Photosynthesis, respiration and whole plant carbon budget of the seagrass Thalassia testudinum

Abstract

The photosynthesis versus irradiance (P/I) response of turtlegrass from Florida Bay was measured using the oxygen evolution of intact short shoots enclosed in sealed chambers, and found to have a light-saturated P/I behaviour. Green photosynthetic leaves account for only 15.0% of the total biomass. The remaining 85% is apportioned into belowground short shoots, rhizomes and roots. Leaves had higher respiration rates (7.4 μg O2 g-1min-1) than belowground structures (0.9-4.6 μg O2 g-1min-1), and accounted for 42.6% of total plant respiration. Under average summer light conditions, the daily carbon budget was positive as deep as 4 m, suggesting that plants can survive at this depth. -from Authors