title: The influence of sublethal concentrations of sulfur dioxide on morphology, growth and product yield of the duckweed Lemna minor L.
abstract: There was no disturbance in the growth of Lemna minor L. with a SO2concentration of up to 0.3 ppm in air. A SO2concentration of 0.6 ppm caused an initial depression of the growth rate of about 25%, but in the course of adaptation, the rate rose to the values of the control. The average dry weight per frond was not influenced by the SO2fumigation. The initial sporadic appearance of chloroses by fumigation with 0.6 ppm SO2was considered a sign of the proximate toxicity limit for Lemna minor L. With 0.15 ppm SO2in air, the size of the fronds was reduced. The average surface of the fronds was diminished by 0.3 ppm SO2for about 16% as compared with the control plants.The protein remained quantitatively uneffected up to a SO2concentration of 0.6 ppm. As a qualitative influence of SO2, the nitrogen content of the proteins remained constant, but the sulfur content of the proteins increased.Under 0.3 and 0.6 ppm SO2, the starch content decreased immediately by 20-30%, under 0.15 ppm SO2the decrease reached the same level after a longer time than in the case of the higher concentrations.The SO2concentrations up to 0.6 ppm had no effect on chlorophyll concentration.The contents of C, N, H, P, K, Na, Ca, Mg, Mn, and Fe were not effected by SO2fumigation.
  
  
  CONCLUSIONS
  SO2may have some effects on product yield, even under low concentrations, without provoking acute damage; the plant is able to adapt by regulation of its metabolism, and enters a new steady state.
authors.affiliation: Pflanzenphysiologisches Institut der Universität Bern, Altenbergrain 21, CH-3013, Bern, Switzerland.
authors.forename: H
authors.initials: H
authors.lastname: Fankhauser
authors.affiliation: Pflanzenphysiologisches Institut der Universität Bern, Altenbergrain 21, CH-3013, Bern, Switzerland.
authors.forename: Chr
authors.initials: C
authors.lastname: Brunold
authors.affiliation: Pflanzenphysiologisches Institut der Universität Bern, Altenbergrain 21, CH-3013, Bern, Switzerland.
authors.forename: K H
authors.initials: KH
authors.lastname: Erismann