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Abstract Detail


Pteridological Section/AFS

Husby, Chad E [1], Oberbauer, Steven [1], Delatorre, Josť [2], Oreste, Vittorio [2].

Salinity tolerance ecophysiology of the giant horsetail, Equisetum giganteum, in the Atacama Desert, Chile.

SOIL salinity is a major environmental stress for wild and cultivated plants in many parts of the world. However, scientists have yet to determine a basic set of adaptations necessary for salinity tolerance in all vascular plants. Although a large body of research exists on plant responses to salinity stress, almost all such studies have dealt with spermatophytes. Therefore, studies of salinity tolerance mechanisms in pteridophytes hold promise for revealing the fundamental adaptations that all salt tolerant vascular plants may share. Perhaps the most basal pteridophytes to exhibit salinity tolerance are certain members of the genus Equisetum, including the giant horsetail, Equisetum giganteum. The most unusual environment in which E. giganteum occurs is the Atacama Desert in northern Chile. In the river valleys of the Atacama Desert, high soil salinity often greatly restricts native and cultivated plant diversity. Equisetum giganteum is the only pteridophyte that occurs in the high salinity regions of the Atacama valleys and often constitutes a significant vegetation component, forming dense stands of stems more than 4 m high with diameters reaching 3.8 cm. Our field studies in the Atacama have revealed that E. giganteum exhibits similar stomatal conductances and photochemical efficiencies of photosystem II across a wide range of groundwater salinities. This species lowers the osmotic potential of its cytoplasm with increasing salinity and attains its highest pre-dawn stem turgor pressures at moderate salinities. Equisetum giganteum effectively maintains low Na concentrations in its xylem fluid and cytoplasm when soil water Na is high. Furthermore, this species maintains very high K/Na ratios in its xylem fluid and cytoplasm when soil waters have very low K/Na ratios. These findings suggest that E. giganteum is well adapted to salinity stress and that efficient K uptake and Na exclusion may be important stress adaptations.


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Related Links:
Giant Horsetails website: contains detailed information on biology of Equisetum giganteum, E. myriochaetum and E. x schaffneri
Plant Stress website: contains extensive information on plant stress physiology


1 - Florida International University, Deparment of Biological Sciences, 11200 SW 8th St., Miami, Florida, 33199, USA
2 - Universidad Arturo Prat, Agricultura del Desierto, Campus Huayquique, Av. Arturo Prat 2120, Iquique, , Chile

Keywords:
salinity
water potential
osmotic adjustment
osmotic potential
chlorophyll fluorescence
plant stress
stomatal conductance
sodium
postassium
physiological ecology
environmental physiology
Equisetaceae.

Presentation Type: Oral Paper:Papers for Sections
Session: 25-11
Location: 268/Holt
Date: Monday, July 31st, 2006
Time: 4:45 PM
Abstract ID:550


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