Micromorphology of stem surface in three species of Bambusa (Poaceae, Bambusoideae) with a focus on its impact on plant-insect interactions

Abstract

The aim of this study was to analyse the microstructure of the young stem (culm) surface in tree bamboo species of the genus Bambusa (B. chungii, B. emeiensis and B. multiplex). We examined the outermost layers of culm sheaths and internodes using scanning electron microscopy. The species studied show differences in the presence of trichomes and waxes on sheaths and internodes: only trichomes on sheaths of B. emeiensis, only 3-dimensional epicuticular wax coverage on internodes of B. chungii and sheaths of B. multiplex, and a combination of trichomes and waxes on sheaths of B. chungii and internodes of B. multiplex. Trichomes in all three species studied are of the same type (non-glandular, non-branched) with a similar structure (unicellular, hollow inside, with thin wall) and shape, but have different dimensions. The epicuticular wax coverage in both B. chungii and B. multiplex are composed of longitudinally aggregated rodlets. The degree of coiling and dimensions of the aggregates as well as diameter of the terete rodlets, their number in rows, and the number of rows in aggregates differ among the species. The contribution of trichomes and the epicuticular wax coverage to the plant protective function against insects is discussed. Hairy and waxy stem surfaces, hampering the access of ants to aphid colonies via reducing ant attachment ability, represent the phenomenon called stem guard syndrome.