Greenhouse Lighting
(book excerpts)Light is essential for growing plants in greenhouses. The rate of growth and length of time a plant remains active is dependent on the amount of light it receives. Light energy is used in photosynthesis, the plant’s most basic metabolic process. When determining the effect of light on plant growth there are three different aspects of light that should be considered: quality, intensity, and length of the day (photoperiod). All three of these characteristics of light affect the growth and development of crops, though in different ways and in varying magnitudes. Light quality describes the wavelengths (colors) of light. Red and blue have the greatest impact on plant growth. Green light is the least effective (the reflection of green light gives the green color to plants). Blue light is primarily responsible for vegetative leaf growth. Red light, when combined with blue light, encourages flowering. Light intensity is the total amount of light supplied to the plant, which is then used for photosynthesis; up to a point, the higher the light quantity, the more energy a plant can sequester in photosynthesis. Light duration (i.e., photoperiod) is important because the ratio of light to darkness each day controls processes such as flowering and form of growth in many plants. Natural light is notoriously unpredictable but essential for plant growth, and up until recently, light has largely been out of the grower’s control. By supplementing or replacing natural light with artificial lighting, growers can control and manipulate light in a greenhouse to control the photoperiod, minimize crop stress, optimize photosynthesis, and help make agriculture more sustainable. In commercial greenhouses, several strategies can be used to help manage light levels throughout the day and seasonally. For example, daily light integral can be used to predict the exact amounts of daily light required to enhance plant growth rates and save energy for systems using supplementary lights. Growers have a variety of lighting options to choose from, including incandescent bulbs, halogen incandescent bulbs, fluorescent lamps, compact fluorescent lamps, high-intensity discharge lamps, and light-emitting diodes.
Click on the following topics for more information on greenhouse lighting.
Topics Within This Chapter:
- The Electromagnetic Spectrumy
- Photosynthetically Active Radiation
- Recommended PPFD for Plants
- Light Quality and Photomorphogenesis
- Light Wavelengths Impact on Plant Development
- UV Light
- Blue Light
- Red Light
- Far-Red Light
- Green and Yellow Light
- Plant Shading
- Greenhouse Supplemental Lighting
- Full-Spectrum versus Partial-Spectrum Lighting
- Full-Spectrum Lighting
- Partial-Spectrum Lighting
- Light Intensity
- Light Units
- Photometric: Foot-Candles and Lux
- Quantum: Moles of Photons
- Radiometric: Watts
- Effects of Light Intensity on Plant Growth
- Light Requirements for Plants
- Length of the Day (Photoperiod)
- Plant Response to Photoperiod
- Creating Artificial Short Days
- Operation of Black-Cloth Curtains
- Blackout Materials
- Greenhouse Temperture Regulation
- Creating Artificial Long Days
- Day-Extension Lighting
- Night-Interruption Lighting
- Cyclical Lighting
- Lighting Options for Controlling Photoperiod
- Incandescent Light Bulbs
- Compact Fluorescent Lights
- High-Intensity Discharge Lamps
- Light-Emitting Diodes
- Supplemental versus Photoperiodic Lighting
- Carbon Dioxide and Supplemental Light
- Daily Light Integral
- Maximize Transmission of Sunlight
- Calculating Daily Light Integral
- Quantum Sensors
- Foot Candle Meters
- Quantum Sensors
- Daily Light integral Maps
- Managing Daily Light Integral
- Daily Light Integral Requirements for Greenhouse Crops
- The Effects of High Daily Light Integral on Plants
- The Effects of Low Daily Light Integral on Plants
- Daily Light Integral and Greenhouse Temperature
- Greenhouse Lighting Systems
- Benefits of Supplmental Lighting
- Lamp Types for Greenhouses
- Incandescent Bulbs
- Halogen Incandescent Bulbs
- Fluorescent Lamps
- Compact Fluorescent Lamps
- Full Spectrum T5 Fluorescent Lights
- High-Intensity Discharge Lamps
- Light-Emitting Diodes (LEDs)
- Controlling Greenhouse Lighting
- Determining Greenhouse Lighting Requirements
- Calculating the Number of Lamps for Supplementing Lighting
- Selecting a Light Fixture
- DLC Approved
