Etiolation

Etiolation /iːtiəˈleɪʃən/ is a process in flowering plants grown in partial or complete absence of light.

[1] It is characterized by long, weak stems; smaller leaves due to longer internodes; and a pale yellow color (chlorosis).

[2] Etiolation is controlled by the plant hormones called auxins, which are produced by the growing tip to maintain apical dominance.

Auxin diffuses, and is transported, downwards from the tip, with effects including suppressing growth of lateral buds.

Cryptochrome 1 responds to increasing amounts of blue light when the shoot reaches the surface.