Effects of drought and high temperature on photosynthesis and chlorophyll fluorescence characteristics of rapeseed leaves
To better understand the effect of drought and high temperature on rapeseed (Brassica napus L.),photosynthesis of fast plant variety 29005 was stressed by drought (no irrigation for 6d till the relative soil water content reaching ～ 15％) and heat (for 7d,40℃ for 16h at daylight,35℃for 8h in dark for each day) in growth chamber.Changes of photosynthetic and chlorophyll fluorescence parameters were investigated,and key enzymes of photosynthesis were detected.Results showed that plant growth and photosynthesis of 29005 were inhibited under two stresses.Net photosynthetic rate (Pn),stomatal conductance (Gs) and transpiration rate (Tr) were largely declined under progressive drought stress,while chlorophyll fluorescence parameters,including maximal photochemical efficiency of PS Ⅱ (Fv/Fm) and maximal photosynthetic electron transport rate (ETRmax),showed relatively slow decrease.Meanwhile,these 2 parameters were considerably recovered after rewatering for 3 days.Comparing with those under drought stress,Pn,Gs and Tr were decreased slowly after heat stress,and Fv/Fm and ETRmax were sharply declined.Moreover,Fv/Fm and ETRmax were further decreased even after recovery from heat.Rubisco activity was not significantly changed under drought,but decreased obviously under sustained high temperature.The above results indicated that carbon assimilation part in rapeseed photosynthesis was mainly affected by drought,while the inhibition of rapeseed photosynthesis by drought stress was reversible,and the adverse effect on later growth and development was relatively weak after stress recovery.On the contrary,high temperature was more likely to cause irreversible damage to PS Ⅱ in leaves,which further resulted in severe damages on photosynthesis,growth and development of plant.
国家科技期刊平台
NSTL
万方数据
维普
