| Abstrakt: |
Abstract: a1_The aim of this work was to study the acclimation of photosynthesis in a boreal grass (Phalaris arundinacea L.) grown in controlled environment chambers under elevated temperature (ambient + 3.5°C) and CO2 (700 μmol mol−1) with varying soil water regimes. More specifically, we studied, during two development stages (early: heading; late: florescence completed), how the temperature response of light-saturated net photosynthetic rate (P sat), maximum rate of ribulose-1,5-bisphosphate carboxylase/oxygenase activity (V cmax) and potential rate of electron transport (J max) acclimatized to the changed environment. During the early growing period, we found a greater temperature-induced enhancement of P sat at higher measurement temperatures, which disappeared during the late stage. Under elevated growth temperature, V cmax and J max at lower measurement temperatures (5–15°C) were lower than those under ambient growth temperature during the early period. When the measurements were done at 20–30°C, the situation was the opposite. During the late growing period, V cmax and J max under elevated growth temperature were consistently lower across measurement temperatures. CO2 enrichment significantly increased P sat with higher intercellular CO2 compared to ambient CO2 treatment, however, elevated CO2 slightly decreased V cmax and J max across measurement temperatures, probably due to down-regulation acclimation. For two growing periods, soil water availability affected the variation in photosynthesis and biochemical parameters much more than climatic treatment did. Over two growing periods, V cmax and J max were on average 36.4 and 30.6%, respectively, lower with low water availability compared to high water availability across measurement temperatures. During the late growing period, elevated growth temperature further reduced the photosynthesis under low water availability. |
