Effects of seed pre-treatment with a calcium paste on the growth, phytohormone content, and enzyme activities in bean (Phaseolus vulgaris L.) seedlings grown under high NaCl stress

Abstract

SummaryThe effects of the application of a novel calcium paste (CRH) [a 2:6:1 (w/w/w) kneaded mixture of calcium sulphate, ground rice bran, and humic acid] as a seed coating on the growth, gibberellic acid (GA3) and abscisic acid (ABA) contents, and activities of carbonic anhydrase (CA) and nitrate reductase (NR) in the leaves of Phaseolus vulgaris L. seedlings grown under 120 mM NaCl saline stress were studied. Two greenhouse experiments were performed, each over 5 weeks, in a completely randomised design with four treatments [control (seeds not treated with CRH or NaCl); or seeds treated with 120 mM NaCl; CRH; or 120 mM NaCl + CRH] were applied with four replicates. The results indicated that NaCl stress significantly reduced plant growth, leaf photosynthetic pigment levels, ascorbic acid (AsA), nitrogen (N), and calcium (Ca) contents, and the Ca:Na ratio. The activities of CA and NR, and the content of GA3 were also decreased by 120 mM NaCl. In contrast, the free proline, sodium ion (Na+), and ABA contents of leaves were increased by 120 mM NaCl. However, the application of CRH to seeds prior to sowing mitigated the toxic effects of NaCl stress on bean seedlings and improved their growth characteristics, as well as leaf contents of photosynthetic pigments, AsA, free proline, N, and Ca. Ca:Na ratios, and CA and NR enzyme activities were also enhanced by CRH, while Na+ ion and ABA levels were reduced. This study highlights the potential ameliorative effects of CRH in mitigating the phytotoxicity of NaCl stress in seeds and growing seedlings. We recommend using CRH as a seed coating to enhance the early stages of plant growth in saline soils.