弱光下生长的高产小麦品系PH01-35旗叶光合机构对不同光强的响应

Response of Photosynthetic Apparatus to Different Irradiance in Flag Leaves of High-Yielding Winter Wheat PH01-35 Grown under Low Light Conditions

为了解弱光下生长的小麦叶片在不同光强下PS II和光合电子传递链的工作状态,解释其突然转入强光下时发生光抑制和光破坏的原因,以PH01-35为材料,采用大田人工遮光的方法,测定了小麦旗叶叶绿素含量、光合特性参数及快速光曲线。弱光处理15 d后,旗叶叶绿素含量明显上升,净光合速率、光补偿点、光饱和点、表观量子效率、羧化效率均出现不同程度的下降。与250μmol m-2 s-1的弱光适应3 h相比,1 200μmol m-2 s-1的强光适应3 h后,弱光下生长叶片的快速光曲线初始斜率下降幅度较大,曲线下降部分的斜率、最大相对电子传递速率、半饱和光强的上升幅度均小于自然光下生长的叶片,光能利用能力较低,其非光化学猝灭系数NPQ也明显低于自然光下生长的叶片,为自然光下生长叶片的87.5%。弱光下生长的小麦叶片光能吸收能力增强,但较低的光能利用能力和过剩光能耗散能力是其转入自然强光后易发生光抑制甚至光破坏的主要原因。

To further explain the mechanism of photoinhibition and light damage in wheat （Triticum aestivum L.） leaves when it was suddenly transferred from low light to high light conditions, the responses of photosynthetic apparatus in shaded leaves of the high-yielding winter wheat line, PH01-35, were examined using chlorophyll fluorescence and gas exchange techniques. After 15-day shading, the chlorophyll content increased greatly, but the net photosynthetic rate （Pn）, light compensation point （LCP）, light saturation point （LSP）, apparent quantum yield （AQY）, and carboxylation efficiency （CE） all decreased. Compared with leaves grown in full sunlight, the initial slope （a）, decline slope （13）, maximum relative electron transport rate （rETRmax）, and minimum saturating irradiance （Ek） of rapid light curves in leaves grown in low light were lower when the plant was transferred from low light intensity of 250 umol m^-2 s^-1 to high light intensity of 1 200 umol m^-2 s^-1. Non photochemical quenching （NPQ） in leaves grown in low light was significantly lower than that in leaves grown in full sunlight, indicating that the ability of light use and thermal energy dissipation was limited in leaves grown in low light. The wheat leaves grown in low light were more suscepti- ble to photoinhibition due to low CO2 assimilation and photoprotective ability, such as xanthophylls cycle-dependent dissipation of excessive energy, despite the better energy absorbability in low light conditions.