56 CHANGES DURING GERM IN A TION AND GRO WTH 



time with a few drops of concentrated HgSO^, and 

 applying Fehling's test, the reduction will be seen to 

 take place with greater rapidity, owing to the fact that 

 the maltose has been hydrolysed to glucose. 



Some ungerminated barley should be ground up 

 with water and the solution treated in the same way as 

 above. It will be found that with Fehling's solution a 

 very slight reduction, if any, takes place. 



Photo-synthesis. 



The photo synthesis of the carbohydrates and other organic 

 matter from the carbon dioxide of the atmosphere is probably 

 accompHshed by the primary formation of hydrogen peroxide 

 and formaldehyde under the influence of the plant chlorophyll : — 



C02 + 3H20 = H.CHO + 2H202. 

 Both of these products are toxic to plants, but the formaldehyde 

 is immediately polymerised to hexose sugars, and the hydrogen 

 peroxide is decomposed by the universally existing plant catalase. 

 Both are thus removed as soon as formed. 



35. Plant Catalase. 



The existence of catalase in the green leaf may be 

 shown as follows : — About 6 grams of fresh leaves 

 are pounded in a mortar with a little sand, transferred 

 to a small flask, and mixed with 25 c.c. of 20-volume 

 hydrogen peroxide. The flask is completely filled with 

 water and fitted with a stopper carrying a delivery 

 tube leading under the surface of water, a test-tube 

 being inverted over the end. The delivery tube is also 

 filled with water, and the whole apparatus allowed to 

 stand in a warm place for some time. Oxygen is 

 evolved and is collected in the test-tube, and may be 

 recognised by the ordinary tests. 



The experiment should be repeated with a similar 

 quantity of leaves which have previously been plunged 

 for a short time into boiling water, whereby the catalase 

 is destroyed. 



