【作者】 张文丽；

【导师】 山仑； 吴冬秀；

【作者基本信息】 河南大学 ， 植物学， 2004， 硕士

【摘要】 节水农业的中心是提高自然降水和灌溉水利用效率，在这方面也存在着巨大潜力。为实现这一目标，根据作物各生理过程对水分亏缺的敏感程度，确定作物对土壤水分亏缺的下限指标，建立节水高效的灌溉制度是农田水分管理的重要手段。玉米苗期是玉米节水的主要阶段，要实现玉米节水灌溉，研究玉米苗期各生理过程与土壤水分的关系是很有现实意义的。通过对玉米各生理过程随土壤水分连续的动态变化规律及静态对比条件下的变化规律的进一步研究，确定出玉米的最适土壤水分供给水平，以期为节水农业灌溉提供理论基础。 通过对土壤逐步干旱条件下玉米幼苗气体交换参数动态变化的研究发现，在土壤逐步干旱初期，玉米的光合速率、蒸腾速率有所升高，在土壤相对含水量为90％时达最大。其后随土壤干旱的加剧，玉米的光合速率、蒸腾速率开始下降，下降初期较缓，自70％后几乎呈直线。分析表明这种变化是由气孔因子和非气孔因子交替或综合调节的结果。单叶水平的水分利用效率与土壤相对含水量之间呈抛物线关系，其最大值出现在土壤相对含水量为65N左右。由叶片的相对含水量与土壤相对含水量之间的模拟曲线显示，土壤相对含水量在60％以上时，叶片相对含水量变化较缓，几乎保持在一个水平上。以上现象的机制可能是，当土壤相对含水量在60％以上时，由于叶片代谢反应的调节使叶片相对含水量得到维持，同时也使叶片的光合速率对气孔的轻微关闭变得不是很敏感，而蒸腾速率一直保持对气孔开度的敏感性，结果导致了水分利用效率的增加，至土壤相对含水量在65％左右时达到最大。当土壤水分的进一步干旱，因叶片代谢调节的有限，使得光合速率对干旱变得敏感，结果导致单叶水分利用效率的逐渐降低。本实验结果显示，土壤相对含水量为60％是玉米苗期节水的一个关键值，低于此值玉米苗的叶片相对含水量就开始迅速降低，生长受到抑制。与叶水势的相关分析表明叶水势在—0.8Mpa是气孔最敏感的一个阈值点，也是光合速率和蒸腾速率与叶水势关系变化的一个临界值。 通过对在静态对比条件下不同土壤相对含水量对玉米幼苗的影响的研究发现，土壤相对含水量在40％—70％范围时，玉米叶片光合速率和蒸腾速率有所下降，但对叶片的水分利用效率的影响却不大，并且土壤相对含水量为70％时，玉米叶片的光利用效率、羧化效率以及月‘冲目睁勺亩月分刁刘口习匕.目火分月卜们网睡月口.之几月匕植株的生长几乎不受到水分胁迫的影响，因此提出土坡相对含水量为70%是玉米苗期适宜的供水上限，高于70%则不利于节水。通过对不同干早处理复水至充分后玉米幼苗的影响发现，不同干早处理被复水至充分后，均表现为气孔导度增大、光合能力恢复、单叶水分利用效率提高，甚至出现补偿现象，这种补偿现象与复水前水分干早程度和复水后水分充足持续的时间有关。其中，土城相对含水t为50%一70%的处理组被复水后，植物对光的利用效率也出现了补偿效应，其狡化效率也大幅度恢复，光合潜能有所提高，因此认为土坡相对含水t在50%是玉米苗期实施节水的最低范围闽值点。 本研究为玉米在苗期实施节水灌溉确定了一定的最适土集水分供给水平，也为节水农业灌溉提供了理论墓础。更多还原

【Abstract】 Improving water use efficiency of natural rainfall and irrigation is the core issue of water-saving agriculture, and it has great potential. It is essential to understand the sensitivity of every physiological process to water deficit and the threshold of crops to soil water deficit in order to establish a high efficiency water-saving system. Seedling stage is the crucial stage in maize to improve water use efficiency. So, studying the relationship between every physiological process and soil water content is of important practical significance in order to carry out water-saving irrigation. The author conducted the experiments with following three treatment groups: progressive drying; constant soil water continuum; drought with rewatering, to study the physiological responses of maize (Zea mays L.) to soil water content and to confirm proper water-providing amount and time in seedling stage of maize.The dynamic of photosynthetic parameters of Z. mays.L during seedling stage were studied in response to progressive drought The results showed that photosynthetic rate (Pn) and transpiration rate (Tr) increased a little with the declining of soil water content during the early drought days. When soil relative water content (SRWC) was 90% Field Water Capacity (FWC), bom Pn and Tr reached the maximum. Then they began to decrease with unceasing drought .The rate of decreasing was slow when soil water was higher than 70% FWC, but decreased linearly with decreasing soil water when soil water was lower than 70% FWC. It was indicated that the changes were caused synthetically or alternately by stomatal and non-stomatal factors. The curve of water use efficiency of single leaf (WUE) to SRWC was a parabola, its maximum occured under soil water content of 65% FWC. By analysing the curve of leaf relative water content (LRWC) to SRWC, the author found that when SRWC was above 60%, the change of LRWC was mild, nearly keeping on the same level, which was suggested to be the result of adjustment of leaf metabolic reaction. The adjustment also made Pn to become insensitive to stomatal closure, while Tr was always keeping sensitive to stoma, which resulted in single leaf WUE of enhancing. When SRWC was about 65%, WUE reachedthe maximum. With more drought and SRWC was less than 60%, Pn became sensitive to stomatal closure since the adjustment of leaf metabolic reaction was limited, which resulted in single leaf WUE of decreasing. It was concluded from the above results that SRWC 60% was the key to water-saving irrigation at seedling stage of maize. Under this soil water content, LRWC decreased rapidly and the growth was restrained. By analysing with leaf water potential , it can be found that stoma was the most sensitive to with leaf water potential when at -0.8Mpa, and it was also a crucial point to Pn and Tr.In constant soil water treatment, the effects of soil relative water on different physiological parameters of maize seedling were studied. It was found that Pn and Tr decreased when SRWC was 40%-70%, while WUE was little affected. At the same time, light use efficiency, carboxylated efficiency and the growth of maize were hardly affected when SRWC was 70%. Based on above results, it was infered that SRWC 70% was the upper threshold for proper water-providing and it was of little benefit to water-saving beyond this range.By rewatering for different invariable soil relative water to 100% FWC, the author found that Pn and WUE restored to normal level, and even exceeded the normal level. The intensity and occurring time of compensatory effects was changed with soil water level and days after rewatering. Especially, light use efficiency of maize showed compensatory reponse, and carboxylated efficiency was increased a lot when rewatering from 50%-70% to 100% FWC. So, 50% FWC can be considered to be the minimum value of water-saving during seedling stage of maize.The present studies provided theoretical basic for water-saving irrigation and were helpful to ascertain the proper water-providing range for seedling of更多还原