Study On The Physiological Characteristics Of Low K-Tolerant Rice Seedlings Under Simulated Drought

Using young seedlings of GuiBao8 and its' aberrant offspring(D4 generation ) introduced into exogenous gene as the experimental materials,the morphologic characteristics of the root system and its physiological and biochemical change and their drought-resistance were studied under 20%PEG6000 treatment to simulate drought.The results showed as follows:1. Under the treatment,the root length of strain was enhanced to a certain extent, while the root weight was inhibited,and almost stop at late stage of stress. There are obvious difference between GuiBao8 and its' offspring(D4 generation ) under treatment with drought and the control under normal irrigation,but there was no significant difference between the treated materials under drought.2. Under the treatment,the evident changes of physiological metabolism were observed, leaf RWC water potential and the active uptake area of root were all decreasing. The balances were destroyed between free radical and scavenging agents, the cell membrane was injured because of the accumulation of active oxygen.MDA contents and electrolytic coefficient of membrane permeability increased. While SOD firstly increased and then decreased,and Pro contents increased rapidly.Root activity had the same trend as SOD.There was no significant difference between the materials under normal irrigation,while the significant difference was found between GuiBao8 and its' aberrant offspring(D4 generation ) under drought stress.3. Under the treatment,the photosythesis of seedlings was strongly inhibited.It was mainly due to the decrease of stoma conductance and the concentration of intercellular CO₂ at early stage. With the stress time extended,the concentration of CO₂ increased gradually,yet stoma conductance still decreased,the inactive photosynthetic components became the main inhibition factors.There was significant positive correlation between transpiration and phothsynthetic rate(R=0.98).The phothsynthetic rate,stoma conductance and transpiration of the aberrant offspring were higher than the GuiBao8 under drought stress.This suggested,from the view of photosynthetic characteristic,that the drought resistance of aberrant offspring was stronger.Under the treatment,the drop of leaf water potential,leaf RWC,the absorption area of root of the aberrant offspring was smaller than GuiBao8 and its ascend range of MDA contents,Pro contents and electrolytic coefficient of membrane permeability were smaller too.However its SOD activity and root activity were higher than GuiBao8, moreover,there were significant or highly significant differences between all the indexes.These indicated that the comprehensive drought resistantce of the aberrant offspring was stronger than GuiBao8.