NOTES ON RECENT RESEARCH, 



i L05 



Tbmpbbatube and Leaf Assimilation. 



Carbon Dioxide Assimilation, The Effect of Temperature on. 



Note by Miss (iabriello L. C. Matthaei (Ann. Bot, vol. xvi., No. 64, 

 p. 591). Abstract of paper read before Section K of the B'ritieh Associa- 

 tion, Uelfast, 1902. "This investigation differs from any which have 



preceded it on the same subject in the attention paid to uniformity in 

 the environment of the leaves before the experiment, Recent work has 



shown that both the assimilation and the respiration of a Leaf depend on 



its previous nutrition and temperature* For this reason a separate: leaf 

 was used for each temperature, Care being taken to keep them for some 

 time under exactly similar conditions. Leaves of the Cherry Laurel 

 (I'runus La/urocerasus) were employed throughout. . . . The lowest 



temperature at which assimilation could be detected was — 0" (). This 

 is the first well-established case of assimilation below 0 C. For tem- 

 peratures between — {)" C. and 88° 0. it was found that assimilation is 

 affected in exactly the same way as is respiration. Provided the illumi- 

 nation is sufficient, the assimilation increases with the temperature. At 

 any given temperature the leaf is only capable of a limited absolute amount 

 of assimilation, and increase of illumination beyond the amount requisite 

 for this maximal amount produces no further effect at all. A greater 



assimilation can only be obtained by increasing the temperature. Thus 

 the fundamental condition regulating the assimilation is the temperature, 



the intensity of the light occupying a secondary position similar to that 



of the percentage of carbon dioxide:. . . . For temperatures above 88 fl C. 



the result is complicated by the injurious effects of the temperature. 



The fatal temperature for Cherry Laurel Leaves is in the region of 41- 

 45° C, but the specific resistance of the leaves is very variable. Death 



is shown by a rapid decrease in the respiration, but it may be Several 

 hours before this ceases entirely. Kxposure to light has a most marked 

 effect in increasing the resistance of Leaves to the: effect of high tempera- 

 tures. Most interesting results were obtained from the prolonged ex- 

 posure of leaves to high temperatures* it was found that respiration of 

 a leaf in the dark fails off much more rapidly than that of a leaf in the 

 light, and the former can in no case be taken as a measure, of the bitter. 

 At first assimilation and respiration arc equally and similarly affected 

 by the temperature, but later the assimilation censes while respiration IB 

 still active." — B. f. L. 



Cabbon Dioxide and Gbowth, 



Carbon Dioxide, Effect of, on Plant-growth. By Paul Chapin 

 (Flora, vol. xci. 1902, pp. 848 879, t. xxi., and one cut). This research was, 

 unfortunately, completed before recent English publications, to which no 

 reference is consequently made. (1) Experiments on Fungi (a) Ger- 

 mination of spores.— -Spores of Aspergillus n/iger germinated in an 

 atmosphere of as much as 90 per cent, of CO , but took five flays. At 

 40 -60 per cent, they germinated in three days but formed no sporangia, 

 while at lower concentrations they did. Those of Peni&ilttum glou&um 

 showed similar relations, but formed spores at JO per cent. CO*, while 



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