冬小麦蒸腾效率对土壤水分响应的生理机制探讨

通过盆栽试验,研究了两种生态型冬小麦(石家庄8号和洛旱2号)在三种土壤水分条件下(L:田间持水量的60%~65%;M:田间持水量的70%~75%;H:田间持水量的80%~85%)蒸腾效率的变化及其生理机制。结果表明:随着土壤水分的降低,植株叶片水势降低,根冠比增加,两个品种间没有显著差异。土壤水分的降低,使植株生物量减少,蒸腾耗水减少,但蒸腾效率提高。L处理下石家庄8号和洛旱2号植株水平的蒸腾效率分别提高119.0%和62.2%。植株叶片光合速率与蒸腾速率随土壤水分的减少不断下降,但叶片水平的蒸腾效率提高,且与植株水平蒸腾效率呈极显著正相关(R2=0.96)。气孔导度随土壤水分的减少而降低,并与蒸腾速率呈极显著正相关(R2=0.97),表明蒸腾主要受气孔因素调节;光合速率随土壤水分减少而降低,但胞间CO2浓度升高,表明光合主要受非气孔因素调节,这种调节机制使得植株在干旱胁迫下更高效利用水分。试验结果初步揭示:光合与蒸腾调节机制的差异构成了试验品种在干旱下蒸腾效率提高的生理基础。

Physiological Response of Transpiration Efficiency of Winter Wheat to Soil Moisture

Pot experiment was conducted to study the response of transpiration efficiency of two ecotypes of winter wheat varieties(Shijiazhuang8;Luohan2) and its physiological mechanism to three different soil moisture conditions(L:60%-65% of field capacity;M:70%-75% of field capacity;H:80%-85% of field capacity).The results showed that leaf water potential decreased,and the root shoot ratio increased with the decreasing of soil moisture,but there was no significant difference between the two varieties.Lowering soil water content resulted in a reduction of biomass and water use for transpiration,however the transpiration efficiency at plant level was increased,it was increased by 119.0% and 62.2% for Shijiazhuang8 and Luohan2 in L treatment. With soil moisture decreasing,leaf photosynthetic rate and transpiration rate was reduced continuously,but transpiration efficiency at leaf level increased.There was a significantly positive correlation between the transpiration efficiency at plant level and at leaf level(R~2=0.96).Stomatal conductance was reduced with the soil moisture lowing,and it significantly positive related to transpiration rate(R~2=0.97),which indicated that transpiration was mainly regulated by stomatal factor;while photosynthetic rate reduced and intercellular CO_2 concentration raised,which indicated that photosynthesis was mainly adjusted by non stomatal factors.Such regulating mechanism makes more efficient use of water in the plant under lower level of soil moisture conditions.The preliminary results suggested that the different regulatory way of photosynthesis and transpiration constitute the physiological basis of higher transpiration efficiency under low soil moisture conditions.