Studies on the Relation between the Trolerance of Crops to Soil Acidity and that to Low pH : 16. 0n the calcium and magnesium concentration in fractions extracted from root by various solutions

Abstract

Milk vetch and Italian ryegrass were cultivated in water solutions with different composition. Roots of these plants were successively extracted with 66% EtOH (Fr.1), cold water (Fr.2), O.1M acetic acid in 75% EtOH (Fr.3), 0.3% NaOH in 60% EtOH(Fr.4), 1N〓NaC1(Fr.5), 2% acetic acid (Fr.6) and with 5% HC1 (Fr.7). The residual material was ashed (Fr.8)and Ca and Mg in these fractions were determined, The results obtained were as follows : 1. When the concentration of Ca in culture solution was strongly lowered from the standard concentration, the concentration of Ca in each fraction decreased slightly indicating that the rate of Ca transport to top was reduced. At very high Ca concentration in culture solution, calcium carbonate and Ca bound to pectic acid besides water soluble Ca greatly increased. First two Ca fractions probably came from the excess Ca, being absorbed more than the amoun to be transported to the top in a short period. Italian ryegrass, which required lower Ca concentration fo culture solution for optimum plant growth, was cultivated at standard Ca concentration and low Ca concentration. The two largest Ca types of the root, Ca bound to pectic acid and tribasic calcium phosphate, were smaller in amount and on the other hand the reactive Ca soluble in alcohol was high. This pattern of distribution of Ca appeared to explain the less repuirement of Ca in root and the more translocation fo Ca to the top by this plant. In Italian ryegrass, whose plant growth was not suppressed too much at low Ca concentration, the amount in the root of calcium carbonate and Ca bound to pectic acid were reduced but no reduction was observed in both types of transportable Ca, soluble in alcohol and in water. This may be attributed to the effective transport of Ca to the top at low Ca solution. At excess Ca concentration in culture solution, Ca bound to pectic acid and especially tribasic calcium phosphate accumulated markedly in root. 2. The Ca bound to pectic acid and protein were directly depressed by increase of Mg concentration in solution caused by the competitive effect of Mg. The amount of tribasic calcium phosphate was not affected by direct competitive effect of Mg but was depressed by the decrease of concentration ot Ca in root. When the concentration of Mg in culture solution was so increased as to reduce Ca bound to pectic acid and tribasic calctum phosphate by the competitive effect of Mg, the plant growth was reduced. 3. At low Al concentration of 0.5ppm in culture solution, the binding of Ca to protein and pectic acid and accumulation as tribasic calcium phosphate were inhibited. At high Al concentration of 5ppm, accumulation of calcium carbonate was also inhibited besides the last two types. In Italian ryegrass, which was tolerant to Al toxicity, the depression of Ca in above three types at the Al concentration of 0.5-5ppm in culture solution was little. 4. At low pH solution of 4.3 in culture solution, alcohol soluble Ca in root was depressed as compared with that of pH 5.3 and resulted in the depression of translocated Ca at the top. And the accumulation of tribasic calcium phosphate in root was also inhibited in this case. In milk vetch, which was susceptible to the injury of high H ion, the amount of Ca bound to pectic acid in root also decreased as well as the above two types of Ca, at low pH of solution. At high pH value of 6.3 in culture solution, Ca concentration of tribasic calcium phosphate and Ca bound to pectic acid increased as compared with that of pH 5.3. 5. The concentration of Mg fractiond, which were bound to pectic acid, soluble in alcohol and soluble in alcohol with acetic acid, increased with increase of Mg concentration in culture solution. In milk vetch, whose growth was severely reduced by excessive Mg concentration in culture solution, the concentration of Mg in above three types easily increased at Mg concentration of 2-15ppm in solution. [the rest omitted]