RESPIRATION AND NET PHOTOSYNTHESIS OF COTYLEDONS DURING ESTABLISHMENT AND EARLY GROWTH OF PROPAGULES OF THE MANGROVE, AVICENNIA-MARINA, AT 3 TEMPERATURES

Respiration and net photosynthesis of discs excised from cotyledons of Avicennia marina (Forssk.) Vierh. were measured at temperatures of 17, 21 and 25-degrees-C in a Gilson Respirometer. Cotyledonary material was also analysed for TNC (total non-structural carbohydrates). Rates of respiration and net photosynthesis were significantly different at the three temperatures, with the lowest rates recorded in each case at 17-degrees-C and the highest at 25-degrees-C. TNC values revealed an initial decrease, followed by a small increase, and thereafter a drop to fairly constant low levels. While seedlings at 25-degrees-C grew well, very little growth was recorded at 17-degrees-C. Growth at the different temperatures was related to the relative excess of photosynthesis over respiration. The ecological implications of these results are discussed.