Cell Structure and Dynamics of Galactomannan Secretion in Caesalpinia pulcherrima (Leguminosae) Endosperm

Galactomannans are a typical reserve polysaccharide in the endosperm of leguminous seeds; they turn the endosperm hard when dry and gelatinous and swollen when hydrated. Although galactomannans of several species have been biochemically characterized, little is known about their deposition within the endosperm. This study aimed to clarify how polysaccharides, galactomanans according to the literature, are produced and stored in the endosperm of Caesalpinia pulcherrima seeds by describing its structural and ultrastructural features throughout development. Samples of seeds at different developmental stages were collected and processed for study under light and electron microscopy. During development, the endosperm of C. pulcherrima undergoes substantial anatomical modifications associated with cellular cycles of polysaccharide release that gradually accumulates in the intercellular spaces. Endosperm cells exhibit an active Golgi apparatus with intense polysaccharide production, confirming their secretory function. In the mature endosperm, polysaccharides are stored in periplasmic and intercellular spaces rather than in thickened cell walls, as previously reported for other Leguminosae. By showing that galactomannans accumulate in periplasmic and intercellular spaces rather than in cell walls, our findings expand current understanding of endosperm diversity in Leguminosae and provide a foundation for future comparative studies on galactomannan synthesis and deposition across the family.