July 7,1923 
Temperature Effects in Plant Metabolism 
25 
The sand was a mixture of 1 kgm. 100 mesh and 2 kgm. 50 mesh 
angular grains of quartz for each culture jar. It was rendered free of 
nutrients by extraction with hot 20 per cent HN 0 3 and thorough wash¬ 
ing, followed by leaching with lime water. The mixture had a water 
holding capacity of 42 per cent. 
After standing in the climatic chambers a sufficient period to insure 
temperature equilibrium, the 12 jars of sand were planted on March 12, 
and watered to the extent of 10 per cent of the sand by weight. Radi¬ 
cles appeared above the sand on March 14, at the higher temperature 
and one day later in the other case. On the latter date the covers 
were removed and there were added 0.2 gm. MgS0 4 .7H 2 0 and 0.4 gm. 
KN 0 3 P er j ar > * n solution. 
The water plane of the sand was raised to 13.5 per cent on March 17. 
By March 21, higher percentage and vigor of germination were apparent 
at the lower temperature. On April 2, 16 of the 18 plants in this case 
were expanding the first true leaves, while only 8 plants had reached 
this stage at the higher temperature. A further addition of nutrients 
was applied per jar on April 4 as follows: 0.1 gm. MgS 0 4 . 7 H 2 0 , 0.2 
gm. KN 0 3 , and 0.01 gm. ferric citrate. The newer leaves were pale 
green at this time, and noticeably mottled at the higher temperature. 
On April 8, the moisture plane of the sand was raised to 17 per cent. 
Buds appeared in both series of cultures on April 14, but they were 
more numerous at the higher temperature. On this date each jar re¬ 
ceived the following nutrients: 0.3 gm. MgS 0 4 . 7 H 2 0 and 0.6 gm. KNO s . 
The final application of salts per jar was made on April 25, as follows: 
0.6 gm. MgS 0 4 . 7 H 2 0 , 1.2 gm. KN 0 3 , 0.39 gm. Ca (N0 3 ) 2 4H 2 0, 0.075 gm. 
KH 2 P 0 4 , 0.075 gm. NaCl, and 0.015 gm. ferric citrate. At this time the 
plants at the lower temperature were uniform in size, while the other 
series was irregular in this respect. On April 29, the water supply was 
raised to 20 per cent of the sand, or about optimal for the plants. 
Conspicuous differences in the reproductive phase of growth soon 
appeared. Thus on May 2 all of the plants at the lower temperature 
were in full bloom, while only a few plants were in bloom at the higher 
temperature. Thickening of the stems was rather prominent in the 
latter case. On May 6 several seeds were developed to considerable 
size at the lower temperature, while only one seed had appeared at the 
higher temperature by May 10. 
After taking photographs on May 16, the cultures were harvested. 
Plants with only two true leaves or decidedly pale in leaf color were 
rejected. There remained 16 plants at the lower temperature and 13 
at the higher. These were separated into leaves and stems, excluding 
the seed parts. The data of climatic factors and chemical analysis are 
assembled in Tables VII and VIII. The appearance of the plants is 
shown in Plate 2, B, while Plate 4 shows a portion of the climatic records. 
Graphs constructed from the atmometric data appear in figure 2. 
Comparison of the climatic data of this experiment with that of 1920 
was less satisfactory in the present case. This is to be ascribed largely 
to less effective functioning of the humidifiers, due to deterioration of 
the toweling. In future development of the apparatus humidification 
will be accomplished by means of spray nozzles. The variation of the 
lower temperature range here was greater than that of the upper range, 
while the reverse was true in the earlier experiment. As a general 
average, the temperature was maintained at about 5°C. between the 
temperature planes here, but the average planes of operation were about 
