Zagros (drought tolerant) and Pishtaz (drought susceptible) cultivars were classified on the basis of shoot dry weight and were used as plant material in this study. Total chlorophyll, carotenoids, antocyanins, proline, soluble sugar contents, lipid peroxidation, antioxidant enzyme activities and protein patterns were determined. Seedlings of wheat genotypes were grown in nutrient solution cultures under 16 h d-1 period at room temperature. With the decrease in osmotic potential, total chlorophyll initially increased but then decreased in the tolerant cultivar. The amount of total carotenoids and antocyanins in both cultivars increased in response to drought stress. However, the increase was only significant (P<0.05) at some osmotic potentials. The increase was more pronounced in the tolerant cultivar. Soluble sugars and proline increased significantly in both cultivars, but were higher in the tolerant one. The sensitive cultivar showed higher rates of lipid peroxidation as compared to the tolerant cultivar. Antioxidant enzymes activities increased with the decrease in osmotic potential in both cultivars. The tolerant cultivar exhibited a higher antioxidant activity compared to the sensitive one. SDS-PAGE showed new protein bands under water stress. These results indicated that proline, soluble sugars contents and antioxidant enzyme activities are part of the defense mechanisms which confer water deficit tolerance to wheat cultivars. APX=Ascorbate peroxidase, CAT=Catalase, GR=Glutathione reductase, MDA=Malondialdehyde, ROS=Reactive oxygen species, SOD=Superoxide dismutase.

The effect of salt stress on the pysiological and biochemical responses of the seedlings of eight Eucalyptus species viz. E. kingsmillii, E. tetragona, E. salubris, E. occidentali, E. microtheca, E. camaldulensis, E. globules and E. sargentii was analyzed. Four month-old seedlings grown in greenhouse were watered by five levels of salt solution (0, 50, 100, 150 and 200 mM of NaCl) in five replications with a factorial experimental design. The results indicated that salinity delayed and inhibited the seedlings’ growth after one month, and induced gradual decline in most of the criteria such as leaf area, relative water content and specific leaf area. Moreover, a significant reduction of chlorophyll a, b and total chlorophyll content was observed. Salinity stress raised the content of soluble sugars, proline and glycine betaine. Eucalyptus sargentii as the most tolerant species had the optimum growth up to 200 mM NaCl but E. globulus presented the most sensitive species to salinity stress. At 200 mM NaCl, proline and glycine beatine raised to 10.57 and 27 mg g-1 in the tolerant species (E. sargentii), respectively while proline in the sensitive species (E. globulus) dropped to 0.003 mg g-1. These results suggest that high tolerance of E. sargentii to salinity stress is closely related to lower specific leaf area and enhancement of COMPATIBLE solutions such as proline, soluble sugar, glycine beatine. This would encourage the possibility of propagating E. sargentii in the southern coastal area of Iran. Furthermore, these results provided further biochemical support for the specific abiotic stress tolerance mechanism of Eucalyptus species.

Salinity is a main and common stress which decreases the amount of agriculture products and natural plants in many areas of the world. In this study, the effect of salt stress on three varieties of Lotus corniculatus 'Karaj', 'Jolfa', and 'Ardabil' was investigated. Plants were cultured in hydroponic condition with four NaCl treatments (0, 50, 100, 150 mM). The amounts of proline, glycine betaine, soluble sugars as well as Na+and Cl- were analyzed. The results showed that sodium and chloride content in all varieties significantly increased in shoot (p<0.05). The amounts of proline and soluble sugars significantly increased in all varieties (p<0.05). However, increasing in NaCl concentration raised significantly glycine betaine content in leaves of the varieties (p<0.05). As far as the measured factors are concerned, it seems that 'Jolfa' and 'Karaj' have a higher capacity to tolerate salt stress particularly in 100-150 mM NaCl compared with 'Ardabil'.