SAFS 421 Lecture Notes - Lecture 17: The Leaves, Phytochrome, Gravitropism
9 Dec 2017
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Dark side of a plant produces more auxin so that the plant will grow towards the light source (phototropism) Gravitropism (plant ability to detect gravity and reorient themselves to grow up (roots=positive and shoots are negative)) Reducing transpiration=aba b/c aba is involved in the signaling process between roots and stomata. Some seeds can detect these differences (esp lettuce seeds). Phytochrome system: the biologically-inactive form of phytochrome (pr) is converted to the biologically-active form pfr under illumination with red light. Far-red light and darkness convert the molecule back to the inactive form. Plants use the phytochrome system to grow away from shade and toward light. Unfiltered, full sunlight contains much more red light than far-red light. Any plant in the shade of another plant will be exposed to red-depleted, far-red-enriched light because the other plant has absorbed most of the other red light.
