Journal of Plant Process and Function

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In order to evaluate the effect of water deficit stress on yield and physiological characteristics of some Iranian melon accessions, an experiment was carried out in a split plot based on randomized complete block design with three replicates in research filed of university of Zanjan during 2015. Treatments consisted arrangement of three irrigation levels (100, 70 and 40% ETc) and 7 Iranian melon accessions (Ghalam Ghash, Roshe, Zerke, Rish Baba, Ghobadloo, Garake and Kalyar). In this experiment, antioxidant enzyme activity, stomatal conductance, proline content, leaf relative water content, cell membrane stability index, hydrogen peroxide and malondialdehyde was measured. The results showed that water deficit stress reduced cell membrane stability index, leaf relative water content and stomatal conductance) and yield. The highest proline content in “Garake”, and maximum catalase and peroxidase enzymes activity was observed in “Zerke” and “Gobadloo” respectively under deficit irrigation 40% ETc. Hydrogen peroxide and malondialdehyde contents significantly increased under water deficit stress. According to the results, the highest (65.17%) and lowest (41.16 %) yield reduction was observed in “Zerke” and “Rish Baba” accessions respectively under irrigation 40% ETc compared to irrigation 100% ETc, thah were sensitive and tolerance accession to the water deficit stress, respectively.

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In order to study the effect of physiological and biochemical responses of tomato cv. Rio Grande to foliar spray of Megafol under water deficit stress, an experiment was carried out in a split plot based on randomized complete block design with three replicates in Research Filed of university of Zanjan as during 2015. Treatments consisted arrangement of three irrigation levels (starting irrigation at 100, 75 and 50% ETc) and 4 levels of Megafol (0, 0.1, 0.2 and 0.3%). The results showed that water deficit stress significantly decreased relative water content, chlorophyll content and stomatal conductivity, but increased proline content, electrolyte leakage and catalase (CAT) and peroxidase (POD) enzymes activity. Foliar application of Megafol increased chlorophyll and proline content, CAT and POD enzymes activity and stomatal conductivity under water deficit stress and normal irrigation coditions, and decreased electrolyte leakage, that the 0.2% Megafol treatment had the highest effect. The maximum CAT enzyme activity (0.087 µmol H₂O₂ g^-1 FW min^-1) was achieved in plants sprayed with Megafol 0.2% under defici irrigation 50% ETc. According to the results, foliar application of biostimulants can be proposed on tomato under normal and deficit irrigation.

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12 hybrides of tomato and their parents were evaluated for their response to drought stress in a randomized complete block design with three replications and three irrigation levels (FC, 60%FC, and 40%FC). The studied genotypes were including Kingstone, Petoearly, Bitstoik, LA1607, LA2656, LA2080 and LA1579. Experiments on crossing the genotypes, seedling production and field evaluation, were done in experimental greenhouses and experimental field of Ilam University in 2014-2016. The studied traits consisted of proline, MDA, peroxidase, catalase and ascorbate peroxidase, Relative Water Content (RWC), Chlorophyll a, b and total, electrolyte leakage, total yield, potential yield and single plant yield. The statistical analysis showed that drought stress significantly affected all assessed traits under drought condition. Increase in Proline and MDA content was observed in all genotypes under drought stress. The highest values of proline )31.93 µMgFW^-1) was obtained under severe stress in Petoearly× LA2080. RWC, total yield, potential yield, single plant yield, Chlorophyll a, b, catalase and ascorbate peroxidase contents were reduced and proline, electrolyte leakage and peroxidase content were increased by increase in drought stress. Under severe drought stress, the highest amount of total yield (15.74 t.ha^-1) was observed in LA2656×Petoearly hybrid, Petoearly line (19 t.ha^-1) and LA1579 tester (32 t.ha^-1).

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Nowadays, to ameliorate the effects of environmental stress on agricultural products, the use of biological compounds has drawn much attention. In order to investigate the ameliorating effect of some biological compounds on fluorescence indices, photosynthetic pigments and yield of greenhouse tomatoes under deficit irrigation conditions, a split plot experiment was conducted as a randomized complete block design in the research greenhouse of University of Hormozgan. The experimental factors included three irrigation levels (full irrigation as control, moderate and severe deficit irrigation) as the main factor and foliar application of different biological compounds (control, proline, chitosan and N-Succinyl (NSC) and N, O dicarboxymethylate chitosan (NOC)) as a sub-factor. When biological compounds were applied, the amount of chlorophyll a, chlorophyll a/b, and carotenoids content were increased at each irrigation level as compared to the control, so that the highest increases in these traits were observed with NSC. In most cases, under severe deficit irrigation, the use of biological compounds increased the leaf proline content and the highest increase was observed with the foliar application of proline. Under moderate and severe deficit irrigation conditions the highest values of Fv/Fm were obtained with chitosan and NSC, respectively so that these two compounds caused 22.4 and 21.8% increase in Fv/Fm as compared to the control. The highest taste index (1.06) was observed with the use of chitosan in severe deficit irrigation condition due to increasing in fruit TSS and TA contents. Among the biological compounds, NSC and chitosan had the greatest improving effect on the tomato fruit yield. Thus, NSC foliar application increased fruit yield in control, moderate and severe deficit irrigation by 32.5, 91.17 and 24.33%, respectively. Therefore, according to these results, under deficit irrigation conditions, chitosan and its derivatives can reduce the effects of drought stress on tomatoes more efficiently than proline.

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In this study, the effects of application of titanium dioxide nanoparticles under water deficit irrigation stress in the pre-flowering and grain filling stages on wheat were investigated. For this purpose, this plant was sprayed with %0.02 titanium dioxide in tillering and heading stages and some traits such as plant height, leaf area index, number of fertile tillers, number of seeds, 1000 seed weight, biological yield, harvest index, relative leaf water content, total chlorophyll content, proline and malondialdehyde content and ascorbate peroxidase as well as superoxide dismutase activity were examined. The results showed the positive effects of the application of these nanoparticles on the vegetative and reproductive growth of wheat under normal conditions and stress, so that under drought stress increased the number of fertile tillers, increased the number of seeds  and 1000 seed weight was compared with the non-application of nanoparticles under stress conditions.Under normal conditions and low irrigation stress, application of these nanoparticles during tillering had more favorable effects on vegetative and functional characteristics of the plant compared to the clustering time and increased wheat harvest index in drought conditions. On the other hand, the application of titanium nanoparticles effectively reduced the adverse effects of drought stress in the pre-flowering and grain filling periods whereas increased proline activity. Recent events have increased the ability of wheat to withstand drought stress.

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In order to investigate the effect of biofertilizers and zinc foliar application on the physiological characteristics and nutrient concentration of black cumin under different irrigation regimes, a split factorial experiment was conducted in the form of a randomized complete block design with three replications in Zarghan, Fars province, in 2017 and 2018. Irrigation regimes (providing 100, 75 and 50% of the irrigation water requirement) as the main plot and biofertilizer (mycorrhiza, Phosohate Barvar2, mycorrhiza + Phosohate Barvar2, no biofertilizer) and foliar application (zinc foliar application, no foliar application) were considered sub-plots. In both years of the experiment, the reduction of irrigation water decreased the nitrogen concentration of aerial organs (45%), chlorophyll a (70%), soluble protein (37%), relative water content (40%), biological yield (46.6%), and grain yield (56%) of black cumin. However, it increased traits such as proline (1.35 times), soluble sugar (60%), and electrolyte leakage (1.1 times). Biofertilizer application, especially in combination (mycorrhiza+ phosphate Barvar2), and zinc foliar application increased all the traits mentioned except electrolyte leakage. So in 50% irrigation, the combined application of biofertilizer compared to no application of biofertilizer increased the grain yield by 46% and 49.7% in 2018 and 2019, respectively. The results showed that the application of biofertilizers and zinc foliar application moderates the negative effects of drought stress in black cumin by improving nutrient absorption and physiological characteristics.