Effect of exogenous 5-aminolevulinic acid (ALA) on photosynthesis of NaCl-stressed strawberry plants.

Pot-planted strawberry(Fragaria ananassa Duch.) cultivar Hongjia was used to study the effects of three concentrations of 5-aminolevulinic Acid(ALA)(50 mg/L,100 mg/L,200 mg/L) on the photosynthesis of strawberry plants leaves under 150 mmol/L NaCl stress.Net photosynthetic rate(Pn),transpiration rate(Tr),stomatal conductance(Gs) of strawberry leaves declined greatly under NaCl stress,while the intercellular CO2 concentration(Ci) increased.Exogenous ALA treatment exhibited improvement of Pn,Tr,Gs,and Ci of NaCl-stressed strawberry plants,with statistically significant improvement of Pn by 50 mg/L ALA treatment.NaCl stress raised the minimal fluorescence(Fo),non-photochemical quenching(NPQ) and relative limit of photosynthesis(LPFD) of strawberry leaves,and decreased the maximal photochemical efficiency of PSⅡ(Fv/Fm),potential activity of PSⅡ(Fv/Fo),actual photochemical efficiency of PSⅡ(ΦPSⅡ),photochemical quenching(qP),electron transport rate(ETR) and photochemical rate(PCR) of strawberry leaves.However,Fv/Fm,qP,ETR,and PCR increased significatly in the NaCl-stressed strawberry leaves treated by 50 mg/L or 100 mg/L ALA.50 mg/L ALA enhanced the fresh and dry weight of upground part of strawberry which droped under NaCl stress.In conclusion,exogenous ALA application could alleviate the hurts caused by NaCl stress,leading to high light energy conversion rate and photosynthetic activity,therefore,rich assimilation of strawberry under NaCl stress.