

CHAPTER XXXIV 

 GROWTH CORRELATIONS 



The development of any one organ of a plant is often influenced b}' the 

 physiological processes or physico-chemical conditions prevailing in other 

 organs of the same plant. In short, the shoot is part of the "environment" of 

 the root, which in turn is part of the "environment" of the shoot, similar 

 relationships, often reciprocal, existing between other organs of a plant. Such 

 influences of one organ upon the development of another organ of the same 

 plant are termed groicth correlations or often simply correlations. 



Growth correlations are not only exerted from one organ to another but 

 also between tissues and between cells. The harmonious development of the 

 plant body as a whole is controlled by correlative influences operating recipro- 

 cally from organ to organ, tissue to tissue, and cell to cell. The discussion 

 in this chapter will be restricted almost entirely, however, to some of the better 

 known examples of the correlative influences of one plant organ upon another. 



Not all growth correlations are due to the same internal mechanism. 

 Some influences of one plant organ upon another result from the effect of 

 the first organ upon the distribution of one or more kinds of foods to other 

 organs. Other correlations are due to the influence of the utilization of 

 water by one plant organ upon the internal water relations of other organs 

 (Chap. XVIII). Still others result from the influence of one organ of a 

 plant upon the distribution of essential mineral elements to other organs. 

 Many growth correlations are apparently due to the activity of hormones 

 or hormone-like substances. Growth hormones which are synthesized in one 

 organ are transported to other organs, often profoundly modifying the growth 

 behavior of the recipient organs. Examples of such correlations have been 

 described in the discussion of photoperiodism in the preceding chapter. Dif- 

 ferences in electrical potential from one part of a plant to another may also 

 play a role in the correlative development of plants. 



Correlations between Reproductive and Vegetative Development. — 

 A study of the correlation between vegetative development and fruiting in 

 the tomato plant has been made by Murneek (1925). When tomato plants 

 were deflorated or the fruits were removed as rapidly as they "set" the plants 



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