TRANSPIRATION AND PHOTOSYNTHESIS IN CORN 161 



6. The water requirement was less for plants in the drier cul- 

 tures in all experiments, being least in the 25%, most in the 65% 

 and with the 45% intermediate. The rate of transpiration in 

 GM-H showed the same relation to moisture content as did the 

 water requirement. Thus it appears that the amount of organic 

 substances formed is not at all proportional to transpiration. 



7. The nocturnal transpiration showed the same relationship 

 for the three series as the diurnal and the day to the night gave 

 an approximate ratio of 6 : 1 for all three series. 



8. A great variation occurred in the amount of water transpired 

 from day to day due to changing environmental conditions, but 

 this change seemed to be approximately constant for the three 

 series. 



9. The relative photosynthetic activity was determined by 

 weighing unit leaf areas from the different cultures from time to 

 time. 



10. Plants in the dry soil weighed most per unit area, the 

 medium next and the wet the least. The maximum increase in 

 dry weight per unit area occurred about noon with a slight 

 decrease from this to evening. After dark there is a gradual 

 decrease in dry weight per unit area until dayhght, the greatest 

 loss occurring before midnight. The relation between the three 

 cultures remained approximately the same for the twenty-four 

 hours. 



11. Final soil samples taken at the conclusion of the experi- 

 ments showed a sHght variation of from 1% to 5% from the initial 

 moisture content. 



