July 2, 1917 Variation of Water in Leaves of Corn and Sorghums 43 



Table V. — Average rate of increase of the dry matter for each square meter of leaf for corn, 

 kafir, and milo during each 2-hour period of the day 



Two explanations are possible for these results. The milo plant 

 either manufactures food in the leaves more rapidly than the corn or 

 kafir or the rate of translocation is higher in the latter plants. In most 

 cases, under the conditions of these experiments, the leaves of com 

 were badly wilted during the greater portion of the day. The kafir 

 leaves also wilted, but not to the extent of the corn, while the leaves of 

 milo very seldom showed signs of wilting. The smaller increase in dry 

 matter in the leaves of corn and kafir during the greater portion of the 

 day in comparison to the leaves of milo is evidently due to the severe 

 climatic conditions. The high evaporation of water from the leaves 

 of com and kafir exceeds the intake by the roots; and, as a consequence, 

 the water content is lowered to such an extent as to interfere with the 

 vital processes of the protoplasm. The rise in temperature of the leaves 

 due to the decreased transpiration may also be a factor in lowering the 

 photosynthetic power of these plants. The dry-matter curves in figures 

 i> 7> 8, 9, 10, which represent the results for July 28 and August 11, 1914, 

 and for the four experiments in 191 6, show the marked increase in dry 

 matter in the leaves of milo in comparison to the leaves of corn and kafir. 



SUMMARY 



The variation of the water and dry matter in the leaves of corn and 

 the sorghums was determined by nine experiments in 1914, two in 191 5, 

 and four in 191 6. These experiments were conducted with plants of 

 Pride of Saline corn, Blackhull kafir, and Dwarf milo which were grown 

 in the field, either in a series of plots or in alternate rows on the same 

 plot. Four of the experiments in 1914 extended only through the day- 

 light hours, but all the other experiments ranged in length from 24 to 

 48 hours. In these experiments the water and dry matter in the leaves 

 were determined every two hours during 22 days and 10 nights for corn 

 and milo and during 18 days and 10 nights for kafir. 



The amount of water and dry matter in the leaves of a given variety of 

 plant was obtained for any 2-hour period from 30 leaf samples, each with 

 an area of i square centimeter. A single leaf on each of 30 representa- 

 tive plants furnished all the samples for an experiment extending over 



