THE EFFECTS OF SUB‐LETHAL DOSES OF MCPA ON THE MORPHOLOGY AND YIELD OF VEGETABLECROPS

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Abstract
Summary. The effects of sub‐lethal doses of MCPA‐sodium on the morphology and yield of red beet, turnip and onion and on the morphology of spinach were studied in field and glasshouse experiments. Epinastic responses of beet were seen at 0.003 lb/ac a.c., but no serious formative effects or yield reductions occurred below 0–07 lb/ac and plants were only killed by doses above 0–1 lb/ac. Spinach was affected at 0–06 lb/ac, the lowest dose used, but the plants were not killed at 0–33 lb/ac. Epinasty in turnip occurred at 0–002 lb/ac, and at 0–01 lb/ac many of the roots were abnormal, while spraying with 0–1 lb/ac and above resulted in severe distortion or death of the plants. Onion was the least affected of all the crops studied. When a welting agent was included in the spray epinasty occurred at 0–3 lb/ac, but there were no serious formative effects or yield reductions below 1–0 lb/ac. The symptoms of injury in onion were often transitory because the affected parts were replaced as the bulb developed.Effets de doses sub‐léthatles de MCPA sur la morphologie et If rendement des cultures légumiéres. V. Betteraves, Epinards, Navets et Oignons