Electron microprobe analyses of salt distribution in the halophyte Salicornia pacifica var. utahensis

Abstract

The halophyte Salicornia pacifica var. utahensis grows in the desert saline playa. The fused leaves form succulent stems and have apparently isolated tracheids in the palisade region as observed by scanning electron microscopy. Frozen shoots were fractured under liquid nitrogen and scanned for Na+, K+, and Cl− with an electron microprobe X-ray analyzer. In young shoots, the palisade cells were low in salts, and the spongy cells had higher concentrations. The salt in the spongy cells provides a high osmotic pressure permitting the plant to absorb more water from the soil. As the shoots matured, the concentration of salts increased in the spongy cells, and the amount of salt in the palisades also increased. The salt ions in the palisades were excluded from the organelles and were mainly present in the vacuoles. Eventually, the leaf section collapsed because of the high salt in the palisade and spongy cells, but the vascular region in the shriveled section continued to function. The sections adjacent to the dead shriveled section remained green and succulent. The salt tolerance appeared to be based on the exclusion of the salt from the photosynthetic cells and on the ability of the succulent stem to function even though sections were dead owing to high salt concentration.

Electron‐probe X‐ray Microanalysis: Techniques and Recent Applications in Biology

“…Weber, Rasmussen & Hess (1977) also analysed leaf tissue from Suaeda, using freeze-fractured leaf segments, and reached very similar conclusions. These are known to accumulate sodium chloride, so that salt can account for up to 40 yo of their dry-weight.…”

“…The main conclusion is that the photosynthetic cells of this plant are evidently able to operate in the presence of very high salt concentrations. Weber, Rasmussen & Hess (1977) also analysed leaf tissue from Suaeda, using freeze-fractured leaf segments, and reached very similar conclusions. Highest salt concentrations were found in the spongy tissue; salt content of both this tissue and the outer, palisade cells increased with age of the leaf, though in the photosynthetic cells salt appeared to be excluded from the chloroplasts, possibly by segregation in the vacuoles.…”

The Genetic Basis of Microdifferentiation in Natural and Experimental Populations of Borrichia frutescens in Relation to Salinity

“…The potential exceeds the actual salt content of leaf tissue by a factor of 50. Finally, sequestering of salts has not been demonstrated specifically in B. frutescens, although it has been suggested for several halophytes not possessing salt glands (Weber et al, 1977). The available informtaion suggests that salt tolerance in B. frutescens occurs by salt exclusion at the roots, salt-induced succulence in the leaves and differential salt compartmentation within the cell.…”

Water Use and Salt Balance in Three Salt Marsh Succulents

“…The succulence values for the species studied here indicate that dilution is significant. The high osmotic component of leaf (shoot) water potential measured, together with the lack of enzymatic salt tolerance (Flowers, 1972;Cavalieri and Huang, 1977;Weber et al, 1977), suggests an important role for salt compartmentation. Salt compartmentation has been reported in one species of Salicornia (Weber et al, 1977).…”