A study of the effects of salinity stress in the red mangrove, Rhizophora mangle L.

Abstract

The mangrove habitat exhibits many unique physical features, one of the most important of which is a salinity
gradient. Photosynthetic rates, as measured by leaf stomatal conductance and leaf chlorophyll fluorescence
induction, were tested as indicators of salinity stress in seedlings of the red mangrove, Rhizophora mangle,
grown under five different salinity levels: 0, 15, 30, 45, and 60 parts per thousand. Photosynthetic gas exchange
(measured by stomatal conductance), as well as the light reaction of photosynthesis (measured by chlorophyll
fluorescence) were found to decrease as salinity increased. The use of leaf stomatal conductance and
chlorophyll fluorescence as a measure of photosynthesis allowed a rapid and reliable quantification of the known
stressor, salinity, in seedlings of R. mangle. These non-destructive in-vivo techniques were found to be rapid and
reliable for monitoring photosynthetic stress, an important physiological parameter determining survival and
growth of mangrove plants. These techniques should be considered in forestry management and mangrove
restoration projects to assess plant condition.