Effect of salicylic acid treatment on cadmium toxicity and leaf lipid composition in sunflower

The ameliorative effect of salicylic acid (SA) on cadmium (Cd) toxicity in sunflower plants was studied by investigating plant growth and fatty acid composition. Sunflower plants in two leaves stage were exposed to CdCl2 treatment (0, 50, 100, 150 and 200 µM) and then were treated with salicylic acid (0, 250 and 500 µM) as foliage spraying. One week after the last salicylic acid treatment,plants were harvested and growth parameters were measured . Oil of leaf was extracted in a Soxhlet system and fatty acid composition were measured by gas chromatography (GC). Statistical analyses showed excess Cd reduced growth parameters (fresh weight and length of stems and roots, fresh weight and number of leaves)and SA increased them compared with the control. Maximum reduction in these parameters was at 200 µmol Cd and 0µmol of SA. Cd caused a shift in fatty acids composition, resulting in a lower degree of their unsaturation and an increase in saturated fatty acids in sunflower leaves,whereas SA improved them. SA, particularly increased the percentage of linolenic acid and lowered that of palmitic acid by the same proportion. These results sugg membrane integrity due to lipids est that SA could be used as a potential growth regulator and a stabilizer ofprotection of cadmium-induced oxidative stress to improve plant resistance to Cd stres

Biochemical responses of Alfalfa (Medicago sativa L.) cultivars subjected to NaCl salinity stress

This investigation was conducted to determine NaCl salinity effects on antioxidant enzyme s activities, reducing sugar contents and lipid peroxidation in two alfalfa cultivars. Plants grown in solution cultures were subjected to 0, 100, 150 and 200 mM solutions of sodium chloride. Yazdi and Diabolourde alfalfa were used as tolerant and sensitive cultivars, respectively, in a germination experiment under similar conditions. Results show that the amount of reducing sugars and the activities of peroxidase (POD), catalase (CAT), ascorbate peroxidase (APX) and superoxide dismutase (SOD) enzymes increased with the increase in salt concentration. However, SOD activities decreased at high salt concentrations. The increase in the activities of antioxidant enzymes in response to salt treatments was higher in the tolerant cultivar. The results also show that salt treatment provoked an oxidative stress in both cultivars, as shown by the increase in lipid peroxidation. However, the level of lipid peroxidation was higher in the sensitive cultivar. The increase in antioxidant activities could also be a response to the cellular damage induced by NaCl. It seems that the tolerant cultivar has a better mechanism to cope with the deleterious effects ROS produced under salt stress.Key words: Alfalfa, antioxidant enzymes, malondialdehyde, salt stress

The Effects of Excess Copper on Antioxidative Enzymes, Lipid Peroxidation, Proline, Chlorophyll, and Concentration of Mn, Fe, and Cu in Astragalus neo-mobayenii

To probe the physiological and biochemical tolerance mechanisms in Astragalus neo-mobayenii Maassoumi, an endemic plant around the Cu-rich areas from the North West of Iran, the effect of different copper concentrations at toxic levels on this plant was investigated. Copper was applied in the form of copper sulfate (CuSO4·5H2O) in four levels (0, 50, 100, and 150 μM). We observed no visible symptoms of Cu toxicity in this plant species. During the exposure of plants to excess copper, the antioxidant defense system helped the plant to protect itself from the damage. With increasing copper concentration, superoxide dismutase (SOD), peroxidase (POD), and catalase (CAT) activities increased in leaves and roots () compared with that of the control group. The chlorophyll amount gradually declined with increasing Cu concentrations. However, reduction in the 50 μM level showed insignificant changes. Enhanced accumulation of proline content in the leaves was determined, as well as an increase of MDA content (oxidative damage biomarker) (). The results indicated that Cu contents in leaves and roots enhanced with increasing levels of Cu application. The Fe and Mn contents in both shoots and roots significantly decreased with increasing Cu concentration. Finally, the mechanisms of copper toxicity and copper tolerance in this plant were briefly discussed

Investigating of a wide range of concentrations of multi-walled carbon nanotubes on germination and growth of castor seeds (Ricinus communis L.)

Carbon nanotubes act as regulators of plant germination and growth and are able to change the morphology and physiology of plant cells. The castor plant (Ricinus communis L.) belongs to the Euphorbiaceae family and is a very important medicinal plant. The aim of this study was to investigate the effect of 10 different concentrations of multi-walled carbon nanotubes (MWCNTs) (2, 5, 10, 20, 50, 75, 100, 125, 250 and 500 μg · ml–1) alongside the control under laboratory conditions on the germination and growth of castor seedlings. The results demonstrated that the maximum percentage of germination (96.7%) and relative germination percentage (100%) were found in the concentrations of 50 and 100 μg · ml–1, respectively, and the highest germination rate (53.3%) and the mean germination time (4.6 days) was seen in the concentration of 75 μg · ml–1. However, no statistically significant differences were found between the different concentrations in any of the germination factors. In the concentration of 100 μg · ml–1, there was a significant increase in the seedling vigor index I (400) when compared with the concentrations of 5 and 10 μg · ml–1. The maximum seedling vigor index II (11.3) was found in the concentration of 100 μg · ml–1 and was significantly different from the control and all applied concentrations. The length of radicle in the 100 and 125 μg · ml–1 had a significant increase when compared with the control and the concentrations of 10 and 50 μg · ml–1. The maximum seedling length (4.6 cm) was seen in the concentration of 100 μg · ml–1 where there was a significant increase with 10 μg · ml–1. Moreover, in the 100 μg · ml–1 concentration, the largest number of rootlets (8.6) was seen and when compared with the control and concentrations of 5, 10 and 50 μg · ml–1, there was a statistically significant increase. The maximum wet weight (0.3 g) and dry weight (0.1 g) of seedlings were obtained in the concentration of 100 μg · ml–1 and when compared with the control, there was a significant increase. It was found that in all factors related to the growth of seedlings, the concentrations of 10 and 50 MWCNTs had an inhibitory effect on the response index. The MWCNTs concentration of 100 μg · ml–1 was considered as the optimum concentration in the growth stage of castor seedlings

Drought stress effects on photosynthesis, chlorophyll fluorescence and water relations in tolerant and susceptible chickpea (Cicer arietinum L.) genotypes

In order to evaluate morphological and physiological traits related to drought tolerance and to determine the best criteria for screening and identification of drought-tolerant genotypes, we grew two tolerant genotypes (MCC392, MCC877) and two sensitive genotypes (MCC68, MCC448) of chickpea under drought stress (25% field capacity) and control (100% field capacity) conditions and assessed the effect of drought stress on growth, water relations, photosynthesis, chlorophyll fluorescence and chlorophyll content in the seedling, early flowering and podding stages. Drought stress significantly decreased shoot dry weight, CO2 assimilation rate (A), transpiration rate (E), and PSII photochemical efficiency (Fv/Fm) in all genotypes. In the seedling and podding stages, PSII photochemical efficiency was higher in tolerant genotypes than in sensitive genotypes under drought stress. Water use efficiency (WUE) and CO2 assimilation rate were also higher in tolerant than in sensitive genotypes in all investigated stages under drought stress. Our results indicated that water use efficiency, A and Fv/Fm can be useful markers in studies of tolerance to drought stress and in screening adapted cultivars of chickpea under drought stress