NO. 15 AERIAL FERTILIZATION OF WHEAT JOHNSTON 5 



POT EXPERIMENTS 



The results of the experiments in which wheat plants were grown 

 in pots and enclosed in clear cellulose acetate cylinders are sum- 

 marized in table 2. The general appearance of the plants in this 

 experiment is shown in plate 3. 



Table 2. — Suiiunary of 1934 Experiment zvith Wheat Grozvn in Pots 



Data Pot I Pot 2 Pot 3 Pot 4 Pot 5 Pot 6 



CO2 concentration (relative 



to normal air) 7. i 



Plants per pot 3 



Average data per plant: 



Number of tillers.... 10 



Number of stalks.... 6 



Length of stalks (cm.) 52 



Weight of heads (g.). 1.2 



Weight of straw 4.8 



Total weight 6.0 



No. of grains 4.7 



Weight of grains.... 0.134 



Weight per grain.... 0.029 



Culture 3, no forced ventilation. 



Culture 4, ventilated by slow stream of air. 



Culture 5, not enclosed. 



As noted above, Marquis wheat was planted in these pots on April 

 14. On April 23 the carbon dioxide and air mixture treatments were 

 started. The rate of flow was approximately 2 liters a minute. By 

 May 24 the plants in pot 5 had the best color, although all were 

 slightly yellow, with leaves somewhat rolled. Temperatures on clear, 

 hot days continued to be excessive in these cylinders in spite of the 

 open tops. Heads appeared on plants in pots i, 2, and 6 by June 11. 

 On July 13 the plants were photographed (pi. 3), and on the 19th 

 they were harvested. 



Although the conditions of this experiment were not so ideal as 

 could be desired, a few interesting facts appear from the data in 

 table 2. The number of grains and the weight of grain per plant 

 were much higher in pot 5 than in any of the others. The wheat 

 plants in this culture were not enclosed, but were entirely open to 

 the outside air. The lowest yield in number of grains and in weight 

 of grain per plant occurred in no. 3, where the plants were enclosed 

 in a cellulose acetate cylinder and deprived of forced ventilation. The 

 weight of straw was greatest in the cultures receiving the highest 

 concentration of carbon dioxide. It is to be expected that vegetative 

 growth would be helped by the addition of carbon dioxide, but it is 

 evident that grain production was depressed in comparison with no. 5, 

 the open control, when the number and weight of grain were used 

 as the criteria of measurement. When compared with nos. 3 and 4, 



