Effects Of PEG Seed-soaking On Physiology And Biochemistry In Pepper Seedlings Leaves Under Low Temperature And Poor Light

The changes of growth indexes, osmotic adjusting substance, esistant-oxidation enzyme activities, photosynthetic characteristics and chlorophyll fluorescence parameter were investigated in seedling leaves of Xiangyan No.1 pepper and Xiangyan No.16 pepper under low temperature and poor light (15℃/5℃(day/night), 100μmol·m-2·s-1) with 25% polyethylene glycol (PEG) seed-soaking. The main results showed as follow:1. Dry weight and stem height/diameter in pepper seedlings leaves were lower than that in the control under low temperature and poor light. The reducement of dry weight and stem height/diameter treated with PEG seed-soaking were smaller under low temperature and poor light.2. Malondialdehyde (MDA) and membrane permeability increased and showed upward trend gradually during the treatment; The SOD, POD and APX activities arrived at highest value then decreased under low temperature and poor light. Compared to the control, the reducement of SOD, POD and APX activities treated with PEG seed-soaking were smaller under low temperature and poor light. It showed that PEG could protect the integrity and stability of membrane, and enhance the cold resistance of pepper seedling.3. Proline (Pro) and soluble protein (Pr) contents in pepper seedlings leaves increased and showed upward trend under low temperature and poor light. Compared to the control, the increment of Pro and Pr contents treated with PEG seed-soaking were smaller under low temperature and poor light. Extent of increment was obviously lower than that in the control.4. The net photosynthetic rate (Pn), stomatal conductance(Gs) and transpiration rate (E) decreased and the intercellular CO2 concentration(Ci) rose in different degree under low temperature and poor light. The extent of reduction of Pn, Gs, E and the extent of increment of Ci treated with PEG seed-soaking was obviously lower. The effect of photosynthesis in pepper seedlings leaves caused by low temperature and poor light was significantly decreased.5. The Fv/Fm,фPSⅡ, Fv'/Fm', qP and Chl(a+b) content in pepper seedlings leaves decreased under low temperature and poor light. The extent of reduction in Fv/Fm, Fv'/Fm', qP,фPSⅡand Chl(a+b) content treated with PEG seed-soaking was obviously lower than that in the control. PEG seed-soaking could increase the PSⅡphotochemistry activities in pepper seedlings leaves under low temperature and poor light.6. The mitigative effect of cold-sensitive pepper treated with PEG was bigger than that of low-temperature tolerant varieties under low temperature and poor light.