What is the role of auxin in phototropism?
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auxin help to grow the plant at the shoot tip it has acidic medium
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Plants use hormones to control the growth of roots and stems. When a plant releases a growth hormone in response to an external stimulus we call the resulting directional growth a tropism
One type of tropism is phototropism: growth in response to light. Phototropism may be either positive (towards the light) or negative (away from the light).
Phototropism requires the absorption of light by proteins known as phototropins. Phototropins change to a new conformation (a new shape) when they absorb certain wavelengths of light. The new shape causes phototropins to act as ‘on switches’ for a gene that regulates the activity of auxins.
Auxins cause cells to become longer. Therefore, by releasing auxins on one side of a stem but not on the other side, a stem will bend because one side becomes longer than the other.When a stem detects directional light it moves auxins from its sunny side to its shady side, which causes the shady side to bend toward the light. Bending toward light allows plants to absorb more sunlight and be able to photosynthesize at a faster rate.
Auxins cause cells to become larger in the following way: 1) they cause cells to actively transport hydrogen ions out of the cell, making the outside acidic; 2) the acid outside the cell makes the cell wall softer; 3) softer cell walls make the cells more stretchable; and 4) stretchy cells are bigger because the internal pressure inside the cell causes the cell wall to bulge out.
One type of tropism is phototropism: growth in response to light. Phototropism may be either positive (towards the light) or negative (away from the light).
Phototropism requires the absorption of light by proteins known as phototropins. Phototropins change to a new conformation (a new shape) when they absorb certain wavelengths of light. The new shape causes phototropins to act as ‘on switches’ for a gene that regulates the activity of auxins.
Auxins cause cells to become longer. Therefore, by releasing auxins on one side of a stem but not on the other side, a stem will bend because one side becomes longer than the other.When a stem detects directional light it moves auxins from its sunny side to its shady side, which causes the shady side to bend toward the light. Bending toward light allows plants to absorb more sunlight and be able to photosynthesize at a faster rate.
Auxins cause cells to become larger in the following way: 1) they cause cells to actively transport hydrogen ions out of the cell, making the outside acidic; 2) the acid outside the cell makes the cell wall softer; 3) softer cell walls make the cells more stretchable; and 4) stretchy cells are bigger because the internal pressure inside the cell causes the cell wall to bulge out.
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