1. Chapter 39
Plant Tropisms

2. Opaque shield over curvature
Figure 39.5
RESULTS
Shaded side
Control
Light
Illuminated side
Boysen-Jensen
Light
Darwin and Darwin
Figure 39.5 Inquiry: What part of a grass coleoptile senses light, and how is the signal transmitted?
Light
Gelatin (permeable)
Mica (impermeable)
Tip removed
Opaque cap
Trans- parent cap
Opaque shield over curvature

3. Excised tip on agar cube
Figure 39.6
RESULTS
Excised tip on agar cube
Growth-promoting chemical diffuses into agar cube
Control (agar cube lacking chemical)
Offset cubes
Control
Figure 39.6 Inquiry: Does asymmetrical distribution of a growth-promoting chemical cause a coleoptile to grow toward the light?

4. Primary root of maize bending gravitropically (LMs) (b)
Figure 39.24
Statoliths
20 m
Figure Positive gravitropism in roots: the statolith hypothesis.
(a)
Primary root of maize bending gravitropically (LMs)
(b)
Statoliths settling to the lowest sides of root cap cells (LMs)

5. Figure 39.25
Figure Altering gene expression by touch in Arabidopsis.

6. (a) Unstimulated state (b) Stimulated state
Figure 39.26
(a) Unstimulated state
(b) Stimulated state
Side of pulvinus with flaccid cells
Leaflets after stimulation
Side of pulvinus with turgid cells
Figure Rapid turgor movements by the sensitive plant (Mimosa pudica).
Pulvinus (motor organ)
Vein
0.5 m
(c) Cross section of a leaflet pair in the stimulated state (LM)