Stem Diameter Variation Subjected to Full Irigation and Drought Stress in Cotton

WANG Xiao-sen; MENG Zhao-jiang; DUAN Ai-wang; LIU Zu-gui

Abstract：With those cottons planted in soil barrels, the distinguish of stem diameter's relative variation (RV), maximum diameter shrinkage(MDS) and daily increase(DI) between full irrigation treatment(T0) and drought treatment (TI) was researched by randomized block design experiment. The result indicate the cotton's stem of TI treatment shrinked with the decreasing of soil water content and couldn't recover its stem size at night as the stem of T0 treatment did, and its RV line declined sharply compared with the RV line of T0 treatment, but they didn't share the same declining trend of RV among those cotton stems of TI treatment. Furthermore, there was negative correlation between MDS and DI, which indicated the bigger stem shrinkage, the more difficult its recovery. The value of daily average leaf stomatal conductance in TI treatment got smaller because of serious water stress. In addition, there was a better correlation between MDS and available radiation which was the main reason of stem daily shrinkage. For those reasons above, we came up with 60% (account for field water capacity) relative soil water content as the key point of keeping RV same between TO and TI treatments, and 40% relative soil water content as the least soil wa-ter content below which the available water in cotton stem might be exhausted by the transpiration, and the notion of standard stem variation and its regression equation.