Plant Physiology and Growth

The foods and fibers that we use from plants are the product of complex biological and metabolic reactions that occur at a microscopic level within plant cells. What we cannot see, we often take for granted. Metabolism is the group of vital biochemical reactions that occurs in the cells of all living organisms including plants. Plant growth and development require many essential metabolic processes. Metabolic energy transformation are critical for plants' surviaval and are the foundation for the human food source. In this regard, the processes of photosynthesis and respiration require special consideration.

Another specialized metabolic reaction important to agriculture is biological nitrogen fixation. Biological nitrogen fixation is a symbiotic relationship between a plant and a soil bacterium that enables plants to use atmospheric nitrogen for growth. Because many crop plants contain from 80 to 95 percent of water, I will also discuss the process of water movement and transpiration.

The effects of radiation levels on the physiology of coffee plants are important as well, once the Coffea arabica L. species come from Ethiopian forests, where it can be found under the protection of trees. Early coffee plantations were shaded by planting trees to simulate their natural habitat. However, in many situations, the coffee plant grew and had better production without shading. As a result, shading was abandoned in regions at the same time in which cultivars were being genetically improved to present high production under full sun conditions.This cultivation system under full sun has been successfuldue to the high phenotypic plasticity of the coffee tree plants in acclimating to different radiation levels. (DaMatta et al., 2007;Chaves et al., 2008)