Lecture 8. Growth & Development Flashcards by Clare Balanay

the first to suggest that there
were “organ forming substances” in plants which
were produced in the leaves and translocated
downwards.

Julius von Sachs

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studied tropism in plants and
suggested that plant growth may be under the
control of special substances.

Charles Darwin

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organic compounds other than
nutrients within small amount that promote or
otherwise modify any physiological processes
in plants.

Plant regulators

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Two groups:

a.Natural
b.Synthetic

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found naturally in plants, i.e.
hormones

a.Natural

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human made

b.Synthetic

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Both groups regulate or influence:

a.Cell division
b.Cell differentiation
c. Root and shoot growth
d.Senescence (plant ageing)

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cause faster growth

Promoters

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reduce growth

Inhibitors

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*Major classes of hormones:

a. Auxins
b. Gibberellins
c. Cytokinins
d. Abscisic acid (ABA)
e. Ethylene
f. Jasmonate (JA)
g. Salicylic acid (SA)
h. Strigolactones (SL)

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Auxins uses:

Phototropism
Geotropism
Apical dominance

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plant growth toward a light source

Phototropism

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plant growth in response to
gravitational forces

Geotropism

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terminal buds prevent
the development of
lateral buds on plant
stem.

Apical dominance

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Promote cell division and delay aging of leaf by breaking down chlorophyll.

Cytokinins

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Used as growth promoter in tissue
culture.

Cytokinins

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absorbance of light
with subsequent activation of the absorbing
molecules, followed by a series of chemical
reactions leading to a general plant response to
the relative lengths of light and dark periods.

Photobiological process

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any response by a
plant to the duration and order of sequence of
light and dark periods.

Photoperiodic response

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Examples of hotoperiodic responses are:

a.Flowering
b.Vegetative growth
c.Internode elongation
d.Seed germination
e.Leaf abscission

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flower when the day lengths
are less than their critical photoperiod, e.g.
chrysanthemums and poinsettias

Short-day plants

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flower when the day length
exceeds their critical photoperiod e.g. wheat,
pea, barley

Long-day plants

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flower regardless of the
night length, e.g. cucumbers, roses, tomatoes

Day-neutral plants

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*It is a plant pigment that is held
responsible for photoperiodism.

Phytochrome

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*Absorbs red light

Phytochrome

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# T or F Subjection of long- and short-day plants to cycle other than 24 hours demonstrate that flowering in plants more of a response to the dark period than to the light.

True

As light intensity is increased, the number of flowers produced ________ because light intensity affects the amount of sugar flowing to the meristematic regions capable of initiating floral primordia.

also increases

the alternate periods of light and dark received by plant for flowering.

Photoinductive cycles

________ refers to the color or wavelength reaching the plant's surface.

Light quality

________ have the greatest impact on plant growth.

Red and blue

_____ light is primarily responsible for vegetative leaf growth.

Blue

_____ light encourages flowering.

Red

acquisition or acceleration of the ability of the plants to flower by a chilling treatment.

Vernalization

experiments point to ________ as site of vernalization.

the growing point or the stem apex

temperature from ______ is effective if period of vernalization is 105 days.

3-17 C

Grafting of vernalized organ to a receptor plant will ________.

induce the receptor plant to flower.

substance produced by vernalization transocated from the graft to receptor that induced flowering.

Vernalin

age at which plant is sensitive to vernalization varies from species to species.

Age factor

Plants vernalized can be devernalized by exposure to a high temperature at about _____.

35 C

Arrested growth because of the lack of some necessary external environmental factors.

DORMANCY

Arrested growth because of internal limitations.

Rest stage

In temperature zones where there are seasonal changes, the plant is able to escape damage due to cold environment by being _____.

dormant

Wild weed infestation is arrested because they are killed during _____.

winters

-blockage of any one of the steps leading to germination.

Seed Dormancy

Causes of seed dormancy

1.Hard seed coat 2.Immature embryo 3.After ripening 4.Specific light requirements 5.Effect of imbibition 6.Temperature effect 7.Presence of germination inhibitor

More sensitive to day length rather than cold temperature shortening of day length.

Bud Dormancy

Done by the bud if plant is leafless; bud dormancy is caused by a dormancy-inducing hormone produced as a result of stimulus receptor of the buds and leaves.

Perception of light stimulus

Compounds breaking bud dormancy

1.Ethylenechlorohydron 2.Thiourea 3.Gibberellin

found to induce sprouting of dormant of potato tube and to break dormancy of fruit trees when applied in vapor form.

Ethylenechlorohydron

cause multiple sprouting

Thiourea

natural compound; stimulates synthesis of new DNA and protein.

Gibberellin

Breaking dormancy requires depression of gene because genome of dormant buds is depressed that no RNA is synthesized.

Gene depression

-Resumption of growth by the embryo and its development to an independent seedlings.

SEED GERMINATION

Process of seed germination:

1.Diffusion of water or absorption of water through the pores of the seed 2.Imbibition or adsorption of water evidenced by swelling of the seed 3.Breaking of dormancy 4.Activation of the embryo 5.Emergence of the radicle

Factors affecting seed germination:

1.Water 2.CO2/O2 3.Temperature 4.Light quality and intensity, photoperiod

___ light induces germination, ___ light inhibits

red, blue

The development of flower primordia can be divided into three stages with varying optimum temperature: 1.Initiation 2.Cell growth 3.Final stage

1) 20 C 2) 8-9 C 3) 23 C

The presence of the vegetative and reproductive organs at the same time will result to competition for food within the plant. The reproductive organs have the greatest drawing forces for this limited resource that the development of these organs usually result in the senescence of other organs.

SENESCENCE

________ is the deterioration that ends the functional life of an organ or organism.

Senescence

Only _________ do not undergo senescence. This phenomenon is accompanied by a decline in contents of starch, chlorophyll, protein and RNA in the leaves.

meristems

Hydrolytic breakdown products are transported to the _____ regions of the plants.

younger

Color changes to brilliant ones because of the unmasking of the chlorophyll is _____.

lost

Causes of senescence:

1. Competition for nutrients given by reproductive organs 2. Production of inhibitors 3. Changes in enzyme patterns

- Reproductive organs are believed to produce substances which are translocated to vegetative organs causing ________.

senescence

Lecture 8. Growth & Development Flashcards

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