Bark anatomy in Croton draco var. draco (Euphorbiaceae)

Abstract

Many arboreal forms of the genus Croton (ca. 800 spp.), amply distributed in the Americas, have latex‐producing cells in their bark, which is widely used in traditional medicine to treat skin infections and some forms of cancer. Studies validate its ethnomedicinal use—more than 20 pharmaceutically important secondary metabolites have been reported for its latex and bark—but anatomical and ecological studies are scarce. Given this species’ ample distribution, laticifer abundance could be affected by the environment. We tested this for genetically similar trees growing in two types of vegetation in Veracruz, Mexico at sites commonly visited by traditional doctors. We describe the bark anatomy of C. draco, focusing on the laticifers, histochemically characterize the bark and the latex extracted from it, and document differences in laticifer abundance in the two environments. We have also identified another cell type (what we call type B) in the secretory latex system and describe it histochemically and microscopically. The location of bark cells that contain essential oils is reported here for the first time. Given the genetic similarity of the trees at both sites, the between‐site variation in the number of laticifers in stem and branch bark appears to be an effect of the environment.

Efficiency of the Polyethylene-Glycol (PEG) Embedding Medium for Plant Histochemistry

“…Thus, Karnovsky's fixative provides an ideal mixture of these two compounds for an efficient fixation because formaldehyde can "pre-stabilize" the tissue while waiting for the glutaraldehyde to diffuse through the sample (Paljärvi et al 1979). Even though fixed samples have been more rarely used in plant histochemistry, some authors have been successfully using FAA (formaldehyde, acetic acid and ethyl alcohol solution) (Farías et al 2009) or Karnovsky's solution in their tests (Cahill et al 1989). The results of the current study reinforce the applicability of Karnovsky's solution for histochemical analyses, and its usefulness when fresh material is not available.…”

Microscopic Characterization of Croton cordiifolius Baill. (Euphorbiaceae)

“…In C. draco was reported the presence of fibers in the external phloem. 32 Farías et al 32 also observed crystals in the sclerenchyma. According to Franceschi and Nakata, 34 the morphology of the crystals produced can be of a single type throughout the plant, or several types being each specific for a particular organ, or several types within the same organ.…”

“…In C. rhamnifolius the cortical region is composed by collenchyma and parenchyma, while in C. rhamnifolioides, C. draco and C. cordiifolius only parenchyma is found. [31][32] However, in the cortical parenchyma of C. rhamnifolioides were observed fibers, laticifers and starch, 31 while in the cortical parenchyma of C. draco were found crystals, 32 besides the other mentioned elements for C. rhamnifolioides. In this study is also verified the presence of all these elements previously mentioned for the cortical region of the other species of Croton, however, it is also noted the presence of lignified cells.…”

Morphoanatomy and pharmacognostic study of the wood of Croton echioides, the Northeastern Marapuama

“…This tissue contains compound starch grain ( Figure 6C) and abundant laticifers ( Figures 4A, 4B, 5A, 5B, and 6A, 6C, and 6D). According to Farias et al (2009), the presence of latex in the cortical portion of the stem is common in many species of the genus Croton. Although few studies describe the anatomical tissues of the stem of species of Brazilian Croton, Silva (2006) reported the occurrence of laticifers located near the region of the stem phloem of C. floribundus.…”