Effects of drought and chlorocholine chloride on seedling growth and photosynthesis of two cultivars of wheat (Triticum aestivum L.)

Effects of drought and chlorocholine chloride as a growth regulator for net photosynthesis, stomatal conductance, transpiration rate, relative water content percentage and chlorophyll content as well as seedling length, root to shoot dry weight ratio and relative growth rate of two wheat cultivars (Zarrin and Sardari) seeldings were studied. Sardari is known as a drought tolerant cultivar. Seeds were soaked in 0.2 percent solution of CCC or distillated water as control, for 20-h. After dried in air, seeds were planted in plastic pots and placed in a growth champer. Two weeks seeldings were exposed to drought by withholding water. Control seedlings were irrigated, regularly until the end of experiment. Photosynthesis, stomatal conductance, transpiration rate, chlorophyll and relative water content were reduced under water deficit, but relative water content of Zarrin in comparison to Sardari cultivar was more reduced under severe stress. The seedlings length were reduced with CCC in both cultivars, but photosynthesis increased significantly, and it is regard to increasing of total chlorophyll content and number of stomata per area unit. Also seedlings root to shoot dry weight increased with CCC. Relative growth rate average of two cultivars decreased significantly in response to drought, especially in Zarrin cultivar In optimal humidity condition, Zarrin cultivar shows more growth and photosynthesis, but under water deficit, sardari is more tolerant, close the stomata for water maintaining, more resistant to nonstomatal limitation factors and can return to normal condition after rewatering. Chlorocholine chloride can help seedling to grow vigorously to resist with drought. Key words: Growth, Photosynthesis, Wheat, Drought, Chlorocholine Chloride