A greenhouse is a structure enclosed entirely by transparent materials such as glass, rigid plastic, or a thin plastic (polyethylene film) that protect plants from the effects of wind, cold, dehydration, and insects while still admitting the light they need to grow. Greenhouses allow for regulation of microclimatic parameters such as temperature and humidity, giving plants the most optimal environment in which to grow. However, the single most important variable with respect to plant growth and development—light—often becomes a limiting factor.
The influence of light on the production of various plants, such as vegetables, fruits, flowers and herbs has been well documented. Plant cultivation in greenhouse heavily relies on sunlight, of which the availability depends strictly on weather conditions. Natural sunlight is not always attainable in sufficient quantities. Supplemental lighting is often used in permanent rigid plastic and glass greenhouse structures to extend daylight hours during winter seasons with short periods of solar radiation or to fill in the natural fluctuations in sunlight due to weather.
at the Open Lighting Product Directory (OLPD)
