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EFFECT OF LIGHT QUANTITY ON PLANTS 

1) phototropism - response of plants to light 
    a) plants bend towards areas of higher light intensity. 
2) photosynthesis  
    a) light reaction - increases with increasing light intensity 
    b) stomata - C3 and C4 plants: open in light; close in dark 
    c)  stomata - CAM plants: open in dark; close in light 
3) temperature - high light intensity increases temperature due to: 
    a) absorption of radiation, especially IR; greater with darker colors 
    b)  greenhouse effect  
4) transpiration - greater in high light intensity due to heat buildup, but transpiration may decrease 
                           if it gets too bright then too hot, which will cause the stomata to close.   
5) sun versus shade plants

a) leaf structure

sun grown leaf
- thicker, due to thicker palisade parenchyma layer
shade grown leaf
- thinner, due to thinner palisade parenchyma layer
- therefore, higher proportion of spongy mesophyll
- larger size
- softer and more pliable

b) optimum light intensity

shade plants: have a low optimum light intensity
sun plants: have a high optimum light intensity

6) photooxidation - destruction of chlorophyll by high light intensity.
7) etiolation - elongated, pale green to yellowish growth due to low light intensity.
8) blanching - lack of color development due to exclusion of light; 
                         - used on cauliflower, asparagus and celery.
9) light acclimatization - conditioning of plants to low light intensity interior environments.