Common and giant ragweed control with imazethapyr

Thomas Orville Ballard, Purdue University

Abstract

Dry afterripened and cool-moist stratification treatments were investigated for breaking giant ragweed seed dormancy. Phenol extractable proteins were separated using isoelectric focusing and SDS-PAGE electrophoresis. No germination was observed following dry afterripening at 4, 8, and 20 C and stratification at 8 C. Stratification a 4 C resulted in 33% and 58% germination at 60 and 90 d, respectively. Three, silver stained, polypeptides were observed in the axis and cotyledons of afterripened and 30 d 4 C stratified seeds. These polypeptides were not observed in 60 d 4 C stratified seeds. The absence of these polypeptides was associated with stratification treatments that resulted in the removal of seed dormancy. Relative growth rate parameters were used to evaluate the responses of common and giant ragweed to foliar applications of imazethapyr. Untreated plants demonstrated similar relative growth rates. The relative growth rate of treated plants was 50% lower than untreated plants by 21 days. At 56 days, the relative growth rate declined 13% and 38% in common and giant ragweed, respectively. A steady decline in giant ragweed relative growth rate between 21 and 56 days indicated plant death. An increase in relative growth rate of common ragweed corresponded with the initiation of lateral axillary buds and plant growth. Relative growth rate parameters measured changes in common and giant ragweed before visual responses were apparent. Translocation and metabolism of imazethapyr were investigated in common and giant ragweed. By 72 h, 52% and 30% of the applied $\sp{14}$C-imazethapyr was absorbed by common and giant ragweed, respectively. Imazethapyr translocates both acropetally and basipetally. A greater percentage of radioactivity accumulated in the lower foliage and roots of giant ragweed than common ragweed. Within the treated leaf, 81% and 68% of the radioactivity were metabolites in common and giant ragweed, respectively. Common ragweed metabolized a greater percentage of the parent imazethapyr to inactive glucose conjugate than did giant ragweed. Differential control of common and giant ragweed was attributed to differences in both translocation and metabolism.

Degree

Ph.D.

Advisors

Bauman, Purdue University.

Subject Area

Botany|Botany|Plant propagation

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