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Ecophysiology of xerophytic and halophytic vegetation of a coastal alluvial plain in northern Venezuela
Author(s) -
LÜTTGE U.,
POPP M.,
MEDINA E.,
CRAM W. J.,
DIAZ M.,
GRIFFITHS H.,
LEE H. S. J.,
SCHÄFER C.,
SMITH J. A. C.,
STIMMEL K.H.
Publication year - 1989
Publication title -
new phytologist
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 3.742
H-Index - 244
eISSN - 1469-8137
pISSN - 0028-646X
DOI - 10.1111/j.1469-8137.1989.tb00692.x
Subject(s) - halophyte , dry season , ecophysiology , botany , perennial plant , biology , growing season , photosynthesis , salinity , horticulture , ecology
summary The perennial halophytes, Batis maritima L., Sesuvium portulacastrum L., and Portulaca rubricaulis H.B.K. which inhabit the extreme environment on parts of the salt plain and at the edges of the vegetation islands of Ciénega el Ostional were examined to determine their strategies for growth and survival in the rainy and dry seasons. All of the three species are leaf‐succulents. High leaf‐sap osmotic pressures, xylem tensions and Na + and Cl − levels indicated that S. portulacastrum and B. maritima are salt‐accumulating halophytes. Succulence, leaf‐sap osmolalities and Na + and Cl − levels increased in the dry season in B. maritima by a factor of 1.5‐2.0 and in S. Portulacastrum by a factor of 1.9–2.7. B. maritima also accumulated sulphate with a two‐fold increase of concentrations in the dry season. In S. portulacastrum Na + accumulation much exceeded Cl − accumulation and oxalate synthesis was found to serve charge balance. In this species the compatible solutes, proline and pinitol, were clearly detectable in both seasons; their levels increased by a factor of about 6 in the dry season. Exchange of water vapour and CO 2 was measured with a portable steady‐state porometer. Photosynthesis in B. maritima showed little response to the transition from the rainy to the dry season while S. portulacastrum was severely impaired in the dry season, showing pronounced midday depressions of gas exchange and about 40% inhibition of light‐saturated rates of CO 2 uptake. P. rubricaulis shed its leaves in the dry season. According to carbon isotope ratios (δ 13 C), B. maritima (δ 13 C =−26.4‰) and S. portulacastrum (δ 13 C =−25.8 ‰) are C 3 plants while P. rubricaulis (δ 13 C =−12.3‰) performed C 4 photosynthesis.