Effects of 5-aminolevulinic acid(ALA) on growth and photosynthesis of pepper plants under low temperature stress

Pepper variety Chaoyue No.5 was selected as material to study the effects of spraying 5-aminolevulinic acid(ALA) on growth and photosynthesis of pepper during flowering under low temperature stress in the heated glass greenhouse simulating a plastic film.The results showed that spraying 25 mg/L ALA significantly increased the height,stem diameter,fresh weight,dry weight and chlorophyll content of leaves,as well as the net photosynthetic rate(Pn),intercellular CO2(Ci),stomata1 conduct(Gs) and transpiration rate(Tr),but decreased the stomata limitation(Ls) and water use efficiency(WUE).When the plants were out of low temperature stress,the growth and chlorophyll content of pepper with ALA treatment were still significantly higher than those of low temperature treatment.The Pn,Gs and Tr of pepper with low temperature treatment were significantly lower,but were improved by ALA treatment more than those of normal temperature control.It indicates that spraying exogenous ALA can improve photosynthesis and growth of pepper plant by raising the chlorophyll content and relieving the stomatal inhibition of leaves under low temperature stress.