Paragraph: The purpose of this paper is to focus on mechanisms used by Rhizophora mangle and Avicennia germinans to manage salt balance in a saline environment. Other topics to be addressed include a brief overview of each species' adaptive suite, physiological ramifications of each plant's salt balance strategy, and the ultimate effect of that strategy on the plant's ability to compete. R. mangle is considered a salt excluder because it prevents most salt from entering the plant at the root-water barrier. A. germinans is considered a salt excreter because its primary mechanism for maintaining salt balance is to excrete excess salt through salt glands on the leaves. Speculations will be made based on salt balance strategy regarding reasons for each species' success in its respective part of the intertidal zone. The theme of my presentation will be that these cases emphasize the far-reaching effects of specific physiological mechanisms on the "big picture" of plant survival.
Outline:
I. Abstract
II. Introduction
A. Why we should learn about mangroves
B. Specific problems associated with growing in tidal areas
III. Rhizophora. mangle
A. Overview of strategy
B. Physiology of the salt exclusion barrier
C. Related physiological functions that are affected by this strategy
IV. Avicennia germinans
A. Overview of strategy
B. Physiology of salt glands
C. Related physiological functions that are affected by this strategy
V. Comparisons between the plants
A. Comparison of strategies
1. Physiology
2. The cost of being a halophyte
B. Growth site selection and competition
VI. Conclusion
References:
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Balsamo, R.A., and W.W. Thomson. 1993. Ultrastructural features associated with secretion in the salt glands of Frankenia grandifolia (Frankeniaceae) and Avicennia germinans (Avicenniaceae). Am. J. Botany 80(11): 1276-1283.
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LŸttge, U. 1997. Physiological Ecology of Tropical Plants. Heidelberg, Germany: Springer.
Morrow, L. and N.H. Nickerson. 1973. Salt concentrations in ground waters beneath Rhizophora mangle and Avicennia germinans. Rhodora 75(801):102-106.
Sobrado, M.A., and E.D. Greaves. 2000. Leaf secretion composition of the mangrove species Avicennia germinans (L.) in relation to salinity: a case study by using total-reflection x-ray fluorescence analysis. Plant Science 159(1):1-5.
Tomlinson, P.B. 1986. The Botany of Mangroves. Cambridge, U.K.: Cambridge Univ. Press.
Waisel, Y. 1972. Biology of Halophytes. Ed: Kozlowski, T.T.. Physiological Ecology series. New York, NY: Academic Press.
Werner, A. and R. Stelzer. 1990. Physiological responses of the mangrove Rhizophora mangle grown in the absence and presence of NaCl. Plant, Cell, and Environment 13(3):243-255.
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