On the Mechanisms of Light‐induced Germination Inhibition of Phacelia Tanacetifollv

Germination of seed of Phacelia tanacetifolia is inhibited by several mechanisms. In addition to physical restraints imposed by the seed coats, the seed contains a water‐soluble inhibitor which is independent of light or temperature for its activity. Available evidence also points to the presence of 1 or more light‐activated inhibitors which are not easily leached from the seed. The blue‐light‐activated inhibition can be negated by high oxygen tensions or mechanical abrasion of the micropylar end of the seed. The suppression of germination by far‐red or red light can be negated by abrasion but is only partially reversed by oxygen. Combinations of abrasion and high oxygen tensions negate both light‐induced and temperature‐induced inhibitions of germination.