Conclusion: The plant's "eye" (the part that senses light) is in the tip, and it sends a signal from the tip to the growing region.
38.7 The Darwins'Phototropism Experiment The top drawings show some of the ways in which seedlings grown in the dark were "blindfolded"; the lower drawings show the results the Darwins observed in each case.Their observations led them to hypothesize the existence of a growth-promoting signal produced by the coleoptile.
coleoptile is sharply inhibited. If the tip is carefully replaced, growth resumes, even if the tip and base are separated by a thin layer of gelatin. The hormone moves down from the tip, but it does not move from one side of the coleoptile to the other. If the tip is cut off and replaced so that it covers only one side of the cut end of the coleoptile, the coleoptile curves as the cells on the side below the replaced tip grow more rapidly than those on the other side.
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This ebook provides an introductory explanation of the workings of the human body, with an effort to draw connections between the body systems and explain their interdependencies. A framework for the book is homeostasis and how the body maintains balance within each system. This is intended as a first introduction to physiology for a college-level course.