Download Plant Responses Handout

Name:
Date:
Auxins: Pg. 807
1. Auxin is produced by________________ and______________.
2. How does auxin move through the plant?
__________________________________________________________
3. What is the main function of this hormone?
__________________________________________________________
4. Describe how auxin effects cell elongation?
__________________________________________________________
5. What does auxin induce?
__________________________________________________________
6. How does this hormone affect fruit production?
__________________________________________________________
7. Hoe does this hormone affect flower production?
__________________________________________________________
Cytokinin: Pg. 808
1. Cytokinin is produced by________________.
2. How does cytokin move through the plant?
________________________________________________________________
3. What is the main function of this hormone?
________________________________________________________________
________________________________________________________________
4. How do cytokinins affect cell division?
________________________________________________________________
________________________________________________________________
5. How do cytokinins counteract auxin?
________________________________________________________________
________________________________________________________________
6. Explain how cytokinins affect senescence of organisms.
________________________________________________________________
________________________________________________________________
Auxin moves only downward but gravity does not cause its movement. It is generally
produced by apical shoot meristems and developing leaves. Auxin promotes growth by
stimulating cell elongation. It triggers enzyme activities that loosen the cell wall fibers
(normally tightly woven)
Auxin also stimulates cell division. It activates the vascular cambium and promotes the
formation of lateral roots by the pericycle. Auxin inhibits the growth of lateral buds.
Inhibits roots small quantities promote root growth. Slight increases inhibit it. Auxin
production by seeds stimulates fruit growth. If eggs are not fertilized, ovules do not
become seeds and auxin cannot be produced. The lack of auxin results in abscission of
the flower.
Auxin also prevents fruits and leaves from off prematurely. It can be sprayed on to
prevent from falling off. high concentration → uncontrolled growth, death
example: some herbicides- 2,4-D, 2,4,5-T (components of agent orange)
Cytokinins
stimulate cell division major source is the roots oppose auxin by: move upward
promote growth of lateral buds as plant grows, lower buds are more under the influence
of cytokinins prevents leaf senescence
Senescence
Senescence refers to the aging and eventual death of a plant or plant parts.
When plant parts senesce, nutrients are withdrawn and redistributed via the phloem.
In deciduous species (species that lose their leaves), nutrients move to the stems and roots
for storage.