Absorption, Distribution, and Destruction of Indoleacetic Acid in Plum Stem Cuttings

Abstract

C14-[alpha]-labeled indoleacetic acid was used in determining absorption, translocation, and destruction of IAA in greenwood stem cuttings of Marianna 2624 plum (Prunus cerasifera X P. munsoniana) by the use of radioautographic and counting techniques. The auxin was added as a 4000/ppm solution in 50% alcohol, into which the base of the cuttings were dipped for 5 seconds. No difference was observed in the amount of IAA taken up by leafy and leafless cuttings. IAA moved in both acro-petal and basipetal directions. In leafy cuttings the radioactivity was distributed throughout the entire cutting 24 hours after treatment. Adventitious roots induced by IAA treatments showed appreciable amounts of radioactivity 28 days after treatment. At this time considerable radioactivity was still evident in all parts of the cutting. Cuttings treated with [alpha] -labeled IAA showed detectable amounts of radioactivity in the respiratory CO2 within 12 hours from treatment. Within 60 hours the respiratory CO2, precipitated as BaC14O3, counted 675 net counts per minute. By the 7th day this value had decreased to 42 net counts per minute. The respiratory CO2 still showed some radioactivity 30 days after treatment. Tissue slices prepared from Marianna 2624 plum stem tissue metabolized [alpha]-labeled IAA very readily, since appreciable amounts of C14O2 were detected within 1 hour after treatment.