The leaves of cotton cultivars Qalandri, MNH-93, Rehmani and S-12 were stressed for 2 h
at 30 (control), 35, 38, 40, 42, 43, 44, 45 and 46°C to quantify the damage caused to
chloroplast photosynthetic apparatus by chlorophyll fluorescence technique. There was 10-30% decrease in Fv/Fm ratio up to the temperature stress of 40°C. But at 44°C the
cultivars showed considerably higher damage to photosynthesis process by recovering only
10, 13, 37 and 50% of the Fv/Fm ratio by the cultivars MNH-93, Qalandri, Rehmani and
M. A. Sethar, V. Mala Pahoja , Q. I. Chachar and D. L. Laidman , 2001. Impact of Optimal and Superoptimal Temperatures on the Photosynthetic Apparatus of Cotton Leaves. Journal of Biological Sciences, 1: 1088-1092.