不同水分状况下棉花茎直径变化规律研究

利用DD型直径生长测量仪持续监测筒栽棉花茎秆直径的动态变化，对茎直径在不同天气的日变化规律、水分胁迫条件下不同生长阶段的变化规律及其与环境因素的关系进行了研究。结果表明，茎直径变化测量参数能较好地反映棉花水分状况，但茎直径变化受外界环境因素和作物自身发育特性共同影响，在不同生长阶段，宜采用不同参数作为水分诊断指标。在茎生长阶段，茎直径最大值随时间的变化能较好地反映棉花水分亏缺程度，而不同水分处理间的日最大收缩量差异不显著；在茎成熟阶段，日最大收缩量对水分亏缺的反应非常敏感，是适宜的水分诊断指标。对影响茎直径变化的环境因素进行分析后得出，土壤水分、辐射和空气饱和差影响最大，相对湿度次之，气温和风速的影响很小。在此基础上建立了棉花茎直径日最大收缩量与环境因子之间的回归模型，可为利用茎直径变化评价作物缺水状况提供依据。

Stem diameter variations of cotton under different water conditions

Stem diameter variations of cotton cultivated in pots were monitored continuously by using stem growth measurement transducer(DD-type). The diurnal variations of stem diameter under different weather conditions and the stem diameter responses to water deficits at different growth stages were investigated, while the influences of environmental variables on stem diameter variations were evaluated. The results showed that parameters derived from stem diameter measurements were reliable plant water status indicators. Since stem diameter variations reflect the combined effects of environmental variables and plant vegetate characteristic, the influence of phenology on stem growth must be taken into account when selecting suitable plant water status indicators. During stem growth stages, the trend of maximum stem diameter (MXSD) had greater response to water stress but there were no obvious differences in maximum daily shrinkage (MDS) under different water conditions. Conversely, MDS can be a reliable indicator of plant water status at the stem mature stages with its high sensitivity to water deficits. Then, stem diameter variations were correlated to environmental factors. Soil water content, radiation and vapor pressure deficit (VPD) were found to be the predominant factors affecting MDS, followed by the relative humidity, while air temperature and wind velocity had the least effect. The established relationship between MDS and environmental variables (radiation, vapor pressure deficit, relative humidity, and soil water content) can be used to detect crop water deficits.