温室内作物茎秆直径变化对基质含水率的响应

Response of stem diameter of vegetable crops to soil moisture in greenhouse

通过对北京地区温室内黄瓜和番茄生长期茎液流(SF)和茎直径变化(径差SD)过程以及同期温室内微气象因子的连续观测,利用相关分析方法分析了总辐射通量密度和饱和水汽压差(VPD)对茎液流和茎直径变化的影响以及茎直径变化与基质含水率的关系。发现SF与SD与温室内总辐射通量密度间的相关性并不显著,而与VPD的相关性均达到了极显著水平。分别对每日12∶00、13∶00、14∶00和15∶00的SD(与每日6∶00的茎直径之差)与VPD进行相关分析,均通过了0.01水平的显著性检验,其中以14∶00的相关系数最大。以各种作物每日14∶00的SD/VPD(径差与饱和水汽压差的比值)与基质含水率进行相关分析,表明两者间有极显著正相关关系。而且,在不同基质含水率范围内,每日14∶00的SD/VPD值保持在一个相对稳定的区间,说明14∶00的SD/VPD对基质中的水分状况很敏感,可以作为启动温室灌溉系统的参考指标。

Based on one year experiment, variations of microclimatic factors such as light intensity, ambient temperature and relative humidity in greenhouse were analyzed. The diurnal stem diameter difference （SD） and sap flow rate （SF） of greenhouse crops, e. g, cucumber and tomato were observed during this year. Both the variation of SF as an index of transpiration and SD as an index reflecting the water balance inside the stem were influenced by weather and shading screen, the maximum of SF and minimum of SD during daytime were stronger on sunny days no matter shading screen than those on overcast days and weaker on sunny days with shading screen than those without it. This implied that the shading screen could influence the crop transpiration. Furthermore, the microclimatic factors influencing SF and SD were explored using correlating analysis methods, the results showed that the radiation in greenhouse had no significant correlation to SF and SD, whereas the correlation coefficient between the vapor pressure deficit （VPD） and SF and SD at 12 ： 00, 13： 00, 14： 00, 15： 00 during reproduction stages of cucumber and tomato respectively were calculated, results showed that the correlation coefficients at 14 ： 00 were the biggest; and there was a strong linear relationship between the SD/VPD at 14： 00 and soil moisture, and SD/VPD at 14 ： 00 was relatively constant in a larger value at high water content than that at low water content, so the SD/VPD at 14 ： 00 might be suggested as an index to wake up the irrigation system.