Auxin production by phylloplane fungi

Abstract

DURING a study of the distribution of fungi on living leaves of sycamore (Acer pseudoplatanus) a succession of filamentous forms has been found, with Aureobasidium pullulans colonizing the expanding leaves, followed by Cladosporium herbarum and finally by Epicoccum nigrum. These three species have commonly been found on the surfaces of green leaves of a wide range of plants which have been studied by many workers. The veinal distribution of these fungi on sycamore led to a search for them in surface-sterilized leaves, and all three species have been isolated1. Aureobasidium, however, has also been isolated from surface sterilized bud scales, shoots and even from the roots of seedlings, and it has been described as an endophyte in sycamore and other trees2. The relationship between Aureobasidium and the higher plant could be in the form of symptomless parasitism, or, conversely, there could be some benefit to, or other influence on, the higher plant. Aspects of the physiology of the three common filamentous phylloplane fungi have been investigated to see if growth promoting substances can be produced by them, for Jump3 suggested that a phytohormone produced by A. pullulans (Dematium pullulans) may have been responsible for forking in red pine. © 1971 Nature Publishing Group.