1 / 20

ORGANIC COMPOUNDS

This comprehensive overview explores the fundamental concepts of plant growth and differentiation, discussing various types of growth including determinate and indeterminate growth. It highlights the role of plant hormones such as auxins, gibberellins, cytokinins, abscisic acid, and ethylene in regulating these processes. Key interactions like apical dominance and senescence are examined, along with plant movements and responses to environmental stimuli. The discovery of hormonal effects on growth and development is crucial for understanding agricultural practices and plant biology.

saber
Télécharger la présentation

ORGANIC COMPOUNDS

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  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

  19. END

More Related