JOURNAL OF PLANT PROCESS AND FUNCTION
Year:2013 | Volume:2 | Issue:3|Papers Count:7

Nowdays, effects of decreased ozone and increased UV radiation have been studied by many researchers. The aim of this study was to investigate the effects of UV-B and UV-C radiations on Melissa officinalis L and to study the impact of salicylic acid in reducing the harmful effects of radiation on plants. The Melissa officinalis L. plants were treated with 28±2oC temperature for about 60 days. The light intensity was 150 m mol m-2 S-1 and the photoperiod condition was 8-16 hours. UV treatment was applied after the six-leaf stage and UV-B radiation was applied for a period of 15 days application for 20 minutes. But UV-C radiation was applied every other days for 15 days in and time of each application was 8 minutes. Salicylic acid was sprayed on the plants after the sixleaf stage with a concentration of 1 mM. The results indicated that the UV-B and UV-C radiations led to reduction in dry and fresh weight, root elongation and shoots. The radiations also reduced the photosynthetic pigments (chlorophyll a, chlorophyll b and carotenoid) sugar content and total soluble proteins amount. The malondialdehyde and phenylalanine ammonialyase compounds content and UV- absorbing compounds were increased under the effect of UV-B and UV-C radiations. The results showed that treatment with salicylic acid reduced. The damage to the plant which had been created due to UV-B and UV-C radiations and was able to compensate for modified factors that had been changed because of ultra violet radiations.

Cadmium (Cd) is easily absorbed by root system in many plant species and due to its solubility in water and toxicity is considered as a major pollutant. A factorial pot experiment was conducted on two cultivated and wild safflower species, in which four cultivated genotypes (Arak-2811, Saffire, C111, and AC-Sterling) and four wild genotypes (Arak, Shiraz, Isfahan and Azari) were treated by four levels of Cd (0, 1, 5, and 10 mg CdNo3/kg soil). Based on Cd Tolerance Index, chlorophyll (Chl) concentration and lipid peroxidation Ac-Sterling, Isfahan, and Arak-2811 were ranked tolerant and Arak, C111 and Shiraz ranked sensitive to the Cd stress. Wild and cultivated safflowers did not appear to differ in terms of the latter attributes. The greatest activities of ascorbate peroxidase (APX) and catalase (CAT) were observed to be at the 5 mgkg-1 level of Cd. The tolerant genotypes indicated a greater increase in their APX and CAT activity, compared to the sensitive genotypes. It was concluded that the enzymatic antioxidant defence system in safflower played a major role in its response to Cd and APX and CAT antioxidants played a more crucial role in this regard, relative to GR.

Metalloid arsenic is considered as one of the most important environmental contaminant compound. Some plant species can grow in arsenic contaminated soil capable of reducing arsenic toxicity. Nowadays, phytoremediation, as a new and friendly environmental technique employs the use of plants to remediate contaminated soil. Previous studies proved that Isatis cappadocica is an arsenic hyperaccumulator plant. Accordingly, we conducted this experiment to compare the interaction of arsenic and phosphorus on osmolytes content of I. cappadocica for better understanding of the mechanisms applied by this species. Therefore, the plants were grown for 6 weeks in a medium, embedded with combinations of 50, 200, 800 & 1200 mmol l-1 arsenic and 5, 50, 200, 800 & 1600 mmol l-1 phosphorus, respectively. The osmolytes content and the arsenic concentration of harvestable parts were determined. The highest concentration of arsenic was obtained in plants treated with 1200 mmol l-1 As and 5 mmol l-1 phosphorus. Increasing arsenic concentration in the medium led to increase of osmolytes (soluble sugars, proline and protein). The ability of Isatis to accumulate more than 700 mg kg-1 arsenic in the shoots, illustrated the high resistance of this herb to arsenic and the existence of efficient mechanisms including accumulation of osmolytes.

Drought stress represents the most limiting factors for agricultural productivity in arid and semiarid regions of the world. This experiment was conducted to evaluate some of the effects of drought stress on root morphological attributes and dry matter yield in tall fescue Festuca arundinacea. Twelve genotypes were assessed under three levels of moisture regime (non-stress, moderate drought stress and severe drought stress) according to a factorial experiment based on a completely randomized design with 3 replications in 2011. The genotypes were grown in the plastic pots (60×12 cm) and root traits were measured at 0-30 and 30-60 cm depths. Results indicated that the effects of moisture regime, genotype and their interaction were significant for all of the measured traits. Moderate drought led to significant increase in root dry weight, but severe drought did not affect it. With augmentation of the drought stress, the root/shoot ratio increased about 30 percent and 54% in 0-30 cm and 30-60 cm depth of root, respectively. Moderate and severe drought led to 15% and 30% decrease in plant dry weight, respectively. Some genotypes such as 21P produced high dry matter yield and expanded root system which could be used for future breeding programs.

One of the major tissue damage following exposure to stress in plants is caused by the oxidative stress. In this study, effects of different levels of methyl isothiocyanate on biochemical parameters and antioxidant enzyme activity such as ascorbate peroxidase, catalase and guaiacol peroxidase in seedlings of Lepidiun sativum L. under in vitro were investigated. The seeds of Lepidium sativum (Garden Cress) were sterilized and cultured in MS medium. After 20 days, seedlings were treated with concentrations of 0.01, 0.1 and 1 mM methyl isothiocyanate (various levels of stress) under sterile condition. After 3 days, result showed that chlorophyll a, chlorophyll b, total chlorophyll, carotenoids and protein were significantly decreased, while reduced sugar, proline and antioxidant enzymes were increased in seedlings which were under oxidative stress. Thus methylisothiocyanate appeared to induce oxidative stress and activation of the plant's defenses parameters. The maximum and minimum at concentrations of 1 mM and 0.01 mM methyl isothiocyanate observed respectively.

Theaim of this study was to investigate the effects of nano silver and multi wall carbon nanotube levels on some morphological and physiological traits of faba bean. This factorial experiment was conducted in a completely randomized design with three replications and two treatments with four dufferent concentrations (0,100,200 and 300 mgl-1). The results showed the total number of seeds germinated, shoot length, root length, shoot weight and dry weight, root weight and dry weight and root tolerance had significant differences at Ag and multi wall carbon nanotube treatments (p<0.01) whereas, T50 and germination rate traits showed no differences under nanoparticle treatments. Nanoparticles concentrations had significant effects on shoot fresh weight and shoot dry weight indices, germination rate and T50 (p<0.05) and shoot length, root length, root fresh and dry weight, root tolerance index and total number of germinated seeds indices (p<0.01). Shoot length and root dry weight under 200 mg/l concentrations, showed significant differences with other treatments and root tolerance, root fresh weight and root length, showed highest significant decrease under 300 mg/l concentration. The interaction effects of treatments, had significant effects on germination rate (p<0.05) and other indices (p<0.01). Root dry weight, root tolerance and number of germinated seeds under 300 mg/l, and germination rate indices under 100 mg/l and T50 index under control treatment, showed the highest significant decrease.

Salinity is one of the limiting factors of growth and development of the plants having a negative effect on morphological and physiological processes in plants. In order to reduce these adverse effects, different compounds and regulators could be used. In this study, the effect of hormone salicylic acid (SA) at 3 levels (0, 1 and 2 mM) to relieve stress (NaCl soluble at concentrations of 0, 50, 100 and 200 mM) was investigated at germination stage. Seedling length, dry weight and biochemical parameters such as the content of photosynthetic pigment, protein and anthocyanins were assayed and then analyzed by SPSS software. Recent results showed that high salt concentrations significantly reduced the morphological characteristics. But, exogenous 1 mM SA, in salt stress increased the length and the weight. Biochemical parameters such as content of photosynthetic pigments, soluble proteins and anthocyanins were also reduced by stress and in the presence of SA, anthocyanin content increased significantly compared with control and stress conditions. The positive effect of salicylic acid on the inhibitory effect of lower salt concentration (1 mM) was more than concentration of 2 mM. Also most promotive effect was observed in 50 mMNacl with 1 mM SA treatment. On the basis of our results, it seems that the use of low concentrations of salicylic acid reduced the harmful effects of salinity in plants.