Plant Responses Flashcards
What is a stimulus in plants?
A stimulus is something that causes a response in an organism.
What is the most common response by plants to stimuli?
The most common response by plants to stimuli is a growth response.
Name three stimuli that plants respond to.
Light (phototropism), gravity (geotropism), and water (hydrotropism).
What is a tropism?
A tropism is a change in the growth of a plant in response to an external stimulus.
What is positive tropism?
Positive tropism is when a plant’s growth is towards a stimulus.
What is negative tropism?
Negative tropism is when a plant’s growth is away from a stimulus.
What are external factors that regulate plant growth?
External factors include light intensity, day length, gravity, and temperature.
What are internal factors that regulate plant growth?
Internal factors include chemicals called growth regulators, which are produced in meristematic regions.
What is a growth regulator in plants?
A growth regulator is a chemical that controls the growth of a plant.
Where are growth regulators produced in a plant?
Growth regulators are produced in meristematic regions like root tips and shoot tips.
What are auxins?
Auxins are a group of growth regulators that promote growth, such as Indoleacetic Acid (IAA).
Name two production sites of auxins.
Auxins are produced in shoot tips and developing seeds.
What role do auxins play in plant growth?
Auxins promote stem and root elongation, fruit development, and cell differentiation, and they regulate phototropism and geotropism.
What is apical dominance?
Apical dominance is when the auxin produced in the apical tip inhibits lateral growth, leading to dominant upward growth.
What is apical dominance?
Apical dominance is when the auxin produced in the apical tip inhibits lateral growth, leading to dominant upward growth.
What effect does Indoleacetic Acid (IAA) have on roots and shoots?
Low concentrations of IAA cause root growth, while high concentrations promote shoot growth and inhibit root growth.
What is the function of ethene in plants?
Ethene is a gas that causes fruit ripening, leaf fall, and is involved in the aging of plants.
What is the role of abscisic acid in plants?
Abscisic acid responds to harmful conditions by triggering dormancy in buds and seeds, inhibiting germination, and causing stomata to close during dry conditions.
Where is auxin (I.A.A.) produced in plants, and what does it do?
Auxin (I.A.A.) is produced in the meristem region at the tip of the stem and travels down the stem to stimulate growth in different areas.
How does auxin (I.A.A.) cause a plant to bend towards light in phototropism?
When exposed to light on one side, auxin diffuses down the shaded side of the stem, increasing its concentration there. This causes the shaded side to elongate and grow more than the sunny side, bending the stem towards the light.
What is phototropism?
Phototropism is the bending of a plant stem towards light due to the uneven distribution of auxin (I.A.A.), which causes more growth on the shaded side.
How is ethene used commercially in agriculture?
Ethene is used to ripen bananas or other fruit. Bananas are picked green, and ethene is used to stimulate ripening just before distribution.
What is the purpose of rooting powders in plant propagation?
Rooting powders contain synthetic auxins like NAA, which stimulate rapid root formation on stem cuttings.
Why do plants need adaptations for protection?
Plants need to protect themselves against adverse external environments, such as hot conditions, infection by microorganisms, and herbivores.
What are structural/anatomical adaptations for plant protection?
Examples include tough bark, waxy or thick cuticles, stoma closing in certain conditions, and the formation of stings or thorns to prevent herbivore consumption and reduce water loss.
How do guard cells help plants conserve water?
Guard cells change shape when they lose water, causing the stomata to close, which reduces water loss.
What are chemical adaptations in plants for protection?
Plants produce heat shock proteins to protect enzymes at high temperatures, and phytoalexins in response to infections, which can attack microorganisms and stimulate other plants to respond.
What are phytoalexins, and what do they do?
Phytoalexins are stress proteins produced by plants in response to microorganism infection. They attack microorganism cell walls and stimulate other plants to defend themselves.
