Effects of Root Environments on Mineral Composition of Vegetable Foods

Abstract

Effects of root environments on absorption of mineral nutrients in plants are examined using excised roots of barley (Hordeum vulgare L.). Radioisotopes and multi compartment transport boxes [see method column] were used to understand separately absorption and translocation in cases of several ions. Effects of hydrogen ions (pH) and calcium ions (Ca2+) have been studied as important factors of root environments. At pH 3, substantial ion absorption has been lost except in the case of iron. Iron absorption looks rather like adsorption, because negligible radioactive iron can be found in the outer sections of excised roots examined. At pH 3.0 where a quick adsorption or absorption of iron is found, the hydrogen ion concentration is equivalent to 1.0 mM. Even though this low pH level is fatal to plants, similar severe condition can be seen in a solution culture experiment, after the renewal of complete nutrient solution containing a few mM of ammonium, whenever ammoniumtolerant plants have grown up sufficiently. Calcium disturbed absorption of other ions as like a commonly accepted theory in the field of plant nutrition. Calcium interruption is more severe to sodium, monovalent cation, than to iron and manganese, polyvalent cations. However there is exception that an available fraction exuded into the terminal compartment through xylem is rather stable between non-and 0.5 mM calcium levels. Besides the difference of carried fractions between the non and the low calcium treatment is not clear in the roots apart from the radio-activated tip section. The calcium effect to reduce the acid injury can be observed by its decreasing tendency in the leak of sodium or manganese during its translocation at pH 3.5.