Abstract: Sodium nitroprusside（SNP） was used as nitric oxide（NO） donor， the effects of different concentrations of exogenous NO on the protocormlike bodies（PLBs） from Dendrobium officinale， including the growth， chlorophyll content， the activity of sucrose synthase （SS） and the accumulation of polysaccharide were studied. The results showed that a low level of SNP was beneficial for the growth of protocormlike bodies， but the high level of SNP could promote the synthesis of polysaccharide. The dry weight of PLBs cultured in 0.50 mmol·L-1 SNP medium was 36.9% more than its control on the 28th day， and the total chlorophyll content on the 14th day was 1.33 times of the control. The polysaccharide content in the treatment of 1.00 mmol·L-1 SNP was 1.59 times of the control， while the activity of sucrose synthetase significantly increased. Taken together， 0.50 mmol·L-1 SNP showed the best effect， which could promote the dry weight， chlorophyll content， sucrose synthetase activity and the content of polysaccharide， and the above indexes were significantly higher than other treatments. While cPTIO， nitric oxide scavenger， was added， the growth of PLBs， sucrose synthase activity and polysaccharide accumulation were all inhibited.

Key words: Dendrobium officinale, protocormlike bodies, nitric oxide, chlorophyll, sucrose synthase, polysaccharide