Effects of abscisic acid on photoinhibition in maize plants

Abstract

Effects of short- and long-term abscisic acid (ABA) treatments on CO 2 assimilation, PSII photochemistry, and the xanthophyll cycle were investigated in maize plants during exposure to high light (1500 μmol m −2 s −1). Under non-photoinhibitory condition, both short- and long-term ABA treatments showed no effects on PSII photochemistry and carboxylation efficiency but induced a similar decrease in CO 2 assimilation and stomatal conductance. The pool size of the xanthophyll cycle was increased in long-term ABA-treated plants but not in short-term ABA-treated plants. When exposed to high light, there was a significant decrease in the maximal efficiency of PSII photochemistry (Fv/Fm). However, such a decrease was less in long-term ABA-treated plants but greater in short-term ABA-treated plants than in control plants. There was no difference in Fv/Fm between control and short-term ABA-treated plants after exposure to high light for longer time, e.g. 60 min. Similar results were observed in the actual PSII efficiency, photochemical quenching, CO 2 assimilation and carboxylation efficiency. The xanthophyll cycle pigment contents and non-photochemical quenching (NPQ) were significantly higher but malondialdehyde content was lower in long-term ABA-treated plants than in control plants. However, there were no significant differences in the xanthophyll cycle pigment contents, NPQ and malondialdehyde content between control and short-term ABA-treated plants. The results suggest that short-term ABA treatment had no effect on photoinhibition or even induced aggravated photoinhibition, while long-term ABA treatment led to increased resistance to photoinhibition, which was associated with higher CO 2 assimilation capacity and enhanced xanthophyll cycle.