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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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