91. FUNCTIONS OF ESSENTIAL ELEMENTS: HIGHER PLANTS 



Element 



Occurrence in Plant^ 



Functions 



(A) 



(B) 



(C) 



Cytoplasmic membranes? 



Boron 



Inverse relationship between boron level and water perme- 

 ability of membranes and moisture content of tissues. 

 The element is necessary for: 



(a) Cell division and differentiation. 



(b) Translocation of sucrose and possibly other sugars. 



Calcium 



Calcium pectate 



Salts of organic acids 



Calcium pectate may be a constituent of the middle lamella. 2 

 Calcium precipitates organic acids. 



10 



Carbon 



All organic compounds^ 

 Bicarbonate ion 



Carbon is the key element in all organic molecular 



structures . 

 The ion is involved in anion absorption or exchange. 



Copper 



Tyrosinase 



Ascorbic acid oxidase 

 Laccase^ 



Tyrosinase is a polyphenoloxidase involved in reduction of 

 molecular oxygen (terminal step In aerobic respiration). 

 The oxidase may be concerned in respiratory oxidation. 



15 



20 



25 



30 



Hydrogen 



All organic compounds 



occurring in plants^ 

 Bicarbonate ion 



The element is a component of these compounds. 



The ion is involved in anion absorption or exchange. 



Iron 



Peroxidase 



Cytochrome oxidase 

 Catalase 



Peroxidase breaks down peroxides and transfers active 



oxygen to oxldizable substances . 

 The oxidase plays a role in reduction of molecular oxygen. 

 Catalase effects the release of molecular oxygen from 



hydrogen peroxide. 



Magnesium 



Chlorophyll 

 Co- carboxylase 



Enolase 



Hexoklnase 

 Magnesium pectate 



Chlorophyll is essential for photosynthesis. 

 Co- carboxylase is the co-enzyme for the 



function of carboxylases. 

 Enolase is necessary in glycolysis (from 2-phosphoglyceric 



acid to 2-pho'sphopyruvic acid). 

 Hexoklnase brings about transphosphorylation of glucose. 5 

 Magnesium pectate may be a constituent of the middle 



lEunella.2 



Manganese 



Arginaset 

 Unidentified enzyme 



Unidentified enzyme 



Arginase converts arginine to urea. 



The enzyme brings about catabollsm of oxaloacetic acid into 



pyruvic acid and carbon dioxide in respiration. 

 The enzyme is apparently required in ascorbic acid synthesis. 



35 



1*0 



1*5 



Molybdenum 



Unidentified enzyme? 



The element appears to effect the reduction of nitrate to 

 ammonia. 5 



Nitrogen 



Proteins 



Chlorophyll 



Many organic con^jounds 



The element is a component of proteins, the chief organic 



constituents of protoplasm. 

 Chlorophyll is essential for photosynthesis. 

 The element is important in the assimilation of sugars. 



Oxygen 



Most organic compounds^ 



Bicarbonate ion 



The element is a component of these coiqx>unds. 



The element is the final receptor of hydrogen in aerobic 



respiration. 

 The ion is involved in anion absorption or exchange. 



/l/ The element occurs in, or in association with, the compound or structure listed. The list is not 

 exhaustive. /2/ The middle lamella is an intercellular layer flanked on each side by the primary 

 cell walls. /3/ These compounds include carbohydrates, fats, proteins, vitamins, hormones, and 

 chlorophyll. /A/ The enzyme is of limited distribution, and its function is unknown. /5/ Nature 

 of relationship undetermined. 



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