name all plant hormones and their functions.
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AUXIN
You’ve seen auxin in action. Well you haven’t seen the actual auxin molecule itself with the naked eye, but you’ve seen what it can do to a plant grown near a window. Have you ever wondered how a plant bends towards sunlight? Well, it has to do with auxin in the stem. Darwin and his son were curious about it, too. (Published in: The Power and Movement in Plants) However, they didn’t know at the time what exactly was causing plants to bend toward the light. Auxin itself wasn’t discovered until the late 1920s, and it was the first of the 5 major types of plant hormones to be studied. Auxin has lots of jobs but most importantly it stimulates growth, and if a plant doesn’t naturally produce auxin itself, it will die. So you can see auxin is pretty important. The technical alias for auxin is indole-3-acetic acid or IAA (just incase you ever see it written is “IAA” – it means the same thing as “Auxin”).
Auxin is involved in cell growth and cell expansion, so it is produced primarily in parts of the plant that are actively growing like the stem (specifically, the very tiptop of the stem). This is where it gets interesting. Auxin is transported (read: active process – requires energy) in one direction in a plant – downward from the top to the bottom, like a one-way road from the stem tip to the roots. It is the only plant hormone known to do this. Therefore the concentration of auxin is highest at the top of the plant and decreases as you get closer to the roots, this controls the overall shape of the plant and helps keep the primary stem of a plant the leader.
Have you ever seen the top of a single stem of tree that is pruned sprout into more than 20 new stems? That is because auxin maintains apical dominance it prevents lots of lateral buds and branches from growing on the side of the stem. When you prune the primary stem of a plant, the source of the auxin is removed, then no single stem is dominant anymore – apical dominance is removed.
GIBBERELLIN
Gibberellin causes some similar effects in plants as auxin, but it is a very different hormone. Gibberellins were discovered originally in Japan. A fungus called Gibberella fujikuroi infected rice plants and caused them to grow too tall and fall over. The infectious fungus produced a chemical that stimulated the growth in rice plants. The chemical was isolated and named Gibberellin after the fungus. It was later found that plants naturally produce variations of these chemicals!
Gibberellins play an important role in several developmental stages in plants, but their claim to fame is making stems longer. Gibberellins promote stem elongation between nodes on the stem. A node is a place on a stem where a leaf attaches, so gibberellins elongate the internodes. It is easiest to see the absence of gibberellin in dwarf plants and rosette plants – there is very little space between nodes on a stem and the leaves are clustered toward the base of the plant.
CYTOKININ
Who knew that fish could play a role in the discovery of a plant hormone? Aged herring sperm DNA can promote cell division. The molecule that is responsible for this was named kinetin. Soon after, a substance that had the same biological effect as kinetin was found in plants, it stimulated plant cells to divide when in culture with auxin. The substance was named cytokinin and it is involved in cell division and in the making of new plant organs, like a root or a shoot. Cytokinins are produced in the root apical meristems (very tip of the roots) and travel upward hitching a ride with water and traveling up the stem through the xylem. The movement of cytokinins is passive – it does not require energy!
Cytokinins are like the fountain of youth in plants. They delay senescence or the natural aging process that leads to death in plants. In the cell cycle, cytokinins promote the movement from the G2 phase to the M phase. In other words, they encourage cells to divide!
You’ve seen auxin in action. Well you haven’t seen the actual auxin molecule itself with the naked eye, but you’ve seen what it can do to a plant grown near a window. Have you ever wondered how a plant bends towards sunlight? Well, it has to do with auxin in the stem. Darwin and his son were curious about it, too. (Published in: The Power and Movement in Plants) However, they didn’t know at the time what exactly was causing plants to bend toward the light. Auxin itself wasn’t discovered until the late 1920s, and it was the first of the 5 major types of plant hormones to be studied. Auxin has lots of jobs but most importantly it stimulates growth, and if a plant doesn’t naturally produce auxin itself, it will die. So you can see auxin is pretty important. The technical alias for auxin is indole-3-acetic acid or IAA (just incase you ever see it written is “IAA” – it means the same thing as “Auxin”).
Auxin is involved in cell growth and cell expansion, so it is produced primarily in parts of the plant that are actively growing like the stem (specifically, the very tiptop of the stem). This is where it gets interesting. Auxin is transported (read: active process – requires energy) in one direction in a plant – downward from the top to the bottom, like a one-way road from the stem tip to the roots. It is the only plant hormone known to do this. Therefore the concentration of auxin is highest at the top of the plant and decreases as you get closer to the roots, this controls the overall shape of the plant and helps keep the primary stem of a plant the leader.
Have you ever seen the top of a single stem of tree that is pruned sprout into more than 20 new stems? That is because auxin maintains apical dominance it prevents lots of lateral buds and branches from growing on the side of the stem. When you prune the primary stem of a plant, the source of the auxin is removed, then no single stem is dominant anymore – apical dominance is removed.
GIBBERELLIN
Gibberellin causes some similar effects in plants as auxin, but it is a very different hormone. Gibberellins were discovered originally in Japan. A fungus called Gibberella fujikuroi infected rice plants and caused them to grow too tall and fall over. The infectious fungus produced a chemical that stimulated the growth in rice plants. The chemical was isolated and named Gibberellin after the fungus. It was later found that plants naturally produce variations of these chemicals!
Gibberellins play an important role in several developmental stages in plants, but their claim to fame is making stems longer. Gibberellins promote stem elongation between nodes on the stem. A node is a place on a stem where a leaf attaches, so gibberellins elongate the internodes. It is easiest to see the absence of gibberellin in dwarf plants and rosette plants – there is very little space between nodes on a stem and the leaves are clustered toward the base of the plant.
CYTOKININ
Who knew that fish could play a role in the discovery of a plant hormone? Aged herring sperm DNA can promote cell division. The molecule that is responsible for this was named kinetin. Soon after, a substance that had the same biological effect as kinetin was found in plants, it stimulated plant cells to divide when in culture with auxin. The substance was named cytokinin and it is involved in cell division and in the making of new plant organs, like a root or a shoot. Cytokinins are produced in the root apical meristems (very tip of the roots) and travel upward hitching a ride with water and traveling up the stem through the xylem. The movement of cytokinins is passive – it does not require energy!
Cytokinins are like the fountain of youth in plants. They delay senescence or the natural aging process that leads to death in plants. In the cell cycle, cytokinins promote the movement from the G2 phase to the M phase. In other words, they encourage cells to divide!
jack69:
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Answered by
2
Auxins: It increases the growth of plant..
Gibberelins: It helps in stem elongation..
Cytokinins: It promotes cell division..
Abscissic Acid: It is a plant growth inhibitor..
Ethylene: It affects ripening of a plant.. This is different from other plant hormones as it exists in gaseous form...
Thank You !
Gibberelins: It helps in stem elongation..
Cytokinins: It promotes cell division..
Abscissic Acid: It is a plant growth inhibitor..
Ethylene: It affects ripening of a plant.. This is different from other plant hormones as it exists in gaseous form...
Thank You !
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