| Abstract: | Influence of macrobicycle ?Kryptofix 222”? on calcium- and strontium-uptake of bush bean seedlings Macrobicycle ?Kryptofix 222”? (4,7,13,16,21,24-Hexaoxa-1,10-diazabicyclo-8,8,8-hexacosane) is the only known organic compound which chelates Sr (pK = 8.0) stronger than Ca (pK = 4.4). Therefore it was proved in experiments with 10 days old seedlings of bush beans, whether Kryptofix enables plants to discriminate between the physiological important Ca and the undesired Sr in favour of Ca. The following results were obtained: 1. At a constant (equimolar) supply of CaCl2 + SrCl2 (50 μM/l each) increasing levels of Kryptofix raised the Ca/Sr-ratio of the seedlings from 0.8 (without Kryptofix) to 2.7 (with 150 μM Kryptofix/l) by reducing their Sr-content and increasing their Ca-content correspondingly. 2. Despite of reduced Sr-uptake the translocation of Sr to the primary leaves was promoted by Kryptofix (presumably via preventation of Sr fixation by the xylem vessels and in the surrounding tissue), whereas no influence exists on the movement of Ca. 3. At low CaCl2 + SrCl2 supply (5 μM/l each) the bean seedlings showed similar Ca and Sr-contents (Ca/Sr-ratio about 1.07), both in the presence or absence of equimolar Kryptofix concentrations. 4. With increasing CaCl2 + SrCl2 supplies (25–125 μM/l each), bean seedlings without Kryptofix increasingly favours Sr- against Ca- uptake (reaching a Ca/Sr-ratio of 0.49). On the contrary, in the presence of equimolar concentrations of Kryptofix (50–250 μM/l) there is an increasing preference of Ca versus Sr-uptake (Ca/Sr = 1.89). |
