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Herbicidal action of root-applied glufosinate-ammonium
Glufosinate-ammonium (GLA) is a post-emergence herbicide that inhibits glutamine synthetase (GS), synthesis of glutamine from glutamate. This inhibition results in NH4+ accumulation and ultimate plant death. GLA is usually effective as foliar spray at concentrations over 200 mg/L. Research on root applied GLA is lacking. The current research studied the effects of root-application of GLA on tomato plant growth, foliar NH 4+ accumulation, and ethylene evolution. ^ In a dose-response experiment under hydroponics, phytotoxicity symptoms appeared on tomato seedling with 25 or 50 mg GLA X at 6 days after treatment (DAT). Under soil conditions, GLA higher than 7.5 mg/pot caused toxicity symptoms in 2 days. With 3 and 5 mg/pot symptoms appeared at 4 DAT. 1.5 mg GLA/pot at 5 DAT. With an increase of GLA rate, shoot NH4+ concentration increased in hydroponics or soil experiments. In a time course experiment, at 4 DAT, GLA at 25 mg/L caused foliar toxicity symptoms and overall stunting, and ethylene evolution increased dramatically. At 9 DAT, plants died. Accumulation of NH4+ caused by GLA was mainly in the foliage and increased with time; that caused by exogenously supplied NH4+ was in roots and non-phytotoxic during the duration of the experiments. ^ If AOA or STS was added into nutrient solution with GLA at 25 mg/L, AOA delayed the appearance of toxicity and NH4+ accumulation but STS had no suppressive effects on their presence. AOA completely inhibited ethylene evolution during the experiment but STS did not low ethylene evolution by plant receiving GLA. ^ Effects of foliarly applied GLA and soil-applied GLA were compared. At 3 DAT, tomato plants sprayed with 1.5 or 3 mg GLA/kg soil started showing symptoms on top leaves. At 5 DAT, all foliarly treated plants became poisoned by GLA, and those receiving 1.5 or 3 mg GLA from soil started showing poisoning. Tomato plant growth was retarded slightly by GLA applied at more than 1.5 mg/plant during 5 days of growth. ^ Effect of degradation time of efficacy on GLA in soil was studied. At 4 days after transplanting, GLA induced toxicity symptoms and reduced biomass. GLA after 5-days degradation in soil caused higher shoot NH4 + accumulation than 10–20 days degradation. ^ Root-applied GLA under hydrophonics or soil conditions can cause foliar toxicity symptoms, foliar accumulation of NH4+, and ethylene evolution on tomato plants. ^
Biology, Plant Physiology
"Herbicidal action of root-applied glufosinate-ammonium"
(January 1, 2001).
Electronic Doctoral Dissertations for UMass Amherst.