Accumulation of amino acids and glycinebetaine by NaCl treatment and its relation to salt tolerance in three gramineous plants

Two gramineous weeds, early watergrass (Echinochloa oryzicola Vasing) and foxtail (Setaria viridis (L.) Beauv.), and rice (Oryza sativa L. cv. Nipponbare) were exposed to salinity stress. The leaf water status, levels of amino acid, proline, and glycinebetaine of seedlings during the 7 days following root treatment of 50 and 100mM NaCl were measured. Foxtail and early watergrass were able to maintain a high turgor and high relative water content under the salinity condition. Proline content in leaves was also increased by salt stress in these plants, but this was lower in rice than in foxtail or early watergrass. Glycinebetaine content was also increased by salinity in the two weeds. However, glycinebetaine was not detected in rice leaves. It was suggested that these osmotica were associated with a greater capability for osmotic adjustment in the above weeds, resulting in implementation of the salt tolerance.