Abstract Detail

Development and Structure

Quintanar Castillo, Angélica [1], Pace, Marcelo [2].

The first report of a cambial variant in the Bunchosia clade (Malpighiaceae): Ontogeny and structure of the included phloem wedges in the old-world genus Tristellateia.

Tristellateia is a paleotropical genus of woody vines and represents one of the nine lineages in Malpighiaceae that dispersed from the New World to the Old World. In recent collections, we noted the presence of included phloem wedges in stems of Tristellateia, a type of cambial variant that had not been previously reported in Malpighiaceae and the first cambial variant outside of clade Tetrapteroids. Using Tristellateia greveana as a model, here we describe the ontogeny of the included phloem wedges. In the early stages of growth, the stem of T. greveana has a single, continuous, regular cambium, and by a differential activity of the vascular cambium, the phloem begins to form small invaginations that match the interfascicular regions. Subsequently, these invaginations become increasingly more conspicuous resulting in phloem wedges that are flanked by wide limiting rays that have abundant prismatic crystals. The cambium becomes discontinuous, with portions included on the interior of the phloem wedges and portions in between these wedges. In some wedges the limiting rays and part of the secondary xylem appear to exert pressure on both sides of the wedge, beginning to encapsulate them within the wood forming included phloem islands. Furthermore, the phloem wedges present a greater abundance of prismatic crystals and druses than the inter-wedge region. Phloem wedges are a cambial variant that occur in some families and can be defined by either the continuity or discontinuity of the cambium. Here we described the formation of wedges with a discontinuous cambium, followed by wedge inclusion in the wood. This type of cambial variant is not only rare in other plants, but also represent a novel type of cambial variant for the family Malpighiaceae and potentially a synapomorphy for the genus Tristellateia. Moreover, the presence of prismatic crystals in secondary phloem has not been reported in other family members rather than a couple of genera in the clade Bunchosia suggesting this feature could be another synapomorphy for the clade. This work is part of a project that seeks to understand the evolution and diversity of the vascular system in the group through the anatomy and ontogeny under a phylogenetic context.

1 - Universidad Nacional Autonoma De Mexico, Posgrado en Ciencias Biologicas, Instituto de Biología, Cto. Zona Deportiva S/N, C.U., Coyoacan, Mexico City, DIF, 04510, Mexico, Mexico City, EX, 04510, México
2 - Universidad Nacional Autonoma de Mexico, Botany Department, Circuito Zona Deportiva sn, Mexico City, DF, 06700, Mexico

Keywords:
cambial variant
development
stem anatomy
vascular system
Malpighiales
vines.

Presentation Type: Oral Paper
Session: DS3, Development and Structure III
Location: /
Date: Thursday, July 22nd, 2021
Time: 11:00 AM(EDT)
Number: DS3005
Abstract ID:747
Candidate for Awards:Katherine Esau Award,Developmental and Structural Section Graduate Student Registration Award