Plant growth, metabolism and adaptation in relation to stress conditions. XXIV. Salinity-biofertility interactive effects on proline, glycine and various antioxidants in Lactuca sativa.

Abstract

Proline and glycine contents in lettuce plants appeared to show additional significant increments, in response to treatment with phosphorein biofertilizer, above those increments maintained in response to salinization. Administration of nitrobein biofertilizer to the NaCl media led to significant increases in proline and glycine contents above the water control levels, but the amino acid content of NaCl-treated plants appeared consistently higher than that content in NaCl + nitrobein-treated plants. Supplemental addition of phosphorein to the salinized culture media induced significant increases in the contents of antioxidant compounds, throughout the experimental period. As compared with the saline control values, total ascorbate (ASA + DASA) and total glutathione (GSSG + GSH) contents were found either to decrease (with 4 and 6 mmhos NaCl) or to increase (with 8 and 10 mmhos NaCl) significantly in response to addition of nitrobein to the saline culture media. The activities of superoxide dismutase (SOD), catalase (CAT), ascorbate peroxidase (APO) and glutathione reductase (GR) in the salinized lettuce plants fortified with the recommended dose of phosphorein or nitrobein were, in general, significantly up-regulated above the salinized control levels; the magnitude of up-regulation being dependent on the concentration of NaCl, the stage of growth and on the enzyme under investigation. With lettuce plants, the present results are discussed in relation to applicability of two biofertilizers to sodic salty soils in Egypt.