THE ABSORPTION OF CALCIUM SALTS BY SQUASH 



SEEDLINGS* 



RODNEY H. TRUE AND R. B. HARVEY 



Bureau of Plant Itidustry, U. S. Department of Agriculture 



In the course of a former investigation^ carried on with the white 

 lupine (Lupinus albus L.) as a test plant, it was found that the rate of 

 absorption of electrolytes by seedlings from solutions of the usual 

 mineral nutrients was influenced to a great degree by the chemical 

 character of the substances offered. In simple solutions it appeared 

 that the usual salts of potassium were not absorbed producing rather 

 an outgoing current of ions from the seedlings into the solutions; 

 in magnesium solutions a small absorption took place in the more 

 dilute solutions, while in calcium solutions absorption was much greater 

 and took place in the most dilute solutions. It appeared from the 

 behavior of the lupine in the solutions of calcium sulphate and calcium 

 nitrate that in each case the quantity absorbed is limited, even though 

 the supply may contain a large excess, and the effect of the anion 

 appears to be subordinate to that of the Ca ion in determining the 

 quantity absorbed. 



It was found by preliminary experiments by the present authors 

 that this condition of things does not apply to all kinds of plants. 

 The common garden squash, sweet corn and soy bean were found 

 to behave quite differently with respect to the anion employed with 

 the Ca ion. In this paper the records of a series of experiments are 

 presented showing the absorption from a series of solutions of three 

 of the commoner inorganic salts of calcium by the seedlings of Cucur- 

 hita Pepo L. of the horticultural variety known as Early Prolific 

 Marrow. 



Before considering the evidence on which the conclusions here 

 advanced are based a word concerning the method is in order. 

 Selected seedlings obtained from seeds germinated in chopped sphag- 

 num were grown in carefully prepared solutions contained in prac- 

 tically insoluble glass beakers. The concentration of ions of each 

 solution was noted daily by taking conductivity readings by means 

 of an accurate wheatstone bridge. The temperature throughout was 



* Published by permission of the Secretary of Agriculture. 

 1 True, R. H., & Bartlett, H. H. Am. Journ. Bot. 2: 278. 1915. 



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