The photosynthesis responses of three cotton cultivars Helius, Avangard - 264 and Chirpan - 539 to drought during flowering-boll formation stage were studied. Drought stress ( 35 - 40 % of field water capacity) significantly depressed net photosynthetic rate and photosynthetic pigments content but had little effect on apparent electron transport rate of cotton plants from all cultivars. Following the model of Long and Bernacchi (2003), it was calculated that the drought enhanced photorespiration to prevent cotton photosynthetic apparatus from oxidative damages. Among the studied cultivars, the highest tolerance showed cv. Chirpan - 539. net photosynthetic rate in the drought-stressed plants from this cultivar was diminished in the lowest degree and fully recovered soon after the stress.
Photosynthesis response of plants from three cotton cultivars to soil drought