Identifier: philtrans04373862 (find matches)
Title: Experimental Researches on Vegetable Assimilation and Respiration. III. On the Effect of Temperature on Carbon-Dioxide Assimilation
Year: 1905 (1900s)
Authors: Matthaei, G.
Subjects: Proceedings of the Royal Society of London Philosophical Transactions of the Royal Society
Publisher: Royal Society of London

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s of Complete Curve. In synthesising from the figures, given before, the complete curve showing therelation between temperature and assimilation, this effect of the seasonal change onthe value of the assimilation must be borne in mind. The experiments representedin figs. 3 and 5 were all carried out in April, during the period of decreased activity.From fig. 3 we obtain the value for the maximal assimilation at all temperaturesfrom —6° C. to 11° d; from fig. 5 for all temperatures from 15° C. to 40o,5 CThese values are placed together in the accompanying diagram (fig. 6), and it will beseen that fig. 5 forms an almost exact continuation of fig. 3. From fig. 4 we knowthat after 40° 0. the assimilation rapidly decreases up to 43° C, we may, therefore, M 2 84 MISS G. L. 0. MATTHAEI ON EXPERIMENTAL RESEARCHES ON continue the steep decrease in fig. 6. This gives the complete curve from —* 6° 0.to +43° C. Therefore, under optimal conditions of light and supply of C02, the Fig. 6.
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-IO° o° +K)° +20° +300 +400 Temperature. assimilation rises rapidly with rise of temperature until within a few degrees of thetemperature fatal to the leaf. We see then that for every temperature there is a certain intensity of light beyondwhich further increase in the illumination produces no effect on the assimilation,except indirectly by increasing the internal temperature of the leaf The influenceof the intensity of illumination and of the percentage of C02? are therefore of thesame secondary nature, and can only affect the assimilation by reducing it if theyare below the required optimal amount for the particular temperature. iv. Conclusions. (1) Corresponding to each temperature there is a certain definite amount ofassimilation which may be termed the maximal assimilation for that temperature1 VEGETABLE ASSIMILATION AND RESPIRATION. 85 this cannot be exceeded, and will not be reached unless both light and C02 supply areadequate. (2) These maximal amounts increase rapidly wit

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