فهرست مطالب مریم مظفریان

Selenium is a beneficial element with antioxidant characteristics that can improve plant growth and increase plant resistance to environmental stress. In order to study the effect of different concentrations of selenium on growth parameters, antioxidant enzyme activities, antioxidant properties and total phenol of hot pepper cv. Suryankhi Cluster in a hydroponic culture, this experiment was carried out in a completely randomized design with three replications the treatments were consisted of five Se concentrations (0 as control, 3, 5, 7 and 10 µM). The results showed that Se application at the rate of 3 µM increased growth traits such as stem length, shoot and root fresh and dry weight. The highest root length was also observed in plants treated with 7 µM Se. The activity of antioxidant enzymes such as Catalase and Peroxidase markedly increased at 7 µM Se. Antioxidant activity increased with increasing Se concentration, showing the highest activity at 10 µM Se. Total phenol increased by application of 3 and 5 µM Se and then decreased at 7 and 10 µM compared to 5 µM Se. Proline content significantly increased at 10 µM compared to the control. In general, it can be concluded that selenium application may improve plant growth and increase phenolic content and antioxidant activity of hot pepper.

Aluminum (Al), cobalt (Co), sodium (Na), selenium (Se), and silicon (Si) are considered as beneficial elements for plants. They are not required for all plants but they can improve the growth and development of some plant species. Selenium is an essential element for human with antioxidant and antivirus functions but is not considered essential for higher plants. Selenium is reported to be protective against cancer and more than 40 types of diseases are associated with Se deficiency. The amounts of selenium in food also depend on the amount of the element in the soil. However, its beneficial role in improving plant growth and stress tolerances is well established. Plants revealed different physiological reactions into the Se levels, some specious accumulate it unlike some which are sensitive and Se is a toxic element for them. Some studies showed that Se can reduce adverse effects of salinity, drought, high and low temperatures and also heavy metal stress by enhancing antioxidant defense and MG detoxification systems. Pepper is one of the most important vegetable crops which have strong antioxidant properties. The effect of Se on vegetable especially on hot pepper is not well documented.
Present experiment was designed in order to study the effects of different concentrations of selenium on vegetative growth and physiological trait of hot pepper (Capsicum annum cv. kenya) in hydroponic conditions in the greenhouse at the Department of Horticulture Science, Islamic Azad University of Shiraz (Iran) under natural light with a day/night average temperature of 25/17 °C, relative humidity of 50±8.5% and photoperiod 14/10 (day/night). This experiment was carried out based on completed randomized design (CRD) with 5 Se levels at (0 as control, 3, 5, 7 and 10 µM) with 3 replications. 30 days old seedling with uniform size were selected and transplanted into 4 L pot containing a mixture of peat moss and perlite (1:1). The nutrient solution was a modified Hoagland’s solution and each plant received 400 mL nutrient daily. Selenium concentrations were added by 0, 3, 7 µM Na2SeO3 (Merck, Germany) 10 days after transplanting. Leaf number (by counting), leaf area (with leaf area meter), relative water content (RWC), membrane stability index (MSI), chlorophyll and carotenoids content were determined one month after treatment applications. All data were subjected to one-way ANOVA by Statistix 8 (Tallahassee FL, USA) and the means were compared for significance by the least significant difference (LSD) test at p The results showed that selenium supplement at 5 µM significantly increased relative water content by 12.8% compared to control. Se increased root growth and thus absorbed more water and increased RWC in present experiment. Selenium at 7 and 10 µM Se increased membrane stability index by 33.61 and 80.06, respectively, compared to control which may be due to increasing potassium by Se application. Selenium at 3 and 5 µM increased leaf area by 24.6% and 25.1% relation to plants which were grown without Se supplementation. Leaf number increased by application of 5 µM Se about 15.14% and chlorophyll a, b and total increased by 64.67%, 38.5% and, 55.8%, respectively, in comparison with plants grown without Se application. Carotenoid content was not affected by different Se concentrations. Se increase chlorophyll content by increasing Mg and Fe absorption, or protect of chlorophyll content against chloroplast enzymes. The highest leaf area was observed at 3 µM Se in comparison with other treatments. Se at 5 µM is beneficial for growth, photosynthesis pigments, and leaf area and leaf number. Se application had no beneficial influence on lateral shoot. The highest starch concentration was observed at 5 µM Se in comparison with other treatments and control (by about 60% in comparison with plants were grown without Se application).
In general, the result of present study indicated that selenium at low concentrations improved plant growth (such as leaf area and leaf number), physiological trait (relative water content and membrane stability index) and photosynthesis pigments (chlorophyll a and b) of hot pepper in hydroponic conditions. Also, it is suggested that this experiment should be repeated on some other important vegetable during growth and reproductive stages in hydroponic and soil condition and also on hot pepper quality and quantity of fruit.

Silicon (Si) is one of the beneficial elements for plants، which improves quantity and quality of yield، decreases evaporation and transpiration and enhances plant resistance to abiotic stresses. In order to evaluate the effect of Si and nano-silicon (N-Si) on growth، morphological and photosynthesis attributes of tomato، cultivar Falcato، an experiment was carried out in a hydroponic system، based on a completely randomized design، with two Si and N-Si levels (1 and 2 mM) and Si-free nutrient solution (as control)، and four replications. Such traits as chlorophyll index (SPAD)، photosynthesis، nutrient uptake، stem diameter، relative water content and morphological changes like density of trichomes were measured during the experiment. At the end of the experiment، fresh and dry weights and root volume were measured. Results revealed that Si was more effective than N-Si on fresh weight and mesophyll conductance. Concentrations of 1 and 2 mM Si increased fresh weight and mesophyll conductance، respectively. However، this concentration did not affect dry weight and relative water content significantly. N-Si was more effective than Si on photosynthesis and photosynthetic relative water content. The highest photosynthesis and lowest transpiration rate was measured in 2mM N-Si. Application of Si and N-Si decreased relative water content and the least water uptake was in 2mM N-Si treatment. In conclusion، Si or N-Si، with 20-30 nm particle diameter and optimum tomato growth conditions (without abiotic stresses) increased photosynthesis، fresh weight، relative water content and decreased nutrient solution uptake under hydroponics.

The superabsorbent polymer withholding water and disperse it gradually to roots increase soil water capacity. To study the effect of superabsorbent polymer on decreasing water stress effect as well as increasing irrigation efficiency a factorial experiment based on randomized block design with 4 replicates was design. Treatments were 0، 10 and 20 % V superabsorbent and irrigation levels 25، 50 and 100% field capacity in greenhouse of Shiraz University. The results were shown that drought stress decreased chlorophyll content، fresh and dry weight but did not effect on fruit parameters at 5%. Superabsorbent improved tomato growth in stress condition and in 50% FC،10% superabsorbent increased relative water content to 14%and fresh weight of root to 60%. Chlorophyll content increased to 22% in 25%FC with 20% superabsorbent relative water content and root fresh weight increased 28 and 53% respectively. In 25%FC with 20% superabsorbent. Superabsorbent elevated hazardous effect of drought stress and with holding the water in root zoon cues normal plant growth.