Degradation of cell membranes is one of the consequences of cold stress. In this study, changes in profile of fatty acids (FA) were investigated in leaves of different clover genotypes exposed to cold stress and the most tolerant genotype was selected. Experimental treatments included factors, such as sampling time at two levels (autumn and spring), planting date at two levels, and 10 clover genotypes (7 cultivars of Persian clover and 3 cultivars of berseem, red ,and crimson clover). Lipid percentage was found to be influenced by season, planting date, and cultivar type. Persian clover (lately maturity) showed the highest lipid percentage by 3.5% and total unsaturated FA percentage by 79% and the lowest values were observed in crimson clover. Cold stress in autumn caused a 20% decrease in lipid percentage. Also, it caused a 21% increase in total saturated FA percentage, and 5 and 20% decrease in total unsaturated FA percentage and unsaturated /saturated FA ratio, respectively. Delay in planting date reduced percentage of lipid in clover cultivars. In all the cultivars, percentage of unsaturated FA was higher than that of saturated FA. Thus, the unsaturated FA percentage can be used as a criterion for selecting genotypes with respect to cold tolerance. In this regard, Persian clover (lately maturity) was the most tolerant genotype under cold stress conditions.
In order to understand, the physiological and biochemical mechanisms of Trichoderma longibrachiatum (TL) and spermidine (SPD) polyamine treatment on cadmium (Cd) tolerance phytoremediation in purslane (Portulaca oleracea) plant and the activity of anti-oxidants enzyme (CAT, APX, POX, SOD), hydrogen peroxide and proline content as well as determination of cadmium accumulation in shoots, roots, soil and their ratio to each other, a factorial experiment was performed in a completely randomized design with three replications and three treatments. In the current study, mitigative roles of SPD and TL were assessed in Cd stressed Portulaca oleracea plants. SPD (1, 0.5, and 1 mM) was applied after 20 days of sowing on the branches and leaves of plants inoculated or without TL inoculating in the presence of Cd (0, 30, 60 and 90 mg.kg ). Cd stress and coexistence with TL increased the activity of antioxidant enzymes and leaf soluble protein in purslane plants. Also, the application of SPD, especially at 0.5 mM, resulted in a higher increase in leaf protein under cadmium stress in inoculated plants. Proline parameter responds differently to TL. SPD application reduced the severity of these changes. The amount of H2O2 was significantly reduced in plants when treated by both TL and SPD. Significant differences were observed between 0.5 and 1 mM of SPD in terms of the Cd uptake in the TL inoculated purslane shoots. Inoculated purslane plants treated by either 0.5 or 1 mM of SPD had lower Cd uptake and greater BF. In general, the results showed a synergetic effect between TL fungi and SPD application on improving the Cd phytoremediation in the purslane plant.
