MINERAL NUTRIENTS AND NITROGEN 201 



The Functions of the Mineral Nutrients. — ^A study of these 

 elements in relation to plant growth brings oiit many im- 

 portant facts : 



(1) We do not thoroughly understand the role of some of 

 th^e elements. 



(2) That the action of these elements varies when applied to 

 different species of plants. 



(3) That the action of these elements varies with reference 

 to the amount in the soil. 



(a) Phosphorus is a necessary part of the nucleo-protein of 

 the cell and is found in comparatively large amounts in the 

 seeds and in the seedlings. It has been noted that phosphorus 

 migrates from the mature stems to growing tips ajid to seeds 

 as they approach maturity. 



(&) Potassium is an. important factor in the formation of 

 carbohydrates and proteids. If it is not present, starch is not 

 produced and protein formation is abnormal. Furthermore, 

 the cells elongate, but there is no nuclear and cell division. 

 It has been noted that seeds and other parts of the plant 

 rich in protein are usually well supplied with potash but 

 without a definite ratio of the two compounds. Many fruit 

 growers believe that potassium causes trees to ripen the wood 

 better and is therefore a protection against winter and earlv 

 spring injury from frost. It is also believed by many that it 

 tends to improve the color and quality of apples, but this has 

 not been demonstrated. 



(c) Magnesium is believed to be an important factor in the 

 transfer of phosphoric acid for assimilation. It is absolutely 

 necessary for the development of chlorophyll. It is like phos- 

 phorus in that it is very abundant in growing tips and in seeds 



