Abstract: Based on cotton flooding experiment of different duration through pot culture in seeding stage,a series of physiological indices in leaf,such as chlorophyll content(Chl),chlorophyll relative value(Rc),chlorophyll fluorescence(F0,Fm),malondialdehyde(MDA),nomadic proline(Pro),dissoluble sugar(DS),peroxidase(POD)and superoxide dismutase(SOD),were observed,to analyze the responses to waterlogging stress.The results indicated that,after waterlogging,chlorophyll hydrolysis rate was higher at the first 3 days,the peak value of chlorophyll fluorescence decrease occurred between the 6th to 9th day.It figured that stagnant water on the field should be drain off in 3 days after waterlogging stress,to avoid the photosynthetic efficiency being strongly inhibited.The balance of normal physiological metabolic process in cotton leaf was broken after waterlogging,some new negative changes occurred,as MDA content increasing and the activity of SOD decline.Some other positive changes were accompanied,as the increasing of DS and Pro content and the activity of POD,for protecting active tissues.These physiological indices appeared regularly changing characterized by fast-slow-fast,which can be simulated in unary cubic regression curve model.

Key words: Waterlogged stress, Physiological metabolism, Chlorophyll content, Chlorophyll relative value, Chlorophyll fluorescence, Malondialdehyde, Dissoluble sugar, Nomadic proline, Superoxide dismutase, Peroxidase