Vascular structure contributes to shoot sectoriality in Selaginella kraussiana

Abstract

Selaginella species are characterized by regular anisotomous dichotomous divisions of the shoot apical meristem, giving rise to two new axes (branches) which differ in size. A vital process is the formation of vascular connections, which enables continuous communication and consequent functional and developmental integration of a plant during branching. Here, we present the sequence of developmental changes in the vascular system of Selaginella kraussiana related to dichotomous branching. Stem vasculature in Selaginella kraussiana consists of two meristeles which change in arrangement during shoot development. Using dye tracers, we documented developmental functional isolation of meristeles associated with the specific structure of the stelar system, which results in a spatiotemporal sectoriality of the shoot. We discuss sectoriality in terms of possible significance for shoot development.

What can lycophytes teach us about plant evolution and development? Modern perspectives on an ancient lineage

“…Lycopodium clavatum and Lycopodium annotinum ; Figure 3; Gola et al, 2007). However, the vascular tissue arrangements of some lycophytes such as Selaginella can be difficult to characterise, as many species can have two or more protosteles (referred to as meristeles), which change their arrangement as the stem develops (Gola & Jernstedt, 2016). In contrast, monilophytes are siphonostelic, having a parenchymatous pith inside the xylem core.…”

“…Ferns differ from seed plants as the stele has interruptions in the main vascular cylinder at points of leaf insertion known as leaf gaps (solenostelic or dictyostelic), while seed plants can have many vascular bundles around the pith (eustelic; Figure 3; Gifford and Foster, 1989). Clearly, vasculature is common to all tracheophytes but cell type and vascular architectures are highly diverse (Gola & Jernstedt, 2016; Matsunaga, Cullen, & Tomescu, 2017). Such differences should be taken into account in selecting models for vascular evolution and development.…”

Drought‐induced lacuna formation in the stem causes hydraulic conductance to decline before xylem embolism in Selaginella

“…Trabeculae cells have a well-developed Casparian strip at the anticlinal cell walls, which may be additionally covered with a thin layer of cutin forming the trabecular ring (McLean & Juniper, 1979). The presence of a Casparian strip has been demonstrated to efficiently restrict the transport of water-soluble compounds from the vascular tissue into the apoplast of cortical cells (Gola & Jernstedt, 2016). Water in the xylem must traverse the trabeculae to irrigate photosynthetic tissue.…”

Origin & Evolution of the C3HDZ-ACL5-SACL Regulatory Module in Land Plants

“…Shoots have dorsi-ventral organization; leaf primordia arise in pairs and have a central vascular bundle (Figure 4A). During their growth, both SAM and root apical meristems (RAM) have dichotomous branching (Gola, 2014;Gola & Jernstedt, 2016;Harrison et al, 2007;Otreba & Gola, 2011). The SAM consists of one or two apical cells (Gola, 2014;Harrison et al, 2007) that produce the rest of the cells of the shoot, included the provascular cells at either side of the shoot (Gola & Jernstedt, 2016).…”

“…During their growth, both SAM and root apical meristems (RAM) have dichotomous branching (Gola, 2014;Gola & Jernstedt, 2016;Harrison et al, 2007;Otreba & Gola, 2011). The SAM consists of one or two apical cells (Gola, 2014;Harrison et al, 2007) that produce the rest of the cells of the shoot, included the provascular cells at either side of the shoot (Gola & Jernstedt, 2016). The S. kraussiana shoot vasculature is described as a protostele with two meristeles (see Glossary), or vascular bundles (Figure 4A) (Gola & Jernstedt, 2016).…”