Bar Ben Zeev

1 Introduction Photosynthesis is the primary process by which plants assimilate carbon. In C3 leaves, net CO2 assimilation (An) depends on both biochemical reactions and the diffusion of CO2 from the atmosphere to the chloroplast (Farquhar and Sharkey 1982).

Abstract Stomatal responses to atmospheric conditions are critical for balancing plant CO2 gain with water loss. Yet, the question of whether stomata respond directly to humidity or to the rate of water loss (transpiration) remains unresolved due to the tight coupling between these variables. To decouple them, we manipulated water vapor diffusivity using Helox (21% O₂, 79% He), where vapor diffuses 2.33 times faster than in air, and Argox (21% O₂, 79% Ar), where it diffuses 0.75 times slower.