Document: LAU-3-29-18

The effects of light availability and salinity levels on mangrove seedling growth.

HOFFMAN, L.L.*, N.P.R.ANTEN and D.D.ACKERLY

Stanford University, Stanford, CA USA ¹

Abstract:
We studied how salinity levels and light availability influence the growth of mangrove seedlings. We grew two species of neo-tropical mangroves, Avicennia germinans and Rhizophora mangle, in a multi-factorial greenhouse experiment with three salinity levels (7, 23, 55 ppt NaCl) and four light levels (5, 12, 25, 50% photosynthetically active radiation, PAR). Plants of both species growing at low light did not exhibit significant differences in whole plant biomass at different salinity levels. The negative effects of high salinity on whole plant growth became apparent only at higher light levels. Specifically, in R. mangle at low salinity, light availability and growth were positively related. At high salinity, increasing the light availability had no effect on plant growth. However, at medium salinity, there was an intermediate optimum with the most growth at 25% PAR. In A. germinans, growth was positively related to light availability at both low and medium salinity, but at high salinity, increasing light availability did not increase growth. In general, root/leaf area increased with increasing salinity and with increasing light availability. At a given light level, plants at high salinity had less transpiration/root mass and transpiration/leaf area than low salinity plants. At a given salinity level, the higher light plants transpired less per unit root mass but slightly more per unit leaf area than low light plants. These results suggest that the salinity level at which a seedling grows affects its ability to utilize light for growth. Field studies seeking to understand mangrove forest dynamics and patterns of seedling regeneration should consider both salinity levels and light availability and the interactions between these two factors.

Keywords: mangrove, salinity, light

This abstract is being presented at: 2:30 PM in session:
Oral Session #10: Light Relations in Plants.