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Alloxydim‐sodium, methyl 3‐[1‐(allyloxyimino)butyl]‐4‐hydroxy‐6,6‐dimethyl‐2‐oxocyclohex‐3‐enecarboxylate sodium salt, is a selective herbicide which controls grass weeds in a wide range of broad‐leaf crops. Spray retention, tested at two growth stages, was generally greater for the broad‐leaf crops (cotton, sugarbeet, flax, beans and peas) than for wild oat (Avena fatua L.), blackgrass (Alopecurus myosuroides Huds), barley and couch grass [Agropyron repens (L.) Beauv.], and did not contribute to selectivity between susceptible and tolerant species. Broad‐leaf crops tolerated 2820 g alloxydim‐sodium ha−1, three times the recommended rate used to control annual grasses. Differential uptake and translocation were not factors contributing to selectivity. In wild oat, blackgrass and sugarbeet, uptake and translocation of 14C continued during a period of 14 days after treatment with [14C]alloxydim‐sodium. Translocation in susceptible and tolerant species was predominately symplastic. Over 40% of the applied 14C was eliminated from treated wild oat, blackgrass and sugarbeet plants within 7 days, due to degradation and volatilisation. A greater proportion of the methanol‐soluble radioactivity extracted from leaves and roots was present as water‐soluble polar metabolites in sugarbeet, than in wild oats, 7 days after treatment. The proportion of unaltered alloxydim in the organo‐soluble fraction of a methanol extract was greater in wild oat than in sugarbeet. Differential metabolism appears to be one of the factors contributing to alloxydim‐sodium selectivity between sugarbeet and wild oat.

Outdoor pot experiments, carried out between 1967 and 1971, mainly with Polygonum lapathifolium L. and Stellaria media (L.) Vill., showed that herbicidal potency of ioxynil and bromoxynil salts and esters was affected by climatic conditions, particularly solar radiation and relative humidity. Multiple regression equations were frequently obtained which accounted for 80% or more of the observed variation in effective dose (ED90). By contrast, experiments in growth cabinets suggested that air temperature was the most important climatic variable; the reasons for this disagreement are discussed. It is concluded that climatic factors affect the potency of ioxynil and bromoxynil via their influence on leaf uptake; ester formulations (emulsions) were much less affected than aqueous salt solutions.

No abstract

SUMMARYApplication of low concentrations of ethylene gas to the sprouts of Arran Pilot elicited many of the morphological and anatomical symptoms of the coiled sprout disorder. Similar effects were observed using 2‐chloroethyl‐phosphonic acid (Ethrel).Obstruction of coil‐prone etiolated sprouts led to enhanced ethylene production for a period of two to three days but this pattern was not shown by non‐coil‐prone sprouts.