BOTANY OF THE LIVING PLANT 



of formaldehyde ii lis during photosynthesis, and to try to 



:n the plant Btarting from artificially supplied 

 maldehyde rather than from carbon dioxide: neither has yielded 



Other in ators have attempted to obtain a 



phot ' carbohydrates from carbon dioxide and 



in artificial ms where the chemistry of the process could 



tudied. Exti cted chlorophyll has been introduced 



into Bome of tl While some investigators claim to have 



■ vntlu inder such conditions, all such claims 



:i sub i strorjg criticism, and so far this line of investi- 



tionhasn isted very mtich in the elucidation of photosynthesis 



in the plant. 



I: a :i\ believed thai the r61e of chlorophyll is not limited to the 



I ii m of light-energy, and to the application of that energy to the 



vnthft. stem ; but that the pigment also participates, possibly 



in the ity of a catalyst, in the chemical changes of photosynthesis. 



One well-known theory assigns a function of this type to the pigment in 



:u<n with the formation of the formaldehyde, which is believed to 



an intermediate product in photosynthesis. 



Appl n of analytical methods to leaves shows that sugars are 



the firs! products of photosynthesis, as already stated. It is probable 



that the simpler suj Glucose and Fructose, are those actually 



med first (see next section). In many plants the initially-formed 



to a considerable extent converted quickly into Starch, 



which acts as a temporary 7 reserve substance. But in a number of 



plants, as for example many Monocotyledons, no starch is formed and 



cumulates as such. 



Estimates of the rates of carbohydrate-synthesis under natural 

 ditions have yielded very variable results: but in order to give 

 of the extent of photosynthesis, it may be mentioned 

 that Sat I Deluded from his measurements that as much as 25 



irbohydrate may be formed within a square metre of 

 S t" during ummer's day. The carbohydrate of the 



I would be mostly in the form of starch, and if this quantity of 

 out on scales it will be seen to be of very consider- 

 able bulk ; in forming that amount of starch the leaf would deprive 

 50 cubic metres of normal atmospheric air of its carbon dioxide. 



In this consideration of photosynthesis we have looked at the 

 P r( from tl indpoint of the plant itself: the process is also 



of profound significance to the animal kingdom, a matter which is 

 Considered al I 1 of this chapter. 



