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Colorado Ag. Science Curriculum Section: Plant and Soil Science Unit: 5 - Environmental Factors Lesson: 2 Light Affects of Plant Growth. OBJECTIVES TO BE COVERED. Determine how light can affect plant growth Identify signs of light stress in plants. Radiant Energy.
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Colorado Ag. Science Curriculum Section: Plant and Soil Science Unit: 5 - Environmental Factors Lesson: 2 Light Affects of Plant Growth
OBJECTIVES TO BE COVERED • Determine how light can affect plant growth • Identify signs of light stress in plants
Radiant Energy • Visible light is a small segment of all the radiant energy given off by the Sun. • Examples: x-rays, gamma rays, ultraviolet rays, microwaves, and radio waves • Radiant energy is measured on the basis of the wavelengths and placed on an electromagnetic spectrum.
Three aspects of how light affects plant growth • Color • Duration • Intensity
Light Quality • Light quality refers to the color or wavelength reaching the plant surface. • Sunlight can be broken up by a prism into respective colors of red, orange, yellow, green, blue, indigo, and violet. (ROY G BIV)
ROY G BIV • R - Red and blue light have the greatest effect on plant growth. • O - Incandescent light is high in the red or orange range but generally produces too much heat to be a valuable light source. • Y • G - Green light is least effective to plants as most plants reflect green light and absorb very little. It is this reflected light that makes them appear green. • B - Blue light is primarily responsible for vegetative growth or leaf growth. • I • V - Fluorescent "grow" lights have a mixture of red and blue colors that attempts to imitate sunlight as closely as possible.
LIGHT DURATION • A plants response to light duration is called Photoperiodism. • Plants are responsive to the length of exposure to light. • Short day plants • Chrysanthemums, poinsettias, and cotton • Long day plants • Radish and lettuce plants, carnation, and ryegrass • Day neutral plants • Rose, potato, tomato, and cucumber
LIGHT INTENSITY • Intensity of light depends largely on the angle of the Sun, clouds, and the dust in the atmosphere. • It is greater in the summer months when the Sun is higher in the sky.
LIGHT STRESS IN PLANTS • Plants will show symptoms of inadequate or too much light. • Plants with inadequate light will often look tall and spindly or “leggy” and blanched in color. • Plants with too much light will often look stunted in its growth.