Objective Secreting mucilage is a special function evolved by the seeds of many plant species to cope with the complex environment, which holds extremely important biological significance. This study aims to explore the properties and physiological functions in water retention and stress resistance of Ulmus pumila seed mucilage. It intends to provide an important theoretical basis for unraveling the ecological adaptation mechanisms of woody plants under adverse stress.

Method Using intact U. pumila seeds and demucilage seeds as experimental materials, with arabidopsis seeds serving as a reference, the physical properties and morphology of the mucilage were observed under a stereo microscope and a scanning electron microscope. The water retention capacity of seed mucilage was analyzed by low-field nuclear magnetic resonance method. The monosaccharide composition of seed mucilage was analyzed by ion chromatography. By comparing the germination of intact elm seeds and demucilage seeds under various stresses, the physiological role of mucilage on seeds was explored.

Result (1) It was observed that the seed mucilage of elm could be released upon contact with water and could be stained by ruthenium red. After imbibing in water, the intact seeds could retain water amounting to 9 times of their own mass, while the demucilage seeds could only retain water equivalent to 1.5 times of their own mass. Compared with demucilage seeds, the content of free water in the intact seeds increased significantly. (2) The mucilage of U. pumila seeds contained six types of monosaccharides, namely galactose, galacturonic acid, rhamnose, glucose, glucuronic acid, and arabinose, with pectin and cellulose as main polysaccharide components. (3) Compared with intact seeds with mucilage retained, the demucilage seeds were more sensitive to osmotic stress, drought stress and environments with different pH values, and both germination percentage and germination potential decreased significantly.

Conclusion The above results indicate that the presence of mucilage has greatly enhanced the seed’s own water absorption and water retention capacities, thereby significantly improving the resistance of elm seeds to salt stress, osmotic stress and highly acidic or alkaline environments.