What are 2 characteristics of tropism?

Two characteristics of tropism are given below.

1) Due to the property of tropism in the plant, roots goes down in the direction of gravity and also goes down in search of water.

2) When seed germinates, the plumule grows in the upper direction in the direction of light due to tropism property. If the property of tropism is not present in plants, the plant does not germinates.