Light dependence of CO₂ gas exchange in leaves of tree species of broadleaved forest in central Russia

Kazan Federal University, Kazan, 420008, Russia

^* Corresponding author: nelly.chizhikova@stud.kpfu.ru

Abstract

The balance between photosynthesis and respiration is an indicator of the productivity and sustainability of both an individual plant and the forest community and reflects the carbon balance of ecosystems. The intensity of plant photosynthesis depends not only on the characteristics of the species, but also on the amount of light entering the leaf surface. The parameters of CO₂ gas exchange in the leaves depending on the light intensity were assessed for three main tree species of mixed temperate forests of the European part of Russia: Betula pendula Roth., Tilia cordata Mill. and Quercus robur L. The net photosynthetic rate was measured on July 26, 2023, in the forest area of the Carbon Povolzhye “Observatory” polygon (Tatarstan, Russia). The measurements are stored in the database PGasEx 1.0. The light curve of photosynthesis was modeled using the modified Michaelis-Menten function. From the Michaelis–Menten equation, the following parameters were estimated for each species: maximum intensity of photosynthesis, respiration rate, light compensation point, point of light saturation, quantum yield of photosynthesis. The maximum net photosynthesis on the leaf surface under light-saturated conditions was greatest for oak, followed by birch and linden, indicating ecological strategies of species.