马铃薯干旱致灾过程中阈值响应及其生理机制

Around the key scientific problem of process from drought occurrence and development to disaster formation in potato, based on a field simulation experiment about the effect of progressive drought stress on potato, we try to investigate the formation process and threshold of drought disaster and physiological change mechanism of potato. In this study, the experiment on potato suffering from water stress will be carried out at Dingxi, Gansu Province, where is the main producing areas of potato in China. Six different water stress treatments will be designed under Rainout Shelter - Water Trough plots. The variation on soil moisture, physiological parameters, plant morphology and yield will be monitored during progressive soil drought. Our aims are: 1) investigate the variation on plant morphology and physiological parameters with the soil moisture decreasing during progressive soil drought, as well as their relationships; 2) determine the threshold of physiological parameters and soil moisture of potato by means of crop physiology ecology mutation characteristics and optimum partitioning clustering method, and reveal the photosynthetic physiological mechanism of threshold formation and changes; 3) determine the soil moisture range from physiological parameter mutation to yield beginning to decline, establishment threshold classification of soil drought based on physiological parameters. In this way, we will quantitatively describe the process of drought-induced disaster in potato. The results will provide some important theoretical knowledge on the drought monitoring and disaster prevention or mitigation in the main producing areas of potato in semiarid region.

围绕马铃薯干旱发生发展到灾害形成过程这一关键科学问题，在马铃薯主产区甘肃定西的遮雨棚-水分试验场开展马铃薯对持续干旱胁迫响应的模拟试验，研究马铃薯受旱致灾的临界阈值及其生理响应机制。通过监测持续干旱过程中马铃薯农田土壤水分、生理特性、形态特征、产量等指标的变化规律，分析马铃薯生理指标、产量对土壤水分持续减少的动态响应及其相互关系。利用生理特性突变特征和最优分割聚类法，确定生理指标达到最大或最小时土壤水分上限及下限阈值，揭示阈值形成及变化的光合生理机制，划分从生理参数突变到产量开始下降时的土壤水分范围，建立基于生理参数的土壤水分阈值分级，定量描述马铃薯受害致灾的土壤干旱等级。期望研究成果为半干旱区马铃薯旱情的准确监测和有效防旱减灾提供重要的理论依据。

本课题围绕马铃薯干旱发生发展到灾害形成过程这一关键科学问题，连续3年开展了马铃薯对干旱胁迫响应的大田模拟试验，进行了马铃薯干旱致灾的过程特征、阈值反应及其生理机制的研究，取得的主要结果有：1）持续干旱过程中，马铃薯农田不同深度的土壤相对含水量（SWC）在波动中持续下降，块茎形成期和块茎膨大期叶片净光合速率（Pn）、蒸腾速率（Tr）、胞间CO2浓度（Ci）、气孔导度（Cond）等光合参数都受到不同程度的限制，明显抑制了植株长高（H）、叶面积（LAI）扩大以及叶绿素（Ch）形成。2）马铃薯植株形态和生理特征对土壤水分亏缺存在敏感性差异，在块茎形成期对持续干旱的敏感指标有Pn、Cond、Tr、H、LAI（P≤0.05），其中光合生理指标对0-60cm深的土壤含水量响应较敏感。3）土壤水分变化和植株形态、光合生理特征、产量等存在一定的对应关系。采用直角双曲线修正模型对不同水分下的叶片进行光响应曲线模拟，认为在一定土壤湿度范围内，Pn和Tr随着SWC的变化先升高后降低，呈现明显的阈值反应：在块茎形成期0-60深SWC为56.5%和59.8%时，叶片Pn（16.1μmol CO2 m-2 s-1）和Tr（4.0mmol H2O m-2 s-1）达到最大值；块茎膨大期0-60cm深SWC为58.9%和58.3%时，叶片Pn（7.1μmol CO2 m-2 s-1）和Tr（1.8mmol H2O m-2 s-1）达到最大值。在受到水分胁迫时，马铃薯叶片具有明显的光抑制和光饱和点“下移”现象，这可以通过减弱对光的利用效率来适应水分胁迫。植株生理过程和土壤水分逐渐减弱的过程具有持续性和累积效应，使得受害程度逐渐加重。4）采用聚类分析法确定了不同土层基于叶片光合参数的土壤水分阈值分级，分为高产高效水（块茎形成期SWC介于53.7%-56.2%，膨大期58.8%-64.8%）、高产中效水、中产高效水、中产低效水、低产低效水等不同等级。随着土壤深度的加深，土壤水分的阈值范围加宽。5）初步确立了马铃薯农田适宜的土层水分亏缺诊断深度为0-60cm土层，不宜过大或过小。该研究结果有一定的科学意义和应用价值，可为半干旱雨养区马铃薯农田的旱情监测和防旱减灾提供一定的理论依据。