Research Regarding the Intensity of Certain Physiological

Agriculture and Agricultural Science Procedia 6 ( 2015 ) 165 – 170

2210-7843 © 2015 Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).Peer-review under responsibility of the University of Agronomic Sciences and Veterinary Medicine Bucharestdoi: 10.1016/j.aaspro.2015.08.054

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“ST26733”, International Conference "Agriculture for Life, Life for Agriculture"

Research Regarding the Intensity of Certain Physiological Processes for Peach Varieties within High Density Plantations

Dorel Hozaa*, Elena Deliana, Adrian Asanicaa, Gheorghita Hozaa aUniversity of Agronomic Sciences and Veterinary Medicine of Bucharest, Faculty of Horticulture, Department of Bioengineering

of Horti-Viticultural Systems, 59, M r ti Ave., Sector 1, Bucharest, 011464, Romania.

Abstract

High density plantations, due to the fact that trees have lower heights, present advantages related to the yield of manual works, but lighting conditions are not always sufficient to ensure a proper synthesis of the organic matter. In order to observe the ongoing of the physiological processes within high density plantations, measurements were made for 8 peach varieties, and the results showed differences for all parameters considered: photosynthetic active radiation, photosynthesis, transpiration and intercellular CO2 concentration. Moreover, measurements made along the shoot showed that the intensity of physiological processes is influenced by the position of leaves and amount of light that reaches them. © 2015 The Authors. Published by Elsevier B.V. Peer-review under responsibility of the University of Agronomic Sciences and Veterinary Medicine Bucharest.

Keywords: leaf, peach, physiological processes

1. Introduction

Peach [Prunus persica (L.) Batsch] is an economically important fruit crop (Lockwood and Coston, 2014) and has become a genetic-genomic model for all Prunus species in the family Rosaceae (Fresnedo-Ramírez et al., 2013).

In the production systems, one of the major objectives is to find the best combination between genetic resources and cultural practices, according to specific environmental conditions, to meet the social demand for a multi-objective quality (Hammer et al., 2006; Quilot-Turion et al., 2012).

* Corresponding author. Tel.: +40213183636; fax: +40213183636.

E-mail address: [email protected]

© 2015 Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).Peer-review under responsibility of the University of Agronomic Sciences and Veterinary Medicine Bucharest

166 Dorel Hoza et al. / Agriculture and Agricultural Science Procedia 6 ( 2015 ) 165 – 170

Functional-structural plant models simulate the development of plant structure, taking into account plant physiology and environmental factors (Allen et al., 2005; DeJong et al., 2012). For peach, the “Virtual Fruit” model and a multi-objective evolutionary algorithm (NSGA-II) integrates such parameters and was used to recommend genotypes characterized by a high fruit quality, resistance to brown rot and adapted to specific technologies of cultivation (Quilot-Turion et al., 2012). An excellent bibliographical synthesis of Martre et al., (2015) treats the ideotype concept in the context of ecophysiological modelling and analyzes how such models are applied to design varietal types or virtual genotypes better adapted to given environment– management combinations.

The interaction between variety and environmental conditions (including those determined by culture system e.g. plant density) is also materialized in the dynamics of tree development and performances, both at leaf and fruit level (Morandi et al., 2012). Nowadays, in the case of Prunus persica, such an interaction is one that refers to phyllochron and a growing degree hour (GDH) thermal time scale model for measuring the phyllochron was proposed by Davidson et al. (2015).

One of the three physiological opportunities recently proposed by Tustin (2014) is the manipulation of tree architecture into new tree configurations, to increase light harvesting capability, when integrated within new planting systems designs.

The photosynthesis is one of the physiological processes strongly influenced by external environmental factors (e.g. temperature, sunlight intensity and quality etc.), as well as factors related to the genetic characteristics of the species, variety etc., which in turn controls the plant growth, survival and feeding it. Studies conducted by Wu et al. (2008) on peach varieties whose maturity was different and exposed to girdling practices that alter the source-sink paths have shown that the influence on net photosynthesis (Pn) was similar. The diurnal variations in Pn depended upon the occurrence and duration of high photosynthetic active radiation (PAR), with higher values when PAR was above 800 mol m-2 s-1. It should be highlighted progress in monitoring midday canopy PAR interception in orchards systems, including peach (Lampinen et al., 2014). However, Palmer (2014) points out that modern performance equipments and techniques available today do not ensure success. The major problem is the implementation of the right questions and finding the best ways to answer them.

Increasing tree density in an orchard is one of the measures aimed to obtain a high productivity of young plantations. Care should be taken in that efficient light penetration and usage into fruit tree canopy is a major challenge for farmers. In this context, studies carried out by Marini and Sowers (1990) have shown an increase of Pn with increasing percent of photosynthetic photon flux (PPF); also, flower density was positively related to PPF percent. Tree density and canopy architecture influence physiological processes such as photosynthesis or transpiration. Génard and Simon (2000) revealed that photosynthesis varied from 5 to 15 mol m 2 s 1 between laterals of different architectures and was influenced by the orientation of the lateral, its size (number of leaves, length, number of shoots), to the angle between the stem and the shoots, the distance between the leaves, and the angle between the leaf and the shoot. In the context of a single tree, its photosynthesis per unit leaf area decreases by a factor of two due to the shadowing. For orchards, the photosynthesis per unit leaf area decreases as a function of the tree density, therefore the variation of photosynthesis per unit leaf area, is mainly determined by the fraction of sunlit leaf area. Also, Costa (1984) stated that between productivity (expressed in number of fruit per trunk and cross-sectional area) and tree density has been an inverse relationship.

Stomatal conductance was influenced by sink–source treatments and exhibited similar diurnal variations with Pn, on all measurement dates. PPF not only influences physiological and biochemical processes rate, but also leaves morphological characteristics (e.g. skin characteristics, leaf area, and stomata density). Furthermore, carbon assimilation is not the only component of plant gas exchange affected by solar radiation intensity. For instance, Lombardini et al. (2009) noticed that stomata density (stomata/mm2), leaf area, and leaflet area of mature pecan [Carya illinoinensis (Wangenh.) K. Koch] trees were greater in sun leaves, than in shade leaves. Specific leaf area was greater in shade leaves than sun leaves.

There is a strong correlation between providing assimilated through the leaves of the tree growth and requirements. With increasing height and crown increased average density of the leaves and the fruit assimilates available for growth was reduced in the bottom of the tree (Chalmers et al., 2005). On the other hand, as Morandi et al. (2012) noticed, differentiated canopy lighting conditions affect the overall tree carbon assimilation and thus the amount of available carbon assimilates for translocation to the growing sinks.

Water use efficiency (WUE) is another physiological indicator that varies with climate, species, stage of growth and development, irrigation system etc. Determinations at the orchard-scale on peach grown in northern China (Ouyang et al., 2013) showed that the diurnal variation of WUE was not correlated with atmospheric water pressure


deficit (VPD) during the trees flowering stage, but was highly correlated cu VPD during the robust growth stage. Measures, such as combination of reflective mulch and water deficit negatively affected leaf physiology, determining an increase of leaf temperature, so induced a decrease of transpiration, stomata conductance, Pn, WUE and quantum yield. It is important to determine the optimal levels for light harvesting (to avoid self-shading) and to maintain productivity in order to develop canopy and crop management practices (Lombardini et al., 2009).

Recently, Palmer (2014) stated: We need more physiology, not less, but we also need a multidisciplinary approach able to tap into the skills and expertise of many branches of science – the big picture, not only in terms of the whole tree and orchard, but also in terms of the skill base .

In order to know the ongoing of some physiological processes within high density plantations, measurements were made for 8 peach varieties.

2. Research Methods

The experiment has been carried out in the Didactical Field of the Faculty of Horticulture Bucharest, during 2011-2012, in a peach plantation of seven years old. In order to know how the cultivar influences some physiological processes at the leaves level, there were studied 8 peach cultivars: Cardinal, Inka, Reliance, Royal Estate, Earlirich, October Star, Late Luka and Rubirich.

Trees were planted at 6 x 1 m and trained as transversal Y (Ypsilon) canopy. The applied technology was one normal for the fruit plantation. Net photosynthesis (Pn), transpiration (E), CO2 substomatal (Ci), photosynthetically active radiation (PAR) and leaf temperature (T) were determined with LCi - Portable Photosynthesis Measurement System (ADC Bioscientific, U.K), during the shoot intense growing process. For all cultivars, three determinations were done, at a height of 2 m above the ground. Correlation analyses were performed on the resulting data.

3. Results and Discussion

Our results indicate that physiological processes intensity depends on cultivar, due to its biological features. Thus, photosynthesis rate ranged between 4.33 mol CO 2 m 2 s 1 in Reliance cv. and 12.15 mol CO2 m 2 s 1 in Inka cv., as against the average value of 9.71 mol CO2 m 2 s 1 (Figure 1).

Figure 1. Net photosynthesis of some peach cultivars ( mol CO2 m 2 s 1) The transpiration values were closer amongst each other, except Cardinal cv., for which was registered a

maximum value of 6.49 mmol H2O m 2 s 1, as against the minimum value of 2.24 mmol H2O m 2 s 1 noticed for Royal Estate. The average value for all eight cultivars was 3.66 mmol H2O m 2 s 1 (Figure 2).


Figure 2. Net photosynthesis of some peach cultivars ( mol CO2 m 2 s 1)

Substomatal carbon dioxide concentration (Ci) was situated around 600 mmol mol -1 (Figure 3) and as we can observe, higher Ci is accompanied by higher photosynthesis rate (e.g. Rubirich cv.), while less Ci is related to lower photosynthesis rate (e.g. Reliance cv).

Figure 3. Substomatal CO2 concentration

Correlation analyses were performed on the resulting data. As we can see in Figure 4, there was a weak correlation between photosynthesis and temperature, which indicates that this temperature interval did not influence the photosynthesis rate.

These results are consistent with those obtained by Cheng et al. (2009) that showed that Pn increased with increasing temperature to about 300 C, maintained at constant values between 30-34 0C, then there was a marked decrease, as the temperature continued to rise.

0100200300400500600700

mmolmol

1

Cultivars


Figure 4. Relationship between photosynthesis and temperature

As mentioned by Losciale et al. (2010), the interaction between the tree and sunlight is the energetic basis of orchard productivity. It can be also noticed the positive linear relationship between transpiration and photosynthesis rate (Figure 5).

An intense transpiration is also assured by a higher stomatal conductance, so a good carbon dioxide supply to chloroplasts, as a raw material in this process is realized, too. On the other hand, a normal stomatal conductance leads to decrease leaf temperature, allowing normally leaf physiological functions (e.g. Pn, WUE and quantum yield) such as previously highlighted results of Pliakoni et al. (2008), too.

Figure 5. Correlation analysis of E with Pn in peach leaves

Substomatal CO2 also positively influenced photosynthesis rate (r2 = 0,445) (Figure 6), as also previous

researchers noticed in peach (Li et al., 2007; Cheng et al., 2009).

Figure 5. Correlation analysis of Ci with Pn in peach leaves


4. Conclusions

The results showed differences for all peach leaves parameters considered: photosynthetic active radiation, photosynthesis, transpiration and substomatal CO2.

The values recorded for photosynthesis were higher for the cultivars Cardinal, Inka and Rubirich and lower for the cultivars Reliance and Royal estate.

The transpiration recorded relatively close values, except for the Cardinal cultivar for which the value was higher.

The content of substomatal CO2 had values between 500 and 650 mmol mol-1, depending on the cultivar.

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Research Regarding the Intensity of Certain Physiological