Experimental Researches on Vegetable Assimilation and RespirationIIIOn the Effect of Temperature on Carbon-Dioxide Assimilation . of lightrepresented by = 1 can at the low temperature be utilised. When the intensity is doubled, the assimilation at 0°4 C. is unaltered, but anincrease is produced at the other temperatures, numbers almost identical beingobtained for all of these. When four times the light is used we find a similarphenomenon. The assimilation at 9° C. is no greater than that corresponding totwice the light, for the temperature exerts its limiting effect and the leaf canassim
Experimental Researches on Vegetable Assimilation and RespirationIIIOn the Effect of Temperature on Carbon-Dioxide Assimilation . of lightrepresented by = 1 can at the low temperature be utilised. When the intensity is doubled, the assimilation at 0°4 C. is unaltered, but anincrease is produced at the other temperatures, numbers almost identical beingobtained for all of these. When four times the light is used we find a similarphenomenon. The assimilation at 9° C. is no greater than that corresponding totwice the light, for the temperature exerts its limiting effect and the leaf canassimilate no more. At 11° C. a higher number is obtained, which, however, is not sogreat as that obtained at 25° C, showing that the leaf can make use of more lightthan is given by = 2, but it cannot use all that of = 4. Sixfold lightgives practically the same result as fourfold light for 11° C, showing that themaximum has been attained. Thus at the temperatures of 0o,4 C, 9° C. and 11° C, by sufficiently increasingthe light, a limiting amount of assimilation has been obtained, different in eachcase. Fig. Temperature. Fig. 3 represents graphically the results of Table VI. Three different curvesare obtained, one with the unit intensity of light, one with twice the light, and one,the true assimilatory curve for the temperatures from — 6° C. to +11° C, with four-fold light. The truth of the hypothesis is, therefore, well-established. * Experiment XXXVI. must be considered merely as regards the ratio yielded. The results obtainedfor - 1 and = 4, though harmonious, are far too small in comparison with the otherexperiments, indicating that the leaf was probably in an abnormal condition. VEGETABLE ASSIMILATION AND RESPIRATION. 71 In considering the ratios given in the last four columns, it is of interest to note that,although the assimilation is not maximal, light of double the intensity does not producefully double the assimilation. It would seem as
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