FATS, WAXES, AND LIPOIDS 155 



formed, which has been found in plants. Three molecules of sorbic 

 aldehyde can be linked together to give an unsaturated aldehyde 

 that can be easily changed to the fatty acids. 



Utilization of Fats in the Plant.— The problem has been attacked 

 by noting the changes which take place in fatty seeds during ger- 

 mination, the assumption being that the reverse change takes 

 place when the fat is built up. Miller (1910) showed that the 

 resting sunflower seed contains less than 1% of fatty acid, but 

 when germination has proceeded far enough for the plumule to 

 show, the fatty acid reaches 30%. Glycerol does not show so 

 readily because it is more easily translocated and consequently 

 harder to detect. 



Ivanov (1912) found that fatty acids increased considerably 

 during germination and then disappeared, the unsaturated ones 

 disappearing first. He believes this is due to the fact that the 

 unsaturated ones are easily transformed into sugars before being 

 oxidized, while the saturated ones are oxidized without being 

 changed into sugar. 



Le Clerc du Sablon found the resting seed of castor bean con- 

 tained 69% of oil and 4% of sugar, while in a seedling 11 cm. 

 high the oil had fallen to 11% and the sugar had risen to 14%. 

 The kind of sugar formed depends upon the nature of the oil. 

 Detmer has suggested that the kind of action which takes place 

 might be represented by the following equation : 



C w H8402+270 = 2(C 6 HioOb)+6C02+5H 2 



oleic acid 



in which case a carbohydrate, carbon dioxide, and water are pro- 

 duced by the oxidation of the fatty acid. It is only reasonable 

 to suppose that the reverse reactions may take place in the build- 

 ing up of fats. 



Fats as a Source of Energy.— In animals, fats are the chief 

 source of stored energy. In plants, however, they are not as 

 important on the whole as carbohydrates, but are found especially 

 in seeds, where much energy must be stored in a small space. 

 Since the fats contain more hydrogen and less oxygen than the 

 carbohydrates, they are able to take on more oxygen and release 

 more energy in the oxidizing process than the carbohydrates. 

 One g. of fat when oxidized gives an average of 9.3 calories of heat 

 energy, while one g. of starch gives only 4.1 calories. Thus, while 



