CHAPTER 



I *r Mineral Nutrition in Re- 

 lation to the Ontogeny 

 of Plants 



W. F. LOEHWING 



T 



he study of mineral nutrition in relation to ontogeny 

 is merely one type of approach to an understanding and control of 

 plants as organisms. A study of this sort becomes primarily an attempt 

 to arrange the known facts of mineral metabolism as a progressive se- 

 quence of events as these relate to the commonly observed growth pat- 

 terns of plants. The major problem is one of integration of somewhat 

 isolated data with the growth process as a whole. It seems desirable to 

 outline the accumulation and distribution of inorganic ions and then 

 to trace as far as possible their connection with tissue differentiation 

 and the progression of the entire life cycle of the plant as a whole. 



An understanding of mineral nutrition in relation to ontogeny is 

 complicated by the fact that numerous meristems give rise continu- 

 ously to new tissues and organs, with the result that various parts of 

 the plant are usually in different stages of development. Thus, com- 

 parable size and age of parts or of the plant as a whole are not neces- 

 sarily criteria of developmental similarity (121). At mid-maturity of a 

 plant, its various parts may display the entire range of development 

 from youth to senescence (//). Upon these developmental differences 

 between parts are superimposed certain ecological contrasts (9^). During 

 growth, a single plant often modifies its environment in such a way 

 that organs appearing in a chronological sequence commonly form an 

 ecological succession (76, 152). Due to the progressive modification of 

 apical meristems in the course of vegetative development, for example, 

 there usually occurs an axial progression from mesomorphy of the 



