3 Lecture 31 “ hormone ” introduced into animal physiology to denote a substance produced in one part of the organism and transferred to another to in f uence a speci F c physiological process was transferred to plant biology as early as 1910. Went and Thimann in 1937 in the Boyce Thompson Institute later demonstrated that the hormone concept was applicable to plants, and the term phytohormone was coined. The modern age of phytohormones began in the 1920s when Fritz W. Went (1929) demonstrated that a substance from the excised tip of the oat coleoptile (seedling shoot) could be absorbed by agar. Further-more, the infused agar block when placed on the cut surface of the coleoptile produced the effect achieved by the excised tip alone. The active substance from the coleoptile tip was later shown to be indoleacetic acid (IAA) or auxin , the natural growth substance that affects cell elongation and other processes. In their book, Hormones and Horticulture , Avery and Johnson (1947) con F dently stated that: A chemical revolution is sweeping through the agricultural world. It is unrivalled by any of the previous great advances in agriculture and, perhaps, by most advances in the biological
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environmentally friendly materials, growth regulators, Thimann, Boyce Thompson Institute