فصلنامه فرآیند و کارکرد گیاهی
سال دوم شماره 3 (پیاپی 5، پاییز 1392)

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_+2 ºC temperature for about 60 days. The light intensity was 150 µ E mˉ² Sˉ¹ and the lightness-darkness condition was8-16 hours. UV treatment was applied after the six-leaf stage and UV-B radiation was applied for a period of 15 days in every other day the time for each application was 20 minutes. But UV-C radiation was applied for 15 days in every other day and time of each application was 8 minutes. Salicylic acid was sprayed on the plants after the six-leaf stage with a concentration of 1 Mm. The results indicated that the UV-B and UV-C radiations led to reduction in dry and wet weight، root elongation and shoots. The radiations also reduced the photosynthetic pigments (chlorophyll a، chlorophyll b and carotenoid) and sugar rate and total soluble proteins amount. The Malondialdehyde and phenylalanine ammonialyase compounds rate and UV- absorbing compounds were increased under the effect of UV-B and UV-C radiations. Surveying results showed that treatment with salicylic acid caused a reduced damage to the plant which had been created due to UV-B and UV-C radiations and was able compensate for changed factors that had been changed because of ultra violet radiations.

Abstract 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) concentrations and lipid peroxidation Ac-Sterling، Isfahan، and Arak-2811 were ranked tolerant and Arak، C111 and Shiraz 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 plays a major role in its response to Cd and APX and CAT antioxidants play a more crucial role in this regard، relative to GR.

Arsenic is considered as one of the most important environmental contaminant compound. Some plant species can grow in arsenic contaminated soil and they are able to reduce arsenic toxicity. Nowadays، phytoremediation as a new and friendly environmental technique employs the use of plants to remediate contaminated soil. Previous studies showed 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 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 μmol l−1 arsenic and 5، 50، 200، 800 & 1600 μmol 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 μmol l−1 As and 5 μmol l−1 phosphorus. Increasing arsenic concentration in the medium lead 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، illustrates 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 region of the world. This research was conducted to evaluate the effect 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 effect 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 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 can 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 seedling Lepidiun sativum L. under in vitro was investigated. The seeds of Lepidium sativum (Garden Cress) were sterilized and then were 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 steril condition. After 3 days، results showed chlorophyll a، chlorophyll b، total chlorophyll، carotenoids and protein significantly decreased، while reduced sugar، proline and antioxidant enzymes increased in seedlings which were under oxidative stress. Thus methylisothiocyanate appears to cause oxidative stress and the activation parameters of the plant''s defenses. The maximum and minimum، respectively، at concentrations of 1 mM and 0. 01 mM methyl isothiocyanate observed.

In order to investigate the effects of nano silver and multi wall carbon nanotube levels on ‎some morphological and physiological traits of faba bean the present study was done. This ‎factorial experiment was conducted in a completely randomized design with three replications ‎and two treatments with four 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 non ‎significant 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 difference 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 10 mg/l ‎and T50 index under control treatment، showed the highest significant decrease. ‎

Salinity is one of the factors limiting the growth and development of the plants that has a negative effect on morphological and physiological processes in plants and in order to reduce these adverse effects used to from growth regulators. 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) consider in licorice plant at germination stage. Seedling length، dry weight and biochemical parameters such as the content of photosynthetic pigment، protein and anthocyanins were 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 weight. Biochemical parameters such as content of photosynthetic pigments، soluble proteins and anthocyanins were also reduced by stress and in the presence 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 inductions observed in Combined treatment of 50 mMNacl with 1 mM SA. On the basis our results، It seems that the use of low concentrations of salicylic acid hormone reduce the harmful effects of salinity in plants.