Role of seagrass photosynthesis in root aerobic processes

The role of shoot photosynthesis as a means of supporting aerobic respiration in the roots of the seagrass Zostera marina was examined. O₂ was transported rapidly (10-15 minutes) from the shoots to the root-rhizome tissues upon shoot illumination. The highest rates of transport were in shoots possessing the greatest biomass and leaf area. The rates of O₂ transport do not support a simple gas phase diffusion mechanism. O₂ transport to the root-rhizome system supported aerobic root respiration and in many cases exceeded respiratory requirements leading to O₂ release from the subterranean tissue. Release of O₂ can support aerobic processes in reducing sediments typical of Z. marina habitats. Since the root-rhizome respiration is supported primarily under shoot photosynthetic conditions, then the daily period of photosynthesis determines the diurnal period of root aerobiosis.