orthotropism Bot.
(ɔːˈθɒtrəpɪz(ə)m)
[f. as next + -ism.]
The condition of being orthotropic; tendency to grow in a vertical direction, upwards or downwards.
| 1885 Vines in Encycl. Brit. XIX. 61/1 Orthotropism is then mainly due to negative geotropism. |