How does this relate to agriculture?
|Figure C: Sunflowers Absorbing Radiation From the Sun|
|Image courtesy of Bridget Lassiter
Plants need to absorb energy from the sun in the form of solar radiation in order to grow (using a biochemical process called photosynthesis). Most leaf surfaces are created to soak up the maximum amount of radiation, and plants have a specific shape or structure in order to ensure that they are as efficient as possible in collecting sunlight. Over time, crop plants have been selected and bred in order to ensure that this shape is such that the plant can intercept as much radiation as possible. For example, corn hybrids have been selected over time to have leaves that are not as upright, but rather grow outward so that more surfaces of the leaf can intercept radiation. Also, some plants have the biological ability to change direction based upon the direction of the sun, called heliotropism. One flower capable of this is the common sunflower.
Most people are familiar with plants growing inside of greenhouses. Greenhouses have been used for many years to exploit solar radiation. People discovered that they could grow crops (such as pineapples) inside greenhouses, which essentially extended the growing season for crops. Before this, tropical crops could not be grown in temperate climates, but were instead shipped long distances, which made them very costly. The concept of a greenhouse (glasshouse) is that solar radiation passes through a clear material such as glass or plastic. The sunlight heats the air and soil inside of the greenhouse, and the plants can also intercept the radiation. The walls of the greenhouse keep the warm air inside from mixing with the cooler outside air. Greenhouses ensure that crops can be grown even when temperatures outside of the glasshouse might be cool.