نشریه فیزیولوژی محیطی گیاهی
پیاپی 60 (زمستان 1399)

Rice is one of the most important food crop which is the staple food for more than half of the world population. The purpose of this study was to evaluate the physical and chemical properties such as plant height, panicle length, number of effective tillers, total number of grains, number of filled grains, number of unfilled grains, 1000-grain weight, biological yield, economic yield, harvest index, chlorophyll index, growth period, total Phenol (TP), antioxidant capacity based on 2,2-Diphenyl-1-Picryl Hydrazil (DPPH) with 30 rice genotypes in a randomized complete block design in the experimental field of Amol Rice Research Institute. Results showed that Amol 1 and Bijar rice varieties had significantly higher antioxidant activities and total phenolic than the other samples examined in this study, respectively. The highest total number of grains, number of filled grains and 1000-grain weight were observed in genotype IR56. The genotypes were grouped into five clusters based on agronomic traits using UPGMA method. The highest mean of yield was related to the fourth cluster and the lowest of this attribute was related to the fifth cluster. Principal components analysis (PCA) explained 79.01% of variation and economic yield, total number of grains, and number of filled grains played the main Experimental Field role. Two principal components accounted for 43% of the raw data of the yield-related traits. The results of this research indicated that use of economic yield, total number of grains, and number of filled grains could be applied as a breeding strategy to obtain high yield rice cultivars.

Stabragh belongs to the Asclepiadaceae family and is resistant to high levels of drought and salinity. Its organs have been used for the treatment of various diseases. In order to study the adaptation and stability of this plant under drought and saline conditions in Golestan province, Gorgan University of Agricultural Sciences and Natural Resources, plant seeds were cultivated in Gorgan, Gonbad, and Aghghala under different degrees of salinity and drought in February, March and April during 2014 and 2015. Plant height, leaf number and area, leaf dry weight, and proline and chlorophyll contents were measured were significant on all traits. Important traits such as proline, chlorophyll, fresh weight, dry weight, and plant height were introduced as the most important traits during the growth season. Data analysis was done through combined analysis of randomized complete block design. Results showed that the effect of regions on plant height, leaf area and dry weight, and also proline content were significant. Also, the effect of year was significant only for height and number of leaves. Effects of planting date and sampling in the adaptation of stabragh to saline and drought environments. Gorgan was the most suitable area for cultivation. Variations in the cultivation dates led to changes in the plants’ level of adaptation and stability.  The best planting date was April. The findings suggest that the plant can tolerate dry and saline conditions of the region and we can consider it as an alternative plant in arid and saline areas of the province.

Mepiquat chloride (PIX) is an important management tool to reduce stress damage in cotton plants during germination. In this study, the effects of different drought levels and the amount of mepiquat chloride (PIX) were investigated on growth indices and antioxidant enzymes as well as the malondialdehyde and hydrogen peroxide contents of seedlings in two cotton cultivars under laboratory conditions. The study was laid in a completely randomized design using 0, 5, and 10 g/l Pix and also under different drought levels using 0, -4, and -8 bar polyethylene glycol 6000 in petri dishes on two cultivars of cotton plant, namely Sahel (drought sensitive) and Shayan (drought resistant). Germination indices as well as physiological parameters of seedlings were measured under drought and Pix treatment after 4 days. Results showed that the use of Pix increased the germination percentage, root length, dry and fresh weights of seedlings, and the activity of peroxidase and catalase enzymes of cotton cultivars under drought stress while drought stress alone reduced these parameters. Drought also increased oxidative indices such as malondialdehyde and hydrogen peroxide in seedlings of Sahel and Shayan cultivars while Pix application reduced these indices. In general, the results of this study showed that the use of Pix improved growth responses and antioxidant system of the two cotton cultivars and the response of cultivar Shayan was better than Sahel.

Plant tissue culture is one of the most important techniques for the production of secondary metabolites. Plant cells are an important and appropriate source for the production of various valuable secondary metabolites. Melissa officinalis L. is an important medicinal plant with applications in treatment and alleviation of heart, nervous system, and gastrointestinal diseases, and particularly in memory enhancement and Alzheimer. This study investigated the effect of various concentrations of zinc oxide nanoparticles (0, 50, 100, 150, and 200 mg l-1) on disinfection stages, establishment, and proliferation of the lemon balm. Also, in order to study the effects of zinc oxide nanoparticles on establishment and proliferation of the lemon balm, explants were cultivated in murashige and skoog media containing zinc oxide nanoparticles at four different concentrations (0, 25, 50 and 75 mg L-1). Results showed that application of 200 mg l-1 zinc oxide nanoparticles significantly reduced fungal and bacterial infections and the number of healthy plantlets was more compared to the other treatments. Also, the second experiment showed that with an increase in the concentration of zinc oxide nanoparticles, the growth and proliferation decreased. Among different concentrations of zinc oxide nanoparticles, 25 mg L-1 had the maximum effect with significant increase in chlorophyll content while 25 and 50 mg L-1 zinc oxide nanoparticle concentrations had the maximum effect on increasing carotenoid contents. According to the findings,خطای ترجمه application of zinc oxide nanoparticles at low concentration (25 mg L-1) improved water and mineral uptake and eventually resulted in an improved growth and proliferation of Melissa officinalis L. plants

Drought stress is the most important factor in decreasing crop yield in most parts of the world. In order to investigate the effect of drought stress on some morphological and physiological traits of sesame plant, an experiment was conducted in a randomized complete block design with three replications. In this experiment, the effects of different levels of drought stress (5%, 10%, 15%, and 25% field capacity) were investigated on the activity of antioxidant enzymes (catalase, polyphenol oxidase, ascorbate peroxidase, and peroxidase, some photosynthetic pigments (chlorophyll a, chlorophyll b, total chlorophyll, carotenoid), some osmotic regulators including proline, and some morphological parameters (number of leaves, root length, stem height, plant height, leaf length, leaf width, dry weight of root, fresh weight of root, fresh weight of shoots, dry weight of shoots, fresh weight of plant, and dry weight of plant). After planting in pots, drought stress (5%, 10%, 15% and 25% of field capacity) was applied at seedling (four-leaf) stage and then the desired traits were measured. Statistical analyses showed that drought stress had a significant effect on all physiological and morphological features at 1% level. Morphological traits and photosynthetic pigments decreased with increasing drought stress (irrigation up to 5% of field capacity). Increasing drought stress levels increased root length in sesame. The highest root length (3.375 cm) was related to 5% of field capacity irrigation and the lowest root length (2.5 cm) was related to control (25% of field capacity irrigation). The highest levels of antioxidant enzymes and proline were also observed at the highest levels of drought stress (5% of field capacity irrigation). Based on the findings, the plant's growth measurements are recommended to be carried out at various developmental stages to find the effects of stress at each stage  so as to get an appropriate understanding of the effects of stress on the plant.

In order to investigate the effect of mycorrhizal fungi under salinity stress conditions on physiological and biochemical properties of Mexican marigold (Tagetes minuta L.), a pot factorial experiment was conducted based on a completely randomized design with two factors and three replications. The first factor was the application of two types of mycorrhizal fungi at three levels (non-inoculation, Rhizophagus intradices, and Funnetiformis mosseae) and the second factor was irrigation with salinity water at 4 levels (0, 40, 80, and 120 mM equal to 0, 3.5, 7, and 10.5 ds/m sodium chloride, respectively). The salinity treatment was applied in the plants at the eight-leaf stage and on three days a week. Results showed that application of salinity stress reduced the relative water content and chlorophyll of leaves. With increasing salinity concentration, the amount of electrolyte leakage, total carbohydrate, and proline increased in leafs. In contrast, the use of mycorrhizal fungi resulted in improved traits measured under salt stress conditions. The amount of proline, total carbohydrate, and electrolyte leakage decreased with the use of mycorrhizal fungi under stress conditions due to the positive effect of these fungi on balancing growth conditions in the plant under salt stress. Also, the highest amount of relative water content and chlorophyll a, b, and total chlorophyll of leaves were observed under non salinity stress treatment and application of R. intradices. According to the results of this research, it can be concluded that the application of salinity stress at 120 mM resulted in a significant reduction in the studied traits. Besides, the application of mycorrhiza fungi at this level of salinity could not improve the negative effects of salt stress. The use of R. intradices compared to the F. mosseae had a greater effect on the improvement of physiological and biochemical characteristics of Mexican marigold under salinity stress conditions at low salt concentration.

In order to investigate the effect of drought stress and nano-TiO2 and salicylic acid foliar application on some physiological traits of Echinaceae purpurea under water, an experiment was conducted in split plot factorial based on RCBD in three replications at the Research Station of the Islamic Azad University, Tabriz Branch, during growing seasons of 2017-2018. The main factors were water deficit stress at three levels of 50, 75, and 100% filed capacity, thefactorial combination of nano-TiO2 (n-TiO2) foliar application at two levels (0.02 and 0.04%) and salicylic acid foliar application at two levels (0.02 and 0.04%), and also distilled water foliar application as control treatment. Findingsshowed a significant effect of water deficit stress on relative water content (RWC) and proline (p≤0.01). Also, interaction of the effects of water deficit stress and nano-TiO2 and salicylic acid foliar application on Chl. b, total Chl., and hydrogen peroxide contents was significant (p≤0.01). Application of water deficit stress treatment up to 50% FC increased proline content by 40% and reduced RWC by 10% compared to complete irrigation (100% FC). Furthermore, 0.04% n-TiO2 and 0.04% SA foliar application increased hydrogen peroxide content by 50% compared to complete irrigation group and the control. The maximum total Chl. Contents of leaves was obtained under 100% FC irrigation and and 0.04% n-TiO2 and 0.02% SA foliar application showing 79.52% increase compared to 100% FC irrigation and no foliar application.

In order to investigate the effect of growth-promoting bacteria on physiologic traitsof new dryland wheat cultivars, a factorial field experiment was carried out in a randomized complete block design with three replications on the farms of Sarablah Agricultural Research Center in the cropping season during 2019-2020. Experimental treatments included different wheat cultivars (Sardari, Karim, Koohdasht, and Rijaw) and different fertilizer sources including control (without fertilizer source), 50% N fertilizer, Azospirillum+50% N fertilizer, Azetobacter + 50% N fertilizer, Azospirillum + Azetobacter+50% N fertilizer, and 100% N fertilizer. The results of this experiment showed that the interaction effect of cultivar × fertilizer sources had a significant effect on the activity of some antioxidant enzymes and physiological properties. Rijaw cultivar × Azospirillum + Azetobacter+ 50% N fertilizer increased the activities of ascorbate peroxidase (80.9%), glutathione peroxidase (80%), catalase (71.7%), peroxidase (74.1%), superoxide dismutase (74%), carotenoids (72.1%), chlorophyll a (86.1%), chlorophyll b (88.2%), and relative water content (45.4%) while reduced the amount of Malondialdehyde (65.9%) and hydrogen peroxide (91.8%). Moreover, Sardari cultivar × control treatment (without fertilizer sources) had the lowest activities of ascorbate peroxidase, peroxidase, superoxide dismutase, and photosynthetic pigments. Therefore, according to the results of the study, wheat cultivar Rijaw × Azospirillum + Azetobacter+ 50% N fertilizer may be recommended for cultivation in dryland conditions considering the improved physiological characteristics and ultimately increased plant growth.

Environmental stresses are among the main factors limiting growth and reproduction of the plants. Cold stress is one of the most important environmental stresses which incurs serious losses to different plant products and is considered as a threat to sustainable plant production. A set of morphological, physiological, biochemical, and molecular changes that occur during the autumn acclimates plant species to the low winter temperatures. Investigation of cold tolerance mechanisms at the cellular levels is a vital step in genetic manipulations for the purpose of improving plants’ resistance against cold. The occurrence of sudden low temperatures either in early autumns or late springs incurs various damages to plants. Cold acclimation during the autumn is necessary for plants to tolerate the low temperatures in winter. Although the overall adaptive process through which plants become tolerant to the low temperature is similar, this phenomenon varies slightly according to the plant species and climate condition. Moreover, when experiencing cold stress, different plant organs show various degrees of injuries, which can be minimized following proper agricultural practices through plant reinforcement. In fact, in time strengthening of the plant and avoiding any stress source can minimize the cold stress damages to the plant. An overview of the causes of cold stress injuries and plant response mechanisms can be helpful in reducing a part of low temperature detrimental effects.