充分灌溉和干旱胁迫对棉花茎直径变化的影响

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

以桶栽棉花为试验材料,采用随机区组试验设计,探讨充分灌水条件下(T0)和一个干旱周期中(TI)的茎直径变化量(RV)、最大收缩量(MDS)及每日生长量(DI)之间的差异。试验结果表明,由于受到土壤水分减少的影响,TI处理棉花的茎杆逐渐收缩得不到恢复,其RV曲线下降和T0处理RV曲线的差异逐渐变大,并且同是TI处理的植株其RV下降幅度也不同;二种条件下棉株的MDS和DI均呈负相关;水分胁迫的加剧导致棉花叶片气孔导度变小。经回归分析二处理MDS和气象因子中的有效辐射有较好的相关性,表明有效辐射是导致茎变化的主因。据此提出土壤相对含水量60%为RV产生差异的临界值,土壤相对含水量40%是棉花茎秆内可被用做蒸腾的水分被完全耗尽的临界值;同时提出标准茎变化的概念及其全回归方程。

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 TO treatment did, and its RV line declined sharply compared with the RV line of TO 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 water 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.