Hormones213-page15

Hormones213-page15 - smooth muscle.) Ethylene Gene Activity...

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Plant Growth Regulators - 15 Similar to seed dormancy, ABA promotes winter bud scale formation on woody plants in preparation for winter dormancy. ABA derivatives, called dormins, are used in commercial nurseries to keep materials to be shipped in dormant conditions. The dormancy can be reversed with gibberellins. ABA is also referred to as the stress activity hormone. For example, ABA promotes stomata closure during leaf water deficit conditions by activating K + ion transport out guard cells. This involves signal transduction pathways with calcium secondary messengers. ABA in this case originates in roots, and detects low water level in root tissues. ABA moves upward into leaves and activates stomatal closure. Ethylene The small hydrocarbon, ethylene, is the sole plant growth regulator known that is a gas. ( You will recall that nitric oxide gas is involved in signal transduction pathways affecting
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Unformatted text preview: smooth muscle.) Ethylene Gene Activity Ethylene activates a sequence of four proteins that ultimately promote transcription. In the absence of ethylene, its membrane receptor (A) located on the endoplasmic reticulum membrane phosphorylates a kinase (B) within the endoplasmic reticulum of the cell which blocks a second ER protein (C). In the presence of ethylene, its ER membrane protein (A) does not phosphorylate the internal ER protein (B), which results in phosphorylating the second ER membrane protein (C). The phosphorylation cascade activates protein (D), which moves into the nucleus activating appropriate transcription factors. Ethylene is the signal molecule for signal transduction pathways that activate a number of tissue growth and development activities throughout the plant, including fruit maturation, leaf abscission and senescence....
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This note was uploaded on 01/08/2012 for the course BIO 213 taught by Professor Makina during the Fall '09 term at SUNY Stony Brook.

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