فصلنامه فرآیند و کارکرد گیاهی
سال نهم شماره 3 (پیاپی 37، Aug and Sep 2020)

Lead is a nonessential element that has a negative effect on plant growth and development. Plant symbiosis with arbuscular mycorrhizal fungi (AMF) in soils contaminated with heavy metals can affect growth of plant, nutrition and tolerance against heavy metals. In this study, the effect arbuscular mycorrhizal fungi Glomus intraradices on the growth, photosynthetic pigments, protein content, proline, phenol and activities of antioxidant enzymes in alfalfa plants under Pb toxicity were examined. The experiment was performed by using two treatments (mycorrhizal and non-mycorrhizal) and five lead concentrations (0, 60, 120, 180 and 240 µm Pb(NO3)2). Results showed that Pb stress decreased plant growth, photosynthetic pigments and protein content, however AMF improved them. Amount of proline, phenol and antioxidant enzymes activity increased with lead increasing. Amount of them in roots of AMF plants in comparison with non-AMF plants increased. Leaves of AMF plants had more superoxide dismutase activity comparison with non-AMF plants. However proline content, activity of catalase and guaiacol proxidase in leaves of mycorrhizal plants, were lower than those of non-mycorrhizal plants. In addition, mycorrhizal colonization significantly decreased with Pb exposure. These results, suggested that G. intraradices can decrease Pb toxicity in alfalfa plants.

Arsenic (As), a metalloid and unnecessary element, is highly toxic to living organisms. It can be accumulated in the environment and enter the food chains through uptake by plants. The present study was designed to assess the response of antioxidant defense system of alfalfa to As (As0, As3+ and As5+) induced oxidative stress at four rates (0, 100, 200, and 300 µM) as a completely randomized design with three replications in the laboratory conditions. Tukey test was used for data analysis. The 90-day seedlings after harvesting, were used to evaluate MDA and H2O2 contents, antioxidant system, including SOD, POD, APX, CAT activities, contents of phenol, flavonoids and anthocyanin. According to the results, root and shoot H2O2 contents of As3+-treated plants, were the highest at the rate of 300 µM and the MDA contents were the highest at the rates of 200 and 300 µM in root and shoot, respectively. However, in 200 µM of As0-treated plants, the MDA content showed a significant decline (P≤ 0.05). The antioxidant responses varied with different treatments. Increased free radical scavenging activity was only observed at lower rates of As5+ in the shoot. Consequently it can be concluded that all of three forms of As, induced oxidative stress, which As3+ (300 µM) was more toxic than As0 and As5+. Nonetheless, the alfalfa plant mitigated As-induced oxidative stress by manipulating the activity of their antioxidant system through increasing contents of total phenol, flavonoids, anthocyanin and changing antioxidant enzymes activities, in different types and rates of As.

Drought stress is one of the main restrictions in plant production in arid and semi-arid regions. Adding superabsorbent agents that maintain water in the soil, is among strategies to cope with drought stress. Therefore, in order to investigate the effect of zeolite superabsorbent on the physiological properties of carrot plants, the experiment was carried out as a factorial in a completely randomized blocks design. The factors were zeolite (0, 2.5 and 5% of soil) and irrigation regime (25, 50, 75 and 100% of the field capacity). The results indicated that the highest total phenol was related to 2.5% zeolite treatment with 75% of field capacity irrigation. The highest amounts of carotenoids, chlorophyll a, total chlorophyll and carbohydrate were belonged to 5% zeolite treatment with 25% of field capacity irrigation. The highest levels of chlorophyll b and anthocyanin were related to 5% zeolite treatment with 75 and 50% of filed capacity, respectively. In conclusion, the application of zeolite in combination with soil, maintained the plant moisture in drought stress conditions and, under 25 and 50% of field capacity the application of 5 % zeolite, improved the physiological capacity of carrots.

As natural plant growth stimulators, amino acids are widely used to improve the yield and quality of crops. Change in enzymes activities of N assimilation (NR, NiR and GS), residual nitrate (NO3-), soluble protein content, and yield of spinach and lettuce plants were investigated under replacing 20% nitrate-N in the nutrient solution by L-glycine and blood meal amino acids. Seeds of the mentioned plants were sown in soilless medium for two weeks in the growth chamber. Seedlings in double leaf stage were transferred into the pots. After 30 days from transplanting, 20% of nitrate in the nutrient solution was replaced by L-glycine and a mixture of amino acids extracted from blood meal. Compared with the full nitrate treatment, amino acids replacement caused decrease in nitrate accumulation in the leaves of studied plants. The decrease in nitrate accumulation was accompanied by a decrease in nitrate reductase activity, an increase in glutamine synthetase and high production of amino acids and chlorophyll content. The amino acids present in the blood meal were more effective than the L-glycine treatment to reduce the nitrate concentration in spinach (1.72%) and lettuce (17.5%). Compared to the full nitrate treatment, partial replacement of blood meal amino acids increased the soluble protein content in the leaves of spinach (67.36%) and lettuce (83.82%). Supplying with amino acids significantly enhanced total nitrogen and dry matter in the studied plants, although effects of blood meal amino acids treatment were higher than L-glycine. Based on the results, partial replacement of nitrate with amino acids could cause decrease in nitrogen accumulation in spinach and lettuce plants.

Salinity stress reduces plant metabolic activity, which reduces plant growth in saline environments. this study aimed to investigate the effect of salinity stress as one of the limiting factors of plant growth and the effect of nanoparticles on stress conditions as one of the auxiliary factors in plant control against stressful conditions by studying physiological factors such as soluble sugars, chlorophyll, carotenoids, Proline, anthocyanins, antioxidant enzymes have been investigated. For this purpose, a factorial experiment was conducted in a completely randomized design with three replications. The first factor is tension Salinity with different concentrations of salt, including zero, 50, 100, and 150 mg per liter and the second factor includes the effect of Au-Ag nanoparticles Was on physiological parameters of Mentha piperita under salt stress. Stress was applied at the vegetative growth stage. The high amount of antioxidant compounds in menthachr('39')s extract provides a possibility of nanoparticle synthesis by mentha extract. In this study, Au-Ag alloy nanoparticles (NPs) which have consolidated properties of nanoparticles of Au and Ag synthesized by mentha extracts (green chemistry method (.The results of experiments on the Mentha piperita showed that salinity stress causes decrease length of root and shoot, fresh and dry weight of leaf and root, chlorophyll a and b, carotenoids,and anthocyanin content. Results also show that it causes increase activity of Catalase and Guaiacol peroxidase enzymes, soluble sugars amount in leaves and roots, and these effects show the greatest difference at a concentration of 150mM NaCl.

Melatonin is a new plant hormone that plays an important role in stress tolerance. For investigation the effect of exogenous application of melatonin on salt tolerance in rosemary (Rosmarinus officinalis L.), a factorial experiment was conducted in a completely randomized design with three replications. The first factor was melatonin (50, 100 µM) and the second factor was salinity stress (6, 9, 12 ds m-1). Water was used for control treatment. In the treated plants with concentrations of 6, 9 and 12 dsm-1 NaCl, stem height decreased compared to the control. Melatonin treatment (100 μM) reduced the effects of NaCl stress. 100 μM melatonin increased leaf growth compared to the control. The highest activity of SOD and POD was recorded in pretreatment plants with 50 and 100 μM melatonin. Melatonin prevented the reduction of chlorophyll content due to salt stress. The lowest ion leakage was related to 100 μM melatonin in control, 6 and 9 dsm-1 NaCl. Also, the highest reduction of electrolyte leakage (with 28.5% reduction) was related to 100 μM MT at 12 dsm-1NaCl. According to the results, 100 μM melatonin was more effective in reducing the effects of salinity stress.

Salinity is an important factor in reduced cucumber yield and quality. Grafting on the resistant rootstock could keep growth near to optimum condition. The aim of the present research is to investigate the characteristics of different rootstocks on physiology and fruit characteristics of cucumber. Treatments were rootstocks [Rn: Nongrafted (Cucumis sativus v. DAVOSII), Rt: Tanbal (Cucurbita maxima), Rg: Ghalyani (Lagenaria siceraria), Rk: Karela (Momordica charantia), Rkh: Khoreshi (Cucurbita pepo)] and salinity concentration included 0 (S1), 30 (S2) and 60 (S3) mM with three replications. Most of the fruit characteristics and physiology parameters like fruit weight and firmness, fruit length/diameter, photosynthesis rate, transpiration decreased with salinity. When grafted plants were used physiological parameters improved in Rkh, Rk at salinity compare with Rn. Fruit quality is mostly improved at Rg in salinity. Generally, using rootstocks like Rk, Rkh, and Rg improved fruit quality and physiological aspect of grafted cucumber in saline soil.