ORGANIC COMPOUNDS - PowerPoint PPT Presentation

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  1. ORGANIC COMPOUNDS

  2. 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

  3. Development Defined • The process of growth and differentiation of cells into tissues, organs, and organisms

  4. 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

  5. Frits Went (1926)

  6. 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

  7. 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

  8. Gibberellins increase stem growth

  9. 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

  10. 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.

  11. 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).

  12. 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

  13. 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

  14. 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

  15. 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

  16. 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

  17. Plant Movements cont. • D. Miscellaneous Movements • 1. Gliding movements • 2. Dehydration movements • 3. Explosive movements

  18. Photoperiodism • A. Discovery • B. Critical Day-length • 1. Short-day plants • 2. Long-day plants • 3. Intermediate-day plants • 4. Day-neutral plants