What is a hormone? What are the characteristics?

1
What is a hormone? What are the characteristics?

• A chemical synthesized in one part of the body
  that is (usually) transported to another part of
  the body to induce a physiological response.
• Active in very small quantities.

2
Hormone Classes

• Auxins
• Cytokinins
• Ethylene
• Abscisic Acid
• Gibberellins
• Brassinosteroids important in proper plant
  stature, growth
• Salicylic acid determines how plants respond to
  pathogens
• Jasmonic acid determines how plants respond to
  insect attack

3
(No Transcript)
4
(No Transcript)
5
Auxins

• Site of synthesis primarily in young leaves or
  shoots
• Transport from cell to cell
• Effects apical dominance, response to light,
  vascular tissue differentiation, formation of
  adventitious roots on cuttings (NAA Rootone),
  synthetic herbicides, prevents fruit drop.

6
(No Transcript)
7
Auxin Transport and Movement

• Usually from shoot tip toward the base of the
  plant.
• Mostly from cell to cell (vascular parenchyma),
  facilitated by protein carriers.

8
(No Transcript)
9
(No Transcript)
10
Cytokinins

• Site of synthesis primarily in root tips, and
  possibly also in actively growing areas such as
  seeds, fruits, and leaves.
• Transport by xylem, from root to shoot tip
• Effects delays leaf senescence, promotes growth
  and cell division in young plants

11
(No Transcript)
12
(No Transcript)
13
(No Transcript)
14
Ethylene

• CH2CH2
• Synthesis triggered by high auxin
  concentrations, wounding, or damage by pollution.
• Effects senescence, fruit maturation, fruit and
  leaf abscission.

15
Ethylene

• Promotes abscission (shedding of leaves, flowers,
  fruits)
• Fruit ripening
• Chlorophyll degraded
• Flesh softens due to digestion of pectin
• Starch, acids, and oils metabolized to sugars

16
(No Transcript)
17
Abscisic Acid (ABA)

• Site of synthesis usually in roots in response
  to water stress. Also in seeds
• Transport exported from roots to xylem
• Effects
• Prevents premature germination of seeds
• Causes stomates to close

18
(No Transcript)
19
Gibberellins

• Site of synthesis Young tissues of the shoot.
  Developing seeds.
• Transport Xylem and phloem.
• Effects
• hyper-elongation of shoots by stimulating cell
  elongation and division.
• Induction of flowering
• Induction of seed germination (substitute for
  cold).
• Beer making.

20
(No Transcript)
21
(No Transcript)
22
(No Transcript)
23
(No Transcript)
24
(No Transcript)
25
(No Transcript)
26
(No Transcript)
27
(No Transcript)
28
(No Transcript)