Abstract
The flower of hydrangeas, as generally known, turns blue in its color, when cultivated in acid soil.
This, according to the report from Allen(1), is explained as a large quantity of aluminium absorption in acid soil, and is also confirmed subsequently by Asen(3)(4)(5) as a result of experimental analyses. Furthermore, it is reported by Post(8) that the acid soil with an acidity of approximately pH 5.5 is the most optimum condition for the cultivation of hydrangeas, and alkaline soil is least suitable for its cultivation.
From what mentioned above, it may be concluded that the successful culture of hydrangeas will be performed in acid soil, but when wanted to have its color in clear red or pink, the soil with neutral or weak acidity will be required.
Therefore, with a view to observe some prospective reactions in the color depending on the acidity of soil, the present experiment was made using a variety of hydrangeas with pink colored-flowers as explained hereunder:
The experiment was carried out through observing several of hydrangeas with pink colored-flowers transplanting from acid to alkaline soil or from alkaline to acid soil on the occasions as those of August 20 (at their full growth period), September 19 (right before the dormant period) and January 13, 1965 (when they were put into a greenhouse after chilled).
As a result, all of the hydrangeas formerly with pink colored-flowers turned into blue colored-flowers, including those of hydrangeas cultivated in the weak acid soil in the early stage of growing period and also those transplanted into acid soil in a greenhouse on January 13, as well as those controlled in alkaline soil throughout the growing season. The hydrangeas, grown throughly in alkaline soil after the potting, gave naturally clear pink colored-flowers. Besides, even those of hydrangeas, which were cultivated in the standard soil with a weak acidity until the growing period or the stage exposed to low temperature and transplanted thereafter into the alkaline soil in a greenhouse, had clear pink colored-flowers. Those of hydrangeas controlled in strong acid soil during the vegetative period of one or two months and transplanted thereafter into alkaline soil, as well as those cultivated in acid soil until the period exposed to low temperature and transplanted thereafter into the alkaline soil in a greenhouse, gave purplish blue colored-flowers.
As the results of chemical analyses of leaves and flowers, phosphorus was found in flowers more densely than in leaves, and those of hydrangeas grown in acid soil contain less phosphorus as compared with those in alkaline soil. Aluminium, on the other hand, was proved to be plentiful in leaves and flowers of hydrangeas cultivated in acid soil during their vegetative period, and less plentiful aluminium was found as those grown in alkaline soil.
As for the relation between the quantiy of aluminium and the color of flower, blue is corresponding to the aluminium amount of 950-2, 900ppm, purplish blue to 300-400ppm, pink to nearly 200ppm.
Anthocyanins, which were extracted by methanol containing 1% of HCI from those of colored flowers with blue, purplish blue, and pink, was developed by means of paper chromatography. As the result the Rf value appeared to be constant without relation to the kind of colors.
