Role of Trichoderma harzianum in mitigating NaCl stress in Indian mustard (Brassica juncea L) through antioxidative defense system
The experiments were conducted to examine the effects of seed priming in solutions (100, 150 and 200 mg L−1) of different synthetic auxins, i.e., 2,4-dichlorophenoxyacetic acid (2,4-D), 2,4,5-trichlorophenoxyacetic acid (2,4,5-T), α-naphthaleneacetic acid (NAA) on growth, grain yield, gaseous exchange characteristics, ionic and hormonal concentrations in two spring wheat (Triticum aestivum L.) cultivars MH-97 (salt intolerant) and Inqlab-91 (salt tolerant). The primed (soaked for 12 h) and non-primed seeds were sown in Petri plates in a growth room as well as in a field treated with 150 mM NaCl. Generally, all synthetic auxins did not increase germination percentage and rate in both cultivars when compared with hydropriming (control), and even decreased these attributes when applied at higher concentrations (200 mg L−1). Nonetheless, under salt stress, NAA (150 mg L−1) was most effective in increasing seedling shoot dry weight, fertile tillers per plant, number of grains per ear and grain yield in both cultivars. The plants raised from seed treated with NAA (150 mg L−1) had lower shoot [Na+] in the salt intolerant cultivar. Moreover, NAA treatment improved root [Ca2+] in both cultivars. Priming agents affected leaf free indole-3-acetic acid (IAA) and indole-3-butyric acid (IBA) concentrations differently in both cultivars. Treatment with NAA (150 mg L−1) lowered leaf free abscisic acid (ABA) and putrescine (Put) concentrations and raised salicylic acid (SA) and spermidine (Spd) concentrations in the salt intolerant cultivar. In conclusion, pre-treatment with NAA (150 mg L−1) showed consistent promotive effects on growth and grain yield in the two cultivars, which were partially attributed to the beneficial effects of NAA-priming on ionic and hormonal homeostasis under salt stress.