Phototropism, adaptation, and the light-growth response of Phycomyces.

The Journal of general physiology

PubMedID: 13691452

CASTLE ES. Phototropism, adaptation, and the light-growth response of Phycomyces. J Gen Physiol. 1961;4539-46.
Phototropic bending can be initiated without the transient changes in growth speed that characterize a light-growth response. The conditions required are a change from a symmetric to an asymmetric illumination pattern while the cell receives a constant radiant flux. Phototropism is thus basically a steady state process. It cannot be founded on differential light-growth responses as in Blaauw's theory. A possible model system for the unequal partition of growth during steady bending is discussed. The fact that light-growth responses show adaptation while phototropic bending does not follows from the different natures of the two responses.