Stomatal conductance and gas exchange in four species of Caribbean mangroves exposed to ambient and increased CO2

Abstract

Stomatal conductance and gas exchange rates in sun leaves were measured in multiple individuals of four species of Caribbean mangroves common to south Florida, USA. Under ambient CO₂ levels (340–360 ppm), stomatal conductance (mol m^-2 s^-1), net primary productivity (g CO₂ m^-2 min^-1), transpiration (g H₂O m^-2 s^-1), and instantaneous transpiration efficiency, ITE, (µmol CO₂/mmol H₂O) were not significantly different among the four species: Rhizophora mangle (Rm), Avicennia germinans (Ag), Laguncularia racemosa (Lr), and Conocarpus erectus (Ce). Under exposure to increased CO₂ (361–485 ppm) there were highly significant (P < 0.001) decreases in stomatal conductance and transpiration, and a highly significant increase in ITE in all four species. However, there was no significant change in net primary productivity in Rm, Ag and Ce, whereas there was a significant decrease (P < 0.01) in net primary productivity in Lr.