Anatomical studies and the variation of raphid idioblasts concentration in the leaves of Araceae kept under different luminosity conditions

Abstract

The Araceae family includes about 105 genera and 3300 species, widely distributed in the Neotropics, including Brazil. The toxic properties of several species of Araceae are responsible for many accidents that occur, especially, due to calcium oxalate crystals in the form of raphids. These raphids develop inside idioblasts, which act as injector cells due to the manner that these crystals are liberated.The objective of this study was to verify a possible variation in the raphids concentration of the leaf tissue from cuttings cultivated under direct and continuous light and from cuttings cultivated under continuous shadow. These plants were compared with control plants, kept under normal luminosity conditions. The studied species were Dieffenbachia picta Schott, Monstera deliciosa Liebm and Philodendron bipinnatifidum Schott. To anatomical studies, free-hand sections and epidermis dissociation were made in both, leaf blade and petiole. Semipermanent slides were prepared according to standard protocols in plant anatomy. It was observed a sensitive increase in the raphid idioblasts concentration in leaf tissues of plants that were kept under continuous light compared to control specimens and to plants grown in continuous shadow. Because that, we concluded that luminous incidence of the former environmental condition led to an increase of toxicity levels in the studied species.