苗期玉米叶片光合特性对水分胁迫的响应

以2个抗旱性不同的玉米品种为材料进行盆栽试验,在苗期设置4个水分梯度,研究气体交换和叶绿素荧光参数及光响应特征。结果表明:随水分胁迫的加剧,除细胞间CO2浓度(Ci)和非光化学淬灭(qN)上升外,其它参数均下降,先玉335(XY335)各参数的变化幅度小于陕单902(SD902);轻度胁迫下品种间气体交换参数差异最大,严重干旱下叶绿素荧光参数差异最大;净光合速率(Pn)和相对电子传递速率(rETR)的光响应曲线拟合结果显示,水分胁迫导致玉米叶片最大光合速率和光能利用率下降,XY335各参数的下降幅度小于SD902;轻度干旱下Pn光响应拟合参数品种间差异最大,严重干旱下rETR光响应拟合参数差异最大。综上表明,水分胁迫导致玉米叶片对强光的敏感性增加,干旱和光抑制对光系统Ⅱ造成的叠加伤害随干旱加重和品种抗旱性弱而加剧,是制约光合作用的主要原因;旱区强光下的玉米幼苗应及时补水,以避免严重干旱和高光强的叠加伤害。

Response of photosynthetic characteristics to water stress of maize leaf in seeding

The response of photosynthetic characteristics in two different drought-resistant maize varieties (XY335 and SD902) was studied by measuring gas-exchange and modulated chlorophyll fluorescence under 4 different water stresses in pots. The result shows that, except Ci and qN increasing, other parameters decreased when increasing water-stress. All parameters of XY335showed little change than SD902.The maximum difference of gas-exchange parameters in light drought between two maize hybrids, However, chlorophyll fluorescence parameters show it in serious drought. Fitted results from photo-repose curves of Pn and rETR showed that water stress has induced photosynthetic potential and light use efficiency, as well as promote photoinhibition, all fitted parameters of XY335 showed little change than SD902. The fitted parameters from photo-repose curves of Pn show the most obvious variance in light drought, the fitted parameters from photo-repose curves of rETR show it in serious drought between two maize hybrids. Summing up and draws a conclusion, increased sensitivity of maize leaves to highlight under water stress. Main cause restraining factors of photosynthesis was that, Photo-system can be overlapping injury by drought and photoinhibition, which Injury will be further intensified as water-stress exacerbated and drought resistance reduced of maize varieties. Maize seedling should make-up water in time to avoid the overlapping injury by drought and photoinhibition under strong light in arid area.