EFFECTS OF LOW TEMPERATURE STRESS ON CHLOROPHYLL FLUORESCENCE CHARACTERISTICS OF COM SEEDLINGS

Low temperature stress is one of major abiotic factors to limit the yield and quality of corn crop.To investigate the effects of low temperature stress on the photosynthesis process,three-leaf stage corn(Zea mays L.Chuandan No.25) seedlings were subjected to several temperature levels(25 ℃,20 ℃,15 ℃,10 ℃,5 ℃ and 0 ℃) for 1 h.Subsequently chlorophyll fluorescence and light response curve were determined.The data obtained in this experiment showed that,as the treatment temperature decreased,the maximum fluorescence(Fm),potential photochemical efficiency(Fv/Fo),maximum photochemical efficiency of PSⅡ(Fv/Fm),the photosynthetic electron transport(ETR),actual photochemical efficiency of PSⅡ(Yield),and photochemical quenching coefficient(qP)were decreased gradually.In contrast,the minimal fluorescence(Fo),and non-photochemical quenching coefficient(qN) were increased.Moreover,the low temperature stress also had some deleterious effects on the apparent quantum(α),the maximal relative electron transport rate(rETRmax) and the semi-saturation light intensity(Ik).These results indicated photosynthesis of corn seedlings is very sensitive to low temperature stress and low temperature damaged the photosynthesis apparatus,resulting in reduction in the light energy absorption,efficiency of light energy conversion and photosynthetic electron transport efficiency.The chlorophyll fluorescence of dynamic parameters of corn seedlings are very sensitive to low temperature and can be employed in the screening of the cold tolerant corn cultivar,accelerating the breeding progress of the cold tolerant cultivar.