Effects of Abscisic Acid Application on Photosynthesis and Photochemistry of Stylosanthes guianensis under Chilling Stress

In our previous study, it was found that abscisic acid (ABA) improved the chilling resistance of Stylosanthes guianensis. In order to determine the effects of ABA on photosynthesis and photochemistry of S. guianensis, an experiment was conducted under controlled condition to determine the effects of exogenous ABA on stomatal conductance (gs), transpiration (E), photosynthetic rate (A) and chlorophyll a fluorescence of this pasture legume. The results showed that ABA treatment reduced A, gs, and E under both chilling (8 °C) and control temperature (28 °C). A of the ABA treated plants returned to a high rate, while that of the water-treated plants remained low when plants were rewarmed after chilling treatment. ABA-treated plants had higher maximum photochemical efficiency (Fv/Fm), non-photochemical quenching (NPQ), quantum efficiency of PS II photochemistry (Φps ii) than water-treated ones during chilling. Although the biomass of S. guianensis was reduced by ABA under control temperature, ABA-treated plants had higher biomass than water-treated ones after 7 days of recovery.