What a Plant Knows by Daniel Chamovitz

Author:Daniel Chamovitz
Language: eng
Format: epub
ISBN: 9781429946230

Knowing Up from Down

In 1758—more than a century before Darwin’s landmark book The Power of Movement in Plants—Henri-Louis Duhamel du Monceau, a French naval inspector and ardent botanist, observed that if he turned a seedling upside down, its root would reorient itself in order to grow down, while its shoot would bend and grow up toward the sky. This simple observation of roots growing as if pulled down by gravity (positive gravitropism) and shoots growing in the opposite direction against this pull (negative gravitropism) led to a number of questions and hypotheses that have continued to influence research carried out in labs around the world. Many scientists who read what Duhamel had to say concluded that the ways in which the roots reoriented themselves had to do with gravity indeed. But Thomas Andrew Knight, a fellow of the Royal Society, pointed out about fifty years later that “the hypothesis [of gravity affecting plant growth] does not appear to have been strengthened by any facts.” While many scientists interpreted Duhamel’s observation as proof that gravity influences the ways a plant grows, none had carried out rigorous scientific experimentation to test this idea, which is what Knight set out to do.

Knight was part of the landed gentry and lived in a castle in the West Midlands region of England, surrounded by extensive gardens, orchards, and greenhouses. He was not trained as a scientist, but as was common for nineteenth-century aristocrats, he used his leisure time to pursue scientific knowledge, and he soon became especially skilled in horticulture. In fact, he turned out to be one of the leading plant physiologists of his time. For his studies on how plants know up from down, Knight developed a very sophisticated experimental apparatus that negated the effect of Earth’s gravity on plant growth while simultaneously applying a new centrifugal force that would act on the roots. He constructed a waterwheel that was turned by a stream running through his estate, and he attached a wooden plate to the wheel so that the plate turned with the wheel. He fastened several bean seedlings around the plate in various positions so that their root tips were facing in all possible directions—into the center, out, at an angle, and so on.

He let the wheel spin at the nauseating speed of 150 revolutions per minute for several days. The seedlings somersaulted with each spin of the plate. At the end of the treatment, Knight saw that all of the roots had grown out from the center of the wheel, while all the shoots grew toward the center.

Download

Copyright Disclaimer:
This site does not store any files on its server. We only index and link to content provided by other sites. Please contact the content providers to delete copyright contents if any and email us, we'll remove relevant links or contents immediately.