Karin Jensvold, age 10, of Tempe, Arizona, for her question:
How does the Venus's flytrap catch and digest its food?
We are used to the idea of plant eating animals. But the idea of animal eating plants is hard to believe. Nevertheless, there are several smallish plants that do devour the meat of insects. They live in regions where meaty food is needed to give them a balanced diet.
The Venus's flytrap grows wild in certain swampy regions of the Carolinas. Here the soil is short of nitrogen compounds. All plant life needs these food chemicals to grow and stay healthy. But plants do not give up easily when things get tough. The lack of nitrogen is a severe hardship ¬but nature has given the Venus's flytrap a most astonishing way to solve it. The soil has little or no usable nitrogen, but there is plenty of it in the tiny bodies of passing bugs. The flytrap has a built in booby trap to catch insects and a way to make the best use of their valuable chemicals.
The flytrap sprouts about ten heart shaped leaves, each one built to spring shut like a miniature bear trap. The plant grows about one foot tall with a center stalk that bears a cluster of small white blossoms. A few new leaves are always sprouting near the ground to take over the trapping duties of the older leaves. The leaf trap is at the end of a flat, hairy base. It is a thick heart shaped fist with a very thick ridge right down the middle. Actually, this heavy ridge is the hinge that springs the trap.
Each half of the heart shaped leaf is called a lobe and there are three sensitive hairs on the surface of each lobe. They are set in a triangle and to cover them glands in the leaf ooze a sticky, glistening stuff that looks like dewy moisture. This is the bait that attracts the passing flies. The outer edges of the lobe are fringed with stiff spikes. When a curious fly goes by, his eye catches the dewy drops of moisture and he stops to investigate. If he lands on the sensitive hairs, his doom is sealed. His minuscule weight is heavy enough to make the hairs trigger the hinge down the middle of the leaf. The two lobes snap shut and their spiky edges form a caged wall to keep the imprisoned fly inside.
Dinner is now served and the Venus's flytrap gets busy digesting it. Strong digestive juices ooze from the leaf and engulf the fly. Its usable chemicals are dissolved and absorbed through the pores of the leaf. The flytrap now has a healthy helping of nitrogen chemicals that seep from cell to cell, performing their vital roles in the complex living processes of the plant. Meantime, all the juicy goodness has been dissolved from the fly. The leaf trap gently opens its fist and the dry husk of the fly blows away on the breezes. Each leaf can trap and digest only a few flies in its lifetime. Then it is replaced by a younger leaf.
The notion of meat eating plants has been stretched way out of bounds. We hear tales of carnivorous plants that are big enough to trap and digest a man. This may sound exciting but it is downright nonsense. On this planet at least, no plant can trap and devour any creature much bigger than a fairly large bug. And we have only a very, very few of these highly specialized members of the plant kingdom.