THESIS ABSTRACT
An investigation into the possible intergenerational effects
of glyphosate on Chrysanthemoides monilifera spp. rotundata.
Gaby Leahy
Year: 1995
Degree: BEnvSc (Hons)
Abstract:
The aerial spraying of low concentrations of Roundup (active
ingredient 36% glyphosate) in winter has been found to successfully
control the weed Chrysanthemoides monilifera spp. rotundata with
little damage to native plants. There is however, the possibility
that glyphosate may cause intergenerational effects on seeds
of both C. monilifera and native species. This study represents
an initial investigation and dealt only with C. monilifera. Bushes
were sprayed with three different concentrations of Roundup.
Fruit at three different stages of development were tagged on
sprayed and unsprayed bushed. Flowers were also tagged at two
difference times after spraying. Glyphosate caused the youngest
fruit stage and most of the flowers from the first time after
spraying to abort. Germination trials were carried out to determine
which pre-sowing treatment gave the greatest percentage germination.
An attempt was made to germinate the seed collected from the
sprayed and unsprayed bushes using the most successful pre-sowing
treatment. Germination of all seeds was very low. It was not
clear whether glyphosate was exerting an external of internal
influence.
As a great number of C. monilifera seedlings are observed to
germinate after fire, the effect of four different temperatures
for three different lengths of time on the percentage viability
of C. monilifera seeds was investigated. No seeds were considered
viable after 90C for 10 minutes and 100C for 5 minutes.
An initial investigation was made into the possibility of painting
radioactively labeled glyphosate onto small non-flowering
C. monilifera seedlings in order to determine seasonal effects
on the movement of glyphosate and photosynthate. The lowest
concentration
of glyphosate used, painted on the upper surface of the leaves,
would potentially be suitable.
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