Effects of Sodium Chloride on Tepary Bean

Abstract

Osmotic adjustment is one of the adaptive responses of plant species to salinity, In tepary bean seedlings, salinity led to osmotic adjustment in different parts of the seedlings. The osmotic potential of the leaves increased to 340rnM(-1MPa)in seedlings treated with - 0.75 MPa NaCl. Water and osmotic potential of leaves and proximal parr of the roots were more negative than the controls whereas the turgor potential remained about the same. The osmotic adjustment of the tepary bean may result from the synthesis and accumulation of free sugars and amino acids or the accumulation of inorganic ions within the tissue. A quantitative analysis of the sugars and amino acids from salt stress treated tepary bean seedlings showed that they would contribute only -0.15 MPa to the osmotic adjustment whereas inorganic ions would contribute -0.45 MPa. The sum of these osmotic potentials is -0.6 MPa which is -0.4 MPa short of the observed osmotic values. These results suggest that additional substances also contribute to the osmotic adjustment of tepary beans.