Lighting

Types of Lighting Natural light: Light that is emitted from electrical or chemical reactions that occur in nature Eg. Sunlight, Moonlight Artificial Light: Man made. Made by electricity or chemical reactions Eg. Light bulbs

Light and its Wavelengths Wavelengths: Light consists of a mixture of different color. Colors are created based on the wavelength

Plants and Lighting Photosynthesis: The process used by plants to make sugar. Sugar is made from joined carbon molecules. Plants need light energy to break apart CO2 and make sugar. Photosynthesis and Wavelengths: -Violet, blue, orange and red is absorbed = used for photosynthesis. -Green is reflected back = do not absorb that light for energy

How do Plants Capture Light energy Pigment Molecules: Special molecules used by plants to transform light energy into chemical energy. Found in the chloroplasts of cells. Pigment Molecules: Chlorophyll A Chlorophyll B Carotenoids

Wavelengths used by Plants

Types of Artificial Light

Incandescent Incandescent light: Light created through a tungsten wire as electrons are squeezed through it. Give off redish yellow light. Life expectancy: 750hrs

Incandescent Pros: Does not require a ballast. Inexpensive to buy. Does not contain harmful chemicals Cons: Has a short life expectancy, Inefficient, produces more heat then light. Consumes large amounts of energy

Metal Halides Metal Halides: Contain mercury and metal halides (metal + bromide, iodide) in gas form. Gives off blue spectrum light. Belongs to the HID group of light Lifespan: 8000hrs Uses: Blue light stimulates vegetative growth (leaves) such as lettuce, cabage and swiss chard HID: High intensity discharge

Metal Halides Pros: High light output compared to incandescent. Blue light is useful for foliage. Cons: Low levels of red spectrum light leads to poor flowering. Produces lots of heat. Expensive to buy and use. Contains mercury.

Fluorescent Fluorescent: low pressure mercury vapor gas bulb. Gives off blue or red spectrum light. How does it work? 1)Electric current gives the energy needed to activate the mercury 2)This causes it to give off ultra violet light energy. 3)The ultra violet light will intern provide energy needed for the phosphorous coating inside the bulb to light up. Uses: Used for seedlings. Larger bulb for adult plants Lifespan: 20,000 hours

Fluorescent Pros: Low heat production. Can be placed close to plants. Efficient electricity use. Wide range of wavelengths. Long life. Cons: Contains mercury. Requires a ballast to control current (ballast replacement if expensive)

High-pressure Sodium High Pressure Sodium (HPS): Contain sodium Gives off large amounts of red light as well as other wavelengths Uses: red stimulates flowering. Increased flowering leads to increased fruit production (tomatoes, peppers, cucumber squash etc.) Life span: hrs Low blue light results in long thin green growth = HPS are often used as supplemental light in greenhouses or indoors with metal halide.

High-pressure Sodium Pros: Gives off large amounts of red which makes it ideal for flowering. Produces bright light. Cons: Produces high amounts of heat. Low production of blue light means it will need to be combined with blue wavelength light. Uses a lot of electricity.

LED LED (light emitting diode): Light produced by electrical current. Wavelengths produced depend on the LED. All visible wavelengths are available. Ratio of blue to red is 6:100. Lifespan: 50,000hrs Uses: Growing plants indoors. Use depends on the ratio of blue:red light. High b:r ratio = Grow foliage Low b:r ratio = Fruit and flowering

LED Pros: Set the light to the requirements of the needs of the plants. Low electricity use. Low heat production. Long lifespan Cons: New technology = Expensive to buy. = Unexpected breakdowns

Summary table: Pros and cons