Photosynthetic Apparatus Responses to Short-term low-temperature Flooding May Contribute to Freezing Tolerance Changes in Forage Grasses

Winter conditions are subjected to rapid climate changes. Increased precipitation and snow melting during warmer winters may result in low-temperature flooding. These factors probably affect plant overwintering strategies. This study investigated the relationships between the photosynthetic adjustment and freezing tolerance following a short-term low-temperature flooding in two forage grasses (Lolium perenne and Festuca pratensis). The effect of flooding on the photosynthetic apparatus acclimation to cold was determined using chlorophyll a fluorescence measurements. Freezing tolerance was estimated using an electrolyte leakage test. It has been shown that genotypes activating non-photochemical mechanisms of photosynthetic acclimation to cold during low-temperature flooding may show increased freezing tolerance. Freezing tolerance reduction observed in Festuca pratensis was probably connected with decreased photochemical activity and photoinhibition of photosynthesis. It can be concluded that photosynthetic apparatus response to low-temperature flooding may contribute to changes in the freezing tolerance. The direction of the changes is associated with different photosynthetic apparatus performance.