How Do Plants Respond to Light?

Light is essential to many functions of plant growth and health. Exposure to adequate light sources helps a plant create energy, flowers bloom and seeds begin to grow. There are three main scientific principles related to how a plant uses light, including photosynthesis, phototropism and photoperiodism. Botanical research has recently identified the relationship between plant protein and light.

According to the University of Illinois website, the process of photosynthesis allows plants to covert light energy into a usable food source. Energy from the sun is used by the plant to be converted into chemical energy. The chemical energy is stored in the plants as sugar, allowing plants to feed upon these stores when necessary.

Phototropism is the process that allows plants to move in response to light stimuli. Many plants will change their position and grow toward their daily light source. This is a process known as phototropism, according to the University of Illinois.

Photoperiodism is the third process by which light elicits a response from plant life. Photoperiodism is a plant's reaction to the dark. In the dark, plants use a pigment known as phytochrome to determine its reaction to darkness. The pigment responds to red and far red light and can cause a plant to bloom, seeds to germinate, and can trigger a plant to become dormant, according to the University of Illinois.

Plants can be divided into three categories involving how a plant uses light to trigger its flowers to bloom. These categories include long day, short day and day neutral plants. Long day plants require more than 12 hours of light daily in order to bloom properly. Short day plants require more than 12 hours of a night time to generate the blooming sequence. Day neutral plants do not require a specific amount of day light or darkness in order to bloom.

Like blooms, seeds may also be light sensitive, according to the University of Illinois. Some seeds, like lettuce and weeds, require light sources in order to germinate. Seeds may stay dormant in the soil for years before they are exposed to sun through tilling. Then the seeds will begin to sprout and grow.

A study funded by the National Science Foundation conducted in 2007 yielded new information about how a plant's response to red and far red light in the dark determines its ability to grow, germinate seeds and bloom. Red and far red light trigger a response in the pigment protein called phytochrome A. The phytochrome A changes shape and binds to plant proteins known as FHY1 and FHL, according to the PhsyOrg website. This helps the phytochrome A travel to the nucleus of plant cells and triggers plants to bloom, seeds to germinate and other responses. According to an article about the study published by Cornell University, scientists now believe plants may be able to store their phytochrome proteins to use on an as-needed basis.