Plants

The Sun effects how plants grow. The right amount of sunlight causes a plant to grow and bear fruit during the growing season. In years when there is too much rain and a lot of cloudy days farmers don't have crops that are as big as when the sunlight and rain are in the right amounts. The Sun sets the schedule of when plants have their main growing season. Plants are autotrophs, which means they make their own food. But they couldn't be without the Sun. Most plants convert sunlight to food through a process called photosynthesis.

Plant Growth

Anything that effects the direction a plant moves is called tropism. When plants move toward light it is called phototropism. When plants are exposed to light they will always turn toward the light and away from the shade. In this same way leaves will always tilt toward the Sun in order to get more light.

A plant hormone called auxin makes the plants grow toward the light by making the plant grow more on the shady side. When it does this it tilts toward the light. When plants have a lot of auxin the stems grow more rapidly and get longer. Auxin is also is also in the roots of plants because it is sensitive to gravity as well as light. This makes the roots grow downward like they need to do at the same time as the plant grows upward.

The Sun Sets Plants Schedules

In the Northern Hemisphere, the length of time it is light constantly varies, in the summer the days are long and it is light sometimes until 3 in the morning. In the winter it sometimes is dark at 4 in the afternoon! The only time we have the same amount of daylight and darkness is on March 21^st and September 23^rd. Each day the amount of sunlight plants get changes. After each change the plants are triggered to do certain things. If the change is one where the plant gets more light it can trigger the plant to flower. If the change is one where it means this particular plant will be getting less sunlight it might signal to the plant that it is time to drop leaves, or prepare for winter. These responses are called photoperiodism.

Color Changing

"To the best of our knowledge, our Sun is the only star proven to grow vegetables." - Philip Scherrer, 1973

In the fall when we get less sunlight a substance called photochrome tells plants to form winter-resistant buds as well as seal off the flow of water to their leaves. Photochrome is like a little clock inside each plant that senses the changing amounts of light. As the amount of water and chlorophyll gotten from the Sun changes the color of many tree and plant leaves change. This is why we have so much color in the plants and tree leaves in the fall.

Located in the cells of plants there are tiny saks called chloroplasts. Choloroplasts contain chlorophyll. Chlorophyll absorbs all colors of visible sunlight except yellow and green. Because yellow and green light is reflected instead of absorbed, chlorophyll makes plants look green.