[Seasonal variations in contents of some non-volatile carboxylic acids in Sempervivum tectorum L].

Isocitric, citric, malic, and succinic acids are found in S. tectorum. Their contents, measured at various times during the year, show remarkable changes. Isocitric acid always dominates and reaches distinct maxima in December and June. During the winter and in the course of summer the quantity decreases, and in February and August there are minima of the amounts of this acid. The contents of citric and malic acids show a maximum during the winter months. The quantity of succinic acid increases in winter, too, but the highest values are found in the beginning of spring. The variations in the quantity of total acids are, as a result of the very high percentage of isocitric acid, essentially in accordance with the variations of the latter. The amount of total acids is highest in June and smallest in August.The factors temperature, photoperiodism, and endogenous annual rhythm are suggested to be responsible for the fluctuations in contents of the acids. A comparison with the behaviour of soluble carbohydrates suggests that acids take part in the regulation of storage of carbohydrates. Definite statements cannot be made, because the distribution of acids in the compartments of the cell is not known.