Photosynthetic efficiency in rhizophoracean mangroves with reference to compartmentalization of photosynthetic pigments

Photosynthetic pigments are localized in protein complexes of chloroplast m embranes and their role in photosynthesis has long been established but the ir efficiency has not been measured in many species. The photosynthetic eff iciency of four rhizophoracean mangroves, Rhizophora apiculata, R. mucronat a, Bruguiera cylindrica and Ceriops decandra was studied in randomly collec ted propagules from Pichavaram mangrove forest (southeast coast of India) b y estimating the concentration of photosynthetic pigments in protein comple xes of the thylakoid membrane. Reaction centre chlorophyll (RC-chl) was max imum in B. cylindrica and minimum in R. mucronata. Of the total amount of c hlorophylls, RC-chl constitutes about 50%. The light harvesting complex chl orophyll (LHC-chl) was highest in C. decandra and lowest in R. mucronata. N et photosynthesis was found to be higher in B. cylindrica and lower in R. m ucronata with the respective CO2 fixation of 20.52 and 10.83 mu mol m(-2)s( -1). A positive correlation was obtained between RC-chl and net photosynthe sis. The stomatal conductance to CO2 influx was also found to be high and l ow in B. cylindrica and R. mucronata respectively. We refer the chlorophyll s present in the reaction centre and light harvesting complex as "membrane bound chlorophyll" and propose to use this as an index for measuring the pr oductivity of mangrove species.