Glandular trichomes and laticifers in leaves of Ipomoea pes-caprae and I. imperati (Convolvulaceae) from coastal Restinga formation: structure and histochemistry

Glandular trichomes and laticifers occur in I. pes-caprae (L.) Stweet (Convolvulaceae) and I. imperati (Vahl) Griseb. However, the importance of their secretion for the species survival in Restinga'' environments had not yet been investigated. This study aimed to anatomically and histochemically characterize such secretory structures in the two species, indicating which type of laticifers they have and whether or not the trichomes secret saline solution. Moreover, knowing the composition of secretion can help to clarify the species strategies of survival under the stressful conditions in halophilous ecosystems. Leaf samples were used in light microscopy analyses. Both species have multicellular glandular trichomes on the leaf blade, and laticifers on the mesophyll and midrib. Trichome secretion is mucilaginous, but sodium was not detected, and therefore, such trichomes are not salt glands. Laticifers are typical and classified as articulated non-anastomosing, and are not covered by an epithelium, as reported in some studies. Mucilage secretion by the glandular trichomes can aid in the species survival in the Restinga''. The species latex contains terpenoids and rubber, which may constitute important defenses against herbivores.