Changes in exudate composition during the development of the ovary glands in Aptenia cordifolia

Abstract

Summary Constituent monomers of the polysaccharide fraction of ovary exudates obtained from flowering Aptenia cordifolia-plants were separated (after hydrolysis) using anion exchange chromatography of their borate complexes and were analysed subsequently by colorimetric detection. The polysaccharide composition of the exudates shows a demonstrable correlation to the developmental stages of the ovary glands. There is no significant variation in polysaccharide composition during the pre-degenerative stages (in total about 10 days), with exception of a moderate quantitative increase of glucose, xylose, galactose, arabinose, glucosamin, and galactosamin and of a moderate decrease of galacturonic and glucuronic acids. In contrast, during the transition period from the pre-degenerative to the degenerative stage, there is a dramatic quantitative increase of xylose, galactose and arabinose; a strong decrease of glucose and glucosamin; and a complete disappearance of the uronic acids. This significant change in the polysaccharide composition is probably based in large part upon an enzymatic digestion of the gland cell walls. From the polysaccharide composition of the different phases can be concluded that pectic substances are initially secreted. Subsequently, other non-cellulosic polysaccharides which contain a large portion of glucose, galactose and arabinose are secreted, as well as small quantities of glycoproteins. During the degeneration of the ovary glands, presumably xylan-based hemicelluloses are accumulated in the ovary exudate. By comparison of the polysaccharide composition with the gland ultrastructure at different stages, it is shown that the transport and the extrusion of pectic substances, of glycoproteins, and of other non-cellulosic polysaccharides probably proceeds via the Golgi apparatus. Also demonstrated is that the hemicelluloses are contributed to the exudate during cell wall digestion. The identification of gentiobiose and melibiose indicates the existence of gentianose and raffinose, or of their oligomers in the polysaccharide fraction.