Effect of elevated boron concentrations on the growth and yield of barley (Hordeum vulgare L.) and alleviation of its toxicity using different plant growth modulators

摘要

This study was carried out to assess the role of elevated concentrations of boron in barley (Hordeum vulgare L. cv. Giza 123) growth and yield as well as to test the involvement of some plant growth modulators in counteracting the boron-mediated retardations to improve its tolerance. Barley grains were treated with B concentrations of 0, 0.5, 1.5, 3.0 and 6.0 mg L-1 (as boric acid). The alleviation of the growth inhibition in the presence of 3.0 mg L-1 B was investigated by adding the following growth modulators: glutamic acid (1 or 3 mM ), glycine (1 or 3 mM), ascorbic acid (2 or 5 mM), salicylic acid (1 or 5 mM) and calcium chloride (1 or 5 mM). Barley grains were cultivated and samples were collected at vegetative (22-day-old), flowering (45-day-old) and harvesting stages (92-day-old). At vegetative stage, the application of 0.5 mg L-1 boron significantly increased (P ≤ 0.05) shoot fresh weight by 1%. The addition of 0.5 and 1.5 mg L-1 boron significantly increased (P ≤ 0.05 and 0.01) growth parameters (shoot and root fresh and dry weights) by 5%, leaf area by 4.5% and 7%, Chl a and Chl b contents by 3% and 7% at vegetative and flowering stages, respectively, and yield by 5.5%, compared to non-boron treated barley. The inhibitory effects of boron on barley growth started at concentrations above 3.0 mg L-1, causing decrease in all the measured parameters. The five tested growth modulators alleviated boron toxicity at 3.0 mg L-1 at the following sequence: salicylic acid (1 mM), calcium chloride 5 mM ≥, ascorbic acid (2 mM) ≥, glycine (1 mM) and glutamic acid (3 mM). The boron-alleviating efficiency of either 1 mM salicylic acid or 5 mM calcium chloride recommended their application when cultivating barley in boron contaminated soils.