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Global warming is one of the major concerns of the current century. Net shading and foliar application of salicylic acid are options to protect plants against heat stress. This study investigated the protective effects of shading net and salicylic acid on vegetative growth, flowering and fruit attributes of apricot. Experimental treatments included net shading (green-50%) and salicylic acid (0.1 mM; three times foliar application), which were applied on trees of three apricot cultivars. The study was performed in the Horticultural Research Station of Horticultural Department, University of Tehran, Karaj, Iran in years 2019-2020. Shoot recurrent growth length, flower density, flowers, and fruits drop percentage, and fruit quality characteristics, as well as relative water content of leaf, cell membrane stability index, photosynthetic pigment, chlorophyll fluorescence were evaluated. Net shading could reduce leaf temperature by an average of 4.5 °C. It also increased the shoot recurrent growth length and flower density. The yield and quality of apricot fruits were affected by cultivar under the shade condition. The shading reduced evaporation and improved the water status (RWC) of apricot leaves and photosynthetic systems function. Since the net shading caused a delay on fruit ripening time and has negative effect on fruit coloring, the proper time for netting is near or after fruit harvesting especially in early ripening cultivars. Foliar application of salicylic acid in three intervals increased flower bud formation. Salicylic acid increased the leaf relative water content and photosynthetic system function. The results showed that salicylic acid made apricot trees more tolerant to heat stress. In general, application of green 50% net-shading after fruit harvesting is a chose of interest to improve flower formation and vegetative growth and SA application will reduce stress all the time of application during hot growth season. [ABSTRACT FROM AUTHOR]

Introduction: Persian walnut (Juglans regia) is an economically important nut fruit species cultivated worldwide for its nutritious kernel and timber quality wood. Walnut trees are mostly hetero-dichogamous and, depending on the genotype, some cultivars are protogynous, while others are protandrous. Although selfing is possible when male and female blooms overlap, the dichogamy of the species promotes outcrossing. In addition to sexual reproduction, some reports indicate that elements of apomixis may occur in commercial orchards of walnut varieties and in the last two decades, nut production by apomixis has been reported in walnut. However, there are no reliable studies on the occurrence of apomictic reproduction based on cytoembryological observations and/or molecular marker-progeny tests. This study addresses the combined use of molecular and cytological analyses to gain new insights into the population genetics and reproduction systems of J. regia. Methods: We systematically analyzed the reproductive origin of individual progeny plants from 8 different cultivated walnut genotypes using microsatellite genotyping and carried out cytohistological investigations of 5 cultivated walnut genotypes arising seed sets from isolated flowers, to shed light on the mode of reproduction. Results and discussion: These cytometric and genotyping analyses did not support any asexual mode of reproduction or asexual propagation by seed and all individuals studied were identified as zygotic plants produced by crossing. Likewise, the cytological findings did not confirm completely the first component of apomixis, namely apomeiosis. On the other hand, according to histological evidence, adventitious embryony seems to take place at low frequency. Overall, our findings suggest that the occurrence of gametophytic apomixis is unlikely in J. regia, but sporophytic apomixis cannot be completely ruled out. [ABSTRACT FROM AUTHOR]

Introduction: Persian walnut (Juglans regia) is an economically important nut fruit species cultivated worldwide for its nutritious kernel and timber quality wood. Walnut trees are mostly hetero-dichogamous and, depending on the genotype, some cultivars are protogynous, while others are protandrous. Although selfing is possible when male and female blooms overlap, the dichogamy of the species promotes outcrossing. In addition to sexual reproduction, some reports indicate that elements of apomixis may occur in commercial orchards of walnut varieties and in the last two decades, nut production by apomixis has been reported in walnut. However, there are no reliable studies on the occurrence of apomictic reproduction based on cytoembryological observations and/or molecular marker-progeny tests. This study addresses the combined use of molecular and cytological analyses to gain new insights into the population genetics and reproduction systems of J. regia. Methods: We systematically analyzed the reproductive origin of individual progeny plants from 8 different cultivated walnut genotypes using microsatellite genotyping and carried out cytohistological investigations of 5 cultivated walnut genotypes arising seed sets from isolated flowers, to shed light on the mode of reproduction. Results and discussion: These cytometric and genotyping analyses did not support any asexual mode of reproduction or asexual propagation by seed and all individuals studied were identified as zygotic plants produced by crossing. Likewise, the cytological findings did not confirm completely the first component of apomixis, namely apomeiosis. On the other hand, according to histological evidence, adventitious embryony seems to take place at low frequency. Overall, our findings suggest that the occurrence of gametophytic apomixis is unlikely in J. regia, but sporophytic apomixis cannot be completely ruled out. [ABSTRACT FROM AUTHOR]

AbstractGrape is a staple crop in many parts of Iran which has shown moderate sensitivity to salinity stress. Water and soil salinity is one of the major environmental stresses that strongly affect the production of agricultural products, including grapes. To overcome the harmful effects of salinity, different methods and materials are used, one of which is the use of nitric oxide. In order to explore the impact of nitric oxide on the mitigation of the negative effects of salinity stress on four grape cultivars and rootstocks (‘Bidaneh Sefid’ (Sultana) and ‘Yaghouti’ cultivars, and 140Ru and 1103 P rootstocks), a pot experiment was performed in a factorial based on a randomized complete block design with three replications. Plants were subjected to three sodium chloride (NaCl) levels of 0 (control), 25, and 50 mM and three levels of sodium nitroprusside (SNP) of 0 (control), 0.5, and 1 mM. Results indicated that increasing SNP concentration caused an increase in growth indices such as leaf area, shoot and root length, fresh and dry weights of leaves, shoots, and roots, and leaf relative water content (RWC). Furthermore, salinity decreased the concentrations of potassium (K+), calcium (Ca2+), magnesium (Mg2+), and iron (Fe2+) in leaves, while increased the amount of sodium (Na+) and chlorine (Clˉ) as well as the electrolyte leakage (EL). In addition, SNP at 0.5 and 1 mM could increase the growth efficiency and RWC as well as the elements such as K+ and Mg2+ while decreased the absorption of Na+ and Clˉ as well as the EL in plants under salinity. According to the obtained results, SNP at both concentrations (0.5 and 1 mM) had a pronounced effect on reducing the negative effect of salinity in the evaluated grape rootstocks and cultivars. In general, the positive effects of SNP on ‘Yaghouti’ and ‘Bidaneh Sefid’ cultivars were higher than those on 140Ru and 1103 P rootstocks. [ABSTRACT FROM AUTHOR]

Changes in freezing tolerance of four pomegranate (Punica granatum L.) cultivars, including 'Alak Torsh' (AT), 'Tabestaneh Torsh' (TT), 'Poostsefid Torsh' (PT), and 'Poostsyah Shirin' (PS), and its correlation with physiological and antioxidant responses were investigated in shoot samples during cold acclimation and deacclimation. Half part of shoot samples exposed to controlled freezing temperatures (−11,-14, and −17ºC) to determine lethal temperature (LT50) values based on relative electrolyte leakage method, and the other part was used for measuring physiological parameters at each time-point from September 2016 to March 2017. Totally, seasonal patterns were similar in four cultivars and their freezing tolerance changed depending on air temperatures and acclimation state alteration. In pomegranate shoots, LT50 values showed a positive correlation with MDA, starch, and antioxidant enzyme activity and a negative correlation with soluble carbohydrates, proline, and total phenolic content. The highest SOD, POD, and PPO activity for countering the stressful effect of low temperatures during acclimation and deacclimation, and the highest osmoregulant and total phenolic content coincided with the maximum cold hardiness in mid-winter. Of all studied cultivars, 'PS' started the acclimation phase later, but it showed the highest freezing tolerance (−16.98ºC) in mid-winter and resisted entering deacclimation phase to a greater extent (−15ºC). [ABSTRACT FROM AUTHOR]

To investigate the effect of NaCl salinity (0, 4, 8 and 12 dS m-1) on some morpho-physiological indices of Rosa damascenea Kashan genotype, a factorial pot experiment was designed based on randomized complete block design with four replications and three pots per replication (with total of 48 pots) on open air countineued for two years, and results of the second year data are reported. The results showed that salinity stress reduced fresh and dry weight of leaves and shoots. Also, the relative water content (RWC) of leaf and shoot decreased under salinity stress. Mean comparison showed that chlorophylls and carotenoids content were inversely associated with increasing salinity levels. The lowest levels of chlorophyll and carotenoids were observed in 12 dS m-1 treatment. Antioxidant enzymes activity such as superoxide dismutase (SOD), catalase (CAT) and guaiacolytic peroxidase (GPX) increased by increasing salt stress, although the lowest activity was observed in control treatment. Total phenol content of the leaves was also affected by increased salinity stress, but there was no significant difference between treatments. In addition, the results showed that by increasing salinity stress, the amount of soluble proteins decreased and its lowest amount was observed with 12 dS m-1 treatment. According to the results, salinity stress reduced plant growth by its effects on physiological and biochemical characteristics of Rosa damascena. Thus, it seems that the Damask Rose can tolerate a salinity level of up to 8 dS m-1, without detrimental effects on plant growth. [ABSTRACT FROM AUTHOR]