Tropisms

A tropism (TROH-piz-uhm) is a response in which a plant grows either toward or away from an environmental stimulus. Growth toward an environmental stimulus is called a positive tropism, and growth away from a stimulus is called a negative tropism. Each kind of tropism is named for its stimulus. For example, plant growth in response to light coming from one direction is called phototropism. Thus, in Figure 31-5, the shoot tips of a plant that grow toward the light source are positively phototropic. Types of tropisms are summarized in Table 31-2.

Phototropism

Phototropism is illustrated by the appearance of the sprouts in Figure 31-5. Scientists have observed that light causes the hormone auxin to move to the shaded side of the shoot. The auxin is thought to cause the cells on the shaded side to elongate more than the cells on the lighted side. As a result, the shoot grows toward the light and exhibits positive phototropism.

Sirens Sleep Solution

Sirens Sleep Solution

Discover How To Sleep In Peace And Harmony In A World Full Of Uncertainty And Dramatically Improve Your Quality Of Life Today! Finally You Can Fully Equip Yourself With These “Must Have” Tools For Achieving Peace And Calmness And Live A Life Of Comfort That You Deserve!

Get My Free Ebook


Post a comment