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Concept 39.4 - Plants respond to a wide variety of stimuli other than…
Concept 39.4 - Plants respond to a wide variety of stimuli other than light
Mechanical Stimuli
Plants are sensitive to mechanical stress
Thigmomorphogenesis
The change in form that result from mechanical perturbation
"Touch specialists"
Acute responsiveness to mechanical stimuli
Example
Tendrils coil rapidly around supports
The contact stimulates a coiling response caused by differential growth of cells on opposite sides of tendril
The directional growth in response to touch: Thigmotropism
Undergo rapid leaf movements in response to mechanical stimulation
Plant Mimosa pudica
When compound leaf is touched, it collapses and its leaflets fold together
Result from a rapid loss of turgor in cells within pulvini
Environment Stresses
Devastating effects on plant survival, growth, and reproduction
An important factor: Determining the geographic ranges of plants
Not tolerate environmental stress: die or out completed by others
Types of environment stresses
Drought: ABA production, reducing water loss by closing stomata
Flooding: Formation of air tubes that help roots survive oxygen deprivation
Extreme temperatures
Heat Stress: Synthesis of heat-shock protein, which reduce protein denaturation at high temperature
Cold Stress: Adjusting membrane fluidity; avoiding osmotic water loss; producing antifreeze protein
Salt Stress: : Avoiding osmotic water loss by producing solutes tolerated at high concentrations
Gravity
Gravitropism occurs as soon as a seed germinates
root grows into the soil
shoot grows toward sunlight
Gravity detection of plants: settling of statoliths
Statoliths
specialized plastids containing dense starch grains
located in certain cells of the root cap
Falling statoliths may not be neccessary for gravitropism
Dense cytoplasmic components settle under the influence of gravity
In plants' responses to gravity, or gravitropism
Roots display positive gravitropism
Shoots exhibit negative gravitropism