Comparative leaf micromorphology and anatomy of the dragon tree group of Dracaena (Asparagaceae) and their taxonomic implications

Abstract

Micromorphological features of the leaf epidermis and the inner structure of leaf tissues of eight arborescent taxa of the genus Dracaena were analysed using light and scanning electron microscopy. The plants are xeromorphic or mesomorphic. Their leaves are isobilateral and amphistomatic, and the stomata are anomocytic and tetracytic. The mesophyll in all the species is divided into an outer chlorenchyma and a central region with colourless water-storage cells, chlorophyll cells and vascular bundles. Water-storage cells have wall bands and reticulate thickenings on the walls. The article describes and illustrates several new quantitative and qualitative leaf characters of the dragon tree group. Our findings can be used to identify the dragon tree group leaves, while the shape of epidermal cells and stomata types may be useful in the identification and classification of fragments of fossil leaves. We conclude that D. ombet and D. schizantha are not two distinct species, but should be treated as subspecies of D. ombet.

What We Know and What We Do Not Know about Dragon Trees?

“…schizantha, and D. serrulata). Based on morphological similarities [43,44] as well as DNA analyses (our unpublished data), D. ombet subsp. schizantha display some similarities not only with D. ombet subsp.…”

“…The leaf microstructure of Dracaena species ranges from mesomorphic to xeromorphic. Mesomorphic traits are the slightly bulging stomata, or stomata that are located at the level of other epidermal cells (e.g., D. draco, D. kaweesakii) [43,84] (Figure 3d), although slightly sunken stomata could also be observed (e.g., D. jayniana) [43]. Such stomata are more or less distributed in rows (D. draco, D. tamaranae, D. jayniana) [43,84], but the entirely scattered stomata were also observed (D. kaweesakii) [43].…”

“…The cuticle of more mesomorphic species is thinner, ranging approx. from 1 to 13 µm and fiber bundles are mostly hypodermal [43,84,85] (Figure 3b). The drought resistance of these species could also be very high, despite the more mesomorphic appearance, as a recent study on young transplants of mesophytic D. marginata confirmed [86].…”

The foliar characters in Callitris (Callitroideae, Cupressaceae s. str.) and their evolutionary and ecological significance

“…An identical Florin ring morphology is also known in some angiosperms (Oladele ); a recent example is that of some Dracaena species (Klimko et al. ). For angiosperms, the term commonly used for the rings is cuticular rim (Oladele ; Klimko et al.…”

“…For angiosperms, the term commonly used for the rings is cuticular rim (Oladele ; Klimko et al. ). Pariyar et al () have recently argued that Florin rings can have benefits both in humid and in xeric environments.…”