Appreciation of tolerance at the impact of thermal stress on photosystem ii activity in the leaves of pedunculate oak (Quercus robur L.) trees of different ecological origin

Extreme weather events with high temperatures and strong sunlight have increased alarmingly in the last few decades, considerable affecting plant photosynthesis. In this study, the impact of thermal stress on photosystem II activity in the leaves of pedunculate oak trees (Quercus robur L.) of different ecological origin was assessed. Four days after the thermal shock application with a temperature of 50°C during 20, 40, 60 minutes, the processes of recovery on photosystem II activity in the leaves of the oak trees in the investigated provenances took place with different speed and fullness. The recovery of the functional state of photosystem II in the leaves of the trees showed that in the environmental conditions of the ,,Plaiul Fagului” reservation territory an advanced thermotolerance to the thermal stress action was specifi c for the origin from the north of the country (Edinet). The leaves of the trees of local and southern origin showed a low resistance to the thermal stress action. The advanced adaptation capacity, the high growth rate of the trees from the northern provenance suggest that the acorn harvested from the oaks of northern origin can be used for the works of extension of the afforestation areas in the central area of the Republic of Moldova.