July 7, 1923 
Temperature Effects in Plant Metabolism 
27 
When the relative numbers of plants selected are considered, it appears 
that the development of dry matter in the leaves was appreciably lower 
at the lower temperature. The generally greater development of height 
of plants at the higher temperature is shown in Plate 2, B. Only well- 
filled and apparently normal seeds are considered in the data. On this 
basis there was a marked deficiency of the reproductive function at the 
higher temperature. This merits attention in connection with the 
chemical composition of the plants. With regard to the latter factor, the 
only distinct difference is in the polysaccharid content of the stems. In 
this respect the experiment agrees with the one conducted upon soil in 
1920, in that the plants grown at the lower temperature contained about 
5 per cent more of this constituent. It seems desirable to suggest that, 
in connection with the limited general development of these cultures, 
those at the higher temperature may have been unfruitful because of an 
unfavorable balance between nitrogen and carbohydrate content, accord¬ 
ing to the conclusions of Kraus and Kraybill {16). 
SUMMARY 
(1) A brief digest of the literature has shown variations of form and 
composition of plants in response to variations of climatic factors. In 
certain cases the decrease of temperature appears to have been specifically 
associated with increase of polysaccharids in the plants. The impor¬ 
tance of these relations to problems in physiology is mentioned. 
(2) Red clover (Trifolium praetense) grown in two greenhouses at 15 0 
and 20.6° C. average temperatures, with constant soil water supply, but 
with 47 per cent excess of evaporation at the higher temperature and 44 
per cent excess of solar radiation at the lower one, contained about 4 per 
cent more of polysaccharids in the tops of the plants grown at the lower 
temperature than in the other case. The crude protein content of the 
plants was least at the lower temperature, but not in proportion to the 
difference of polysaccharids. 
(3) Chambers for the control of atmospheric temperature and humidity 
are described. 
(4) Buckwheat (.Polygonum fagopyrum) grown in soil cultures with a 
uniform supply of soil moisture at average atmospheric temperatures 
of 17.5 0 and 22.8° C., with evaporation 7.2 per cent greater at the higher 
temperature than at the lower one and with the reinforced solar radiation 
3.6 per cent greater in the latter case, contained 5.8 per cent more starch 
in the seeds and 5.2 per cent more polysaccharids in the stems at the 
lower, as compared with the higher, temperature. The nitrogen con¬ 
tents of the stems and leaves varied inversely as the polysaccharid con¬ 
tents, but not proportionately so. 
(5) Buckwheat {Polygonum fagopyrum) grown in sand cultures with 
uniform supplies of water and nutrient salts at average atmospheric 
temperatures of 20.1 0 and 25.7 0 C., with evaporation 10 per cent less at 
the higher tetnperature than at the lower one, and with reinforced solar 
radiation equal in the two cases, contained 4.8 per cent more polysaccha¬ 
rids in the stems at the lower temperature than at the higher one. The 
plants grown at the higher temperature produced no seeds of normal 
appearance. 
(6) From the results herein presented, it appears that independent of 
its indirect effects through modifying the soil and independent of certain 
variations of atmospheric humidity and total magnitude of exposure to 
