رضا فتوحی قزوینی

Climate change has affected the rates of chilling and heat accumulation, which are vital for flowering and production in temperate fruit trees. In this study, the chilling requirement of kiwifruit was analyzed by using the dynamic (CP) and chilling hours (CH) model, and the heat requirement was analyzed by using the growing degree Hours (GDH) model. The results shown that high temperatures at bud swell or woolly bud phase led to the acceleration of the different stages of bud phenology. Also, reduction of chilling requirement delays the events of bud phenology. In addition, a linear and significant relation was observed between chilling requirement and heat accumulation. So, the flowering time of kiwifruit cultivar “Hayward” was significantly affected by the timing and interaction of received chilling and heat accumulation. In the cuttings that received 954 and 1194 chilling hours, the heat requirement for breaking vegetative buds was 10543 GDH and 8251 GDH respectively. With cold-continuing, the heat requirement for breaking buds decreased, and flowering was done in shorter periods. The obtained results showed that the amount of chill recieved is effective in the percentage of bud break, and the number of flower buds formed. Also, the chilling requirements for maximum bud breaking were about 725 CH, and the chilling requirements for maximum flowering were above 954 CH in Hayward cultivar.

Water is one of the most important restrictive factors in the production of agricultural products worldwide. The aim of this research is to study the effects of different levels of irrigation and organic mulch on yield, water productivity, fresh weight, dry matter percentage, hardness, soluble solid content, titratable acid, and chlorophyll index of Granny Smith apple fruit at harvest. For this purpose, factorial experiment was performed in a randomized complete block design with three replications in 2019. Irrigation treatment were applied at supply levels of 100, 75 and 50 percents of tree water requirement (ETc) and organic mulch to thicknesses of zero, 4, 8 and 12 cm. The results showed that the highest average of fresh weights of fruit were allocated to 75 and 100 percent water supply levels and organic mulch treatment at thicknesses of 8, 4 and 12 cm had a significant positive difference in fresh weight of fruit compared to the control, respectively. The average yield of mulched trees was 11.52 percent more than control trees, the highest yield was obtained in treated trees with 8 cm of mulch. Fruit SSC and the firmness of fruit were improved at 50 percent irrigation. The interaction of 8 cm mulch treatment with 75 percent irrigation had the most amount of fruit acid. Both chlorophyll a, b and total decreased with increasing drought stress and improved with the application of mulch treatments .In addition, interaction of both experimental treatments, increased water productivity and benefit per drop unit area.

 Drought is one of the most important environmental stresses that affects various plants such as ornamental plants. The identification and selection of ornamental tolerant genotypes is essential for landscape projects. Understanding the mechanisms that enable plants to adapt to drought stress can help to select the most tolerant genotypes for cultivation in arid and semi-arid regions.

 For this purpose, a research was conducted as a factorial experiment based on completely randomized design with eleven genotypes and two levels of irrigation (irrigation as Control and severe drought) at Ramsar Citrus and Tropical Fruits Research Institute.

 The first symptoms of drought stress were observed after 10 days in the Juniperus horizontalis (G1) genotype (the most sensitive genotype) and were not recovered and dried after 15 days. G3 and G5 genotypes (Ravande-mamouli and Ravande-setarei, respectively) showed drought stress after 28 days (most tolerant genotypes) and recovered at the end of the stress period after irrigation. Drought stress decreased photosynthetic pigments in studied genotypes. The content of soluble sugars, proline, and total soluble protein increased under drought stress conditions and the highest amount was observed in G3 genotype 30.8 mg g-1 DW, 30.5 μg g-1 DW, and 965.2 μg g-1FW, respectively. Under drought stress condition, the highest concentration of hydrogen peroxide, malondialdehyde and electrical conductivity were observed in G11, G4, and G10 genotypes respectively compared to control plants. In addition, the most enzyme activity of superoxide dismutase (85.57%), total phenol (181.09%) and total flavonoid (98.46%) was evaluated in G3, G5 and G8 respectively. Also, chlorophyll changes indicate the response of plants to environmental stresses such as drought during drought stress, the concentration of abscisic acid and ethylene increases, which stimulates the activity of the enzyme chlorophilase and causes chlorophyll degradation. The reduction of photosynthetic pigments under drought stress also seems to be related to changes in nitrogen metabolism to proline production and reduced chlorophyll synthesis because the precursor of chlorophyll and proline is glutamate. Furthermore, one of the biochemical changes that occur in plants under drought stress is the accumulation of ROS. Numerous reports have stated that drought stress increases ROS production. Drought-induced oxidative stress causes lipid peroxidation and membrane damage. It seems that in some genotypes with low levels of malondialdehyde, the membrane damage is severe and leads to more electrical conductivity. Genotypes with more electrical conductivity are more damaged by drought stress. In some genotypes, such as G2 and G11, there was a positive correlation between malondialdehyde content and electrical conductivity, but in others, such as G1, there was a negative correlation. Although the amount of malondialdehyde in this genotype is low, electrical conductivity is very high. In other words, this genotype should be a genotype sensitive to drought stress. The tolerance of the plant to various environmental stresses may be related to the level of activity of the enzymes responsible for scavenging ROS. The antioxidant response to water scarcity depends on the severity of stress and type of plant species. Therefore, different genotypes increased their antioxidant activity to reduce the effects of oxidative stress, and the high antioxidant activity was observed for G5 compared with other genotypes which can be contemplated as drought-tolerant genotype. The accumulation of compatible metabolites such as soluble sugars and proline in plants under drought conditions can help to protect them against stress. The proline and soluble sugars accumulation under stress conditions reduce lipid peroxidation and acts as a free radical scavenger. According to the results, drought stress induced accumulation of proline and soluble sugars in the genotypes of Juniperus and the highest accumulation of proline was related to G3. Therefore, this genotype can be introduced as drought-resistant genotype.

 The results of the current study showed that drought stress significantly affected some biochemical parameters in all eleven genotypes. However, a variation in drought susceptibility was observed among genotypes. The studied genotypes in this experiment had different responses to drought stress and it seems that they utilized different mechanisms for stress tolerance. Genotype of G3 (Ravande -mamouli) was the most tolerant genotype to drought stress based on the highest levels of superoxide dismutase, soluble sugars, proline, and soluble protein. Genotype of G5 was also tolerant to drought stress with high superoxide dismutase activity and the largest amount of total flavonoid production. Therefore, increasing of compatible metabolites and antioxidant system are effective protective mechanisms against oxidative damage under drought stress.

Kiwifruit is one of the main exportable agricultural products, during which large quantity of kiwifruit was annually exported from Iran. Low percentage of winter bud break and malformed fruits incidence is the main factors for low productivity in Hayward Kiwifruits. Because the exportable fruits quantity was positively correlated with bud break percentage, flower number and normal fruits percentage. Therefore, the main objective of current study is to evaluate bud break and malformed incidence percentage in some kiwifruit vineyards in Talesh and Rudsar in West and East of Guilan province respectively.

This experiment was conducted as a completely randomized design in nine kiwifruit vineyards in both east (Rudsar) and west (Talesh) of Guilan province. Three uniform Hayward kiwifruit vines with four canes were selected in each vineyard. Climate conditions in two regions were also studied. Bud break percentage, flower number per winter bud, aberrant fruit percentage (flat and fan fruit percentage) and bud index for aberrant fruits was investigated.

The results of orthogonal test showed that there is a significant difference between two regions for bud break percentage, flower number per bud and malformed fruits percentage (flat and double fruit percentage) and bud index for flat and fan fruits. Bud break percentage varied (45.5-58.76%) in Talesh vineyard and (30.7-45.39%) in Roodsar. Furthermore, aberrant fruits percentage was (2.04-5.85%) in Talesh and (2.1-5%) in Roodsar. There were significantly different in terms of the number of flowers per kiwi winter bud in different vineyards. This value varied between (1.81-2.59) and in Rudsar (1.78-1.18). There was a significant difference between different vineyards in terms of cane diameter, average number of buds in cane, percentage of flowering buds, number of flowers in winter buds, percentage of flat and fan fruits. The incidence place of flat and fan fruits on the canes was the same independently to vineyards, but double fruit formation place was dependently to vineyard. The most flat and fan shape fruits was found on node 2 and 3 of current season shoot, however, double and triple fruits incidence was found in node 1 and 2.

Overall, the results showed that bud break percentage and aberrant fruits incidence was varied to environmental condition and orchard practices. These conditions caused disorders incidence in Hayward kiwifruit by affecting on vine physiology

Boron deficiency can be a limiting factor for flowers and fruits formation in some olive orchards. The appropriate time of boron foliar application in different areas and cultivars needs more investigations. This study was conducted to investigate the effects of spraying with an optimum concentration of boron (350 mg/l) at different phenological stages: after fruit harvest in autumn (first stage), the onset of flower bud formation in winter (second stage), during anthesis in spring (third stage), alone or in combination, on flowering  and fruit formation in three olive cultivars (Bella di, Mission and Koroneiki). The characteristics such as inflorescences number, total flowers number, complete and incomplete flowers percent, final fruit-set, percentage of pollen germination, and leaf and inflorescence boron content were evaluated. Boron spraying increased the percentage of pollen germination in all three cultivars compared to control. Spraying  in first stage and in combination of the first and the second stages increased the total number of flowers and inflorescences in Koroneiki and in combination of all three stages increased these characteristics in Mission. Bella di with spraying in second stage and in combination of second and third stages, and Koroneiki in third stage had the highest percent of complete flowers. The highest percent of fruit-set was observed in combination of the first and the third stages, and in combination of the second and the third stages in Koroneiki and then in combination of all three stages in Mission. Spraying in combination of the second and the third stages increased leaf and inflorescence boron contend in all three cultivars.

Deficit irrigation is one of the effective methods for increasing water use efficiency in fruit orchards under arid and semiarid climates. In this study, the effects of deficit irrigation (50 and 75% ETc) during pit hardening and after harvest on growth characteristics and fruits yield and quality of Japanese plum trees cv. Friar were studied during two consecutive years. The results showed deficit irrigation reduced the number of nodes as well as the length of nodes and shoots. However, the effect of deficit irrigation on reducing shoot length was significantly high, when applied after fruits harvest. Flowering density and fruit set percentage in the following year were not affected by RDI. Total fruit yield and acceptable fruits of 50 ETc was significantly lower than control, but no significant difference was found for control and 75% ETc. Deficit irrigation have no significant impact on fruit dry matter but fruit firmness of 75% ETc (2.3 kg/cm2) at the end of the storage was significantly higher than 50% and control (1.2 and 1.85 kg/cm2). The lowest SSC and TA were found in fruits at the end of the storage when irrigated with 50% ETc. Overall, irrigation with 75 ETc is recommended because of saving water and without negative effect on fruit yield.

Glycine betaine (GB) is an important compatible solute that acts as a substitute for water molecules release protein and membrane protection and also acts as active oxygen scavengers. In some plants، accumulation of this compound causes resistance to various stresses such as low temperature. In this experiment، the effect of exogenous application of GB and low temperature stress was investigated on Mexican lime in factorial experiment based on complete randomized design with three replications. Glycine betaine was applied at five levels (0، 2. 5، 5، 7. 5 and 100 mM) and also plants were subjected to five temperature treatments (2، 0، -2، -4 and -6°C). Results showed that spraying by 7. 5 and 10 mM GB as compared to other concentrations apart from the temperature at 2°C significantly increased the activity of peroxidase (POD) during the stress. Also، 10 mM of GB increased the total protein during the low temperatures in leaf tissues significantly. However، different concentrations of GB had not any clear effact on other characteristics such as lipid peroxidation (MDA)، ion leakage (EC)، total antioxidant capacity (DPPH sc%) and superoxide dismutase (SOD). It seemed that GB had protected the proteins such as peroxidase. In this study SOD content did not change during treatments that may depended on the low duration of stress. In addition، GB without antioxidant role in Mexican lime، could not protect the membrane from proxidation.