Micromorphology and Histochemistry of the Laticifers from Vegetative Organs of Asclepiadoideae species (Apocynaceae)

Micromorphology and main substances of the laticifer walls and latex of Asclepias curassavica, Fischeria stellata, Gonioanthela axillaris, Matelea denticulata, and Oxypetalum banksii were analyzed and compared with those of Apocynacean Cerrado species. Laticifers of the studied species from different rainforest vegetations exhibit similar features. The walls are primary, highly hydrated, pectic-cellulosic, and firmly attached to adjacent cell walls. The latex is milky white, constituted by polysaccharides, including mucilage, proteins, lipids, including fatty acids, phenolic compounds, and alkaloids; however, Fischeria and Gonioanthela differ from the other species for also producing neutral lipids. The latex of the investigated species is related to plant defense against herbivory, and may be toxic and inhibit microorganism proliferation. Also, it can coagulate, sealing plants wounds and working as a physical barrier. These latex properties provide greater adaptive advantage to these plants in relation to non-latescent plants.