Effects of osmotic stress caused by NaCl or polyethylene glycol on root growth of maize at seedling stage

Lower osmotic stress caused by drought or salinity at early stage of plants is an important reason for reduction of plant growth.It is still unknown,however,whether the osmotic stress arising from these two different factors inhibit the root growth through same wise.In this experiment the root growth of three maize varieties Denghai 11,Zhengdan 958,Suyu 16 was measured by Root Analysis System under isoosmotic stress caused by NaCl or polyethylene glycol(PEG).The results showed that root growth of salt-resistant maize was greatly reduced under osmotic stress arising from PEG than the same osmotic stress arising from NaCl.As for drought-resistant maize,it showed an opposite tendancy.Lower osmotic stress caused by NaCl or PEG led to decease root length of all maize varieties used in this experiment,but their effect on average root diameter could be observed significantly only in salt-resistant variety.These phenomenon showed that the effect of lower oxmotic stress arising from NaCl on maize root development was different from that caused by PEG,which means a different response mechanism of plants between salt stress and drought stress.Reducing degree of root growth under salt stress may be an adaptive capacity of salt-resistant variety to saliferous environment.