Abstract
Soil salinity reduces plant growth and is a major factor that causes decreased agricultural productivity worldwide. Seaweed polysaccharides promote crop growth and improve plant resistance to abiotic stress. In this study, polysaccharides from brown seaweed Lessonia nigrescens polysaccharides (LNP) were extracted and further separated and fractionated. Two acidic polysaccharides (LNP-1 and LNP-2) from crude LNP were obtained and characterized. The latter had a lower molecular weight (MW) (40.2 kDa) than the former (63.9 kDa), but had higher uronic acid and sulfate content. Crude LNP and LNP-2 were composed of mannose, glucuronic acid, fucose, and xylose, whereas LNP-1 has little mannose. Moreover, the effects of the three polysaccharides on plant salt tolerance were investigated. The results showed that crude LNP, LNP-1, and LNP-2 promoted the growth of plants, decreased membrane lipid peroxidation, increased the chlorophyll content, improved antioxidant activities, and coordinated the efflux and compartmentation of intracellular ion. All three polysaccharides could induce plant resistance to salt stress, but LNP-2 was more effective than the other two. The present study allowed to conclude that both MW and sulfate degree contribute to salt resistance capability of polysaccharides derived from L. nigrescens.
Highlights
Soil salinization is a major environmental problem that restricts crop growth and yield worldwide, mainly due to osmotic stress and ion toxicity (Rivero et al, 2014)
The three polysaccharides differed in the amount of carbohydrate, protein, uronic acid, and sulfate content (Table 1), with Lessonia nigrescens polysaccharides (LNP) showing a significantly lower carbohydrate content (67.4%) than either LNP-1 (87.3%) or LNP-2 (84.0%)
Our study demonstrated that exogenous supply of polysaccharides from L. nigrescens could alleviate the adverse effects of salt stress on the growth of wheat seedlings through improving antioxidant activities and regulating the efflux and compartmentation of intracellular ions
Summary
Soil salinization is a major environmental problem that restricts crop growth and yield worldwide, mainly due to osmotic stress and ion toxicity (Rivero et al, 2014). High salt concentration in the soil has a devastating effect on plant metabolism, disrupting cellular homeostasis and uncoupling major physiological and biochemical processes. Plants have evolved a ubiquitous mechanism of salinity resistance, involving synthesis and accumulation of compatible compounds, sodium sequestration in vacuoles, and enhancing antioxidant enzymes activities. These specific strategies regulate cell penetration and control ion and water homeostasis to minimize stress damage and sustain growth
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