Sixty-day-old cotton plants were treated with the sodium salt of 2,4-D (2,4-dichlorophenoxyacetic acid) in acid-equivalent amounts of 0.1, 1.0, or 10.0 mg. to determine the effect of large amounts of 2,4-D on (a) translocation of the stimulus into seed embryos formed prior to application and (b) its persistence within the plant as shown by injury to embryos subsequently formed. Cotton plants at the developmental stages of seedling, floral primordia: and anthesis were also treated with 2,4-D acid-equivalent amounts of 0.01 and 0.04 mg. to determine the effect of plant age on the transmission of the 2,4-D stimulus into seeds developed subsequent to the application. 2. All seeds from bolls (1-15 days old) set prior to treatment with 0.1 mg. or 1.0 mg. produced seedlings which exhibited symptoms of 2,4-D injury. Bolls in the 10.0-mg, series failed to develop. 3. Some seedlings from seeds produced in bolls initiated 8 weeks after application in the 0.1-, 1.0-, and 10.0-mg, series exhibited ~,4-D injury. Seeds formed 24 weeks after application did not yield malformed seedlings in any series. 4. Plants treated with 0.01 or 0.04 mg. of 2,4-D at the seedling or floral primordia stage showed no significant transmission of the stimulus into the seed embryos. 5. Seed embryos formed in bolls initiated in a 5-week period subsequent to application at the anthesis stage showed significant 2,4-D injury. 6. A discussion is presented of some factors determining whether cotton seed embryos formed subsequent to application will be injured by the 2,4-D stimulus.
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McIlrath et al. (1951) studied this question.