geotropism
/ˌdʒiːə(ʊ)ˈtrəʊpɪz(ə)m
/noun [mass noun] Botany
The growth of the parts of plants in response to the force of gravity. The upward growth of plant shoots is an instance of negative geotropism; the downward growth of roots is positive geotropism.It was shown that gaseous ethylene inhibits both growth and geotropism in plants, and ethylene is endogenously produced by fruits....
- Geotropism occurs in two forms: positive geotropism to which the root responds by growing downward; and a negative geotropism, which causes the stem to grow upward.
- Transversal geotropism is a direction of growth that is vertical to the shoot axis.
Derivatives
geotropic
/ /dʒiːə(ʊ)ˈtrɒpɪk / adjective ...- Seed viability was assessed using the criterion of normal seedling development, i.e. emergence of the hypocotyl, radicle geotropic growth, and the opening of cotyledonary leaves.
- Cholodny proposed that ‘growth hormones play an essential role in the mechanism of the geotropic reaction’.
- These stem adaptations, combined with the presence of adventitious roots and negatively geotropic roots in nitrogen-fixing alders, facilitate the supply of oxygen in waterlogged soils.
Origin
Late 19th century: from geo- 'earth' + Greek tropē 'turning' + -ism.