Effect of drought stress on seed germination and osmotic regulating substances of Pinus yunnanensis.

The germination test of Pinus yunnanensis seeds was conducted under artificial drought stress treated with different mass concentration of polyethylene glycol(PEG-6000) in order to explore the effect of drought stress on the seed germination by measuring the radicle length and hypocotyl length of the young seedlings.The results showed that the seed germination was promoted under the low suitable PEG mass concentration.The germination rate,the average daily germination rate and the germination index all reached the peak values under the condition with 5% of PEG-6000 mass concentration.However,the values of P.yunnanensis seed germination indexes declined along with the increment of PEG mass concentration.With the development of water stress(with the increase of concentration of PEG-6000),the length of hypocotyls was decreased gradually,whereas the radicle length increased firstly and then decreased.These results indicated that the seed of Pinus yunnanensis germination were inhibited under the high PEG mass concentration.The contents of soluble sugar and proline increased along with the increment of PEG-6000 concentration,indicating that they were the main osmotic regulating substances in the course of P.yunnanensis seed germination under drought stress.