Effects on Strawberry Photosynthesis and Relations to Anti-oxidant Enzymes of ALA

Pot-planted strawberry was used to study the effects of ALA topdressing on the photosynthesis,chlorphyll fluorescent properties and anti-oxidant enzyme activities and MDA contents of strawberry plants.The results indicated that ALA topdressing at 100 mg/L significantly increased the net photosynthetic rate of strawberry leaves and that the increasing effect probably had something to do with its increasing effect on chlorophyll content and carboxylation efficiency and lowering photorespiration.The kinetic data of chlorophyll fluoresecence revealed that ALA topdressing reduced the non-variable fluorescence(F_o) of strawberry leaves at high light intensity(1 500 μmol·m~(-2)·s~(-1)),which indicated that ALA has certain protecting effect on photosynthetic membrane system.ALA topdressing could not only remarkably raise the maximum fluorescence(F_m) and variable fluorescence(F_v) of strawberry leaves but also increase the actual photochemical efficiency of PSⅡ(Φ_(PSⅡ)),photochemical quenching(qP) and non-photochemical quenching(NPQ),electron transport rate(ETR),photochemical rate(PCR),and antennae heat dissipation rate,thereby lowering the PFD limitation,and this showed that chlorophyll fluorescence yield and antennae heat dissipation were two respects in protecting photosynthetic organs and improving photosynthetic efficiency.The measurements of anti-oxidant enzymes and the treatment results of diethyldithiocarbamate(DDC),the inhibitor to SOD activity,revealed that the enhancing effect of ALA on strawberry photosynthesis had something to do with its improving effect on the activities of other anti-oxidant enzymes.