Ch. 32 - Plant Responses Flashcards
What is tropism?
Tropism is the change in the growth of plant in response to a stimulus.
What are 5 types of tropism and what involve?
Phototropism involves light. Geotropism involves gravity. Thigmotropism involves touch. Hydrotropism involves water. Chemotropism involves chemicals.
What is the difference between positive and negative tropism?
Positive tropism involves the plant moving towards the stimulus while in negative tropism, the plant moves away from it.
What is a growth regulator?
A growth regulator is a chemical that controls the growth of a plant.
How does auxin’s inhibiting and promoting qualities change with its concentration?
Auxin is a root promoter and a shoot inhibitor in small concentrations. However, auxin in large amounts works oppositely.
Where are growth regulators produced, and how are they transported?
Growth regulators are produced in meristematic regions (root/shoot tips). They are transported by vascular tissue.
Give examples of a growth promoter.
Auxin
Give examples of a growth inhibitor.
Indole-3-acetic acid (IAA) or C2H4.
What are the functions of auxin?
Auxin stimulates stem elongation and root growth. It also assists with phototropism and geotropism.
How is auxin used in horticulture?
Auxin ripens fruit. It’s used in micropropagation. It’s a weed killer. It’s used to make seedless fruit. It’s used for rooting powder.
Describe the process of phototropism.
When sunlight is overhead, IAA molecules are produced by the apical meristem. They are distributed evenly in the shoot. When the sunlight shines at an angle, IAA molecules move to the far side and induce elongation on that side. The cell elongation results in the shoot bending towards the light.
