Abstract
BackgroundSoil salinity, one of the major abiotic stresses affecting germination, crop growth, and productivity, is a common adverse environmental factor. The possibility of enhancing the salinity stress tolerance of Cassia obtusifolia L. seeds and seedlings by the exogenous application of 5-aminolevulinic acid (ALA) was investigated.ResultTo improve the salinity tolerance of seeds, ALA was applied in various concentrations (5, 10, 15, and 20 mg/L). To improve the salinity tolerance of seedlings, ALA was applied in various concentrations (10, 25, 50, and 100 mg/L). After 10 mg/L ALA treatment, physiological indices of seed germination (i.e., germination vigor, germination rate, germination index, and vigor index) significantly improved. At 25 mg/L ALA, there was a significant protection against salinity stress compared with non-ALA-treated seedlings. Chlorophyll content, total soluble sugars, free proline, and soluble protein contents were significantly enhanced. Increased thiobarbituric acid reactive species and membrane permeability levels were also inhibited with the ALA treatment. With the treatments of ALA, the levels of chlorophyll fluorescence parameters, i.e., the photochemical efficiency of photosystem II (Fv/Fm), photochemical efficiency (Fv'/Fm'), PSII actual photochemical efficiency (ΦPSII), and photochemical quench coefficient (qP), all significantly increased. In contrast, the non-photochemical quenching coefficient (NPQ) decreased. ALA treatment also enhanced the activities of superoxide dismutase, peroxidase, and catalase in seedling leaves. The highest salinity tolerance was obtained at 25 mg/L ALA treatment.ConclusionThe plant growth regulator ALA could be effectively used to protect C. obtusifolia seeds and seedlings from the damaging effects of salinity stress without adversely affecting plant growth.Electronic supplementary materialThe online version of this article (doi:10.1186/1999-3110-54-18) contains supplementary material, which is available to authorized users.
Highlights
Soil salinity, one of the major abiotic stresses affecting germination, crop growth, and productivity, is a common adverse environmental factor
The present paper provides the first evidence of the capability of aminolevulinic acid (ALA) to protect C. obtusifolia seeds and seedlings against salinity stress, significantly contributing to the understanding of the ALA role in promoting salinity stress tolerance
The indices of seeds treated with only NaCl (CK2) significantly differed from the control (CK1).The indices improved after the treatment of ALA (CK3, 10 mg·L-1)only
Summary
One of the major abiotic stresses affecting germination, crop growth, and productivity, is a common adverse environmental factor. Several protective mechanisms change to different extents with increased amounts of oxygen free radicals. Such mechanisms include those involving free radical and peroxide scavenging enzymes, e.g., superoxide dismutase (SOD), peroxidase (POD), and catalase (CAT) (McDonald 1999; Li et al 2008). H2O2 removal via a series of reactions is known as the ascorbate glutathione cycle In this cycle, ascorbate and glutathione participate in a cyclic transfer of reducing equivalents resulting in the reduction of H2O2 to H2O using electrons derived form nicotinamide adenine dinucleotide phosphate (Goel and Sheoran 2003). Some other symptoms of salinity stress include malondialdehyde increase, protein degradation
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