| Summary: | Due to its ability to forming dense mats in small waterbodies, duckweeds are often
considered as nuisance plants in some freshwaters. Up to now, few techniques had been
tested aiming towards managing duckweeds, but all of them had appeared to have some
disadvantages. As an attempt to find a new effective management tool, a laboratory
experiment assessing the influence of barley straw (BS) extract addition – a substance
used in algal bloom control, upon the growth of the duckweed Lemna valdiviana,
was performed. Reaction on two various concentrations of BS extract were
quantified by measurements of changes in duckweed biomass and root length. The results
showed that plants which have received the extract increased their biomass slower than
that of the control, however only those with the addition of smaller amounts of BS
differed significantly from the controls. Furthermore, BS addition stimulated the root
growth in both experimental tanks. This implies that the mean roots length was higher,
although the statistical differences were insignificant. As possible explanation for the
observed changes we suggest that: (1) the growth inhibition of Lemna valvidiana
under exposition to BS extract might be induced by an uptake of organic compounds
from which some (phenolic substances) are (probably) toxic; (2) competitive interactions
with the microbial communities developed upon the duckweed roots might play a role as
well.
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