Effects of PEG Simulated Drought Stress on Seed Germination and Growth Physiology of Quercus variabilis

In order to study the water tolerance of Quercus variabilis in seed germination stage,the effects of different concentrations(0%,5%,10%,20%,30%)of PEG stress on seed germination,growth,protective enzyme activities and the organic osmoregulation substances were measured with choosing fresh cork oak seeds and using Petri dish and filter paper germination method.The correlation analyses were done between seed germination,radicle growth rate and PEG stress.The results showed that:(1)With the increasing of drought stress,seed germination rate,vigor index,germination index and radicle length of cork oak were all increased then decreased,showing that low concentration PEG stress(5%,10%)can promote the cork oak seed germination and growth,whereas high concentrations(20%,30%)had inhibition effects.(2)The regression equation between seed germination,radicle growth rate and PEG stress showed that the critical and the maximum value of the seed germination of Q.variabilis were 32.01% and 36.99%,while the corresponding radicle growth rates were 30.1% and 33.35% under the PEG stress.(3)With the increase of PEG concentration,three protective enzyme(SOD,POD and CAT)activities and contents of three kinds of organic osmoregulation substances were presented different responses,but had a same rising trend.Thus it can be seen that cork oak seeds increased protective enzyme activities and contents of osmotic regulation substances in vivo to adapt to the water stress,making the inhibition degree of germination and growth to the minimum.