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In biology, phototropism is the growth of an organism in response to a light stimulus. Phototropism is most often observed in plants, but can also occur in other organisms such as fungi. The cells on the plant that are farthest from the light contain a hormone called auxin that reacts when phototropism occurs. This causes the plant to have ...
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 ...
Within the 20-year timespan, many scientists have actively contributed to examining and reevaluating Hager's acid-growth hypothesis. Despite the accumulation of observations that evidently identify the final target of the auxin-induced action to be H +-ATPase, which excretes H + protons to the apoplast and take in K + ions through its rectifying K + channel in the following years, the ...
Auxins act to inhibit the growth of buds lower down the stems in a phenomenon known as apical dominance, and also to promote lateral and adventitious root development and growth. Leaf abscission is initiated by the growing point of a plant ceasing to produce auxins.
In phototropism, auxin is transported to the side of the plant shaded. This is accomplished through the PIN transport proteins. PIN proteins act as a conduit for auxin, allowing auxin to flow between cells. As auxin accumulates on the shaded side of the plant, the hormone promotes cell elongation in the cells.
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 ...
Polar auxin transport (PAT) is directional and active flow of auxin molecules through the plant tissues. The flow of auxin molecules through the neighboring cells is driven by carriers (type of membrane transport protein) in the cell-to-cell fashion (from one cell to other cell and then to the next one) and the direction of the flow is determined by the localization of the carriers on the ...
Darwin also drew attention to the similarities between animals and plants, e.g., sensitivity to touch (thigmotropism), light sensitivity (phototropism), and gravity . Darwin used various methods of enquiry: usually setting up rigorous controlled experiments which are clearly explained in the text, reporting the results and then drawing general ...