The effects of ABA and GA3 treatments on resistance to frost and high-light treatment in oilseed rape leaf discs

Abstract

The experiments were performed to check the effects of exogenous ABA and gibberellin on photosynthetic apparatus and leaf resistance to freezing. In the experiment, two cultivars (winter and spring) of oilseed rape were used in the experiment. Discs, cut out from leaves of cold acclimated plants grown at 12 and 20 °C at similar PPFD levels, were immersed for 72 hours in growth regulator solutions. Some of discs were additionally subjected to high radiation. Independently on cultivar studied, the effects of growth regulator treatments were significant only in leaves developed at 20 °C. ABA treatment increased frost resistance, promoted photosynthetic activity measured in cold and inhibited expansion of leaf-disc area, whereas GA3 evoked opposite effects. The treatment with growth regulators particularly affected the resistance of photosynthetic apparatus to high light. In this case ABA treatment decreased, whereas GA3 increased photoinhibition of PSII. The outcomes may suggest that in the ABA-treated plants PSII is better protected against photoinduced inactivation both by the increase in effectiveness of photosynthetic dark reactions at high light/low temperature conditions, increased energy dissipation in xantophyll cycle and enhanced accumulation of anthocyanins. GA3 treatment may affect the resistance to photoinhibition directly via decrease in anthocyanins contents and indirectly through increase of elongation growth rate in the tissue.