夏玉米茎流速率和茎直径变化规律及其影响因素

为了揭示夏玉米茎流速率和茎直径的变化规律及其影响因素，该研究对夏玉米生育中期的茎流变化和茎直径微变化过程进行监测，分析了二者的日变化过程及相关关系、茎流速率与环境因子之间关系、茎直径随土壤含水率的变化规律。结果表明：茎流速率日变化过程呈单峰曲线型，其变化受太阳辐射、饱和水气压差、风速等气象因子的影响显著，通过对实测数据的分析得到了茎流速率与上述气象因子的线性回归方程，为今后利用气象因子预测夏玉米的叶面蒸腾量提供了基础；茎直径微变化的日变化过程也呈现明显的昼夜变化规律，白天收缩，夜晚复原，每日茎直径最大值随土壤含水率的降低而减小，二者之间呈线性相关关系，依据这一关系可利用茎直径微变化诊断作物缺水状况。

Change of sap flow rate and stem diameter microvariation of summer maize and influenct factors

In order to reveal the daily variation process of sap flow rate and stem diameter and its impact factors, field experiments were conducted to collect data of summer maize in middle growth period at Daxing Station, and then the relationship between daily variation process of sap flow rate and stem diameter, the relationship of sap flow rate and environmental factors, as well as the relationship of the microvariation of stem diameter with soil moisture were analyzed. Results showed that the curve of daily sap flow rate variation process was unimodal, and significantly affected by solar radiation, vapor pressure, wind speed and other meteorological factors. A linear regression equation was obtained through analysing the data of sap flow rate and meteorological factors, which may provide a basis for prediction of leaf transpiration of maize using meteorological data. Moreover, the daily change of stem diameter was significantly different in the daytime and at night, i.e. shrank in the daytime and recovered at night. The maximum of daily stem diameter decreased with decreasing soil moisture, forming a linear relationship between them. So crop water deficit conditions can be diagnosed by using the data of stem microvariation on the basis of this relationship.