9700 · 15.2
Control and coordination in plants flashcards
Revision flashcards for Cambridge 9700 Control and coordination in plants (syllabus 15.2). Flip, recall, then mark a real past-paper question.
Card
What is a phytohormone?
A chemical substance produced by a plant that acts as a signal, controlling and regulating growth, development, and responses to the environment. Also known as a plant hormone.
Card
What is the primary role of auxins in shoots?
To promote cell elongation. This is crucial for growth and for directional responses like phototropism and gravitropism.
Card
How does auxin concentration affect root growth compared to shoot growth?
Roots are much more sensitive to auxins than shoots. The optimal auxin concentration for root growth is very low, and concentrations that promote shoot elongation are actually inhibitory to root elongation.
Card
What is the role of gibberellin in seed germination?
Gibberellin breaks seed dormancy. It stimulates the aleurone layer to produce enzymes like amylase, which hydrolyse stored food (starch) into sugars for the embryo to use in respiration and growth.
Card
What is the primary function of Abscisic Acid (ABA)?
ABA is a plant stress hormone. Its main roles are to cause stomatal closure during water stress to conserve water and to maintain seed dormancy.
Card
How does ethene gas influence plant development?
Ethene is a gaseous hormone that primarily promotes fruit ripening in climacteric fruits and controls leaf abscission (the shedding of leaves).
Card
Define positive phototropism and state which plant part exhibits it.
Positive phototropism is the growth of a plant part towards a light stimulus. It is typically exhibited by plant shoots.
Card
Define negative gravitropism and state which plant part exhibits it.
Negative gravitropism is the growth of a plant part away from the direction of gravitational pull. It is typically exhibited by plant shoots, allowing them to grow upwards towards light.