A rare climbing habit: Functional properties of the leaf-climbing monocot Flagellaria indica (Flagellariaceae)

Abstract

Monocot climbers have evolved all types of attachment mechanisms using the surrounding vegetation to reach the sunlight. The monocot climber Flagellaria indica, unique in its attachment type via coiling tendril-like leaf tips, was used to study development and attachment properties. Biomechanical experiments on the attached leaves were combined with anatomical investigations via light and scanning electron microscopy to analyse the functional properties of this unique attachment mode. Anatomical observations of leaf and leaf tip were compared to that of the monocot climber Gloriosa superba (Colchicaceae).The attachment process of modified leaf apices takes 4–5 weeks with the leaf passing different developmental stages. The parallel veined leaf is characterised by closed collateral vascular bundles with adaxial xylem, abaxial phloem and sclerenchymatic bundle sheaths. The anatomy of the modified leaf apex changes during development and attachment. In adaptation to the climbing growth habit the leaf tip shows massive lignified bundle sheaths abaxially and a collenchymatic cell layer adaxially lignifying during attachment. The papillate epidermis cells and a thick wax layer in the attachment region increase the friction between leaf tip and support structure. Host characteristics, leaf properties and stage of attachment affect the stability of the connection between leaf and support. The complex interactions between anatomical and biomechanical properties of leaf and modified tendril-like leaf tip highlight the adaptations of a climber without secondary growth.