Hormones213-page7 - • Apical Dominance Auxin produced in...

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Plant Growth Regulators - 7 Auxins are involved in tropic responses. Both phototropism and geotropism, to be discussed later, result from unequal elongation induced by unequal concentrations of auxin within the elongating cells. o In phototropism, auxins migrate away from light, which accounts for the uneven elongation of cells on the shaded side of a plant, as studied by the Darwin. o In root gravitropism, auxin migrates toward gravity Phototropism uneven elongation Xylem regeneration in wound Auxin stimulates the production of secondary growth by simulating cambium cells to divide and secondary xylem to differentiate. Wound tissue repair is initiated by auxin when portions of vascular bundles are damaged.
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Unformatted text preview: • Apical Dominance: Auxin produced in apical buds tends to inhibit the activation of buds lower on the stems. This is known as apical dominance. Auxin promotes synthesis of strigolactones, growth regulators that repress lateral bud growth. This effect lessens with distance from the shoot tip. Cytokinins (another group of plant hormones moving upward from roots) counter the apical dominance effect of auxins and promote lateral bud development. There is also evidence that electrical signals may promote lateral bud formation in some plants. • Auxins also promote lateral and adventitious root development Auxin applied to shoots on left and center...
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