From their roots to their leaves, plants are populated by microorganisms. The relationships between microorganisms and plants are known; they are the rhizosphere, mycorrhizae, and lichens. However, the aerial environment of plants (called phyllosphere) is a habitat that has recently begun to be studied. It is composed of a variety of microorganisms. The presence of microorganisms in leaves is due to organic molecules such lipids, vitamins and hormones that are present in the cuticle and epicuticle of leaves.
The aerial environment of the leaves is exposed to drastic environmental changes. The temperature throughout the day can vary, reaching up to 55 ° C and down to 5 ° C at night. Leaves are also exposed to strong UV radiation, rain, and wind. Environmental variation modifies the micro-environment of leaves, affecting the composition, structure and amount of the cuticle where the nutrients for microorganisms are found. In spite of the harsh conditions, fungi, yeasts, protozoa, nematodes and bacteria have been found in the phyllosphere; bacteria are the most abundant organisms in the phyllosphere.
Interactions between plants and the phyllosphere are poorly understood. However it has been reported that a leaf covered with microorganisms provides advantages to the plant in the face of water stress. There are also bacteria that have the ability to form waxes that protect the plant from moisture loss through perspiration. Despite the advantages the phyllosphere microorganisms provide to plant, their influence on plant physiology is not known.
biolblogia 