-5- 



CHEMI CAL ELE ivIENTS REqUIRED BY PLAIJTS 



Carbon (C ) - absorbed by leaves as carbon dioxide (CO2). Used in the manufac- 

 ture~"of carbohydrates. A by- or end-product of plant and aniraal respiration 

 and of plant and animal decay. 



Hydrogen (K) - absorbed by roots as water (H2O). Used in making food. 



Oxygen (O) - absorbed by leaves, stems and roots, as oxygen and by roots, as 

 water. Also absorbed by roots in other ions as nitrates, phosphates, etc. 



Phosphorus (?) - absorbed by roots as soluble phosphate ion (PO4). A con- 

 stituent of some of the most important plant proteins. "Phosphorus makes seeds." 



Potassium (k) - absorbed by roots as soluble potassium ion. A catalyst or 

 regulator of vital processes. "Potassium makes sugars and starch." 



Nitrogen (N) - absorbed by roots mainly as nitrate or ammonium ion. Found in 

 proteins and protoplasm. "Nitrogen makes leaves." 



Sulfur (S) - absorbed by roots as the sulphate ion (SO3). A constituent of 



most proteins. Responsible for many characteristic odors and flavors in plants - 



onions, cabbage, etc. 



CaJciun (Ca) - absorbed by roots from soluble lime compounds. Neutralizes acids 

 ill soTTs and plants, and provides for proper absorption of other nutrients. 



Iron (Fe) - absorbed by roots as iron ion. Necessary/ for the formation of 

 chlorcphyll, although not a constituent. Often tied up in alkaline soils. 



Magnesium (Ug) - absorbed by roots from soluble magnesium and lime compounds. 

 A constituent of chlorophyll, an acid neutralizer, an.d perhaps a carrier for 

 phosphorus in plajits. 



Boron (B) - absorbed by roots from borates. A catalyst which is toxic if pres- 

 ent in m re than minute amounts - tied up in alkaline soils. 



Manganes e (Lin) - absorbed by roots. A catalyst - tied up in alkaline soils. 



Copper (Cu) and Zinc (Zn)- absorbed by roots. Catalysts - probably essential 

 to grovj-th. Toxic in more than very small amounts. (A few others may be re- 

 quired in very small amounts.) 



PhotoaynthesiB « the manufacture, from water and carbon dioxide, 

 of primary cai'bohydrate by green plants exposed to (sun) light. 



Equations 6CO2 -t SHgO -^CqEizOq + GOg 



carbon dioxide -f water — *• sugar -f oxygen 



Respiration (breathing) in this process sugar is broken Aown to 

 carbon dioxide and water. 



Equation* CgHi206 "* ^"^2 — * ^^°2 ■*■ 6H2O 



sugar -t oxygen-* carbon ■♦ water 

 dioxide 



— A. P. Tuttle 



