MORPHOLOGY, ANATOMY, AND EXUDATES OF STIPULAR COLLETERS IN CASEARIA JACQ. (SALICACEAE) ACROSS TWO TROPICAL PLANT COMMUNITIES

Premise of research. In Casearia Jacq., one of the largest genera of Salicaceae, stipular glands are taxonomically important, although these structures have not previously been described anatomically. The aims of this study were to clarify the gland type present on the stipules of three species of Casearia and describe anatomical variations of these glands in Cerrado and forest specimens. Methodology. Samples of Casearia decandra Jacq., a typical forest species; Casearia rufescens Cambess., which is endemic to Cerrado; and Casearia sylvestris Sw., which occurs in both vegetation types, were collected. Samples of stipules and apical meristems were collected in the field or obtained from herbarium material and processed according to standard methodologies for anatomical studies. Pivotal results. Glands occur at the apex, on the margin, and at the base of the stipules of C. decandra and only at the apex and the base of C. rufescens and C. sylvestris. The glands consist of a nonvascular, multicellular, parenchymatous central axis, which is covered by a layer of secretory palisade epidermis, and a thin cuticle. No anatomical differences among the glands of the species and specimens were observed. Histochemical tests detected total polysaccharides, pectins/mucilage and proteins in the cytoplasm, the secretion in the subcuticular space, and the exudate. Based on these tests, the glands are colleters. The histochemical results were the same for the secretion produced by colleters of the species from different environments. In general, no correlation was found between gland size and vegetation type (forest and Cerrado). Conclusions. The anatomical structure, early activity, and mucilaginous nature of the secretion allow us to conclude that the stipule glands of the three species of Casearia are the standard type of colleter. This is the first record of colleters on stipules of Casearia, which may be taxonomically useful.