Significance of light-induced hook exaggeration as reinforced by the concomitant anatomical change of germinating tomato seeds.

Progression of the apical hook of tomato, Solanum lycopersicum, exaggerated by phytochrome mediation at the early germination stage, is followed in detail macroscopically and anatomically, and its proposed significance, i.e., survival by securing the seed coat release in the field, is reinforced by new findings. Furthermore, after self-release or artificial removal of the seed coat and the endosperm, no hook exaggeration occurs any more. Similar light-induced hook exaggeration (LIHE) is also found in carrot, parsley and Cryptotaenia japonica, which share some seed characteristics with tomato. These findings also support the above-stated significance.