B 3 Control in plants Flashcards
(30 cards)
What is a plant hormone?
A chemical substance that controls growth and responses to the environment in plants.
What is auxin?
A plant hormone that controls growth by elongating cells, especially in shoots.
What is phototropism?
Growth of a plant shoot towards light.
How does auxin cause phototropism?
Auxin concentrates on the shaded side of the shoot, causing cells there to elongate and the shoot to bend toward the light.
What is gravitropism (or geotropism)?
Growth of a plant root in response to gravity.
How does auxin affect root growth in gravitropism?
Auxin accumulates on the lower side of the root, inhibiting cell elongation, causing the root to bend downwards.
What is gibberellin?
A hormone that stimulates seed germination, stem growth, and flowering.
What is ethene (ethylene)?
A gaseous plant hormone that controls fruit ripening.
How are auxins used commercially?
To promote root growth in cuttings and as weedkillers to kill unwanted plants.
How is ethene used commercially?
To control ripening of fruits during transport so they can be sold ripe.
What is a tropism?
A growth response of a plant to an environmental stimulus.
Why do shoots grow towards light?
To maximise photosynthesis by capturing more sunlight.
Why do roots grow downwards?
To anchor the plant and find water and minerals in the soil.
What role does auxin play in shoot and root growth?
Auxin promotes cell elongation in shoots but inhibits cell elongation in roots.
What is a cutting in plant propagation?
A piece of stem or leaf cut from a plant used to grow a new plant.
How do auxins help cuttings root?
Auxins stimulate root formation on cuttings, helping new plants develop roots faster.
What is selective weedkiller and how do auxins work in it?
A weedkiller that targets broad-leaved plants by disrupting their growth hormones, causing them to grow uncontrollably and die.
What is the role of gibberellins in seed germination?
They stimulate enzymes that break down food stores in seeds to provide energy for growth.
How do gibberellins control flowering?
They can trigger flowering in some plants and increase the size of flowers.
How can gibberellins be used commercially?
To increase fruit size and promote flowering or seed germination.
What is ethene’s role in fruit ripening?
It stimulates enzymes that break down cell walls and convert starches to sugars, softening and sweetening the fruit.
What is the purpose of controlling fruit ripening with ethene?
To allow fruits to be transported unripe and ripened in stores, reducing waste.
What is the difference between positive and negative tropism?
Positive tropism is growth towards a stimulus (e.g., shoots growing towards light), negative tropism is growth away from a stimulus (e.g., roots growing away from light).
What is apical dominance?
When the main shoot tip (apex) suppresses the growth of side shoots, controlled by auxin concentration.
