外源一氧化氮供体SNP对受旱小麦光合色素含量和PSⅡ光能利用能力的影响

Effects of Exogenous Nitric Oxide Donor Sodium Nitroprusside on Photosynthetic Pigment Content and Light Use Capability of PS Ⅱ in Wheat under Water Stress

以-0.5MPa PEG模拟干旱胁迫,0.1mmolL-1SNP作为外源NO供体,从荧光诱导动力学角度研究了干旱胁迫下SNP对小麦光合色素含量的变化和PSII光能利用能力的影响。结果显示,干旱胁迫虽然引起光合色素含量的增加,却减少了PSⅡ反应中心的开放比例(qP),从而限制PSⅡ对光能的利用(F'v/F'm)和光合功能的正常运行(LPFD)。经SNP和PEG同时处理的小麦光合色素含量明显增加,细胞膜相对透性降低,避免因干旱引起的光合功能的限制(LPFD);SNP还能增加受旱小麦PSII开放反应中心的比例(qP),使更多的光能传递给PSⅡ反应中心,减少激发能用于非光化学反应的热耗散(NPQ),从而促使更多的激发能用于光化学反应(F'v/F'm)。另外,SNP减轻了干旱胁迫对PSⅡ反应中心施加的激发压力,引起QA的还原程度(1-qP)降低。因此,干旱条件下外源NO供体SNP可能参与了受旱小麦光合色素的合成和PSⅡ对光能的利用。

Nitric oxide （NO） has emerged as a key molecule involving in the regulation of various abiotic stresses that induces physiological responses in plants. NO acts as an antioxidant to protect chloroplast from oxidative damages by maintaining chloro- plast membrane intactness, thus keeps high activity of PS II. The experiment was conducted under PEG stress of -0.5 MPa, while we chose 0.1 mmol L^-1 sodium nitroprusside （SNP） as NO donor. The effects of SNP on the content of photosynthetic pigments and the ability of utilizing the light in PS II of winter wheat （Triticum aestivum L.） under drought stress were studied through chlorophyll fluorescence kinetic technique. The results showed that the content of photosynthetic pigment increased, but the proportion of opened PSII reaction centers （indicated by qp） decreased under drought stress, thus drought restricted the utilization of light-energy in PS II （Fv/Fm） and the exertion of photosynthetic function （LpFD）. SNP could help to increase photosynthetic pigment content, and decrease the cell permeability, thus avoided decreasing the confined value of photosynthetic function （LpFD） by drought. Furthermore, SNP increased the proportion of opened PS II reaction centers （indicated by qp）, leading to transference of the more excited light-energy to PS II function center, decreased the dissipation of excited energy in antenna pigments （NPQ）, which increased the more absorbed light to participate in photochemical reaction （Fv/Fm）. In addition, SNP alleviated the excited pressure in PS II reaction center imposed by drought and lowered the deoxidization of QA （1 - qp）. Therefore, exogenous nitric oxide donor （SNP） may participate in the synthesis of photosynthetic pigments and the utilization of light-energy in PS II of wheat under drought stress.