外源一氧化氮对干旱胁迫下玉米幼苗光合作用的影响

【目的】探明干旱胁迫下一氧化氮(NO)对玉米幼苗光合作用的调节作用。【方法】以驻玉309为试验材料,在光照培养箱内采用水培的方法,研究了外源NO供体SNP预处理3 d后,进行20%PEG-6000(-0.8 MPa)模拟干旱胁迫3 d后玉米幼苗的生长参数、叶绿体超微结构、叶片气体交换参数、叶绿素荧光参数和D1蛋白表达的变化。【结果】干旱胁迫条件下玉米幼苗的光合速率(Pn)、气孔导度(Gs)及光系统II(PSII)最大光化学效率(Fv/Fm)、PSII潜在活性(Fv/Fo)分别比对照下降了68.4%、87.2%、15.8%、31.3%;而J点的相对可变荧光(Vj)和单位反应中心耗散能量(DIo/RC)则分别上升了20.9%和21.2%;此外,叶片的叶绿体结构明显遭到破坏,D1蛋白的含量显著降低。但是,与干旱胁迫处理相比,经过SNP预处理后进行干旱胁迫处理的玉米幼苗Pn、Gs、Fv/Fm、Fv/Fo明显增加56.6%、202.5%、15.8%、30.7%,而Vj、DIo/RC下降了22.7%和25.4%;叶绿体的类囊体片层恢复整齐,基粒片层变清晰;D1蛋白的相对含量明显增加了94.7%;以上这些变化与干旱条件下SNP预处理后NO含量的增加有关。【结论】在干旱条件下,NO可能参与调节了PSII反应中心D1蛋白的表达并稳定PSII反应中心的结构和功能,以改善玉米幼苗的光合作用和生长发育,从而提高玉米幼苗对干旱胁迫的适应性。

Effects of Exogenous Nitric Oxide on Photosynthesis of Maize Seedlings Under Drought Stress

【Objective】To evaluate the effects of exogenous nitric oxide on the photosynthesis of maize (Zea mays L.) under drought stress. 【Method】The hydroponic experiment was conducted in a growth chamber with the Zhuyu 309 as the material. After being pretreated with sodium nitroprusside (SNP) for three days, these materials were simulated drought stress with 20% PEG-6000 for another three days. The changes of maize seedling’s growth, gas exchange, and chlorophyll fluorescence parameters, chloroplast ultrastructure and expression of D1 protein were investigated; 【Result】The photosynthetic rate (Pn), stomatal conductance (Gs), PSII maximum photochemical efficiency (Fv/Fm), PSII potential activity (Fv/Fo) were decreased by 68.4%, 87.2%, 15.8%, 31.3%，respectively under drought stress; The parameters of relative variable fluorescence intensity at J-step (Vj) and dissipated energy flux per reaction center (DIo/RC) increased by 20.9% and 21.2%. The ultrastructure of chloroplast in the leaf was destroyed and the structure of stacked grana was disintegrated. Moreover, the osmiophilic grains increased and the chloroplast was slowly divorced from the cell wall due to the drought. The content of D1 protein decreased significantly with Western-blotting analysis. However, with the treatment of SNP and then drought stress, the Pn, Gs, Fv/Fm, Fv/Fo were increased by 56.6 %, 202.5 %, 15.8 %, 30.7 % and the Vj decreased by 22.7% and 25.4% compared with the drought stress. The thylakoid lamellae arranged regularly and the grana were clear; and the relative amounts of D1 protein increased by 94.7%. The above changes were related to the increased NO content after SNP pretreatment under drought condition.【Conclusion】These results suggested that NO is involved in regulating the D1 protein expression and stabilizing the structure and function of PSII reaction centers to improve photosynthesis and growth of maize seedlings, which improved the adaptability of maize seedlings to drought stress.