Polysaccharides extracted from Moroccan seaweed: a promising source of tomato plant growth promoters

摘要

The present study investigates the use of seaweed polysaccharides as biostimulants of seed germination and plant growth. Seventeen species of Moroccan seaweeds were collected and screened for their crude polysaccharide content which ranged from 0.3 to 34% (dry weight basis). Chemical analyses of the obtained polysaccharide-enriched extracts (PEEs) were performed. Two bioassays were carried out to study seed germination and growth-promoting activity of PEEs. In the first experiment, the effect of PEEs on tomato seed germination was carried out under in vitro conditions. Half-strength Murashige-Skoog medium was supplemented with different PEEs at the concentration of 0.2mgmL(-1) (w/v). The germination percentage was recorded daily over 4days. In a second experiment, tomato plants were grown in greenhouse conditions and watered with aqueous solution of seaweed PEEs (0.1mgmL(-1)). After 30days, the evaluated plant growth parameters were plant length, fresh and dry weight of plants shoots and roots, as well as chlorophyll content. Results showed that six seaweed species were a promising source of PEEs with beneficial effect on germination, plant biomass, and chlorophyll content. Two green seaweeds: Ulva rigida and Codium decorticatum, two red seaweeds: Gigartina sp. and Chondracanthus acicularis, and two brown seaweeds: Fucus spiralis and Bifurcaria bifurcata enhanced seed germination and plant growth. Nevertheless, the PEEs obtained from the red seaweed Gigartina pistillata inhibited seed germination. Principal component analysis of the results showed positive correlation between the sulfate content of PEEs and shoot dry weight as well as chlorophyll content.