Effects of Drought Stress Simulated by PEG 6000 on Physiological Characteristics of Lobe-leafed Non-heading Chinese Cabbage(Brassica rapassp.chinensis)

In order to evaluate drought resistance of non-heading Chinese cabbage NILs(near isogenic line)of 11Hlines characterized by leaf-lobed phenotype and 11Blines characterized by smooth margin phenotype,the leaf wilting index and physiological changes were examined in a hypertonic gradients created by PEG-6000.The results indicated that with the increase of PEG concentration,their leaf wilting index,water loss rate,relatively permeability of plasma membrane and content of malondialdehyde(MDA)increased gradually.All the indexes were significantly greater than the control(CK), while there was a greater increase in 11Hcompared with 11B.The leaf relative water content of 11B and 11Hdecreased gradually with the increase of PEG concentration.As for 11B,with the drought stress intensity increasing,the activity of superoxide dismutase(SOD),peroxidase(POD)and catalase(CAT)showed the trend of increasing initially and then decreasing.Compared with 11B,the POD activity of 11Hincreased primarily and then decreased,lastly maintain at a high level.The SOD and CAT activity of 11Hincreased gradually.At high concentration of PEG,the SOD and CAT activity of 11H were higher than that of 11B.After comparing the physiological characteristics between11Hand 11Bat the different concentrations of PEG stress,we draw the conclusion that the droughtresistant ability of 11H was greater than 11B.