A study of zinc resistance and accumulation of zinc in scapania undulata (L) Dum

Abstract

Scapania undulata (L.) Dum. is a bryophyte which is common in the upland streams of the North East of England. The zinc resistance of S. undulata from zinc enriched and from low zinc sites was investigated by means of laboratory toxicity tests and field transplants. The results obtained do not suggest that the populations of S. undulata at the zinc enriched sites studied are genetically adapted, zinc resistant ecotypes of the species. The enrichment ratio of zinc in S. undulata at a number of sites was investigated and considerable variation between sites was found. The effects of the concentration of zinc in the medium, light and temperature on the uptake of zinc by S. undulata under aboratory conditions were also investigated. The rate of uptake of zinc was found to increase as the concentration of zinc in the medium increased, up to a concentration of 60 mg 1(^-1). The saturation point was found to be approximately the same for a two day period as for the initial half hour, with some indication of ^ small increase In the rate of uptake of zinc at concentrations greater than 60 mg 1(^-1) over the two-day period. Material incubated in medium containing 1 mg 1(^-1) zinc in the light for a period of four days was found to contain approximately 15% more zinc than material incubated in darkness. The rate of uptake of zinc by dead material at 32 ºC from medium containing 2 mg 1(^-1) zinc was found to be greater than that of live material at 14 ºC and there was some indication of a greater rate of uptake by live material at 24ºC than at l4 ºC. The results of these experiments are discussed in terms of the relative importance's of active and passive mechanisms of uptake of zinc in S. undulata and the validity of using this species for monitoring the levels of zinc in stream waters.