BALANCE OF ROOT AND SHOOT 93 



by reducing the top. The root must furnish the required 

 water and mineral salts, including some form of nitrogen. 

 Man has found that by increasing the relative root absorp- 

 tion by reducing the top he can grow, for the public, many 

 improved plants. Most of our cultivated plants have been 

 so modified by man's "improvement" that they could not 

 survive in the wild state. An experiment of this kind to test 

 the ability of wheat to reseed itself, showed a decrease each 

 year for three years, but none appeared the fourth year. 



Growth of flowers and fruits with their seeds consumes 

 food instead of supplying it as do the leaves. For this reason 

 plants usually flower after they have stored food, and many 

 perennial plants fail to produce annual crops of flowers be- 

 cause the reserve of stored food is too low. Apples often 

 bear fruit only on alternate years but continue to store food 

 each year. Only a few plants (tomato is a good example) 

 bear flowers or grow fruit simultaneously and consume food 

 with extensive stem or root growth. 



The condition of the balance of root and shoot can be 

 determined best by the character of growth, which depends 

 largely on the nitrogen supply, or more definitely the ratio 

 of the nitrogen supply to the carbohydrate content. Because 

 of their functions the problem of the balance of root and 

 shoot and that of carbohydrate and nitrogen ratio may be 

 identical; however the nitrogen supply to the plant may be 

 increased by fertilizer applications. When the nitrogen con- 

 tent of the plant is high and the carbohydrates are available, 

 proteins are made, at the expense of the storage of the carbo- 

 hydrates, resulting in growth instead of food storage in stems, 

 tubers, or fruits. If the nitrogen content is kept high, growth 

 may go on at such an abnormal rate — using so much of the 

 food — that the plant fails to get a storage supply sufficient to 

 cause it to become reproductive, even to form flower buds. 

 Growth with high nitrogen supply results in larger, dark 

 green leaves, longer, thicker internodes, higher water content 



