Differences of the Photosynthetic Properties and Nitrogen Accumulation between Island Cotton and Upland Cotton

Objective] Under the same cultivation conditions, we explored the differences in photosynthetic characteristics between upland cotton and sea-island cotton, and their dry matter and nitrogen accumulation and distribution patterns during the blooming period, to provide a theoretical basis for irrigation and fertilization of island cotton. Method] Using Xinluzhong 75, Xinluzhong 54, Xinhai 35 and Xinhai 48 as materials, we tested the net photosynthetic rate (P_n), leaf temperature, dry matter accumulation and nitrogen absorption and distribution characteristics under the same management conditions. Result] After the flowering stage, when compared with island cotton, the P_n of upland cotton was higher, but the leaf temperature and light illumination were lower. However, the difference in effect of stomatal conductance (G_s) on P_n between island cotton and upland cotton was small. The dry matter accumulation of shoots and the daily accumulation of shoots and reproductive organs in the whole growth period were higher for upland than for island cotton, with a lower dry matter proportion of reproductive organs in the early growth period, and higher in the late period for upland than for island cotton. When compared with Xinhai 48, the initiation of rapid nitrogen accumulation of Xinluzhong 54 was later and its duration was shorter, but the maximum nitrogen accumulation rate was higher; however, the initiation of rapid accumulation time of reproductive organs was later, and its rapid accumulation duration was longer. Conclusion] The dry matter output efficiency, accumulation in reproductive organs and nitrogen accumulation in the later growth period of island cotton were lower than those in upland cotton. Therefore, under production conditions, the proportions of water and fertilizer use should be increased for island cotton according to different regions.