Patty Isalyt age 14. of Columbus. Ohio

What are the different day and night processes in a plant?

We often send green plants to cheer up a sick friend. $ good nurse! however. remembers to take these plants out of the sick room at night and return them in the morning. Green plants change the air around them. They use up certain gases and return others to the air. During the day they pour forth fresh oxygen. During the night they add only carbon dioxide to the air. A sick person needs all the oxygen he can get. So the plants help him during the daylight hours. But after dark they use up oxygen and add only waste carbon dioxide to the sickroom.

Actually. a plant uses up oxygen and gives off carbon dioxide day and night. Like ourselves. it never stops breathing. But during the day time it is also busy making plant sugar. This is done with chlorophyll' the green coloring stuff in the leaves„ By this process carbon dioxide is taken from the air. The carbon is used in the making of plant sugar and the oxygen is returned to the air.

All this time the plant is also breathing in oxygen and breathing out carbon dioxide. But the making of plant sugar goes on at a far faster rate. Altogether' during the days the plant returns more oxygen from its sugar making than it uses in breathing. But sugar making must stop when the sun goes down. The breathing continues. but no more oxygen is given off until the green chlorophyll opens shop in the morning..

A plant. of course. has no nose for breathing. Gases are moved in and out through tiny pores in the surface. There are breathing pores in the root hairs  way below grounds to get the air trapped in the cracks and crevices of crumbly soil. There are breathing pores in the stem and stalk of the plant. The leaves carry most of their breathing pores on the under side where they are less exposed to the drying air. One leaf may have 100,000 of these tiny breathing pores on its under side.

The plant breathes to create energy. just as you do„ It needs this energy to turn plant sugar into the cellulose necessary to stiffen the cell walls of woody stems and stalks. It uses the oxygen in a slow burning process. It combines with the simple plant sugar to break it up. Carbon dioxide and water vapor are formed as waste products in the process. These are the gases that the plant breathes out into the air.

A green plant gives off water vapor day and night as part of its breathing process. But it tends to give off more water vapor during the day timer This is because the daytime air surrounding its leaves tends to be warmer. Warm air is hungry for moisture and dries it out from the plant. A large green tree may give off hundreds of gallons of water during a summer afternoon.. but at night the cooler air can absorb less water vapor from the leafy plant.