Type of Document	Dissertation
Author	Li, Hwei-Yiing
URN	etd-10192005-113329
Title	Mechanisms of action and selectivity of the cyclohexen-one herbicide cycloxydim (BAS 517)
Degree	PhD
Department	Plant Physiology and Weed Science
Advisory Committee	Advisor Name Title No Advisors Found
Keywords	Herbicides Research Herbicide resistance
Date of Defense	1990-09-27
Availability	restricted
Abstract The activity and the selectivity of cycloxydim {2-[1-(ethoxyimino)butylJ-3-hydroxy- 5-(2H-tetrahydrothiopyran-3-yl)-2-cyclohexen-l-one}, code designation BAS 517, were examined flIst with etiolated seedlings of com (Zea mays L.) and soybean [G{vcine max (L.) Merr.]. Etiolated soybean seedlings were not affected by cycloxydim. The degree of growth inhibition of com varied with concentration of cycloxydim and incubation time. Compared to mesocotyls and coleoptiles, radicles of corn were the most sensitive to cycloxydim. Meristematic tissues appeared to be the site of action of cycloxydim as root meristems were the first to show symptoms. A band of reddening tissue developed at meristematic tips followed by the complete cessation of root growth. In a study comparing activities of technical grade and formulated cycloxydim and sethoxydim, {2-[ l-(ethoxyimino )butyl}- 5-[2-(ethylthio )propy11-3-hydroxy-2-cyclohexen-l-one}, formulated compounds were more potent than the technical grade chemicals without formulation additives. Technical sethoxydim was more potent than technical cycloxydim. Root tips excised from com and soybean seedlings were used subsequently for cycloxydim treatments. The activity and selectivity of cycloxydim expressed at the isolated root tip level were similar to those of cycloxydim bioassayed with whole seedlings. However, root tips appeared to be more sensitive than the whole seedlings. Injury at the tissue and cell levels of the 2-mm roThe activity and the selectivity of cycloxydim {2-[1-(ethoxyimino)butylJ-3-hydroxy- 5-(2H-tetrahydrothiopyran-3-yl)-2-cyclohexen-l-one}, code designation BAS 517, were examined flIst with etiolated seedlings of com (Zea mays L.) and soybean [G{vcine max (L.) Merr.]. Etiolated soybean seedlings were not affected by cycloxydim. The degree of growth inhibition of com varied with concentration of cycloxydim and incubation time. Compared to mesocotyls and coleoptiles, radicles of com were the most sensitive to cycloxydim. Meristematic tissues appeared to be the site of action of cycloxydim as root meristems were the flIst to show symptoms. A band of reddening tissue developed at meristematic tips followed by the complete cessation of root growth. In a study comparing activities of technical grade and formulated cycloxydim and sethoxydim, {2-[ l-(ethoxyimino )butyl}- 5-[2-(ethylthio )propy11-3-hydroxy-2-cyclohexen-l-one}, formulated compounds were more potent than the technical grade chemicals without formulation additives. Technical sethoxydim was more potent than technical cycloxydim. Root tips excised from com and soybean seedlings were used subsequently for cycloxydim treatments. The activity and selectivity of cycloxydim expressed at the isolated root tip level were similar to those of cycloxydim bioassayed with whole seedlings. However, root tips appeared to be more sensitive than the whole seedlings. Injury at the tissue and cell levels of the 2-mm roThe activity and the selectivity of cycloxydim {2-[1-(ethoxyimino)butylJ-3-hydroxy- 5-(2H-tetrahydrothiopyran-3-yl)-2-cyclohexen-l-one}, code designation BAS 517, were examined flIst with etiolated seedlings of com (Zea mays L.) and soybean [G{vcine max (L.) Merr.]. Etiolated soybean seedlings were not affected by cycloxydim. The degree of growth inhibition of com varied with concentration of cycloxydim and incubation time. Compared to mesocotyls and coleoptiles, radicles of com were the most sensitive to cycloxydim. Meristematic tissues appeared to be the site of action of cycloxydim as root meristems were the flIst to show symptoms. A band of reddening tissue developed at meristematic tips followed by the complete cessation of root growth. In a study comparing activities of technical grade and formulated cycloxydim and sethoxydim, {2-[ l-(ethoxyimino )butyl}- 5-[2-(ethylthio )propy11-3-hydroxy-2-cyclohexen-l-one}, formulated compounds were more potent than the technical grade chemicals without formulation additives. Technical sethoxydim was more potent than technical cycloxydim. Root tips excised from com and soybean seedlings were used subsequently for cycloxydim treatments. The activity and selectivity of cycloxydim expressed at the isolated root tip level were similar to those of cycloxydim bioassayed with whole seedlings. However, root tips appeared to be more sensitive than the whole seedlings. Injury at the tissue and cell levels of the 2-mm root tips that were treated with various concentrations of cycloxydim was examined after 24 hours incubation. Concentrations of 0.1, 1, and 10 μM cycloxydim caused severe cell vacuolization. A gradient of decreasing injury from epidermal cells toward the center of roots was observed. This pattern of injury appeared to reflect the penetration of cycloxydim into roots along a concentration gradient.
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