THE DYNAMICS OF SIZE INEQUALITY IN SPRING WHEAT POPULATIONS UNDER SEMIARID CONDITIONS AND ITS PHYSIOECOLOGICAL BASIS
半干旱条件下春小麦种群不整齐性动态及其水分生理生态基础

The experiments with water as only limiting factor was designed to study the dynamics of size inequality in spring wheat ( Triticum aestivum L.)populations and its theoretical basis.Of the three density (low,medium,high)wheat populations,the skew( G ) of weight distribution of wheat plants increase with time,and the increase rate is the highest in high density population.The author determined and compared the water absorbing power,transpiration rate,photosynthetic rate of different sized individuals in competition.The results showed that the difference of water absorptive capacity between different sized nearby individuals increase with time due to their scrambling for common limited water resources,the water competition between them cause and speed up the differentiation of transpiration rate,net photosynthetic rate.This article reveals that,under semiarid conditions,the circular feedback relations between crop's water competitive ability and net photosynthetic rate is the essential cause of size hierarchy in crop populations.The authors discuss its molecular mechanism.