Plant Responses To Internal And External Signals Flashcards
Etiolation
Morphological adaptions for growing in darkness; no green tissue being produced
De-etiolation
when exposed to light, shoots and roots begin to grow normally
Plant hormones
Coordinate growth, development and stimuli; ex: Auxin, Abscisic Acid, Cytokinin, Ethylene, Giberellins; produced in low concentration
Tropism
Any response resulting in curvature of organs towards or away from a stimulus
Significance of a tip of a plant.
The tip is the most responsible in absorbing light; therefore it determines curvature due to wanting light
How did they conclude tip determines curvature?
Darwin and Darwin conducted an experiment:
No tip on plant/tip removed: no bending
Opaque Cap; no bending
Transparent Cap: bending
Opaque shield over curvature: bending (tip is not covered)
Auxin
Refers to any chemical that promotes enlongation of coleoptiles; stimulates proton pumps in plasma membrane -> lower pH -> activate expansins (enzymes that loosen walls fabric and allowing cell to expand
What causes apical dominance
Auxin flow from the shoot of a branch simulates growth in lower branches
Cytokinins
Produced in actively growing tissues (roots, embryos, and fruits); work together w/ auxin to control cell division and differentiation; cytokinins, auxin, and strigactone interact in apical dominance
Gibberellins
Growth promoting hormone that affects stem enlongation, fruit growth, and germination; produced in young organs; stimulate growth of cells and stems
Which two hormones have to be present for fruit to develop?
Auxin and gibberellins
What does the release of gibberellins do?
Signals seeds to germinate and endosperm to break down
Abscisic Acid
Plays a role in seed dormancy; seed will only germinate in optimal conditions; ABA removed via rain, light or prolonged cold=dormancy broken; causes stomata to close rapidly when losing water (drought)
Ethylene
Produced in response to stresses like drought, flooding, mechanical pressure, injury and infection
Name 4 Effects of Ethylene
Mechanical stress, senescence, leaf abscission, and fruit ripening
Mechanical stress
Ethylene causes triple response, ability of growing shoot to avoid obstacles-> slowing of stem enlongation, thickening of stem, horizontal growth
Senescence
Programmed death of cells and organs; a burst of ethylene leads to apoptosis, programmed destruction
Leaf abscission
Change in balance of auxin and ethylene control it; prices that occurs in autumn when a leaf falls
Fruit ripening
Burst of ethylene production in fruit triggers ripening
