The Apparent Free Space of Vallisneria Leaves.

The apparent free space of Vallisneria gigantea leaves has been determined by radiosulphate, using two different methods of extrapolation from the curves of absorption and loss. The values obtained are 7.7 ±0.8 per cent and 5.7 ±0.6 per cent respectively on a weight/weight basis. In V. spiralis the value is about 4.5 per cent. Earlier results of others, failing to recognize this passive uptake, are discussed and explained: an extremely strong metabolic accumulation of ions made it experimentally impossible to distinguish the ion quantity representing the outer space. - As for active sulphate uptake, light has a retarding influence. The protoplasts loose actively accumulated radiosulphate in a slow process when the leaves are again transferred to inactive solutions. [ABSTRACT FROM AUTHOR]