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a succulent, halophyte, specialty vegetable, development from emergence through flowering and maturity is largely controlled by photoperiod and may be genotype-dependent. Photoperiod affects timi...

This study was conducted to investigate the effects of heat stress after anthesis on the performance of Photosystem II (PSII) and the enzymatic activity of catalase and ascorbate peroxidase. Two treatments-normal and heat stress-were conducted on four bread wheat cultivars from 7 days after anthesis until maturity. Heat stress led to an acceleration of chlorosis, reduced the efficiency of electron transfer and increased concentrations of malondialdehyde; however, the level of susceptibility varied depending on the cultivars. On the 10th day of heat stress, reductions in fluorescence parameters, depending on the cultivar, were 6.9 to 18.9% for Fv/Fm, 9 to 21% for ΦPSII and 8.3 to 19.4% for F’v/F’m compared to normal conditions. Catalase activity increased after initial exposure to heat stress. However, after 10 days of treatment, catalase activity increased in the Chamran and Aflak cultivars by 32% and 45%, respectively, but it did not change in the Dez cultivar and decreased 22% in Darab2. Ascorbate peroxidase activity decreased in two treatments, while the amount of reduction in heat stress treatment was more than the normal treatment. The highest levels of enzymatic activity were observed in Chamran under heat stress conditions, whereas Darab2 and Dez showed the lowest activity of the enzymes. Chlorophyll fluorescence parameters and chlorophyll index had a significant negative correlation with the levels of malondialdehyde; however, they had a significant positive correlation with the antioxidant activity.&nbsp

Tissue culture technique was used to obtain salt tolerant variants from embryogenic calli of sugarcane ( Saccharum sp. Var. CP48-103) that were cultured on a selective medium containing different levels of NaCl (0, 33, 66, 99 and 132 mM). A total of four plants which regenerated from the tolerant calli were selected but the best in vigor were grown in in vitro and hydroponic systems under salinity stress (with the previous levels) as compared to source variety. With increasing supply of NaCl in both systems, root growth was more adversely affected than shoot growth. Chlorophyll contents showed a decreasing trend and dry matter yield of plants reduced but in a slow rate in tolerant somaclone than source variety. The tissues analysis showed that at high salt concentration, Cl - and Na + content in shoot and root increased. With rising salt concentration from 0 to 132 mM, content of Cl - in shoot and root of tolerant variant changed and was lower than the parent. In conclusion, this variant probably had lowest genetic ratio of shoot: root chloride due to minimum transport of Cl - from the root to shoot. Also this variant had high content of Ca 2+ in shoot and high K + /Na + ratio at all salinity levels. Thus, it probably has genetic potential to avoid harmful ions accumulation. Key words : Sugarcane, salinity, somaclonal variation, in vivo, in vitro.

Tissue culture technique was used to obtain salt tolerant variants from embryogenic calluses of sugarcane (Saccharum sp. var. CP48-103) that cultured on a selective medium containing different levels of NaCl (0, 0.2, 0.4, 0.6, and 0.8% NaCl). A total of four plants regenerated from the tolerant calluses were selected but the best of them in vigor grown in in vitro and hydroponic systems under salinity stress to comparison with source variety. With increasing supply of NaCl in both systems, root growth was more adversely affected than was shoot growth. Chlorophyll contents showed a decreasing trend and dry matter yield of plants reduced but in a slow rate in tolerant somaclonal than source variety. The biochemical analysis showed that at high salt concentration, Cl− and Na+ content in shoot and root increased. With rising salt concentration from 0 to 0.8%, content of Cl− in shoot and root of tolerant variant changed lower than parent showed that this variant had genetic lowest ratio of shoot/root chloride and had minimum transport of Cl− to shoots. Also this variant had high content of Ca2+ in shoot and high K+/Na+ ratio at all salinity levels. Thus it probably has genetic potential to avoid harmful ions uptake.