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42 terms

Plant Hormones

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Auxin (IAA)
Shoot apical meristems and young leavves are the primary sites of auxin synthesis.
Auxin (IAA)
Root apical meristems also produce auxin, although the root depends on the shoot for much of its auxin
Auxin (IAA)
Developing seeds and fruits ocntain high levels of auxin, but it is unclear whether it is newly synthesized or transported from maternal tissues
Auxin (IAA)
Stimulates stem elongation (low concentration only)
Auxin (IAA)
promotes the formation of lateral and adventitious roots
Auxin (IAA)
regulates development of fruit
Auxin (IAA)
enhances apical dominance
Auxin (IAA)
functions in phototropism and gravitropism
Auxin (IAA)
promotes vascular differentiation
Auxin (IAA)
retards leaf abscission
Cytokinins
These are synthesized primarily in roots and transported to other organs, although there are many minor sites of production as well
Cytokinins
Regulates cell division in shoots and roots
Cytokinins
modify apical dominance and promote lateral bud growth
Cytokinins
promote movement of nutrients into sink tissues
Cytokinins
stimulate seed germination
Cytokinins
delay leaf senescence
Gibberellins
Meristems of apical buds and roots, young leaves and developing seeds are the primary sites of production
Gibberellins
Stimulates stem elongation, pollen development, pollen tube growth, fruit growth, and seed development and germination
Gibberellins
regulate sex determination and the transition from juvenile to adult phases
Brassinosteroids
These compounds are present in all plant tissues although different intermediates predominant in different organs
Brassinosteroids
Internally produced brassinosteroids act near the site of synthesis
Brassinosteroids
Promote cell expansion and cell division in shoots
Brassinosteroids
promote root growth at low concentrations
Brassinosteroids
inhibit root growth at high concentrations
Brassinosteroids
promote xylem differentiation and inhibit phloem differentiation
Brassinosteroids
promote seed germination and pollen tube elongation
Abscisic acid (ABA)
Almost all plant cells have the ability to synthesize abscisic acid, and its presence has been detected in every major organ and living tissue
Abscisic acid (ABA)
may be transported in the phloem or xylem
Abscisic acid (ABA)
Inhibits growth
Abscisic acid (ABA)
promotes stomatal closure during drought stress
Abscisic acid (ABA)
promotes seed dormancy and inhibits early germination
Abscisic acid (ABA)
promotes leaf senescence
Abscisic acid (ABA)
promotes desiccation tolerance
Strigolactones
These carotenoid-derived hormones and extracellular signals are produced in roots in in response to low phosphate conditions or high auxin flow from the shoot
Strigolactones
Promote seed germination control of apical dominance and the attraction of mycorrhizal fungi to the root
Ethylene
This gaseous hormone can be produced by most parts of the plant
Ethylene
It is produced in high concentrations during senescenceleaf abscission, and the ripening of some types of fruit
Ethylene
Synthesis is also stimulated by wounding and stress
Ethylene
Promotes ripening of many types of fruit, leaf abscission and the triple response in seedlings (inhibition of stem elongation promotion of lateral expansion and horizontal growth)
Ethylene
enhances the rate of senescence
Ethylene
promotes root and root hair formation
Ethylene
promotes flowering in the pineapple family