Leaves consist of tiny pores known as stomata. Gaseous exchange occurs through diffusion via stomata. Guard cells regulate each of the stomata. Exchange of gases occurs with the closing and opening of the stoma between the inferior of leaves and the atmosphere.

Many wetland plants have gas films on submerged leaf surfaces. We tested the hypotheses that leaf gas films enhance CO₂ uptake for net photosynthesis (P_N) during light periods, and enhance O₂ uptake for respiration during dark periods.Leaves of four wetland species that form gas films, and two species that do not, were used. Gas films were also experimentally removed by brushing with 0.05% (v/v) Triton X. Net O₂ production in light, or O₂ consumption in darkness, was measured at various CO₂ and O₂ concentrations.

When gas films were removed, O₂ uptake in darkness was already diffusion-limited at 20.6 kPa (critical O₂ pressure for respiration, COP_R≥ 284 mmol O₂ m⁻³), whereas for some leaves with gas films, O₂ uptake declined only at approx. 4 kPa (COP_R 54 mmol O₂ m⁻³). Gas films also improved CO₂ uptake so that, during light periods, underwater P_N was enhanced up to sixfold.Gas films on submerged leaves enable continued gas exchange via stomata and thus bypassing of cuticle resistance, enhancing exchange of O₂ and CO₂ with the surrounding water, and therefore underwater P_N and respiration.

Warm Regards,
Jessie
Journal Manager
Journal of Bioremediation & Biodegradation