Osmoregulation in Higher Plants: Effects of NaC1 Salinity on Non-Nodulated Phaseolus aureus L.

Abstract

Phaseolus aureus L. tolerated up to 150 mm NaClext, but with a diminished growth and an accumulation of various organic solutes characteristic of stress conditions. With increasing external salinity NH4+ accumulated in the tissues, ttaining toxic concentrations at the higher levels. In consequence, the production of organic solutes such as asparagine, roline, glycine betaine and free amino acids was different from that in the control plants. Growth reduction corresponding to diminished organic matter production was due to 'ion excess' in the plants. NH4+ toxicity resulted in an increased accumulation of ureides and asparagine. K+, NO3- and asparagines played a key role, while sugars only a minor role as osmotica. However, a role for proline and quaternary ammonium compounds as compatible solutes in plants suffering severe salt stress cannot be eliminated.