光强对玉米幼苗光合特性及环境羟基自由基水平的影响

Effects of Light Intensity on the Photosynthetic Characteristics of Maize Seedlings and the Content of Atmosphere Hydroxyl Radical

在条件可控的密闭培养室中培养玉米幼苗,改变温度、光强及水分等培养条件,动态测量玉米幼苗的光合作用指标以及培养室环境空气中的羟基自由基(.OH)水平.结果显示:在较低光照强度下,玉米幼苗叶片净光合速率(Pn)、最大光化学量子产量(Fv/Fm)、PSⅡ实际光化学量子产量(ΦPSⅡ)、光化学淬灭系数(qP)均随着光强的上升而上升.当光强增大到某一程度时,Pn、Fv/Fm、ΦPSⅡ及qP开始下降,显示高光强下玉米幼苗出现了一定程度的光抑制.无论正常生长条件或低温及渗透胁迫环境下,玉米幼苗生长的培养室空气中.OH水平均明显高于没有植物生长的对照培养室.光照强度没有达到引起光抑制出现的程度时,培养室环境中的.OH水平随光强的变化不明显;当光强上升到引起玉米幼苗出现光抑制时,环境.OH水平明显上升,并且随着光抑制程度的增加而升高.相关性分析表明,较低光照下环境.OH水平与玉米幼苗各项光合作用指标没有明显的相关性,但在光抑制情况下,环境.OH水平与光抑制程度密切相关,并与非光化学淬灭系数qN值呈明显正相关.研究结果为证明植物生长对环境.OH水平的影响提供了依据,同时表明处于光抑制状态比正常光合状态的玉米幼苗对环境中.OH水平的影响更加明显.

The maize seedlings were grown in closed incubators in could be controlled. The photosynthesis indexes of maize seedlings, in the closed incubator were dynamically measured and monitored which light intensity, temperature, and osmotic pressure as well as the content of ambient hydroxyl radical （.OH） The results showed that at lower light intensity, the net photosynthetic rate （Po）, the maximal photochemical quantum yield （FJFm）, PSII actual photochemical quantum yield （PsH）, and the photochemical quenching coefficient （qr） increased with the light intensity. When light intensity was increased to a certain extent, P,, F, JFm, qbPSll and qp began to decline, showing a certain degree of photoinhibition in maize seedlings under high light intensity. Whether in normal condition, or with chilling stress, or osmotic stress, the content of ambient .OH in the maize seedling culture room was significantly higher than the control room with no plant. The level of ambient .OH in the culture room did not obviously change with light intensity below the level that could cause photoinhibition. However, when the light intensity rose to a level that could cause the photoinhibition in maize seedlings, ambient -OH levels were significantly increased with the photoinhibition degree. Correlation analysis showed there was no significant correlation between the .OH level and the photosynthesis index of maize seedlings under lower light intensity. However, in the case of photoinhibition, ambient .OH levels were closely related to photoinhibition degree. In addition, the ambient -OH was shown to be significantly related with the non-photochemical quenching coefficient （qN）. Our research results proved the influence of plants on the ambient .OH level, and showed that maize seedlings under photoinhibition had more pronounced impact on the ambient -OH level than in normal photosynthetic state. Tab 13, Ref20