Figure 1. Schematic representation of the major components of the phyllosphere habitat depicted in cross-section. The boundary layer around the leaf may be several millimetres thick, leading to marked differences in environmental conditions between the phyllosphere and the ambient air. Epidermal cells are covered by a cuticle, which is the first point of contact between microorganisms and the leaf surface proper. The phyllosphere has topographical features such as leaf hairs, glandular trichomes and stomata (depicted here), as well as junctions of epidermal cells, grooves over leaf veins and hydathodes, some of which are favourable sites for microbial colonization. Stomata, hydathodes, wounds and other openings in the leaf allow passage of microorganisms between the inner and outer domains of the phyllosphere. The features depicted in this schema have been drawn to scale.

Figure 2. Scanning electron micrograph of the abaxial surface of a leaf of cantaloupe (Cucumis melo). Leaf hairs, stomata and junctions between epidermal cells are evident. Bar, 100 m.