© 1996 Heron Publishing—Victoria, Canada
Growth and physiological responses of neotropical mangrove seedlings to root zone hypoxia
Karen L. McKee
Wetland Biogeochemistry Institute, Center for Coastal, Energy, and Environmental Resources, Louisiana State University, Baton
Rouge, LA 70803-7511, USA / Received October 25, 1995
Summary
Seedlings of Rhizophora mangle L., Avicennia germinans (L.) Stearn., and Laguncularia racemosa (L.) Gaertn. f. were cultured in aerated or N2-purged solution for 12 weeks to assess their relative responses to low oxygen tensions. All three species responded to low
oxygen treatment by modifying physiological and morphological patterns to decrease carbon loss by root respiration. However,
the extent to which seedling physiology and morphology were altered by low oxygen treatment differed among species. Maintenance
of root oxygen concentrations, root respiration rates and root extension rates by R. mangle demonstrated an ability to avoid low oxygen stress with minimal changes in root morphology and physiology. In contrast, oxygen
concentrations in A. germinans and L. racemosa roots declined from 16 to 5% or lower within 6 h of treatment. Root hypoxia led to significant decreases in respiration rates
of intact root systems (31 and 53% below controls) and root extension rates (38 and 76% below controls) by A. germinans and L. racemosa, respectively, indicating a greater vulnerability of these species to low oxygen tensions in the root zone compared with
R. mangle. I conclude that the relative performance of mangrove seedlings growing in anaerobic soils is influenced by interspecific
differences in root aeration and concomitant effects on root morphology and physiology.
Keywords:
carbon loss, flood tolerance, forested wetland, oxygen, root respiration, tropical trees.
