Plant Regulation and Control Flashcards
(27 cards)
how do plants compensate for their relative immobility ?
by modifying their growth in response to stimuli from the environment
what are Internal factors ?
known as Phytohormones, these are hormones found in plants.
what are External factors ?
environmental factors such as light intensity, temperature, day length & gravity.
how do hormones affect growth by causing as change in?
- Changes in cell division and elongation.
- Death in some parts of the plant.
A hormone’s influence growth is by?
– Changing enzyme activity or permeability of membranes.
– Inhibiting the synthesis of proteins.
What is positive tropism?
– Growth towards a stimulus
What is negative tropism?
– Growth away from a stimulus
Types of Tropisms?
– Phototropism ( towards light)
– Geotropism (roots go down towards gravity)
– Thigmotropism (touch)
– Photoperiodism (flowering)
what is Phototropism?
– is when a plant moves in response to light.
– Stem grows towards light – positive phototropism.
– Roots grow away from light – negative phototropism
what is geotropism?
– is the growth response of a plant in response to gravity.
– Roots exhibit positive geotropism
– while stems and leaves exhibit negative geotropism.
what is Thigmotropism?
is the response of a plant to physical contact (touch).
• Plants that cling to physical structures such as walls exhibit positive thigmotropism.
• Ex. Tendrils of vines wrapping around things, venus fly traps
Hormones are Classified into 5 Groups which are?
– Auxins – Cytokinins – Gibberellins – Abscisic acid – Ethylene
What is the role of Auxin?
– Controls stretching of plant cells
– Stimulate growth of roots that grow out of a stem
– At high concentrations auxins inhibits root growth.
– Inhibits side branch growth – Apical dominance
what happens when there is a Removal of Apical Bud ?
, the lateral buds grow and the plants become thicker.
– If you cut off the tip of a seedling, there will not be any growth or bending of the plant.
what is the role of Cytokinins?
– Responsible for increase in cell division
– Breaks dormancy
– Produced in the roots
– Promotes cell division
what is the role of gibberellins?
Responsible for cell division and growth in cell size
what is ethylene?
is a gas that is released by ripening fruits that encourage the aging processes .
what is the role of Abscisic acid ?
– Responsible for dormancy of various types
– Causes the falling of leaves and fruits – ‘Abscission’
– Produced in older leaves, root cap and stem.
– Occurs in Autumn
what is Photoperiodism?
– When plants may respond to the length of daylight and dark.
– This can have an effect on the timing of flowering in a plant.
what are the 3 types of plants?
- short day
- long day
- day neutral
what do short day plants require?
– require an uninterrupted long period of darkness (long, dark nights) in order to flower.
– They typically flower in early spring.
Even just a flash of light during the long dark may be enough to stop the flowering
what do long day plants require?
- require short periods of darkness to flower (i.e. shorter nights).
- They usually flower in Summer.
what do day neutral plants require?
flowering does not depend on length of day or night
Circadian Rhythm?
- is any activity that follows a 24 hour cycle.
* For example, Mimosa pudica leaves are horizontal during the day but fall into a sleeping position at night
