The Web of Life (80-5) Tropisms


Tropisms are plant movements in response to environmental conditions. There are several tropisms besides phototropism (light exposure) and photoperiodism (day length), including chemotropism (chemical) and gravitropism (gravity).

Thigmotropism is plant response to touching a solid object. The plasma membranes of epidermal cells distort, creating a conduction of action potential through neighboring cells. Protein-based recognition results in calcium signaling, which eventuates in the appropriate response. The process resembles animals’ sense of touch.

Tendrils and vine stems, such as morning glories, coil when they come upon something. Thigmotropism allows vines to climb over other plants or obstacles, thus improving the prospect for peppy photosynthesis.