ABSTRACT
The greenhouse industry already has a major share in the economies of some countries, and it is growing rapidly in other places as well. Countries having major greenhouse productions can be listed as China with a total greenhouse area of over 2.7 million ha, South Korea with more than 55,000 ha, Spain with more than 52,000 ha, Japan close to 50,000 ha, and Turkey with close to 40,000 ha. One major factor hindering future expansion of this industry, however, is the cost required to provide proper environmental control for plant growth. Environment is defined as the total of all external conditions surrounding plants, which comprise physical, chemical, and biological factors; that is, no plant can exist independently from an environment. Factors such as light and radiation, temperature, relative humidity, carbon dioxide (CO2), water, nutrition, insect, and disease stresses are the key environmental components affecting optimum plant growth and yield. From the engineering point of view, the environment provides the initial and boundary conditions in plant biosystems; therefore, an engineer is concerned with i) how much food, feed, or fiber will plants produce in a specific environment; ii) if the environment is not ideal, what needs to be changed and how much; iii) if the cost of changing the environment be compensated for by a profitable increase in output; and iv) what the pertinent social (if any) and environmental impacts are. In order to answer these questions, an engineer needs to have a basic understanding of the physiological bases for plant’s responses to the environment and the physiological aspects of the environment and their effects on the functioning of a whole plant.
This chapter therefore briefly covers basic plant physiology first, and then moves to the impact of major environmental parameters and their interactions on greenhouse plant production. The parameters covered include light and radiation, temperature, relative humidity, CO2, air pollutants, air movement, and altitude.
