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ORGANIC COMPOUNDS. Growth Defined. 1. Increase in mass due to the division and enlargement of cells 2 . Types of growth in plants a . Determinate growth b . Indeterminate growth 3 . Differentiation of cells. Development Defined.

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Growth defined
Growth Defined

  • 1. Increase in mass due to the division and enlargement of cells

  • 2. Types of growth in plants

  • a. Determinate growth

  • b. Indeterminate growth

  • 3. Differentiation of cells


Development defined
Development Defined

  • The process of growth and differentiation of cells into tissues, organs, and organisms


Plant hormones
Plant Hormones

  • Auxins

  • a. Early experiments by Darwin

  • b. Discovery of auxin by Frits Went (1926)

  • c. Characteristics of auxins

  • 1) Sites of production

  • a) Apical meristems

  • b) Buds

  • c) Young leaves

  • d) Other active young plant parts

  • e) Monocots less sensitive to auxins than dicots

  • 2) Polar movement

  • • flow of auxins away from their source of synthesis



  • d. Naturally occurring auxins

  • 1) Indoleacetic acid (IAA)

  • 2) Phenylacetic acid (PAA)

  • 3) 4-chloro-indoleacetic acid (4-chloro-IAA)

  • e. Synthetic auxins and their uses

  • 1) Fruit retention

  • 2) Herbicides (2,4-D) • Agent Orange uncontrolled growth leads to death


  • 2. Gibberellins

  • a. Discovery of "foolish seedling" disease

  • b. Effects of gibberellin

  • 1) Increase stem elongation

  • 2) Breaking of dormancy of buds and seeds

  • 3) Similar to functions of auxins, enhanced when used together



  • 3. Cytokinins

  • a. Discovery of enhancement of cell division

  • b. Stimulants to cell division called "cytokinins"

  • c. Found in meristems and developing tissues, e.g., young fruit

  • d. Effects of cytokinins

  • 1) Enlarging of cells

  • 2) Differentiation of tissues

  • 3) Development of chloroplasts

  • 4) Stimulation of cotyledon growth

  • 5) Delay of aging in leaves


  • 3. Cytokinins

    • The first cytokinin was isolated from herring sperm in 1955 by Miller and his associates (Miller et al., 1955).

    • This compound was named kinetin because of its ability to promote cytokinesis.

    • Cytokininis ubiquitous to all plant species in one form or another.


  • 4. Abscisic Acid (ABA)

  • a. Discovery (1963)

  • b. Location in the plant

  • 1) Synthesized in plastids from carotenoid pigments

  • 2) Common in fleshy fruits

  • a) Prevents seeds from germinating while still on the plant promoted dormancy

  • b) ABA inhibits cell growth

  • c. Other effects of ABA

  • 1) Induces bud dormancy

  • 2) Regulates stomatal opening(water stress brings about an increase in ABA synthesis).


  • 5. Ethylene

  • a.Ethylene has been used in practice since the ancient Egyptians, who would gas figs in order to stimulate ripening

  • b. Produced by fruits, flowers, seeds, leaves, roots

  • c. Hastens ripening of fruits


Hormonal interactions
Hormonal Interactions

  • A. Apical Dominance

  • 1. Defined

  • • suppression of the growth of lateral or axillary buds

  • 2. Auxin and/or cytokinin mediated

  • B. Senescence

  • 1. breakdown of cell components and membranes that leads to cell death

  • 2. Why do plant parts senesce?

  • C. Other Hormonal Interactions


Review
Review

  • 1. growth inhibitors - abscisic acid, ethylene

  • 2. stress hormone, protects plants - abscisicacid

  • 3. closes the stomata - abscisicacid

  • 4. growth promotors - auxin, cytokinin, giberellins

  • 5. a gas – ethylene

  • 6. produces dormancy in seeds and buds - abscisicacid

  • 7. breaks dormancy in seeds and buds – gibberellin

  • 8. stimulates the ripening of fruit – ethylene

  • 9. prevents plant tissues from senescing or aging – cytokinin

  • 10. is produced by the apical bud and inhibits the growth of lateral buds - auxin


Plant movements
Plant Movements

  • A. Growth Movements

  • 1. Movements resulting primarily from internal stimuli

  • a. Helical (Spiraling) movements

  • b. Nodding movements

  • c. Twining movements

  • d. Contractile movements

  • e. Nasticmovements: Venus flytrap, sensitive plant

  • 2. Movements resulting from external stimuli

  • a. Phototropism

  • b. Gravitropism

  • c.Thigmotropism


Plant movements cont
Plant Movements cont.

  • B. Turgor Movements

  • 1. “Sleep” movements (Circadian Rhythms)

  • 2. Solar Tracking

  • 3. Water conservation movements

  • C. Taxes (Taxic Movements)

  • 1. Defined

  • a. Type of movement that involves either the entire plant or its reproductive cells

  • b. Does not occur in flowering plants

  • 2. Types

  • a. Chemotaxis

  • b. Phototaxi


Plant movements cont1
Plant Movements cont.

  • D. Miscellaneous Movements

  • 1. Gliding movements

  • 2. Dehydration movements

  • 3. Explosive movements


Photoperiodism
Photoperiodism

  • A. Discovery

  • B. Critical Day-length

  • 1. Short-day plants

  • 2. Long-day plants

  • 3. Intermediate-day plants

  • 4. Day-neutral plants


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