外源NO调控小麦幼苗生长与生理的浓度效应

Effects of exogenous nitric oxide at different concentrations on the growth and physiology of winter wheat seedlings

在室内人工控制条件下，研究100～2000μmol·L^-1 5个浓度梯度的SNP（外源NO供体）处理后小麦幼苗的生长、水分生理和光合能力的动态变化，探讨外源NO优化调控小麦幼苗生长生理的最适浓度。结果表明，不同的SNP浓度对小麦幼苗地上部和根系的生长具有不同的促进或抑制作用，低浓度（100～200μmol·L^-1）SNP明显增加了根系的可溶性糖、游离氨基酸等渗透调节物质含量，但对根系的干物质积累影响不大。浓度超过200μmol·L^-1的SNP处理后，根系的干物质积累降于对照以下，渗透调节物质含量也开始降低。低浓度SNP处理（100μmol·L^-1）明显改善了小麦叶片的光合性能从而促进地上部干物质与渗透调节物质的积累，且增加了叶片的水势和渗透势。另外，叶片的气体交换参数（Pn、Gs）和叶绿素荧光参数（qP、NPQ）对SNP的反应也表现出明显的浓度效应。因此，外源NO对小麦幼苗生长生理的调控具有一定的剂量效应，100μmol·L^-1 SNP对小麦幼苗生长生理的调控作用最明显。

The dry-matter accumulations and osmotic substances soluble sugar （SS） and free amino acids （FAA） of Triticum aestivum L. shoots and roots, as well as water and osmotic potentials, gas exchanges and chlorophyll fluorescence parameters of the 2^nd leaves numbered from top to down in response to the signals of NO at different concentrations were determined after they were treated with SNP （NO donor, Sodium nitroprusside, Na2Fe （CN）5） at five different concentrations ranging from 100 μmol·L^-1 to 2000 μmol·L^-1. The experiment was conducted under controlled conditions in laboratory. It showed that at different concentrations NO had different effects on the growths of the shoots and roots. At low concentrations SNP significantly increased osmotic substances of the roots at the beginning, but it had less effect on the dry-matter accumulations of the roots. After treated with SNP at 100 μmol·L^-1, the roots significantly increased their SS amount to be transported into shoots, but after treated with SNP at more than 100μmol·L^-1, the leaves decreased their SS amount and dry-matters. The content of FAA was maximal in the treatment with SNP at 200μmol·L^-1. The regulating effects of NO gradually declined with increased SNP concentrations. The dry-matter accumulation and osmotic substances of roots decreased in the treatments with SNP （ at more than 200 μmol·L^-1 ）. The shoots were more sensitive than the roots in response to NO signals. At low concentrations （100 μmol·L^-1） SNP significantly increased the Pn and decreased the Gs of the leaves so that they accumulated more dry-matter and the two osmotic substances （SS, FAA）, and increased their water potential and osmotic potential. In addition, at low concentrations SNP maintained the PSII reaction centers open （qP）, and increased the dissipation of excessive light energy （NPQ）. The effects of NO on the gas exchanges and chlorophyll fluorescence parameters were concentration dependent. Therefore, SNP significantly promoted the growth and regulatd the physiology of wheat seedlings at 100 μmol·L^-1 Hb is a NO inhibitor, and NaNO2 is a by-product of SNP. The experiment proved that NO signals the photosynthesis of wheat seedlings in SNP.