274 PLANT PHYSIOLOGY 



contributing to the accumulation of organic substances in the 

 plant. 



As has already been seen, the basic process of the creation of 

 organic from inorganic substances is photosynthesis. It might 

 be assumed therefore that the introduction of mineral elements 

 necessary for the nutrition of the plant, especially of potassium, 

 which is supposed to participate in some way in the transforma- 

 tions of carbohydrates, would considerably increase photo- 

 synthesis. However, exact experiments carried out by Gassner 

 (1933) have shown that with decreasing doses of potassium, the 

 intensity of photosynthesis does not decrease but on the contrary 

 increases, and only a strong deficiency in potassium suppresses 

 the photosynthetic activity. Of all the elements absorbed by 

 the root system, only nitrogen induces a perceptible increase in 

 photosynthesis. 



The interrelations between the mineral elements and the 

 accumulation of organic substances, therefore, are very compli- 

 cated. Mineral substances participate actively in the formation 

 of new masses of living protoplasm, especially substances such 

 as potassium, magnesium, and phosphorus, which are always 

 present in more or less considerable quantities in meristematic 

 tissues. They contribute to the utilization of the products of 

 assimilation in the structure of new cells, thus leading to an 

 increased growth intensity and to the creation of new assimilating 

 leaf surfaces especially in the first periods of the development of 

 plants. The same effect is produced by nitrogen; it has been 

 definitely established that deficiency in nitrogen leads to a reple- 

 tion of the leaves with unutiUzed carbohydrates. An increase 

 of the photosynthesizing cells leads to a considerable increase in 

 the accumulation of organic substance of the plant as a whole 

 and thus to an increase of the yield. The action of mineral 

 substances may thus be compared with the action of hormones, 

 which control and increase growth. 



The accumulation of mineral substances in the plant is most 

 intimately connected with the accumulation of organic sub- 

 stances; if, on the one hand, appUcation of fertilizers increases 

 the yield, the absorption of mineral elements on the other hand 

 may be accelerated by increasing the rate of the accumulation 

 of organic substances. Such a phenomenon has been observed 

 by Jegorov. The removal of flowers, which caused profuse 



