Effects Of Different Pretreatment On Photosynthetic Apparatus Of Rice Under Water Stress

Water stress severely affect plant growth and development, it has become one of themajor environmental factors, and limited global crop yield and quality. Rice is an importantfood crop in china, and requires higher water. At present, arid, semi-arid area of the regionhas gradually increased in china, and how to improve the drought resistance of rice hasbecome one of the hot research topics. Many studies have shown that pretreatment canimprove plant resistance, and also enable the plant to show cross adaptation. Photosynthesisis the basis of plant growth and development, so study the response of photosyntheticapparatus mechanisms to water stress is particularly important. Therefore, rice was pretreatedin the seed stage, to study the effects of different pretreatment on photosynthetic apparatus ofrice under water stress.In this experiment, we used rice (Oryza sativa L.) as trial material which was pretreatedin seed stage with H₂O,10%PEG,1mMSA,0.1mM the ABA,100mMNaCl solution, riceseedlings were determined in15%PEG-simulated drought stress, photosynthetic pigment(chlorophyll a, chlorophyll b, chlorophyll a+b, chlorophyll a/b), photosynthetic parameters(net photosynthetic rate (Pn), stomatal conductance (Gs), internal CO2concentration (Ci),transpiration rate (Tr)) and fast chlorophyll fluorescence induction kinetics parameters (PS IIreaction center parameters, PS II donor side parameters, PS II acceptor side parameters). Toexplore the differences of photosynthesis, photosynthetic pigments and PSâ…¡under waterstress between pretreatment group and control group (control group without any pretreatment,but for15%PEG stress in the latter period). Results were showed as follows:1. Water stress for2days and4days, Chla, Chlb and Chla+b content of pretreatmentgroup were higher than those of control group for rice seedling leaves, Chla/b ratio is lowerthan control group, indicating that pretreatment can effectively alleviate damage ofchlorophyll under water stress, by improving the content of photosynthetic pigments toenhance photosynthetic characteristics of rice seedlings.2. With the time prolonged under water stress, net photosynthetic rate (Pn) of controlgroup and H₂O pretreatment group decreased significantly, PEG, SA, ABA, and NaClpretreatment can alleviate the reduction of photosynthetic rate, and have a higherphotosynthetic rate of rice under water stress. We also found that control group in later timeof water stress non-stomatal factors is limiting factor in reduced photosynthetic rate, stomatal factors on the photosynthetic characteristics of rice seedlings under water stress can bealleviated by pretreatment of PEG, SA, ABA and NaCl.3. Control group and pretreatment group Wkalmost has no change with the timeprolonged water stress, which indicates that15%PEG water stress has no harm to donor sideof PS II. Water stress for2days, PSII reaction center and PS II acceptor side of control groupwere slightly harmed, but it showed no significant difference compared with pretreatmentgroup on water stress for4days. With the time prolonged under water stres, pretreatmentdidn't make the relevant parameters of PS II reaction center, donor side and the acceptor sidechange, suggesting that pretreatment can maintain PS II a high activity. The summary showsthat15%of PEG water stress does not significantly cause impact of PS II.