MANNITOL AND HEXOSES ARE COMPONENTS OF BULLERS DROP

The mechanism of ballistospore self-propulsion by basidiomycetes invol ves the hygroscopic adsorption of water vapour by a drop of liquid (Bu ller's drop) on the hilar appendix of the spore until it makes contact with another expanding drop, the adaxial drop on the face of the spor e above it. Aliquots of liquid from Buller's drop have been collected from Itersonilia perplexans using micropipettes. Analysis of the dropl ets by microfluorescence assays indicated the presence of mannitol and hexoses. Using the same technique, washings from basidiospore deposit s of I, perplexans, containing the evaporated remnants of Buller's dro ps and the adaxial drops carried away by the spores on discharge, were further shown to contain mannitol and hexoses. Glc analyses of washin gs from spore deposits of a range of basidiomycetes also indicated the presence of mannitol and hexoses. Calculations based on the estimated concentrations of mannitol and hexoses in Buller's drop from itersoni lia show that the concentration of solutes is sufficient to bring abou t the condensation of water vapour from a saturated atmosphere and thu s to cause the growth of Buller's drop at rates previously measured. W hen brought close to, but not in contact with, the surface of an agar plate, crystals of pure mannitol rapidly deliquesced. Mannitol and hex oses contribute significantly to the hygroscopic nature of Buller's dr op in basidiomycetes.