologies, Inc.,
Plainfield, IL, USA) from 6 May 2018 to 29 June 2018 (Fig. 1).
Data collection and statistical analysis
Percent flowering was measured for each photoperiod treatment. Days to visible
bud and days to the first open flower from the start of photoperiod treatments were
counted. Flower stalk length from the medium to the top of the stalk at the first open
flower was measured.
The collected data were analyzed using analysis of variance (ANOVA) using the
SAS program (Ver. 9.4, SAS Institute, Inc., Cary, NC, USA). Mean separation by
Tukey’s multiple range test at p < 0.05 was performed for all data.
10
Fig. 1. Daily average, maximum, and minimum air temperatures in a greenhouse
located at the Experimental Farm of Seoul National University during
photoperiod treatment (from 6 May 2018 to 29 June 2018).
0
5
10
15
20
25
30
35
40
45T
emper
atu
re (
⁰C)
Date
Average
Maximum
Minimum
11
Flowering Response to Chilling (Experiment 2)
Plant materials
These experiments were conducted in a greenhouse located at the Experimental
Farm of Seoul National University, Suwon, Korea. One-year-old E. juncea were
purchased from a commercial farm (Gosan Plant, Pyeongchang, Korea) on 27
October 2018. E. juncea were planted into 10 cm (461 mL) plastic pots filled with
saprolite. These plants received natural chilling in an open field for a month before
chilling treatments and then were cut with the above-ground part 1.0-1.5 cm
remaining. On 30 November 2018, the plants were moved to a container plot filled
with saprolite in an open field or a cold storage room at 5°C for 0, 4, 8, or 12 weeks
or 0, 4, or 8 weeks, respectively.
Daily average soil temperature at a depth of 3 cm was monitored every 30 min
for calculation of chilling requirement under a natural condition using a thermo data
logger (Watch Dog Model 1000, Spectrum Technologies, Inc., Plainfield, IL, USA)
from 30 November 2018 to 22 February 2019 (Fig. 2). The plants which received
natural chilling in an open field or artificial chilling in a cold storage room at 5°C
were moved to a closed plant production system at the university farm (Seoul
National University, Suwon, Korea). In a closed plant production system conditions,
temperature, relative humidity (RH), photoperiod, and light intensity were
maintained at 20°C, 60%, 12 h, and 200 ± 10 mol∙m2∙s1 [fluorescent lamp (TL-D
32W RS 865, Philips Lighting Co., Ltd., Eindhoven, Netherlands) + white LED
12
Fig. 2. Changes in daily average soil temperature under natural and artificial chilling
treatments from 30 November 2018 to 22 February 2019 and 30 November 2018
to 25 January 2019, respectively.
-10
-5
0
5
10
15
Dai
ly a
ver
age
soil
tem
per
atu
re (
⁰C)
Date
Natural chilling
Artificial chilling
13
(LEDT5-9015-DHE, FOCUS lighting Co., Ltd., Bucheon, Korea)], respectively. The
plants were irrigated as necessary with tap water by hand watering. Once every two
weeks each pot received 50 mL of a water soluble fertilizer (EC 0.8 mS∙cm1;
HYPONeX professional 20N-20P-20K, HYPONeX Japan Co., Ltd., Osaka, Japan).
Chilling treatments
For the natural chilling treatment, the plants were transferred from an open field
to a closed plant production system at four different transfer dates (11 November
2018, 28 December 2018, 25 January 2019, and 22 February 2019). For the artificial
chilling treatment, the plants were transferred from a cold storage room at 5°C under
dark conditions to a closed plant production system at three different transfer dates
(11 November 2018, 28 December 2018, and 25 January 2019).
Data collection and statistical analysis
Percent flowering was measured for natural and artificial chilling treatments.
Days to visible bud and days to the first open flower from the transferring date were
counted. Flower stalk length from the medium to the top of the stalk, the number of
visible buds, and flower diameter at the first open flower were measured.
Trials were conducted in a completely randomized design with three replicates
of eight plants per treatment. Statistical analysis was performed using ANOVA in the
SAS system for Windows version 9.4 (SAS Institute Inc., Cary, NC, USA). The
statistical significance of the results was confirmed at the 5% level followed by
14
Tukey’s multiple range tests. All figures were generated using Sigma Plot software
version 10.0 (Systat Software, Inc., Chicago, IL, USA).
To interpret the results in terms of the chill unit (CU), the amount of chilling
required to flowering was calculated. The chill unit model can be used to quantify
winter chill in hours. We used modified chilling hours model (MCHM) and modified
Utah model (MUM) (Table 1). MCHM and MUM were modified based on chilling
hours model (CHM) (Weinberger, 1950) and Utah model (UM) (Richardson et al.,
1974), respectively.
15
Table 1. Temperature ranges for calculating chill unit (CU) in chilling hours model
(CHM), Utah model (UM), modified chilling hours model (MCHM), and
modified Utah model (MUM).
Chill unit model Temperature range
CHM 0°C < T < 7.2°C = 1, else: 0
UM T ≤ 1.4°C = 0
1.4°C < T ≤ 2.4°C = 0.5
2.4°C < T ≤ 9.1°C = 1
9.1°C < T ≤ 12.4°C = 0.5
12.4°C < T ≤ 15.9°C = 0
15.9°C < T ≤ 18.0°C = 0.5
T > 18.0°C = 1
MCHM 5°C < T < 7.2°C = 1, else: 0
MUM T ≤ 5°C = 0
5°C < T ≤ 1.4°C = 0.8
1.4°C < T ≤ 2.4°C = 1
2.4°C < T ≤ 9.1°C = 1
9.1°C < T ≤ 12.4°C = 0.5
12.4°C < T ≤ 15.9°C = 0
15.9°C < T ≤ 18.0°C = 0.5
T > 18.0°C = 1
16
Cold Storage for Delaying Flowering (Experiment 3)
Plant materials
These experiments were conducted in a greenhouse located at the Experimental
Farm of Seoul National University, Suwon, Korea. One-year-old E. juncea were
purchased from a commercial farm (Gosan Plant, Pyeongchang, Korea) on 27
October 2018. E. juncea plants were planted into 10 cm (461 mL) plastic pots filled
with saprolite. These plants received natural chilling in a container plot filled with
saprolite in an open field and then were cut with the above-ground part 1.0-1.5 cm
remaining before cold storage treatment. Daily average soil temperature at a depth
of 3 cm was monitored every 30 min using a thermo data logger (Watch Dog Model
1000, Spectrum Technologies, Inc., Plainfield, IL, USA) from 17 November 2018 to
11 April 2019 (Fig. 3).
On 12 April 2019, the plants were moved to a cold storage room at 0°C for 0, 4,
8, or 12 weeks. After cold storage treatment, the plants were moved to an
environmental-controlled growth chamber (HB-301MP, Hanbaek Scientific CO.,
Bucheon, Korea) at a laboratory (Seoul National University, Seoul, Korea). In an
environmental-controlled growth chamber conditions, temperature, relative
humidity (RH), photoperiod, and light intensity were maintained at 20°C, 60%, 12
h, and 200 ± 10 mol∙m2∙s1 [250 W metal halide lamp (Han Young Electrics Co.,
Gwanju, Korea)], respectively. The plants were irrigated as necessary with tap water
by hand watering. Each pot received 50 mL once every two weeks of a water soluble
17
Fig. 3. Changes in daily average soil temperature before cold storage treatment from
17 November 2018 to 11 April 2019.
-15
-10
-5
0
5
10
15
20
25
30T
emper
atu
re (
⁰C)
Date
Average
Maximum
Minimum
18
fertilizer (EC 0.8 mS∙cm1; HYPONeX professional 20N-20P-20K, HYPONeX
Japan Co., Ltd., Osaka, Japan).
Cold storage treatments
For the cold storage treatment, the plants were stored at a cold storage room at
5°C under dark conditions, and then transferred to an environmental-controlled
growth chamber at four different transfer dates (12 April 2019, 10 May 2019, 7 June
2019, and 5 July 2019).
Data collection and statistical analysis
Percent flowering was measured for each treatment. Days to visible bud and days
to the first open flower from the transferring date were counted. Flower stalk length
from the medium to the top of the stalk, the number of visible buds, and flower
diameter at the first open flower were measured.
Experiments were conducted in a completely randomized design with three
replicates of 4 plants per treatment. Statistical analysis was performed using ANOVA
in the SAS system for Windows version 9.4 (SAS Institute Inc., Cary, NC, USA).
The statistical significance of the results was confirmed at the 5% level followed by
Tukey’s multiple range tests. All figures were generated using Sigma Plot software
version 10.0 (Systat Software, Inc., Chicago, IL, USA).
19
RESULTS AND DISCUSSION
Flowering Response to Photoperiod (Experiment 1)
E. juncea grown under different photoperiod conditions did not show significant
differences in all flowering parameters (Table 2 and Fig. 4). Days to visible bud was
28.8, 26.5, 25.5, 25.0 or 25.6 d and days to the first open flower was 41.3, 42.6, 38.8,
39.6, or 40.8 d under 9, 12, 14, 16, or 24 h, respectively. Flower stalk length was
23.3, 24.6, 25.0, 24.7, or 26.6 under 9, 12, 14, 16, or 24 h, respectively. Flowering
occurred under all photoperiod conditions. Percent flowering was 57, 63, 61, 58, or
85% under 9, 12, 14, 16, or 24 h, respectively. There was no difference in percent
flowering among different photoperiod treatments. LDP only flower or flower most
rapidly when exposed to night durations shorter than a critical photoperiod, whereas
SDP flower when exposed to night period longer than a critical photoperiod (Thomas
and Vince-Prue, 1997). DNP flower regardless of daylength. Many studies have been
conducted on photoperiod response of Caryophyllaceae plants. Arenaria
serphyllifolia L. is LDP, Arenaria fontinalis and Dianthus gratianopolitanus Vill.
‘Bath's Pink’ are DNP, and Dianthus barbatus L. is SDP (Baskin and Baskin, 1987;
Dall'Agnese et al., 2014; Krekule and Hájková, 1972; Padhye and Cameron, 2008).
In this study, the flowering of E. juncea were not influenced by photoperiod. Thus,
E. juncea can be classified as DNP, similar to two previously studied species of
Caryophyllaceae (Baskin and Baskin, 1987; Padhye and Cameron, 2008).
20
Table 2. Flowering characteristics of E. juncea under different photoperiod
conditions (Tukey's multiple range test, p < 0.05).
Photoperiod (h) Flowering (%) Days to
visible bud
Days to first
open flower
Flower stalk
length (cm)
9/15 57 28.8 41.3 23.3
12/12 63 26.5 42.6 24.6
14/10 61 25.5 38.8 25.0
16/8 58 25.0 39.6 24.7
24/0 85 25.6 40.8 26.6
Significance - NS NS NS
NS Non-significant
21
Fig. 4.
Fig. 4. Growth and flowering of E. juncea as affected by different photoperiod
conditions.
9 h 12 h 14 h 16 h 24 h
Photoperiod
22
Flowering Response to Chilling (Experiment 2)
Growth and flowering of E. juncea under 8 or 12 weeks of natural chilling and 8
weeks of artificial chilling were better than 0 and 4 weeks of natural and artificial
chilling (Fig. 5). Without chilling treatment, percent flowering was less than 30%
(Table 3). Percent flowering was 63.9, 82.7, or 81.5% under 4, 8, or 12 weeks of
natural chilling and 43.3 or 62.5 % under 4 or 8 weeks of artificial chilling,
respectively. Percent flowering significantly increased with increasing chilling
duration irrespective of the chilling method. According to results of Padhye and
Cameron (2008), 21% of non-chilled D. gratianopolitanus ‘Bath's Pink’ flowered,
whereas 100% flowering was achieved only after chilling at 0°C. Therefore, D.
gratianopolitanus ‘Bath's Pink’ exhibited a facultative vernalization response.
Days to visible bud and days to the first open flower were significantly decreased
with increasing chilling duration regardless of chilling method. Days to visible bud
and days to the first open flower significantly decreased under natural and artificial
chilling treatments compared with non-chilling treatment. Similar results were
reported in various herbaceous perennial, such as Chinese peony, Solomon’s seal,
Amur Adonis, and Asian fawnlily (Jung and Kim, 2009; Kim et al., 2014; Rhie et al.,
2012; Yeo et al., 2012; Yun et al., 2011). For example, 0% of Paeonia lactiflora
sprouted under non-chilling treatment, whereas more than 70% of the plants sprouted
at 0, 5, or 10°C after 6, 9, or 12 weeks of chilling and 100% sprouting under 12
weeks of chilling regardless of chilling temperature (Rhie et al., 2012). Rhie et al.
(2012) also identified that days to flowering was decreased at 0, 5, or 10°C as the
23
Fig. 5. Growth and flowering of E. juncea at 12 weeks after 0, 4, 8, or 12 weeks of
natural chilling and 0, 4, or 8 weeks of artificial chilling treatments.
24
Tab
le 3
. F
low
erin
g c
har
acte
rist
ics
of
E.
junce
a a
fter
0,
4,
8,
or
12 w
eeks
of
nat
ura
l ch
illi
ng a
nd 0
, 4
, o
r 8 w
eeks
of
arti
fici
al
chil
lin
g t
reat
men
ts.
Chil
ling
trea
tmen
t
Ch
illi
ng
du
rati
on
(wee
k)
Flo
wer
ing
(%)
Day
s to
vis
ible
bud
Day
s to
fir
st
open
flo
wer
A
t fi
rst
open
flo
wer
Flo
wer
sta
lk
length
(cm
) N
um
ber
of
vis
ible
bu
d
Flo
wer
dia
met
er
(cm
) N
on
0
23
.7 bz
89.8
a
103.3 a
20.9
6.7
1.6
6
Nat
ura
l 4
63
.9 ab
80.8 ab
95.2 ab
20.0
8.4
1.8
3
8
82
.7 a
67.0 b
79.5 b
20.6
9.4
1.4
6
1
2
81
.5 a
68.4 b
85.2 ab
17.8
7.1
1.4
8
Art
ific
ial
4
43
.3 ab
80.8 ab
90.9 ab
19.5
8.8
1.7
5
8
62
.5 ab
70.9 b
83.1 b
20.2
9.3
1.7
3
Sig
nif
icance
Chil
ling t
reat
men
t (T
) *
*
**
*
N
S
NS
NS
Chil
ling d
ura
tio
n (
D)
**
**
**
N
S
NS
NS
T *
D
NS
NS
NS
N
S
NS
NS
z M
eans
wit
hin
colu
mn
s fo
llo
wed
by d
iffe
rent
lett
ers
are
signif
ican
tly d
iffe
rent
by T
ukey
's m
ult
iple
ran
ge
test
at
p <
0.0
5.
NS
, *,
** N
on
-sig
nif
ican
t o
r si
gn
ific
ant
at p
< 0
.05, 0.0
1, re
spec
tivel
y.
25
chilling duration was extended from 3 to 12 weeks in Paeonia lactiflora. E. juncea
grown under different chilling conditions did not show significant differences in
flowering parameters including flower stalk length, the number of visible buds, and
flower diameter.
There was a significant difference in percent flowering among chilling
treatments. Even though the chilling duration was the same, percent flowering was
different between natural and artificial chilling. While artificial chilling temperature
was constant at 5°C, the natural chilling temperature has been fluctuated, and the
difference in percent flowering seems to be caused by the temperature difference of
the chilling method (Fig. 2). Outdoor fluctuating temperatures have been accepted
to be more effective in satisfying the chilling requirements than artificial constant
temperatures in many woody plants (Hänninen, 1990; Murray et al., 1989). However,
Myking (1997) found no differences in days to budburst between fluctuating and
constant temperatures in Betula pubescens. In addition, constant temperatures are
more effective in dormancy breaking than fluctuating temperatures in coniferous
species (Lavender and Cleary, 1974).
To quantify the chilling temperature received during chilling treatment, chill unit
was calculated using modified chilling hours model (MCHM) and modified Utah
model (MUM). Choi et al. (1996) reported that root zone temperature is more
important for bud dormancy breaking than air temperature, thus soil temperature at
a depth of 3 cm was measured. Chill unit calculated by MCHM was 562, 1,234, or
1,905 and 675 or 1,347 under natural and artificial chilling, respectively (Table 4).
26
Table 4. Chill units calculated by modified chilling hours model (MCHM) and
modified Utah model (MUM) under 0, 4, 8, or 12 weeks of natural chilling and
0, 4, or 8 weeks of artificial chilling treatments.
Chilling treatment Chilling duration
(week) MCMM MUM
Non 0 0 0 Natural 4 562 497 8 1,234 1,035 12 1,905 1,579 Artificial 4 675 675 8 1,347 1,347
27
The chill unit was 497, 1,035, or 1,579 and 675 or 1,347 under natural and artificial
chilling, respectively, using MUM. The correlation between the chill unit and the
percent flowering calculated by the two models showed that the percent flowering
increased as the chill unit increased (Fig. 6). Based on the correlation between the
chill units calculated by the two models and the percent flowering, the results
indicated that 1,854 CU calculated by MCHM or 1,889 CU calculated by MUM
might be required for over 80% flowering. Many researches on relationship between
chill unit and flowering were reported in various herbaceous perennials. Percent
sprouting was increased and days to sprouting was decreased with increasing
cumulative chill unit in E. japonicum (Kim et al., 2014). Bud break percentage and
flowering percentage were increased and days to bud break and days to flowering
were decreased with increasing cumulative chilling hours calculated using by
MCHM in A. amurensis (Jung and Kim, 2009). In P. odoratum, Days to sprouting
was shortened and percent sprouting was increased with increasing cumulative chill
unit calculated by MCHM under both natural and artificial chilling conditions (Yun
et al., 2011).
28
Chill units
0 500 1000 1500 2000 2500
Flo
wer
ing (
%)
0
20
40
60
80
100
Modified chilling hours model
Modified Utah model
Modified chilling hours model
Modified Utah model
Fig. 6. Correlation between chill units calculated by modified chilling hours model
(MCHM) and modified Utah model (MUM) and percent flowering. The data
shown are the mean ± SE. The lines were fitted to a hyperbola single rectangular
I, 3 Parameter; y = y0 + 𝑎𝑥
𝑏+𝑥.
R2 = 0.7873
R2 = 0.7207
29
Cold Storage for Delaying Flowering (Experiment 3)
Days to visible bud and days to the first open flower significantly decreased
under all cold storage treatments (Table 5). Although there were significant
differences in days to visible bud and days to the first flowering according to cold
storage duration, the flowering season can be extended by delaying the flowering
time by storing the plants at cold temperature. Gonzalez et al. (1998) reported that
cold storage treatment at 5°C lasting six weeks significantly delayed the time of
sprouting in Gladiolus tristis. There were no significant differences in flower stalk
length, the number of visible buds, and flower diameter according to the cold storage
treatment (Table 5 and Fig. 7).
Percent flowering under non-cold storage treatment showed over 80%, but
percent flowering significantly decreased to 58.3, 55.6, or 50.0 under 4, 8, or 12
weeks of cold storage treatment (Table 5). Several studies have reported the negative
effects of cold storage. Molina et al. (2005) identified that the flowering of saffron
(Crocus sativus L.) could be delayed by extending the duration of cold storage, but
this delayed flowering resulted in a significant reduction in spice saffron yield. The
number of flowers and flower size decreased gradually with increasing cold storage
duration in saffron. Upon transfer to forcing conditions, cold-stored corms of saffron
formed flowers earlier than non-cold storage corms. In black willow (Salix nigra)
cuttings, cold storage method can be used to dormancy extension, but survival rates
were 81.3, 43.6, and 43.8% when they were stored for 3, 7, and 12 weeks (Li et al.,
2005). In P. lactiflora, percent flowering of pre-chilling at 0°C for 2 weeks before
30
Tab
le 5
. F
low
erin
g c
har
acte
rist
ics
of
E. ju
nce
a a
fter
0, 4,
8,
or
12 o
f co
ld s
tora
ge
trea
tmen
t.
Cold
sto
rage
du
rati
on
(wee
k)
Flo
wer
ing
(%)
Day
s to
vis
ible
bud
Day
s to
fir
st
open
flo
wer
A
t fi
rst
open
flo
wer
Flo
wer
sta
lk
length
(cm
)
Nu
mb
er o
f
vis
ible
bu
d
Flo
wer
dia
met
er
(cm
)
0
83
.3 a
z 47.0
a
56.6
a
18.7
8
.0
1.4
9
4
58
.3 a
b
42.7
ab
53.8
b
21.9
1
0.2
1
.48
8
55
.6 b
41.5
b
51.8
b
21.0
8.3
1
.63
12
5
0.0
ab
41.8
ab
52.0
b
21.4
1
0.0
1
.73
Sig
nif
icance
*
*
***
NS
N
S
NS
z M
eans
wit
hin
colu
mn
s fo
llo
wed
by d
iffe
rent
lett
ers
are
signif
ican
tly d
iffe
rent
by T
ukey
's m
ult
iple
ran
ge
test
at
p <
0.0
5.
NS
, *,
**
* N
on
-sig
nif
ican
t or
sign
ific
ant
at p
< 0
.05
, 0.0
01,
resp
ecti
vel
y.
31
Fig. 7. Growth and flowering of E. juncea at 12 weeks after 0, 4, 8, or 12 weeks of
cold storage treatment.
32
chilling at 0°C for 6 weeks was 40%, whereas percent flowering of pre-chilling at
10°C for two weeks was 89.6% (Park et al., 2015). Park et al. (2015) also found that
days to flowering was 66.8 or 48.8 d under pre-chilling at 0 or 10°C, respectively,
for two weeks before chilling at 0°C for six weeks. Therefore, the optimum pre-
chilling temperature might be needed to reduce flower bud abortion. Percent
flowering of E. juncea significantly decreased in all cold storage treatments at 0°C,
thus further studies on the storage timing or temperature are needed.
33
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ABSTRACT IN KOREAN
벼룩이울타리는 한국 자생식물이며 여름에 개화하고 하얀색 꽃이
피는 매력적인 특성을 가지고 있어 새로운 관상식물 대상종으로
선정되었다. 벼룩이울타리의 산업화를 위해서는 개화시기를 제어하는
조절 기술의 개발이 필요하다. 본 연구에서는 개화를 유도하기 위해
일장과 저온 처리에 따른 개화 반응을 살펴본 실험 1과 2가 진행되었고,
개화를 지연시키기 위해 저온 저장에 따른 개화 반응을 살펴본 실험
3이 진행되었다. 실험 1에서는 자연적인 저온을 받은 1년생 묘를
온실에서 약 한 달간 9시간 일장 조건에서 순화시킨 후 9, 12, 14, 16,
24시간의 일장 처리가 진행되었다. 일장 실험 결과, 꽃눈분화소요일수,
개화소요일수, 꽃대길이에서는 일장에 따른 유의미한 차이가 나타나지
않았다. 또한, 일장에 따른 개화율에도 차이가 나타나지 않았다. 따라서
벼룩이울타리는 일장에 따른 개화에 차이가 나타나지 않는 중성식물로
분류될 수 있다는 것을 확인하였다. 실험 2에서는 1년생 묘를 사용하여
39
0, 4, 8, 12주 동안 야외에서의 자연 저온 처리와 0, 4, 8주 동안 5°C 저온
저장고에서의 인공 저온 처리를 실시하였다. 저온 처리 후에는 20°C 의
생장상에서 처리에 따른 결과를 지켜보았다. 저온 무처리구에서는 30%
이하의 개화율을 보였다. 저온 처리기간이 증가할수록 저온 처리 방법에
상관없이 개화율이 증가했고, 꽃눈분화소요일수, 개화소요일수는
감소했다. 이러한 결과를 통해 벼룩이울타리의 개화를 위해서는 저온
처리가 필요하다는 것을 확인하였다. 저온을 정량화하기 위해 modified
chilling hours model(MCHM)과 modified Utah model(MUM)을 사용하여
chill unit(CU)을 계산하였다. 자연 저온과 인공 저온 처리에서 개화
특성은 chill unit과 밀접한 관련이 있었다. 본 실험 결과를 토대로, 80%
이상의 개화율을 위해서는 MCHM에서는 1,854CU, MUM에서는 1,889CU
이상이 요구되었다. 실험 3에서는 겨울철 자연 저온에 노출된
벼룩이울타리 묘를 대상으로 0°C의 저온 저장고에서 0, 4, 8, 12주 동안
저온 저장 처리를 실시했다. 꽃눈분화소요일수와 개화소요일수에서는
모든 저온 저장 처리에서 유의미하게 감소하였다. 개화율의 경우에는
40
모든 저온 저장처리구에서 유의미하게 감소했다. 이러한 결과는 저온
저장 방법을 통해 식물의 개화를 지연시킬 수 있지만 저온 저장에 의한
개화율의 감소를 극복하기 위해서는 저온 저장 시기나 저장 온도에 관한
추가적인 실험이 필요할 것으로 확인되었다. 결론적으로, 저온 처리와
저온 저장 방법은 벼룩이울타리의 연중 생산을 위한 개화 시기 조절에
사용될 수 있다.
GENERAL INTRODUCTIONLITERATURE REVIEWFlowering Response to Photoperiod in CaryophyllaceaeFlowering Response to Chilling in CaryophyllaceaeChill Unit Models for Calculating Chilling Hours in Horticultural CropsCold Storage for Delaying Flowering
MATERIALS AND METHODSFlowering Response to Photoperiod (Experiment 1)Flowering Response to Chilling (Experiment 2)Cold Storage for Delaying Flowering (Experiment 3)
RESULTS AND DISCUSSIONFlowering Response to Photoperiod (Experiment 1)Flowering Response to Chilling (Experiment 2)Cold Storage for Delaying Flowering (Experiment 3)
LITERATURE CITEDABSTRACT IN KOREAN
10GENERAL INTRODUCTION 1LITERATURE REVIEW 4 Flowering Response to Photoperiod in Caryophyllaceae 4 Flowering Response to Chilling in Caryophyllaceae 4 Chill Unit Models for Calculating Chilling Hours in Horticultural Crops 5 Cold Storage for Delaying Flowering 7MATERIALS AND METHODS 8 Flowering Response to Photoperiod (Experiment 1) 8 Flowering Response to Chilling (Experiment 2) 11 Cold Storage for Delaying Flowering (Experiment 3) 16RESULTS AND DISCUSSION 19 Flowering Response to Photoperiod (Experiment 1) 19 Flowering Response to Chilling (Experiment 2) 22 Cold Storage for Delaying Flowering (Experiment 3) 29LITERATURE CITED 33ABSTRACT IN KOREAN 38