RECENT ADVANCES IN SCIENCE 303 



with respiration in general. With reference to these papers on 

 plant oxidases, it may be remarked that some of the botanical 

 workers fail to keep themselves informed of the results which 

 are being obtained by workers on the corresponding substances 

 in animal tissues — an unfortunate circumstance in the case of 

 problems which are obviously to a large extent common ground 

 in biology. An interesting contribution to a closely related 

 problem — the connection between light and respiration — has 

 been made by Spoehr (Bot. Gat. 59). It has long been known 

 that respiration (both in plants and animals), as indicated by 

 the liberation of carbon dioxide, is increased by exposure to 

 light, other conditions being equal, and more recently it has 

 been found that respiratory activity is higher during the 

 daytime than during the night in the case of plants kept at 

 constant temperature and in darkness — that is, when the only 

 variable external condition to which the plants are exposed is 

 the air of daytime on one hand, and that of the night on the 

 other. Spoehr made careful determinations of the day-night 

 ratio with normal and deionised atmospheric air, and his results 

 indicate that, as might be expected, there is a definite relation 

 between respiratory activity and the ionisation of the air due 

 to sunlight. In discussing this very remarkable indirect rela- 

 tion between light and respiration, Spoehr points out that 

 various lines of work seem to lead to the conclusion that the 

 accelerating influence of] light and heat on biological oxidative 

 processes may be explained by the necessity for the dissociation 

 or liberation of free valencies in the oxygen molecule — that is, 

 it is in all probability the partially dissociated oxygen that 

 combines with the oxidisable substance in such processes. This 

 opens up a very interesting field for further work, and suggests 

 the probability, for instance, that the respiratory activity of 

 plants in arid regions may (other conditions remaining equal) 

 be higher and show greater day and night variations than that 

 of those in lowlying and moist situations, since atmospheric 

 ionisation is decreased greatly by water vapour and high 

 relative humidity. Shive (Amer. Journ. Bot. 2) points out 

 that since the general problem of the mineral requirements of 

 plants largely remains still to be studied, and since nutrient 

 solutions will have to be used in experiments bearing upon this 

 problem, owing to the harmfulaction of distilledwater on plants, 

 it is important that the standard solution used as a basis of 



