More than just a coating: Ecological importance, taxonomic occurrence and phylogenetic relationships of seed coat mucilage

Studies on the ecological importance of seed coat mucilage have provided valuable information about its roles in critical stages of the plant life cycle. Seed mucilage may, by providing a moist environment and maintaining metabolic activity in the seed, promote seed development. In seed dispersal, seed mucilage influences topochory, epizoochory, endozoochory and hydrochory by anchorage of seeds to soil surface, lubrication or changing the specific weight of the seed. In arid environments, seed mucilage can prevent seeds from drying or initiate DNA repair mechanisms, thereby maintaining the soil seed bank. Seed mucilage reduces oxygen diffusion to the seed and thus has a role in regulating seed dormancy. Due to it being hydrophilous, acting as a physical barrier and containing chemicals, seed mucilage is proposed to promote seed germination in favorable environments. In seedling growth, seed mucilage may lubricate the radicle as it penetrates the soil and be degraded by soil microfloras and thus promote seedling growth. Further investigation of seed mucilage for more species in diverse habitats from the perspectives of evolution, genetics, proteomics, phylogeny and plant-microbe interactions would contribute substantially to our understanding about its ecological importance.