适当遮光对高温强光下番茄幼苗叶片光合功能的影响

Effects of Appropriate Shading on Photosynthetic Function of Tomato Seedling Leaves under High Temperature and High Light

以番茄品种辽园多丽为试验材料,研究适当遮光对番茄越夏栽培过程中常遭遇的高温强光(HH, high temperature and highlight)对叶片光系统Ⅱ及光合机构恢复能力的影响。结果表明:HH和HH下适当遮光(HL, HH with proper shading)均导致番茄幼苗叶片的光合作用效率显著降低,非气孔性限制起主导作用。番茄幼苗叶片PSⅡ反应中心活性降低,PSⅡ电子传递受阻,PsbO和PsbA基因相对表达量降低,即HH和HL对番茄幼苗叶片的主要作用位点为PSⅡ供体侧放氧复合体(OEC)和PSⅡ受体侧QA向QB的传递过程,其原因主要与OEC功能的破坏及D1蛋白的降解有关。HH胁迫下PsbA基因相对表达量降低幅度大于PsbO,并且标准化OJIP曲线上2 ms处相对可变荧光(VJ)的增加幅度大于0.3 ms处相对可变荧光(VK);HL胁迫下PsbA和PsbO基因相对表达量均有降低,但幅度小于HH。说明HH胁迫对番茄幼苗PSⅡ受体侧的伤害程度大于供体侧,HL胁迫下番茄PSⅡ供体侧和受体侧均有损伤,但伤害程度较弱。经12 h恢复后,HH和HL的光合作用能力均有不同程度的提高,适当遮光提高的程度较多,且PSⅡ供体侧和受体侧基本可以恢复到对照水平。此外,HH和HL下番茄幼苗PSⅡ反应中心对光能的捕获及利用能力降低,单位面积有活性反应中心的数量和吸收光能用于电子传递的能量比例均有不同程度的下降,PSⅡ反应中心吸收光能多以热能形式进行耗散。HH和HL经12 h恢复后均有不同程度的增加,HL增加的幅度较明显。因此,在番茄设施越夏栽培的种植和推广时,可以考虑通过遮光网适当遮光的方式缓解高温强光对番茄的产量和品质造成的影响。

To explore the effect of appropriate shading on the photosystem Ⅱ and recovery during the tomato summer cultivation under high temperature and high light(HH), the tomato variety ’Liaoyuan duoli’ was used as the experimental material. The results indicated that photosynthesis of HH and HH with proper shading(HL) was significant inhibited, and stomatal factor plays an important role. In addition, the activities of PSⅡ reaction center in tomato seedling leaves decreased, PSⅡ electron transport was blocked, and the relative expression of PsbA and PsbP genes decreased, which implied that the main action site in response to HH was PSⅡ donor side oxygen release complex(OEC) and the transmission process from QAto QBon the PSⅡ receptor side in tomato seedling leaves. The relative expression of PsbO gene was significantly higher than that of PsbA under HH stress,while the relative expressions of PsbP and PsbA gene under HL stress were all significantly decreased compared with CK, but the decline was less than HH stress. The relative variable fluorescence(VK) at 0.3 ms on the standardized OJIP curve was greater than the relative variable fluorescence(VJ) at 2 ms, indicating that the damage caused by HH stress on the donor side was greater than that in the receptor side on tomato seedlings, while the donor and receptor sides were all damaged by HL, but that was much more weak than HH. After 12 h recovery, the photosynthesis abilities of HH and HL increased to different extents,the degree of appropriate shading increased, and the donor side and receptor sides of PSⅡ could be restored to the CK level.Moreover, the ability of PSⅡ reaction center to harvest and utilize light energy, the concentration of reaction centers(expressed as per unit area of the leaf) and the ratio of excitation energy to absorbed energy were reduced. The absorbed light energy of PSⅡ reaction center was mainly dissipated in the form of heat energy, and HH and HL of absorbed light energy increased to different degrees after 12 h recovery, and the increase of HL was more obvious. Therefore, it can be considered by appropriate shading to mitigate the effects of HH in protected tomato planting over summer.