A new interpretation on vascular architecture of the cauline system in Commelinaceae (Commelinales)

Abstract

The vascular system of monocotyledons, including Commelinaceae, has been studied since the 19 th century, but to date, the proposed vascular architecture models consist of schematic representations partially based on the authors' interpretation. One of the greatest difficulties in studying these systems is the large number of vascular bundles and the complexity of their connections, especially in the monocotyledons which have a nodal vascular plexus. In this study, shoot apex samples of 14 species of Commelinaceae were submitted to three-dimensional analyses (confocal microscopy, X-ray microtomography, graphic vectorization, and whole-mount diaphanization), as well as conventional techniques in plant anatomy. Based on the results, a previously unreported category of bundles is described in Commelinaceae for the first time, as well as the fact that peripheral bundles are not interrupted or end blindly in the periphery of the pith, as previously thought. With this new interpretation of the vascular architecture, three patterns of nodal vascular plexus are proposed: 1) in the first pattern the internal nodal vascular plexus (IVP) forms a continuous cylinder and does not connect to the external nodal vascular plexus (EVP); 2) the IVP forms a cylinder divided into two columns and does not connect to the EVP and 3) the IVP forms a cylinder connected to the EVP. The first description of central bundles in the Commelinaceae might suggests their existence in closely related groups, such as the remaining four families of Commelinales (i.e., Haemodoraceae, Hanguanaceae, Philydraceae, and Pontederiaceae), and even in other distantly related groups of monocotyledons.

Diversity, distribution, development, and evolution of medullary bundles in Nyctaginaceae

“…As pointed out by other authors (de Bary, ; Inouye, ; Pant and Mehra, , ) and observed in the present study, medullary bundles may eventually anastomose or bifurcate in the nodes on their trajectory between the lateral organs and the axis. In our study, this pattern was particularly evident in Colignonia glomerata , with the formation of a nodal plexus, comparable to those described for monocot stems (Tomlinson and Fisher, ; Vita et al., ). Similarly, instead of “ending blindly in the stem” as mentioned by earlier authors (Lambeth, ; Pant and Bhatnagar, ), medullary bundles eventually shifted their trajectory and/or anastomosed with other bundles.…”

“…Although the arrangement of medullary bundles in Nyctaginaceae may be similar in appearance to the stele of monocots, there are differences in origin, development, and structure. Differently from Nyctaginaceae and other plants with medullary bundles, monocots generally possess several bundles seemingly uniformly spaced (i.e., ordered; sensu Korn, ), which may be formed by two types of bundles, the bundles that form leaf traces and cauline (axial) bundles that are not continuous with the leaves (Tomlinson, ; Cattai and Menezes, ; Botânico and Angyalossy, ; Vita et al., ).…”

EvoDevo: Past and Future of Continuum and Process Plant Morphology

“…For example, Kinoshita and Tsukaya [69] wrote: "In the aboveground portion of a typical seed plant, a shoot is composed of the repetition of a unit called a phytomere consisting of a stem and a determinately growing leaf." Rohweder (1963) [99] and more recently Vita et al [100] described and illustrated obvious phytomeres in growing shoots of herbaceous flowering plants such as Commelinaceae while focusing on leaf-related vascular tissue inside the stems, somewhat similar to a chain of inverted cones sticking into each other. The term phytomere is also applied to Arabidopsis, e.g., by Müller-Xing et al [93]: "Phytomeres are metameric units that are composed of internode and node (leaf plus axillary meristem).…”

Particle-Based Imaging Tools Revealing Water Flows in Maize Nodal Vascular Plexus

“…In the study [16], the images of root-soil systems obtained by micro-CT were analyzed to measure the porosity and the displacement fields in the soil near the maize root surface. A combination of micro-CT with the other imaging methods, including confocal microscopy, revealed the vascular architecture of the cauline system in Commelinaceae [17].…”