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

Abstract

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 pro-portion of opened PSII reaction centers (indicated by qP) decreased under drought stress, thus drought restricted the utilization of light-energy in PS Ⅱ (F'v/F'm) and the exertion of photosynthetic function (LPFD). SNP could help to increase photosynthetic pig-ment 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 (F'v/F'm). 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.