The Effect of Sulfur Dioxide on the Inhibitory Influence of Peltigera canina on the Germination and Growth of Grasses

Abstract

Peltigera canina is capable of inhibiting the germination of grass seeds. As the sulfur dioxide content of the atmosphere increases, the inhibitory capacity of P. canina decreases. It has previously been illustrated (Pyatt, 1967) that the lichen Peltigera canina (L.) Willd. collected from the sand dunes at Kenfig (Glamorganshire), Wales, is capable of retarding the rate of germination and of limiting the subsequent growth of seedlings of various species of dune grass. It was observed in the field that grasses generally tended not to grow in close proximity to patches of P. canina. During subsequent investigations, it became apparent that P. canina growing on the sand dunes near the steelworks at Port Talbot was frequently closely associated with grasses. As the only difference between this area and the one previously discussed is in the distance from the pollution source, an investigation was carried out in an attempt to establish whether the P. canina from the polluted area was capable of inhibiting grass germination to an extent comparable with material collected from a very slightly polluted area (Kenfig). As the results earlier obtained (Pyatt, 1967) are in direct contradiction to those 1 I thank Professor G. F. Asprey for advice in the preparation of this paper. The seeds were supplied by Suttons of Reading. I am indebted to the Nuffield Trust for a postgraduate scholarship. 2 Department of Botany, University College, Cardiff, Great Britain. This content downloaded from 207.46.13.52 on Fri, 21 Oct 2016 04:49:08 UTC All use subject to http://about.jstor.org/terms 98 THE BRYOLOGIST [Volume 71