Comparative leaf anatomy of two species of L. (Convolvulaceae): taxonomic importance and adaptations to xeric conditions of the cangas.

BACKGROUND

Accurate species identification is the first step towards establishing conservation strategies, especially regarding rare and threatened species, such as those studied here. Moreover, understanding the responses to the environment and growing conditions of endemic species is necessary for its conservation. This study compares the leaf anatomy of and , which grow on the Brazilian ironstone outcrops (cangas) and exhibit morphological convergence.

METHODS

Leaf anatomical characters of the species were described. Additionally, the leaf adaptive potential of was evaluated, comparing individuals grown in natural canga areas () and cultivated in topsoil (. Quantitative analysis evaluated stomatal density, polar and equatorial diameter of stomata, and thickness of the epidermis and mesophyll.

RESULTS

and can be distinguished by the mesophyll type. is also characterized by the presence of lateral protuberances on the abaxial surface of the midrib. Individuals of under cultivation have lower stomatal density, although their functionality (polar/equatorial diameter) is more significant than those grown in a natural environment; these individuals also exhibit leaves with a thinner cuticle, abaxial epidermal cells with more sinuous walls, a lower occurrence of trichomes and secretory cells (laticifers), and more druse-containing idioblasts in the mesophyll. All these traits are adaptations to growing conditions that include lower light and the absence of water stress.

CONCLUSIONS

Leaf anatomical traits showed to be useful to delimit and in the non-reproductive stage. For individuals of cultivated in topsoil, some features, especially of the epidermis, respond to light and water supply.