Abstract: Twenty-four CMS-based hybrids with five leaf types in upland cotton were made among super Okra leaf, Okra leaf and normal leaf parents by NCⅡ mating design to compare photosynthetic properties of different leaf type hybrids and to study their relationships with yield and fiber properties. Compared with Zhongza29 (CK hybrid), yields of super okra leaf and okra leaf hybrids were obviously lower, but semi-Okra leaf hybrids was 1.16% higher in yield of seed cotton and 2.06% in yield of lint cotton, and 10 days earlier in maturation. Semi-Okra leaf cotton hybrid, CLA 17 × ZR4, which was made by super Okra leaf sterile line and Zheda strong restorer line, had a 13 % higher yield over CK. For fiber properties, semi-Okra leaf hybrids had better quality in fiber length and micronaire value than CK with normal leaf. For photosynthetic indexes at different development stages of plant, semi-Okra leaf hybrids showed higher Pn (net photosynthetic rate), Gs (stomatal conductance ) and Tr (transpiration rate) than normal leaf hybrids at all stages except the harvesting stage, especially Pn was the highest in the flowering stage, but Ci was lower than normal leaf hybrids. There were positive correlation coefficients between Pn and yield-relatied traits at different development stages, of them, yield of seed cotton was the most significant relationship with Pn, boll number and bolls weight were in middle, fruiting branche was the smallest. Investigation of photosynthetic indexes in upper, middle and lower layer leaves of hybrid plants at the boll-setting stage showed that light intensity, light transmittance, Pn and Gs of super Okra leaf and Okra leaf hybrids were higher in the lower layer leaves than those of other leaf hybrids, especially those of super Okra leaf hybrids was the highest values in light transmittance and Pn, increased by 94.12% and 45.54% over CK respectively, but Pn was lower in the upper and middle leaves. Pn and Gs of semi-Okra leaf hybrids were higher in the top, middle and lower layer leaves than those of normal leaf hybrids, such as Pn, increased by 8.06% for the upper layer, 1.7% for the middle layer and 30.77% for the lower layer leaves than CK, respectively. The study indicates that semi-Okra leaf hybrids has better photosynthetic properties which are of benefits to expression of heterosis of yield and fiber properties.

Key words: Cotton, Okra leaf, Heterosis, Photosynthesis