بررسي ارتباط بين محتوي آب نسبي و پارامترهاي تبادلات گازي با مقاومت به خشكي در هفت رقم گندم نان

Relative Water Content and Gas Exchange Parameters of Seven Wheat Genotypes Differing in Drought Resistance

In order to determine the stoamatal and non-stoamatal factors limiting photosynthesis under drought stress, this experiment was conducted on seven wheat cultivars namely : Roshan, M-79-17, M-79-4 (drought tolerant), Azadi and Kavir (semi tolerant), Karajl and Marvdasht (drought susceptible) at the greenhouse of College of Agriculture and Natural Resources, University of Tehran. The experiment was designed as a factorial (factors comprised of two irrigation levels and seven wheat cultivars) of a Randomized Complete Block Design. Whereas relative water content of Marvdasht decreased severely under drought stress, no significant decrease was observed for M-79-4. On the other hand, Roshan exhibited the highest photosynthesis rate and the lowest photosynthesis reduction under drought stress conditions. In contrast, Marvdasht showed the lowest photosynthesis rate and the highest photosynthesis reduction under drought stress. A low photosynthesis rate in drought susceptible cultivars is due to a limitation, or low stomatal conductance, and as well due to non stomatal (low mesophyll conductance, chlorophyll and soluble protein content) factors. Thus it can be concluded that tolerance of genotypes to drought stress is closely associated with their higher stomatal conductance, leaf chlorophyll and soluble protein contents.