Organic compounds
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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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ORGANIC COMPOUNDS

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Organic compounds

ORGANIC COMPOUNDS


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


Frits went 1926

Frits Went (1926)


Organic compounds

  • 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


Organic compounds

  • 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


Gibberellins increase stem growth

Gibberellins increase stem growth


Organic compounds

  • 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


Organic compounds

  • 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.


Organic compounds

  • 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).


Organic compounds

  • 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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