Abstract:The white garlic were fumigated with different concentrations of NO gas (0.1, 0.5, 1.0 μmol·L-1) under anaerobic conditions. The photosynthetic parameters of garlic sprouts were determined with TPS-1 photosynthesis system or calculated according to the theory of Farquhar and Sharkey. The content of RuBP carboxylase-oxygenase (Rubisco) was also assayed simultaneously. Compared to 1.0 μmol·L-1 NO treatment, 0.5 μmol·L-1 NO resulted in increases in net photosynthetic rate (Pn) and stomatal conductance (Gs) ,which were accompanied by decreases in intercellular CO2 concentration (Ci) and stomatal limitation values (Ls) in garlic sprouts. The results showed that the main reason of photosynthetic rate in garlic sprouts treated with 0.5 μmol·L-1 NO was higher than 1.0 μmol·L-1 NO was caused by non stomatal factor. Furthermore, 0.5 μmol·L-1 NO enhanced apparent quantum yield(AQY), carboxylation efficiencies(CE), photosynthetic capacity(Ao), Rubisco content, These results indicated that exogenous NO can improved ability of light reaction, the efficiency of carbon assimilation of and stomatal limitation values in garlic sprouts. Compared to control treatment，1.0 μmol·L-1 NO caused the reduction of Pn, Gs, Ci, AQY，Rubisco content, CE and the enhancement of Ls in garlic sprouts. These results showed that the inhibitive effect of 1.0 μmol·L-1 NO treatment on photosynthetic of garlic sprouts caused by stomatal factor and non stomatal factor together. However, all parameters of 0.1 μmol·L-1 NO treatment had no difference.