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Auxin induces shoot apical dominance; the axillary buds are inhibited by auxin, as a high concentration of auxin directly stimulates ethylene synthesis in axillary buds, causing inhibition of their growth and potentiation of apical dominance. When the apex of the plant is removed, the inhibitory effect is removed and the growth of lateral buds ...
Plant hormones (or phytohormones) are signal molecules, produced within plants, that occur in extremely low concentrations. Plant hormones control all aspects of plant growth and development, including embryogenesis , [ 1 ] the regulation of organ size, pathogen defense, [ 2 ] [ 3 ] stress tolerance [ 4 ] [ 5 ] and reproductive development. [ 6 ]
He isolated and determined the structure of auxin, the first known plant hormone. He spent most of his early career (1935–1965) at Harvard University, and his later career (1965 - 1989) at the University of California, Santa Cruz. [1] He is credited with identifying indole-3-acetic acid as an auxin. [2] Thimann was born in Ashford, England.
However, the mechanism of auxin secretion is at the same time regulated by strigolactones, thus the latter can control secondary growth through auxin. [24] When applied in terminal buds of stem, strigolactone can block the expression of transport proteins required to move auxin across the buds, these proteins are denominated PIN1. [ 24 ]
Indole-3-acetic acid (IAA, 3-IAA) is the most common naturally occurring plant hormone of the auxin class. It is the best known of the auxins, and has been the subject of extensive studies by plant physiologists. [1] IAA is a derivative of indole, containing a carboxymethyl substituent. It is a colorless solid that is soluble in polar organic ...
When cytokinin and auxin are both added together, the cells expand and differentiate. When cytokinin and auxin are present in equal levels, the parenchyma cells form an undifferentiated callus . A higher ratio of cytokinin induces growth of shoot buds, while a higher ratio of auxin induces root formation.
Phytohormones, particularly jasmonic acid (JA), ethylene, and auxin, are central regulators of the long-term developmental changes underpinning thigmomorphogenesis. Among these, JA is a primary mediator, modulating gene expression and enhancing stress tolerance in response to mechanical stimuli.
The auxin indole-3-acetic acid (IAA) regulates concentration of GA 1 in elongating internodes in peas. [37] Removal of IAA by removal of the apical bud, the auxin source, reduces the concentration of GA 1, and reintroduction of IAA reverses these effects to increase the concentration of GA 1. [37] This has also been observed in tobacco plants. [38]