Tropisms and Hormones definitions Flashcards
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Phototropism
Growth movement in plants where they bend towards light, driven by differential cell elongation on the shaded side due to the hormone auxin.
Gravitropism
A plant's directional growth response to gravity, where roots grow downward and shoots grow upward, facilitated by the distribution of the hormone auxin and dense organelles called statoliths.
Statolith
A dense, starch-filled organelle (amyloplast) in plant cells that sinks to detect gravity, aiding in the plant's gravitropic response.
Amyloplast
Organelle in plant cells that stores starch granules and aids in gravity sensing by settling at the cell's bottom, triggering sensory signals for gravitropism.
Auxin
A plant hormone that regulates growth by promoting cell elongation, root formation, and responses to light and gravity, influencing the direction of plant growth.
Plasmodesmata
Channels between plant cells that allow the transport of molecules and communication, facilitating coordinated responses to stimuli.
Gibberellin
A plant hormone that promotes stem elongation, seed germination, and fruit growth by stimulating cell division and elongation.
Abscisic Acid
A plant hormone that regulates stomatal closure, seed dormancy, and inhibits germination, overriding blue light signals to conserve water and delay growth under stress conditions.
Brassinosteroid
A class of plant hormones that regulate growth by promoting cell elongation and division, influencing overall plant size.
Senescence
The gradual decline in cellular function and overall organismal vitality, often regulated by hormones like ethylene, leading to aging and eventual death.
Ethylene
A gaseous plant hormone that regulates senescence, abscission, and fruit ripening by converting starches to sugars and degrading cell walls.
Abscission
The shedding of leaves, flowers, or fruits from a plant, triggered by the hormone ethylene, which degrades cell walls at the base of the petiole.