Laticíferos anastomosados na estrutura primária e secundária do caule de Calotropis procera (Aiton) W.T.Aiton (Apocynaceae)

Abstract

The structural type of laticifers and their distribution in the plant body has economic importance, particularly in rubber-producing plants or those used for the manufacture of medicines. The present study sought to describe the ontogeny of stem laticifers, in primary and secondary structure, of Calotropis procera (Apocynaceae) through structural, histochemical and ultrastructural analyses. In the primary structure, laticifers differentiate from the cells of the fundamental meristem of the cortex and pith and are concentrated adjacent to the outer and inner phloem of the bicollateral bundles. In the secondary structure, laticifers differentiate from the fusiform derivatives of the phloem and are distributed close to the sieve tube elements.

The structural type of laticifers present in the cortex, pith, and secondary phloem is the articulated anastomosed branched type, originating from the dissolution of the transverse and longitudinal walls of the precursor cells. The latex is a mixture of terpenes, alkaloids, flavonoids, mucilage, and protein related to the medicinal value of the species and to defense against herbivores and phytopathogens. The apical meristem and the vascular cambium, where laticifers are formed, are active throughout the year. The vascular cambium produces phloem and laticifers during the rainy season, when the highest values ​​of day length, rainfall, and temperature are recorded. This work expands the knowledge about the development of laticifers in the species and about adaptive aspects, since the species is invasive and successful in dry environments.