INTRAMOLECULAR RESPIRATION OF AEROBES 537 



The extent to which intramolecular respiration suffices to support vital 

 activity depends again upon the specific nature of the particular plant and 

 upon the kind of food supplied. As a general rule aerobic organs in which 

 metabolism is active will be the first to suffer from the lack of oxygen, and 

 hence life can be longer maintained in the absence of oxygen when the 

 temperature is low. Thus seedlings of Zea mays die and cease to evolve 

 carbon dioxide in twelve hours at 40 C., in twenty-four hours at i8C., and 

 may live a few days at still lower temperatures, dying after approximately 

 the same amount of carbon dioxide has .been produced in each case '. 

 Apples and pears may remain living for months at moderate temperatures 

 in an atmosphere of hydrogen or nitrogen ; Lechartier and Bellamy 2 found 

 that two pears weighing 282 grms. produced 1762 mg. of carbon dioxide in 

 five months. On the other hand, fungi and strongly aerobic bacteria soon 

 die owing to their high metabolic activity 3 . Thus Spirillum undula dies in 

 about an hour after the removal of all free oxygen, and so short a period 

 as this does not allow the disturbing influence of starvation or of the 

 accumulation of waste-products to become manifest. 



The value of intramolecular respiration to the plant is not solely 

 dependent upon the amount of decomposition induced, for this varies in 

 different cases. As a general rule the metabolic activity is reduced in 

 aerobes during the absence of oxygen, but in certain phanerogamic 

 seedlings, according to Palladin, it increases. Cotyledons of Vicia faba 

 and of Pisum sativum produce a greater amount of carbon dioxide during 

 intramolecular respiration than during oxygen-respiration, whereas seedlings 

 of Vicia faba and Ricinus produce the same amount 4 . 



Since the metabolic products in Phanerogams are similar to those 

 produced by Saccharomyces and aerobic fungi, it is probable that in them 

 also sugars are mainly consumed in intramolecular respiration, and even 

 although traces only of sugars may be present they may be continually 

 formed from other substances 5 . In the case of mould -fungi and Saccharo- 

 > 



1 Chudiakow, 1. c., p. 360. Cf. also Palladin, Rev. gen. d. Bot, 1894, T. vi, p. 201. Brefeld 

 (Landw. Jahrb., 1876, Bd. V, p. 327) states that seedlings may remain living in the absence of oxygen 

 for weeks or even months, but this requires confirmation, and besides, very young seedlings of penft, Atj^ 

 may reassume the dormant condition characteristic ->f the seed. 



3 Compt. rend., 1872, T. LXXV, p. 1204; 1*74. T. LXXIX, pp. 949, 1006; Kny, Ber. d. Bot. 

 Ges., 1889, p. 164 (Potato-tubers). 



3 On intramolecular respiration of aerobic bacteria, cf. Hesse, Zeitschr. f. Hygiene u. Infect., 

 1893, Bd. xv, Heft i ; Smith, Centralbl. f. Bact, 1895, Bd. xvm, p. 4. 



Palladin, Bot. Centralbl., 1888, Bd. xxxm, p. 103 ; Pfeffer, Unters. a. d. Bot. Inst. z. Tubingen, 

 1885, Bd. I, p. 657; Diakonow, Ber. d. Bot. Ges., 1886, p. 412. 



5 According to Palladir (Rev. gen. d. Bot., 1894, T. vi, p. 209), a supply of sugar favours the 



intramolecular respiration rf etiolated seedlings. The consumption of carbohydrates during the 



intramolecular respiration o<" fruits has been proved by Lechartier and Bellamy, Compt. rend., 1869, 



' T. LXIX, p. 466; Pasteur, Etude s. 1. biere, 1876, p. 260; de Luca, Ann. d. sci. nat., 1878, vi. ser., 



T. vr, p. 302. 



