Influence of Excision and Aging upon K Influx into Barley Roots: Recovery or Enhancement?

The influx of K(+) from (86)Rb-labeled solutions in the concentration range 0.008 to 0.2 mm into roots of intact plants and excised roots of barley plants (Hordeum vulgare [L.]) previously grown in 5 mm CaSO(4) (low K(+) roots) or 0.5 mm CaSO(4) plus 5 mm KCl (high K(+) roots) was measured. A consistent observation of these experiments was a substantial reduction of influx (usually by about 50%) following excision. The possible leakage of K(+) into the medium and subsequent dilution of specific activity of labeled solutions was eliminated as an explanation for influx reduction in excised low K(+) roots. Reduction of transpirational rates was also without effect upon influx into low K(+) roots. Excision followed by 2 hours aging in 0.5 mm CaSO(4) solution revealed that influx values recovered within the 2 hours to the values obtained in intact roots. It is concluded that much of the literature which describes the enhancement of ion uptake following excision actually describes excision damage followed by recovery.