Responses to Mechanical Stimuli
Some touch-induced plant movements involve reversible
changes in turgor pressure.
If water leaves turgid cells, they may collapse, causing plant
If water enters a limp cell, it becomes turgid and may also
Water and Temperature Responses
Abscission involves changes that occur in an abscission zone
at the petioles base.
Hormonal changes lead to differentiation.
Protective layer consists of several layers of suberinimpregnated cells
Separation layer consists
Responses to Light
Phytochrome is involved in:
Inhibited by far-red light and stimulated by red light
in many plants
Only germinate when exposed to direct sunlight
Etiolation is caused by a lack of red light.
Responses to Gravity
Four general steps lead to a gravitropic response:
Gravity is perceived by the cell.
A mechanical signal is transduced into a physiological
Physiological signal is transduced inside the cell and to
Study tips for students
Objectives for chapters 18-22
Below are listed a number of objectives for the material studied in each of the chapters which will be on
the exam. You will be asked to do the things stated in these objectives, or something very simi
Winslow Briggs later demonstrated that auxin molecules
migrate away from the light into the shaded portion of the shoot.
Barriers inserted in a shoot tip revealed equal amounts of auxin
in both the light and dark sides of the barrier.
How Auxin Wor
Animals that Protect Plants
Complex coevolution of plants and animals has resulted in
Relationships that benefit both
Acacia trees and ants
Small armies of ants protect Acacia trees from harmful
Plant provides ants w
Hormones and Sensory Systems
Hormones are chemicals produced in one part of an organism
and transported to another part where they exert a response.
In plants, hormones are not produced by specialized tissues.
Eight major kinds of plant hormones