Non-stomatal limitations of photosynthesis in grassland species under artificial drought in the field

As drought stress is expected to occur more frequently in future climate in central Europe, survival and productivity of grassland species are an important issue. Non-stomatal limitation processes related to the drought-stress inhibition of photosynthesis of selected grassland species were analysed at three locations using leaf gas exchange and chlorophyll fluorescence. The effect of an artificial drought on the non-stomatal limitations differed considerably between species present in the same grassland plot. The maximum efficiency of photosystem II (Fv/Fm), indicator for the intactness of the photosynthetic electron transport, showed only small differences under drought. On the other hand, more pronounced effects were observed for the carboxylation velocity of Rubisco (Vc,max). Vc,max was in Phleum pratense about 20% lower under drought than in control plants, while other species in the same plot were far less affected. The carboxylation velocity of Rubisco is highly sensitive to water deficit and might represent a tool to evaluate the drought response of various species in order to address the performance of grasslands.

Research highlights▶ More frequent and more severe drought periods must be expected for the future. ▶ Strong non-stomatal limitations were detected in grassland species under drought. ▶ Metabolic restrictions are relevant for pastures under reduced water availability. ▶ The relative effects on grasses and legumes/forbs differed for three field sites. ▶ Frequent drought periods may affect productivity and species composition.