Question

How does pitcher plant trap insects?

Answer 1

Normally when one thinks about plants, especially the nutrition mode, the first thing that comes to our mind is that plants are autotrophs, i.e., they harness sunlight and carbon dioxide from the air and make their own food. But there are a few certain plants that are heterotrophic too. They need to consume other organisms and their products to meet their nutritional demands. One such plant is the pitcher plant that traps insects.

Complete answer:
The scientific name of the pitcher plant is Nepenthes sp. It belongs to the family Nepenthaceae under order Caryophyllales.
Its leaves are modified into baskets which look like pitchers along with a leaf that acts as a lid. The flowers of the pitcher plant are colorful and have a nice fragrance which attracts the insects. As soon as an insect enters any one of these pitchers, the lid (leaf) falls and closes the exit. Then the plant secretes digestive enzymes and juices which digest the insect and the nutrients are absorbed by the plant.

Why do pitcher plants need to draw nutrition from insects?
Any plant needs a variety of nutritional factors for its survival. For most of the plants apart from sunlight and carbon dioxide, many other nutrients and metabolites are needed for successful processing of metabolic reaction. Most of these metabolites are readily obtained from the soil.
Now in case of the pitcher plant, the soil in which it primarily grows is deficient in some of these minerals and nutrients. Thus, the pitcher plant has evolved itself to obtain the necessary nutrition from insects.

Note:
How does the pitcher plant sense that an insect has entered one of its pitchers?
This is a game of complete chemical interaction. It is believed that the pitcher plant contains some special chemo-sensitive hairs that are sensitive to the proteinaceous membrane of the insect body. As an insect enters a pitcher, these hairs sense it and then the lid gets closed which is a result of changes in turgor pressure of the cells. Then the process of digestion begins.