Cell wall hydrolases in the seeds of Euphorbia heterophylla L. during germination and early seedling development

Abstract

Activities of cell wall hydrolases of Euphorbia heterophylla L. (wild poinsettia) endosperm were investigated during pre- and post-emergence periods, defined as the time interval before and after 2.2 days from the start of imbibition, respectively. The activities of endo-beta-mannanase and beta-mannosidase are higher over the pre-emergence when compared to the post-emergence period and they may be involved in the process of germination in E. heterophylla. On the other hand, the activities of beta-galactosidase, beta-glucosidase, alpha-xylosidase, beta-xylosidase and glucanases, which hydrolyse CMC, xyloglucans from Hymenaea courbaril or Copaifera langsdorffii, xylan, Avicel and lichenan, are higher over the post-emergence period. Activity on laminarin occurs over both periods. The activity of xyloglucanases was promoted in the presence of oligosaccharide XXLG. E. heterophylla endosperm surrounds the embryo and their cotyledons, which increases in area after 1 day from the start of imbibition. Rather than the mobilization of cell wall reserves the activity of hydrolases over the post-emergence period may be related to facilitation of cotyledon expansion by lowering endosperm resistance. The fraction of water-soluble polysaccharides extracted from the seed coat is composed of mannose (15.9 %), galactose (20.5 %), and glucose (63.6 %) whereas the fraction from decoated seed is composed of glucose (11.0 %), galactose (36.9 %) and xylose (47.9 %).