CHEMICAL COMPOSITION OF PLANTS 59 



filtered, a transparent filtrate showing a strong invertase action 

 will be obtained. After precipitation by alcohol, a dry prepara- 

 tion of invertase readily soluble in water and preserving its action 

 for a rather long time is secured. Of the enzymes that split 

 glucosides, the most important is emulsin, or /3-glucosidase, 

 which hydrolyzes all the glucosides of the /3-group. It is usually 

 obtained from seeds of bitter almonds. The enzyme a-gluco- 

 sidase, closely related to it, acts in the same manner on a-ghico- 

 sides. It is found along with invertase in the extract from yeast. 



In oily seeds, the main nonnitrogenous reserve substances are 

 represented by plant fats. 



In the germination of oily seeds, the stored fat is used very 

 rapidly. Miintz observed that of 8.9 g. of fat found in 20 g. of 

 poppy seeds prior to their germination, after 2 days there were 

 left 6.8 g. and after 4 days only 3.9 g. This consumption of oil 

 is preceded by its hydrolysis, which may be seen from the fact 

 that the quantity of free fatty acids, which is quite negligible 

 in the seeds, grows very rapidly at germination. In the case of 

 the germinating poppy seeds, only 10 per cent of the fat was 

 composed of free fatty acids before germination, but after 2 days 

 this had increased to 53 per cent, and after 4 days to 97 per cent. 

 It was not possible to demonstrate an accumulation of glycerin, 

 as it very quickly undergoes further changes. 



The hydrolysis of fats in germinating seeds is brought about 

 by special enzymes, known under the general name of ''lipases." 

 Lipase is easily obtained by grinding with glycerin germinating 

 castor beans. It will rapidly hydrolyze fats into glycerin and 

 fatty acids. Since the rate of the reaction is considerably 

 increased in an acid medium (pH 5) and since, in hydrolysis, 

 free acids accumulate, the activity of lipase has an autocatalytic 

 character. In the beginning, it proceeds rather slowly and then 

 with ever increasing rapidity. 



14. Decomposition of Reserve Proteins during Germination. 

 Proteolytic Enzymes. — Reserve proteins of the seeds are also 

 subject to hydrolysis during germination. This is brought about 

 by proteolytic enzymes, or proteases. The result of the activity 

 of these enzymes is the accumulation of amino acids. According 

 to the analysis of Jodidi (1925), 95 per cent of the total nitrogen 

 substances in the grain of corn are in the form of proteins. Two 

 days after the beginning of germination the amount of nitrogen 



