不同生育期玉米叶片光合特性及水分利用效率对水分胁迫的响应

利用大型移动防雨棚开展了玉米水分胁迫及复水试验,通过分析玉米叶片光合数据,揭示了不同生育期水分胁迫及复水对玉米光合特性及水分利用效率的影响。结果表明:水分胁迫导致玉米叶片整体光合速率、蒸腾速率和气孔导度下降以及光合速率日变化的峰值提前;水分胁迫后的玉米叶片蒸腾速率、光合速率和气孔导度为适应干旱缺水均较对照显著下降,从而提高了水分利用效率,缩小了与水分充足条件下玉米叶片的水分利用效率差值;在中度和重度水分胁迫条件下,玉米叶片的水分利用效率降幅低于光合速率、蒸腾速率和气孔导度的降幅, 有时甚至高于正常供水条件下的水分利用效率;适度的水分胁迫能提高玉米叶片的水分利用效率,从而增强叶片对水分的利用能力,抵御干旱的逆境;水分亏缺对玉米光合速率、蒸腾速率及水分利用效率的影响具有较明显滞后效应,干旱后复水,光合作用受抑制仍然持续;水分胁迫时间越长、胁迫程度越重,叶片的光合作用越呈不可逆性;拔节-吐丝期水分胁迫对玉米叶片光合作用的逆制比三叶-拔节期更难恢复。

Response of water stress on photosynthetic characteristics and water use efficiency of maize leaves in different growth stage

The field experiments of water stress and rewatering for maize were carried out using the large moving water-proof shed. The effects of water stress on the photosynthetic characteristics and water use efficiency of maize in different growth stages were revealed by the photosynthetic data of leaves. The results showed as followed: water stress led to the decrease of the values of photosynthesis rate, transpiration rate and stomatal conductance and the earlier emergence of peak value of the daily variation of photosynthesis. Compared with the control, the transpiration rate, photosynthesis rate and stomatal conductance of maize leaves were decreased significantly, in order to adapt to the drought under the water stress condition so that the water use efficiency was improved and the difference of water use efficiency between the water stress and normal condition was shrunk. Under moderate or severe water stress condition, the decrease of water use efficiency was less than that of the photosynthesis, transpiration rate and stomatal conductance of maize leaves and the water use efficiency was sometimes even higher than that of the normal environment. The water use efficiency of maize leaves was improved under moderate water stress so that the ability of leaf using water was enhanced and maize better resisted drought environment; the subsequent effects of water stress on photosynthesis and transpiration and water use efficiency was obvious. After water stress and rewater treatments, the inhibition of photosynthesis of maize leaves was still continued. Longer time and more severe the water stress was, the more nonreversible the photosynthesis of maize leaves might be. The inhibition of water stress on photosynthesis of maize leaves was more difficult to recovery from the jointing to silk stage than from three leaf to jointing stage.