Author:

Keywords:

Science & Technology, Life Sciences & Biomedicine, Plant Sciences, Oryza sativa, flooding stress, leaf gas exchange, leaf hydrophobicity, leaf respiration, modelling, plant aeration, submergence tolerance, tissue hypoxia, tissue porosity, RESPIRATORY DOWN-REGULATION, DIFFUSIVE BOUNDARY-LAYERS, OXYGEN DYNAMICS, UNDERWATER PHOTOSYNTHESIS, DIURNAL CHANGES, ROOT AERATION, ORYZA-SATIVA, PLANTS, WATER, CO2, Cell Respiration, Computer Simulation, Darkness, Diffusion, Gases, Light, Models, Biological, Oryza, Oxygen, Permeability, Plant Epidermis, Plant Leaves, Plant Roots, Plant Stomata, Plant Transpiration, Water, 06 Biological Sciences, 07 Agricultural and Veterinary Sciences, Plant Biology & Botany, 3108 Plant biology

Abstract:

Some terrestrial wetland plants, such as rice, have super-hydrophobic leaf surfaces which retain a gas film when submerged. O2 movement through the diffusive boundary layer (DBL) of floodwater, gas film and stomata into leaf mesophyll was explored by means of a reaction-diffusion model that was solved in a three-dimensional leaf anatomy model. The anatomy and dark respiration of leaves of rice (Oryza sativa L.) were measured and used to compute O2 fluxes and partial pressure of O2 (pO2 ) in the DBL, gas film and leaf when submerged. The effects of floodwater pO2 , DBL thickness, cuticle permeability, presence of gas film and stomatal opening were explored. Under O2 -limiting conditions of the bulk water (pO2  < 10 kPa), the gas film significantly increases the O2 flux into submerged leaves regardless of whether stomata are fully or partly open. With a gas film, tissue pO2 substantially increases, even for the slightest stomatal opening, but not when stomata are completely closed. The effect of gas films increases with decreasing cuticle permeability. O2 flux and tissue pO2 decrease with increasing DBL thickness. The present modelling analysis provides a mechanistic understanding of how leaf gas films facilitate O2 entry into submerged plants.