Promotion of physiological resistance in Phaseolus vulgaris L. seedlings grown under salinity stress conditions by using ascorbic acid and biofertilizers

This study examined interaction effect between NaCl, Trichoderma harzianum, and non enzymatic antioxidant ascorbic acid flavonoids, 2,2-diphenyl-1-picrylhydrazyl radical (DPPH), ascorbic acid, peroxidase enzyme profile, and some minerals in Phaseolus vulgaris cv. Nebraska grown for 60 days from sowing. Fresh and dry weight, plant height, and leaf area were reduced with increasing salinity but enhanced with Trichoderma or ascorbic acid treatment. Photosynthetic pigment content (chlorophyll a, b, a+b and carotenoids) decreased with increased salinity, especially at 200 mM NaCl, but ascorbic acid or Trichoderma remarkably increased all pigments. Pigment contents had higher values with ascorbic acid than Trichoderma, especially carotenoids. Salinity increased soluble proteins, amino acids, MDA, and proline in shoots and roots, ascorbic acid or Trichoderma reduced these components. Phenols and flavonoids slightly decreased with increasing salinity, ascorbic acid or Trichoderma slightly increased both components, especially at higher salt concentrations. Shoots and roots exhibited a marked increase in DPPH activity by increasing salinity, ascorbic acid or Trichoderma decreased DPPH activity in shoots and slightly increased it in roots. Shoots and roots exhibited a marked increase in Na+ content, but K+ content increased in shoots and decreased in roots with increasing salt concentrations, ascorbic acid or Trichoderma decreased Na+ in shoots and roots and increased K+ in all organs or treatments compared to control. Peroxidase isozymes are enhanced with various densities and bands under salinity, which more obvious with ascorbic acid and Trichoderma treatment under selected salt concentrations, moreover two isoforms of peroxidase (px1 and px2) were appeared under all treatments.