The Effect of Cu and Zn on the Growth of Marchantia polymorpha and Funaria hygrometrica

Toxic effects of both zinc and copper have been demonstrated in gemmalings of Marchantia polymorpha L. and in germinating spores of Funaria hygrometrica Hedw. Copper was found to be more toxic than zinc in both species. Copper levels above 8 ppm resulted in cessation of protonemal growth and inhibition of spore germination in Funaria, and, much reduced growth of gemmalings in Marchantia. Zinc had the greatest effects on Funaria spores, and showed relatively little effect on Marchantia gemmalings. Many distinct morphological changes were observed in both bryophytes in response to Cu and Zn. Results are discussed in terms of possible uptake processes and in terms of environmental considerations. One facet of the increasing concern with the effects of heavy metals in environmental systems has been an upsurge of interest in their effects on growth and developmental processes in plants. The majority of studies in this area have concentrated on higher plants, with relatively little attention being paid to bryophytes. Such studies which have been reported tend to be concerned with heavy metal uptake. Work by Briggs (1972) indicates that gemmalings of Marchantia clones tolerant to high lead levels are able to grow in ambient lead levels of up to 400 ppm. Brown and Bates (1972), in studies on lead uptake by the moss Grimmia doniana, have demonstrated that tolerant and non-lead-tolerant populations are capable of taking up lead by an apparently physical process, involving the binding of lead to cell walls. However, these workers were unable to provide any unambiguous evidence that lead may inhibit physiological processes in this moss. Pickering and Puia (1969), working with Fontinalis antipyretica, showed that the uptake of Zn by this aquatic bryophyte might be tri-phasic; the initial two phases of uptake being passive, with a final phase of slow active uptake into living cytoplasm. No reports of zinc toxicity in the aforementioned study or in other bryophytes appear to have been published. Studies detailing interactions between copper and bryophytes have been confined to the so-called copper mosses, whose unique dependence on very high copper levels is widely known. Whilst reports indicate that spores of some of these mosses require high Cu levels for germination (Noguchi & Furuta, 1956), virtually nothing is known of the physiology of these interesting bryophytes, or for that matter, of the effect of copper on other, nontolerant species. 1Part of this study formed an undergraduate project by one of the authors (A.J.C.). 2Department of Biology, Liverpool Polytechnic, Byrom St., Liverpool L3 3AF, U.K. This content downloaded from 157.55. 39.138 on Tue, 19 Apr 2016 06:28:42 UTC All use subject to http://about.jstor. org/terms 448 THE BRYOLOGIST [Volume 77 TABLE 1. Effect of various concentrations of copper and zinc on spore germination and germ tube extension in Funaria. Spore germination measured after 5 days. Germ tube elongation measured 5 days after spore germination. Values given in mm. Each value represents the mean of 20 germ tubes. Confidence limits given to p > 0.05. ppm Cu % Germination ppm Zn % Germination Spore germination 1 79 14 63 2 63 28 56