拔节期干旱和复水对春玉米物候的影响及其生理生态机制

Phenological change and its ecophysiological mechanism of spring maize responding to drought at jointing stage and rewatering

物候不仅是气候变化的指示指标,也是作物模型的关键参数。现有研究主要关注物候变化与气候环境因子的关系,关于植物物候变化的生理生态机制研究很少。基于春玉米拔节期干旱与不同时间(抽雄期和吐丝期)复水的田间模拟试验分析表明:(1)不同时间复水均使灌浆期延长,乳熟期推迟(9d),表明物候对前期水分胁迫存在记忆。(2)干旱条件下叶片净光合速率(Pn)、蒸腾速率(Tr)、气孔导度(Gs)和相对叶绿素含量(SPAD)均随物候进程呈先降后升再降趋势,且均在抽雄期达到极小值;不同时间复水均使Pn、Tr和Gs在吐丝期达到极大值,而SPAD则在灌浆期达到极大值;叶水势(LWP)随干旱进程整体呈下降趋势,不同时间复水均只是减缓了其下降速度,表明LWP可用于描述物候对前期水分胁迫的记忆。(3)通径分析和决策系数分析表明,Pn是最主要的物候影响因子,而影响LWP的土壤相对湿度(RSWC)则是物候的主要控制因子,物候的变化是由Pn的累积变化引起,表明存在Pn的物候触发阈值。研究结果为春玉米物候变化的准确预测提供了依据。

Plant phenology is extremely sensitive to climate change.Shift in the timing of plant phenological events serves as a powerful biological indicator of climate change.In the context of global warming,plant phenology has changed accordingly.These changes,in turn,affected the climate system,and exacerbated or mitigated climate change.In particular,plant phenology is also a key parameter of ecosystem model,and it is of great significance to understand the mechanism of phenological changes for improving the simulation precision of the model.Although plant scientists have always been interested in the physiological basis of controlling plant phenological stages,the previous studies mainly focused on the monitoring of phenological changes and the statistical relationship between phenological changes and climatic factors.Few studies have been conducted on the ecophysiological mechanisms of plant phenological changes.The data of phenology and corresponding ecophysiological observation of spring maize was obtained from field simulation experiment that controlled water at jointing stage and rewatering at tasseling or silking stage,respectively.We analyzed the phenological characteristics of spring maize and its relationship with the change of ecophysiological factors,and revealed the ecophysiological mechanism of phenological changes of spring maize.The results are as follows:(1)After the water control at jointing stage,the filling stage was prolonged and the milking stage was delayed(9 days)regardless of rewatering at tasseling or the silking stage.It indicated that the phenology of spring maize would be affected by water control significantly at jointing stage even though rewatered at tasseling or silking stage,and spring maize phenology had memory for early water control.(2)The leaf net photosynthetic rate(Pn),transpiration rate(Tr),stomatal conductance(Gs),and relative chlorophyll content(SPAD)of spring maize showed a trend of decrease⁃increase⁃decrease with time.The Pn,Tr,Gs,and SPAD reached the local minimum at tasseling stage under the water control at jointing stage.The Pn,Tr,and Gs reached the local maximum at silking stage and SPAD reached the local maximum at filling stage after rewatering at tasseling or silking stage.The leaf water potential(LWP)presented a downward trend over time,but only slowed down after rewatering,reflecting that LWP might indicate the memory of early water stress.(3)Path analysis and decision coefficient analysis showed that Pn was the most important factor affecting phenology.The relative soil water content(RSWC)affecting LWP was main control factor.The phenology was only affected by the accumulated change of Pn,indicating that there was a trigger threshold of accumulated Pn in phenology changes of spring maize.The results could improve the ecophysiological cognition of the phenological changes and provide a basis for accurate prediction of the phenological changes of spring maize.