Division of Plant Physiology and Biochemistry, Central Institute for Cotton Research. P. B. No. 125, G. P. O., Nagpur
The response of four cotton genotypes (AKH 4 of G. oboreum L. and SRT 1, B 1007 and C 1412 of G. hirsutum L.) to reduction in light intensity by shading the plants was studied under field conditions. Reduction in light intensity reduced the rate of photosythesis as indicated by reduced NAR, (net assimilation rate) and LAE (leaf area efficiency) but LAR (leaf area ratio) and SLA (specific leaf area) increased. Dry matter of all the genotypes increased significantly with 35 percent reduction in light intensity. When it was further reduced to 65 per cent the dry matter of SRT 1 and B 1007 remained unchanged, that of HKA 4 was the same as under natural light but reduced significantly in C 1412. The genotypes AKH 4 and C 1412 appeared outstanding as they maintained higher seed cotton yields and higher fruiting coefficients by apportioning more photosynthates for seed cotton production even when the light intensity was reduced to 65 percent.
