Short-term Impacts of Soaking Periods and NaCl Concentrations to Photosynthetic O2 Evolution and CO2 Uptake of Mangrove Seedlings from East Sumatera Coastline of Indonesia

Abstract

Many workers have been interested in understanding how stress limits mangrove photosynthesis. However, there are relatively few studies on the combined effects of salinity and soaking conditions on mangrove photosynthetic performance. We clarified the photosynthetic performance of different mangrove zonation species (Avicennia marina, Rhizophora mucronata, and Bruguiera gymnorrhiza) under a combination of salinity and soaking stress by using a liquid-phase O2 electrode combined with CO2 optodes simultaneously. Photosynthesis O2 evolution and CO2 uptake for each mangrove seedlings showed different responses with increasing the soaking period and NaCl concentration. Among three mangrove species, photosynthetic performance in B. gymnorrhiza was decreased significantly as compared to the other tested species. On other side, photosynthetic performance of A. marina was uniquely increased with prolongation the soaking period and NaCl concentration. Our results showed that A. marina maintained the high photosynthetic rate even under the soaking condition. R. mucronata had an intermediate response to NaCl concentration during the soaking periods.