Microscopy observations reveal a new glandular morphology in four Pinguicula L. species

The adaxial leaf surface of butterworts (Pinguicula L.) presents specialized structures for carnivory, such as trichomes and sessile glands. The micromorphology of abaxial leaf surfaces has rarely been investigated; therefore, this study aimed to compare the micromorphology of adaxial and abaxial surfaces through electron scanning microscopy (SEM) and light microscopy (LM). We selected four species occurring in the Eastern Alps. All the species showed the same pattern: trichomes and sessile glands occurring only on the adaxial surface; stomata occurring on both surfaces with significant differences in density and size; and four-cells glands occurring only on the abaxial surface. The four-cells gland is a micromorphological structure that has never been described before, and its eco-physiological function needs to be investigated.