冬小麦对不同土壤水分的生理和形态响应

采用深桶栽培结合测坑法，从冬小麦反青至蜡熟期保持不同的土壤水分，分生育期对小麦的形态、生理和根系进行了测定。结果表明：调控土壤水分可明显改变冬小麦根、冠生长量比率。适宜的土壤水分胁迫（田持的５０％－６０％）可促进冬小麦根系发育，高土壤水分更有利于地上部生长。土壤水分长期低于田间持水量的６０％时，较显著地叶片的增大，从而减小截获光能的总叶面积，最终降低生物学产量和经济产量。土壤水分由“田持”的４６％升高到５５％，光合速率增幅不大，由５５％提高到６４％，光合速率出现跃迁式增高，土壤水分超过６４％后，光合速率几乎为等值。说明光合作用对土壤水分存在一个“阈值”反应，此值为土壤田间持水量的６５％左右。冬小麦的蒸腾速率随土壤水分递增而一直递增；综合考虑蒸腾速率与光合速率及水分利用效率之间关系，可以得出高土壤水分条件下冬小麦存在奢侈蒸腾耗水现象。

Physiological and Morphological Responses of Winter Wheat to Soil Moisture

With deep pots and non weighting lysimeters,different soil moisture stresses are developed and maintained during turn green to maturing stage in winter wheat.The plant physiological and morphological status and development of root under different soil moistures are measured at all growth stages.It has been shown that the rational regulation of soil moisture can change obviously the ratio of root to shoot,suitable soil moisture stress (50% 60% of field capacity)promotes the development of root system and high soil moisture favors the growth of stem and leaf.The experiment results also show that leaf growth rate reduces when soil moisture content is lower than 60% of field capacity,which leads to total leaf area and solar radiation energy intercepted to decrease,and finally reduces the biological and economical yields in winter wheat.When soil moisture rises to 55% of field capacity from 46% of field capacity,photosynthetic rate increases slightly.However as soil moisture rises to 64% of field capacity from 55% of field capacity,photosynthetic rate increases greatly.If soil moisture is more than 64% field capacity of field capacity,photosynthetic rate almost remains stable.This indicates that photosynthetic rate has the threshold response to soil moisture and the threshold value is about 65% of field capacity.The transpiration rate for winter wheat increases with soil moisture.By considering the relationship among transpiration rate,photosynthetic rate and water use efficiency comprehensively,winter wheat has luxury transpiration to consume much more water under high soil moisture conditions.