Responses of photosynthetic physiological traits in transgenic alfalfa expressing multi-functional genes during soil moisture change

Abstract

The photosynthetic and fluorescence characteristics of alfalfa（cv.Xinjiang Daye）and four transgenic lines（SN:transgenic AtNDPK2,SC:transgenic codA,SOR:transgenic IbOr,SAF:transgenic AtABF3）at the early flowering stage were investigated and compared under different soil moisture conditions in a pot experiment.Results showed that the net photosynthetic rate（Pn）,transpiration rate（Tr）and stomatal conductance（Gs）of all lines showed a decreasing trendas soil moisture decreased from 80% FC（field capacity）to 40% FC,while instantaneous water use efficiency（WUEi）exhibited an increasing trend.At 40% FC,Pn values of transgenic lines were 11.19-21.58μmol·m-2·s-1,significantly（P<0.05）higher than that of non-transgenic（NT）plants(6.06μmol·m-2·s-1).There were no differences in WUEiamong all alfalfa lines and the SAF line had the highest value(3.22μmol·mmol-1).As soil moisture decreased,the initial fluorescence（Fo）,maximum photochemical efficiency（Fv/Fm）and photochemical quenching coefficient（qP）values exhibited declining trends,and actual photochemical efficiency（ΦPSⅡ）and apparent electron transfer efficiency（ETR）values initially increased and then declined,while non-photochemical quenching coefficient（NPQ）values showed an increasing trend.The qPvalues of transgenic lines decreased significantly at 50% FC,while that of NT was 70% FC.Under 40% FC,Fv/Fmvalues of transgenic lines were 0.78-0.82,and were significantly higher than that of NT（0.58）.This suggests that the expression of multi-functional genes could improve photosynthetic properties of Xinjiang Daye to some extent and that transgenic codAis able to sustain a high photosynthetic rate,transgenic IbOrline can maintain higher light use ability,transgenic AtABF3 is able to utilize water more efficiently,while transgenic AtNDPK2 had the highest total biomass production with decreasing soil moisture.