Contrasting seed morphology dynamics in relation to the alleviation of dormancy with soil storage

Abstract

We examined the effect of prolonged (up to 450 days) soil burial in the field on seed morphological traits (seed coat structure, permeability) to identify their potential roles in seed dormancy and release. Such traits were examined in species with seeds that demonstrated an obligate requirement for soil storage before germination: the dormant seeds of Anigozanthos manglesii D. Don, Conostylis neocymosa Hopper, Stylidium affine Sonder, and Stylidium crossocephalum F. Muell., and the deeply dormant fruits of Leucopogon conostephioides D.C. We detected species-specific and environmentally induced variation in seed morphology following soil burial. In A. manglesii and L. conostephioides, a significant deterioration of the seed coat or fruit wall and an increased permeability of the seed coat to water and solutes were correlated with germination responses. In these species, the seed coat and (or) fruit wall delayed germination until (morpho) physiological dormancy was broken. In C. neocymosa, S. affine, and S. crossocephalum, weathering of the seed coat, permeability, and germination were not correlated traits. These species appeared to possess physiological dormancy mechanisms and required environmental cues for dormancy release.Key words: physiological dormancy, soil burial, seed coat, morphology.