Quantifying photosynthetic O2 evolution in woody species: a comparative study using portable gas pressure sensing

Abstract

Background and Aim. Photosynthesis represents the fundamental biological transducer of solar energy into chemical potential, sustaining global ecosystems through carbon sequestration and oxygen (O₂) evolution. In the context of rapidly changing urban climates, understanding the physiological performance of diverse tree species, ranging from native foundational species to aggressive invaders, is critical for effective urban forestry management. This study aims to evaluate the efficacy of a modern, cost-effective portable pressure sensor (Globisens Labdisc) for quantifying photosynthetic O₂ evolution and to compare the physiological performance of four distinct woody species under controlled conditions.

Materials and Methods. We conducted a comparative physiological analysis of leaves from Quercus robur (Oak), Ulmus spp. (Elm), Ailanthus altissima (Tree of Heaven), and Populus spp. (Poplar). Photosynthetic activity was measured by monitoring the kinetics of pressure increase in a hermetically sealed, CO₂-buffered system (1% NaHCO₃) under saturating light conditions (450 ± 30 μmol m⁻² s⁻¹). Data were processed to calculate specific photosynthetic rates normalized by fresh weight and time (kPa g⁻¹ min⁻¹), and statistical significance was assessed using one-way ANOVA followed by Tukey’s HSD post-hoc test.

Results. The study revealed statistically significant differences in photosynthetic capacity among the species (p < 0.05). Contrary to expectations for an invasive pioneer, Ailanthus altissima exhibited the lowest specific rate of oxygen evolution (0.119 kPa g⁻¹ min⁻¹). The highest activity was observed in Ulmus spp. (0.159 kPa g⁻¹ min⁻¹), followed by Quercus robur (0.149) and Populus spp. (0.141).

Conclusion. The results demonstrate that while Populus showed the highest gross pressure change, normalization reveals that Ulmus and Quercus possess superior intrinsic photosynthetic efficiency per unit of biomass under these experimental conditions. The Globisens Labdisc proved to be a robust tool for high-throughput physiological screening, offering a viable alternative to expensive IRGA systems for educational and preliminary ecological monitoring.