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 2nd 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 100 μmol•L-1, the leaves decreased their SS amount and dry-matters. The content of FAA was maximal in the treatment with SNP at 200 μmol•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.