Summary:
The growth of plants toward light begins early in their lifecycle. The seeds germinate in the soil and grow upward against gravity. This is an initial clue for orientation. The seeds also contain highly sensitive, light-sensing proteins. These help the plant find the shortest route out to the sun. They even bend in the direction of the sunlight. Plants are able to bend towards the light by elongating the cells of the stem on the side that is the farthest from the light. This is called phototropism.
The substance responsible for the elongation of the cells is auxin. Auxin is a phytohormone that is formed in cells at the tip of the shoot. It is then passed from cell to cell. Export and import proteins push the auxin out of the first cell into intercellular space and then into the next cell until the auxin reaches the target site. the most important export proteins are called PINs. These regulate the direction of the auxin flow. In order to function, PINs require the signal of D6PK protein kinase. The D6KP modify PINs by transferring phosphate groups.
Themes of Nature of Science:
- Science is collaborative
- Science is based on evidence
- Science is subject to debate and tentative
I think this is really cool. Sunflowers actually follow the sun during the day, from rise to set. I think this also shows the importance of repeat ability.
ReplyDeleteI remember reading about an interesting experiment where the tip of a shoot is cut off and a block of agar containing auxin is placed on one side of the cut shoot. It begins to curve away from the block of agar. http://www.biologie.uni-hamburg.de/b-online/e31/1.htm
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