130 



MINERAL SALTS ABSORPTION IN PLANTS 



dungung) of macro- and micro-nutrients to crops. Interest has 

 been aroused in the possibiHty that additional amounts of essential 

 elements may be supplied more economically as sprays on the foliage 

 than by appHcation to the soil. The extensive dissemination of 

 insecticides, fungicides and weed-killers from the air can be con- 



12 3 



Weeks since the start of germination 



Fig. 44 (b). Movement of salts in germinating seedlings 

 Potassium content of cotyledons (O — O), shoots (D — D), roots (x — x) 

 and whole plants (A — A) oi Pisiiin sativum during growth for 4 weeks at 20 °C 

 in the dark in the absence of supplied potassium (Sutcliffe, unpublished). 



veniently combined with that of fertiUzers. The fact that mineral 

 salts can be presented in this way when the crop is already growing 

 actively ensures that a high percentage of the salt is absorbed and 

 there are minimum opportunities for losses by leaching. Since air 

 temperature rather than soil temperature controls foliar absorption, 

 it is said that application of mineral sahs to leaves has a decided 

 advantage over conventional practice with crops growing in cold 



