Photosynthetic response of Halophila ovalis (R-Br.) Hook. f. to combined environmental stress

Combinations of stresses showed an additive effect in comparison to the ind ividual stress responses. It is apparent from these results that thermal, e levated-light or osmotic stress increases the sensitivity of Halophila oval is to any of the other stress factors. Photosynthetic stress was detected u sing chlorophyll a fluorescence. Quantum yield was consistently the most ef fective measure of photosynthetic stress from combination stress exposures. Chlorophyll pigment analysis supported the general decline in photosynthet ic capacity as indicated by the chlorophyll fluorescence; however, several anomalies did occur. (C) 1999 Elsevier Science B.V. All rights reserved.