Effect of the osmotic environment of the seed coat on sucrose and amino acid transport into developing seeds of Lunaria annua, Acer pseudoplatanus and Glycine max

In contrast to the data reported for developing seeds of pea and broad bean, assimilate transport into empty kernels of maize is not reduced by a low osmolality of the substitute medium. Therefore, additional data were collected from representatives of other taxonomical groups. In pulse-labelling experiments with Lunaria annua L. and Acer pseudoplatanus L., sucrose and amino acid transport into empty ovules was strongly reduced by a low osmolality of the medium filling an empty ovule, compared to that seen with high osmolality. In experiments of 8 h without radioiso-topes, a very low osmolality of the medium (about 0 m M ) reduced the rate of sugar and amino acid release from attached seed coats of soybean [ Glycine max (L.) Merr. cv. Fiskeby V], in comparison with a 300 m M mannitol medium. It can be concluded that in all dicotyledonous plants studied (five species), a low osmotic potential of the seed apoplast is one of the most important factors controlling the rate of assimilate transport into developing seeds. At this moment, the data reported for maize have an isolated position.