Effect of sodium chloride on leaf succulence and area of Atriplex hastata L.

Abstract

The effect of NaCl in water cultures on morphology and histology are studied with A. hastata, a semisucculent halophyte with a mesomorphic leaf structure.

NaCl is shown to extend the ontogeny of the living leaf, and to produce an accelerated rate of leaf thickening, which has its main emphasis in the extended ontogenetic period. The most rapid thickening rate occurred when a high salt concentration (0.6 m) was applied to only part of the root system, so as not to impede a rapid general growth rate in the plant.

Maximum leaf areas occurred in 0.1m NaCl cultures, minimum areas in 0.6 m. Epidermal cell areas in a 0. m treatment were double those of the treatment devoid of NaCl and those in the 0.6 m treatment. Numbers of epidermal cells per leaf decreased progressively with increasing concentrations of NaCl.

The salt-induced thickening rate is looked upon as a process superimposed on a rather similar light and moisture-sensitive process. Differences in timing between salt effects on leaf area and succulence are explained by differential vacuolation of epidermis and palisade tissue. The high-salt cultures (0.4–0.6 m, which greatly reduced growth, apparently did not reduce turgor pressures necessary for succulence. It is considered that the data required to explain differences noted in epidermal cell size are relationships between their rates of expansion and the rates of maturation of structural limiting factors.