Coleoptile

Unlike the flag leaves rolled up within, the pre-emergent coleoptile does not accumulate significant protochlorophyll or carotenoids, and so it is generally very pale.

In 1880 Charles Darwin and his son Francis found that coleoptiles only bend towards the light when their tips are exposed.

The Cholodny–Went model is named after Frits Warmolt Went of the California Institute of Technology and the Ukrainian scientist Nikolai Cholodny, who reached the same conclusion independently in 1927.

[3] Coleoptiles also exhibit strong geotropic reaction, always growing upward and correcting direction after reorientation.

The coleoptile acts as a hollow organ with stiff walls, surrounding the young plantlet and the primary source of the gravitropic response.

[5] The coleoptile will emerge first appearing yellowish-white from an imbibed seed before developing chlorophyll on the next day.

The coleoptile grows and produces chlorophyll only for the first day, followed by degradation and water potential caused growth.

In a small number of plants, such as rice, anaerobic germination can occur in waterlogged conditions.