CHAPTER 4 



LIGHT IN ITS RELATION TO GREENHOUSE CULTURE 



Of the many factors which are intimately inter- 

 woven with the growing of greenhouse crops, light 

 is a very important one. Unfortunately, this sub- 

 ject has received scant attention. However, Dr. 

 Stone* of the Massachusetts Agricultural Experi- 

 ment Station has contributed greatly to our knowl- 

 edge on this subject. It is apparent from his work 

 that success with greenhouse crops goes hand in hand 

 with a thorough understanding of the light require- 

 ments of plants. The problem of light has a direct 

 bearing on the physiology and pathology of hot- 

 house crops. 



Physiological Relationship of Light • 



To realize the importance of this subject we must 

 be aware that nearly ninety-five per cent, of the 

 substances contained in the plant is derived frcwn the 

 atmosphere. These substances are manufactured 

 through the action of light on the green matter 

 (chlorophyll) located primarily in the leaves. This 



'Stone, G. E., Massachusetts Agr. Expt Sta. Bui. 144: 3-39, 

 1913. 



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