Role of mucilage in seed dispersal and germination of the annual ephemeral Alyssum minus (Brassicaceae)

Abstract

Seeds of Alyssum minus, an annual ephemeral in shrublands of north-west China, can produce a large amount of mucilage. The primary aim of this study was to explore the role of mucilage in seed dispersal, settlement onto the soil surface and germination of this species. Width of imbibed seeds with mucilage was three times greater than that of seeds without mucilage, and mass of mucilage increased 167 times after imbibition. Expanded dry mucilage significantly increased wind dispersal of seeds. Floating time on water was greatest for seeds without mucilage, and adherence of soil particles to seeds was greater for seeds with mucilage than for those without mucilage. Mucilage increased rate of water uptake and decreased rate of water loss, and it significantly decreased germination of 0- and 4-week-old seeds. Gibberellic acid promoted germination of 0- and 4-week-old seeds with and without mucilage, but its effect depended on seed age and incubation temperature. Seeds with mucilage subjected to water stress during imbibition and/or incubation germinated faster than those without mucilage. Presence of mucilage on seeds during imbibition significantly increased germination percentages under increased water stress, a first report of this phenomenon. The study has shown that the mucilage of A. minus plays an important role in seed dispersal, seed adhesion to soil (thereby minimising removal by water and predators), seed hydration via increasing surface contact with the substrate, and can serve as a water reservoir for germination, especially under moisture stress.