EFFECT OF CALCIUM ON THE UPTAKE AND DISTRIBUTION OF SODIUM IN EXCISED BARLEY ROOTS

The total uptake and relative distribution of Na+ along the root was investigated in excised barley roots (Hordeum vulgare L. cv. Union) of 6‐day‐old plants cultured on 0.25 mM CaSO4. One technique involved cutting the roots at harvest time after different uptake periods into different segments each 2 cm long. These segments were ashed and sodium was measured by flame photometry. For each experiment two treatments were done, one containing calcium in the uptake solution and one without calcium. A second technique involved the measurement of sodium transport, using labelled 22Na+ solution. Although no significant differences could be found between the calcium containing and the calciumless treatments at 24 h, there were clearcut differences for the first 6 to 8 h. The effect of calcium on the first stages of the sodium uptake was a large accumulation of sodium in the part close to the apex with a translocation close to nil; whereas the sodium taken up in the absence of calcium did not accumulate in such large amounts in the apex region but was immediately transported basipetally. Copyright © 1979, Wiley Blackwell. All rights reserved