CHAPTER 6
Phototropism and Phototaxis
KENNETH V. THIMANN and GEORGE M. CURRY
Harvard Biological Laboratories, Cambridge,
Massachusetts
I. Introductory
243
II. "Phototropism" (the Phototactic Response) in Animals ....
246
III. Phototropism in Plants
249
IV. Analysis of the Phototropic Reaction
251
A. The Two Types of Phototropism in Avena Colcoptiles
.
.
.
251
B. Types of Phototropism in Phycomyces Sporangiophores .
.
.
257
C. The Relation between Curvature and the Light-Growth Reaction .
259
V. The Role of Auxin in Phototropism of Plants
263
VI. Nature of the Photoreceptors
269
A. Photoreceptors for Phototaxis
269
B. Photoreceptor for the "Tip Response" of Avena
275
C. Interactions between "Active" and "Inactive" Pigments in the Photoreception Process
283
D. Photoreceptor for the "Base Response" of Avena
....
290
E. Photoreceptors for Phototropism in Lower Plants
.
.
.
.291
VII. Mechanisms
292
A. Variation of Curvature with Dose
292
B. Base Response
294
C. Tip Response
298
D. The Relation between Light Enc-rgy Input and the Response .
.
301
E. Summary
303
References
304
I. Introductory
Movement towards or away from light is one of the most widespread
reactions in living organisms. In higher animals the stimulus is perceived by the eye, whence it is conducted to the brain, and the resulting
nerve current activates specific muscles. In some lower animals like
planarians, however, and in some insect larvae, the perception of light
is not limited to the eyes; for instance, blinding of the amphipod
CapreUa still allows some light-directed movement (I). Furthermore,
blind worms, lamellibranchs, and many simpler creatures like hydroids
and even protozoa react sharply to light. In some of these cases, as also
in the toads (see Laurens, 2), it is the skin which is probably the photo243
Phototropism and Phototaxis
KENNETH V. THIMANN and GEORGE M. CURRY
Harvard Biological Laboratories, Cambridge,
Massachusetts
I. Introductory
243
II. "Phototropism" (the Phototactic Response) in Animals ....
246
III. Phototropism in Plants
249
IV. Analysis of the Phototropic Reaction
251
A. The Two Types of Phototropism in Avena Colcoptiles
.
.
.
251
B. Types of Phototropism in Phycomyces Sporangiophores .
.
.
257
C. The Relation between Curvature and the Light-Growth Reaction .
259
V. The Role of Auxin in Phototropism of Plants
263
VI. Nature of the Photoreceptors
269
A. Photoreceptors for Phototaxis
269
B. Photoreceptor for the "Tip Response" of Avena
275
C. Interactions between "Active" and "Inactive" Pigments in the Photoreception Process
283
D. Photoreceptor for the "Base Response" of Avena
....
290
E. Photoreceptors for Phototropism in Lower Plants
.
.
.
.291
VII. Mechanisms
292
A. Variation of Curvature with Dose
292
B. Base Response
294
C. Tip Response
298
D. The Relation between Light Enc-rgy Input and the Response .
.
301
E. Summary
303
References
304
I. Introductory
Movement towards or away from light is one of the most widespread
reactions in living organisms. In higher animals the stimulus is perceived by the eye, whence it is conducted to the brain, and the resulting
nerve current activates specific muscles. In some lower animals like
planarians, however, and in some insect larvae, the perception of light
is not limited to the eyes; for instance, blinding of the amphipod
CapreUa still allows some light-directed movement (I). Furthermore,
blind worms, lamellibranchs, and many simpler creatures like hydroids
and even protozoa react sharply to light. In some of these cases, as also
in the toads (see Laurens, 2), it is the skin which is probably the photo243