| Summary: | 碩士 === 國立臺灣大學 === 農藝學系 === 82 === Glyphosate [N-(phosphonomethyl)glycine] is a nonselective,
broadspectrum and postemergence herbicide with potential to
control both annual and perennial weeds. It was found recently
that a few plant species such as climbing vines, however, have
higher tolerance to glyphosate and can not be effectively
controlled by the herbicide at recommended rate. The objective
of this study was to compare the response of such plants
including Trachelospermum gracilipes, Lactuca indica，Taiwan
tetrastigma and Commelina undulata to glyphosate. The EPSP
synthase activity of these plants was also assayed to elucidate
its relationship to glyphosate tolerance. Glyphosate caused
significant phytotoxicity on all plant species tested. When
sorghum seedlings were treated with 750ppm for 5 days,they
became chlorotic and wilting.Leaves of L.indica also showed the
same symptoms when treated with 750,1500 and 3000 ppm
respectively for 7 days. The new leaves of T. gracilipes only
showed wilt when treated with glyphosate.It required high
concentration as 3000ppm to cause symptoms on Taiwan
tetrastigma. When C.undulata were treated with 750ppm of
glyphosate,the basal portion of new leaves was severely
chlorotic, and 2000ppm treat- ment would cause the newly opened
flower white in color. Different plant species showed different
levels of EPSP synthase activity. Although sorghum was more
sensitive to gly- phosate,its EPSP synthase activity was higher
than T. gracilipes, L.indica, Taiwan tetrastigma and C.
undulata. That means that the sensitivity of plant to
glyphosate was not determined only by the activity of EPSP
synthase. On the other hand, the growth vigor, leaf surface
characteristics, and the difference in absorption and
translocation of the herbicide may also play an important role
in glyphosate tolerance.
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