Dormancy & Juvenility2

7/30/2019 Dormancy & Juvenility2

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List 4 environmental factors

affecting germination.

2/18/09

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Light

Gas exchange

High temperature water

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Diagram the life cycle of a plant

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Transition

stage

Seed

germination

seedling

Juvenility

maturity

Reproduction

Main factorripening

senescence

Death Life

Cycle

of a

plant

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What happens in the juvenile

stage of plants?

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Plant is in rapid vegetative growth

May not be able to do certain things

i.e. Flower induction

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What happens if flowers are induced

during the juvenile stage of plant

development?

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Plant is in much stress

Remove or snip flower off.

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Do all plant in the juvenile stage

not flower? if not give example.

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No,

Beet flower in juvenile stage

If subject to a period of cold

Also bustle sprouts have 11 week stage of

juvenility

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Leaves Sizes

Number of leaves

Color

Vigor Shape

Stems Pliable

Succulent

Thorns (citrus plants have prickles, but when older arereleased.

size

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What is the physiological

expression of juvenility?

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Juvenile roots more easily than mature wood

Due to lots of endogenous hormones (IAA)

Dont loose leaves readily

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List 3 ways to modify plant

juvenility

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Grafting of buds onto mature stock

Bypasses som aspects of juvenility

Fruiting occurs faster

Advantage: disease control (grafting on diseaseresistance.

Pruning (result in more juvenility)

Chemical treatment GA (increases juvenility

Increases N encourage juvenility

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What is Senecence?

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The beginning of the end

It triggers reproduction (a timed event)

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List 4 physiological changes

during senescence.

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Loss of leaves

Color changes (due to cessation of chlorophyll

synthesis.)

Reduction of synthetic activity

Increase in cell permeability (cell membrane)

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What happens to strawberry or

mangos fruits when they are

removed from the tree?

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They are climacteric

They cease any further development and

jumps to senecense

Due a burst of ethylene

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What is Annual senescense?

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Termination of growth

Triggers start of senescence

The entire plant dies

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Distinguish between perennials

and biennials.

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Perennials

Above ground parts of plant dies

Biennials

Dies like the animals

1st year = vegetative

Folliage dies

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What are deciduous plants?

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Only the leaves dies

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What is different about

evergreens?

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They are day neutral plants

Fruits falls off

Leaves are shed throughout the year

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Compare and contrast animals

and plant senescense

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animals

Decline in hormone

production

Decline in enzyme activity

Decline in metabolism

Loss of vitality

plants

Destructive changes in

morphology

Pigmentation

Shedding of leaves

Reduce foliage production

Decrease in reproduction

Decrease in flowers, fruitingfunctions

Decrease in growth rate

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List 3 environmental conditions

that triggers senescence

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Change in temperature (heat increase

senescence (enzyme degradation)

Darkness

Prolong darkness degrades chlorophyll

Plant leaves yellow

Takes 48 hrs to reverse but stomates do not

reverse

Stress (moisture, nutrients, light)

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What happens to plant when

exposed to prolonged darkness?

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Resistance increases

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What is the relationship between

conductance and resistance?

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An increase in resistance causes a decrease in

conductance (how open the stomates are)

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List 3 modifications of senescence

(slowing down the process).

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Removing flowers and fruits (since

reproduction signals senescence)

Preventing factors that suppresses growth

Nutrients

Water stress

Temperature (high temps)

Aging of clones

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Dormancy & Juvenility2