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Plant Hormones and Responses, Layan Almalki - Coggle Diagram
Plant Hormones and Responses
plant hormones
Auxin (Elongation hormone)
Location: In the apical meristems, buds, young leaves
Example: IAA( indoleacetic acid)
Action: Stimulates lengthening or elongation - Inhibits the dropping of fruit.
Pathway: from one parenchyma cell to the next by active transport in one direction
Mechanism
promoting the flow of hydrogen ions into the cell wall which weakens it.
Then increasing water movement towards the cell, giving it length.
Apical dominance
where plants grow mostly upwards with few side branches
Gibberellins (Growth hormone)
Action: stimulate cell division, and affect seed growth and elongation.
Pathway: transported through the vascular tissue to reach the target tissue.
Dwarf plants
lack Gibberellins
Gibberellins is sprayed on them to increase plant height.
Ethylene( The Ripening Hormone)
Action: Affects the ripening of fruit
Mechanism: weakening cell walls of unripe fruits - causing the break down of complex carbohydrates into simpler ones - giving sweetness to the fruit.
Pathway: Travels through the phloem as well as the space between cells.
Cytokinins (Growth inducing hormones)
induce growth in rapidly dividing cells.
Pathway: Travel to other cells through the xylem.
Promote cell division
Influenced by the presence of auxin. - Promote cell division
Mechanism: stimulating the production of the proteins needed for mitosis and cytokinesis
Plant Responses
1- Nastic responses
a movement that is independent of the direction of the stimulus
Not a growth response, is reversible, and can be repeated
example: Opening of leaves during the day, closing of leaves at night
Once the stimulus ends, the leaves return to their original position.
Tropic responses
tropism
: a plant’s growth response to an external stimulus
positive tropism
: when plant grows towards the stimulus
negative tropism
:when plant grows away the stimulus
Phototropism
: growth in response to light
Gravitropism
: growth in response to gravity
Thigmotropism
: growth in response to mechanical stimuli, such as contact with an object, organism, or wind
Layan Almalki