Lighting

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 WavelengthsWavelengths: Light consists of a mixture of different color.

Colors are created based on the wavelength

Plants and LightingPhotosynthesis: 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 BCarotenoids

Wavelengths used by Plants

Types of Artificial Light

IncandescentIncandescent 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 chemicalsCons: 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: 8000hrsUses: Blue light stimulates vegetative growth (leaves) such as lettuce, cabage and swiss chardHID: 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 plantsLifespan: 20,000 hours

FluorescentPros: 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 wavelengthsUses: red stimulates flowering. Increased flowering leads to increased fruit production (tomatoes, peppers, cucumber squash etc.) Life span: 15 000 hrsLow 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: 50,000hrsUses: Growing plants indoors. Use depends on the ratio of blue:red light. High b:r ratio = Grow foliageLow 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 lifespanCons: New technology = Expensive to buy. = Unexpected breakdowns

Summary table: Pros and cons