Section 8
Chapter 7,145

Compartmental analysis of efflux of potassium rubidium 86 and rubidium rubidium 86 from roots of intact plants by barley hordeum vulgare of high and low potassium status and after excision of the shoot

Kasimir Klemedtsson, A.; Pettersson, S.

Physiologia Plantarum 83(3): 511-517


ISSN/ISBN: 0031-9317
DOI: 10.1111/j.1399-3054.1991.tb00128.x
Accession: 007144996

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The classic compartment analysis of ion efflux from roots is often applied with the assumption that there is a system of 3 compartments in series. However, complex ion transport across the root tissues, as well as influences from the shoot, may complicate the picture. The present experiments were performed to study the immediate effects that excision of the shoot before the experiment exerts on the efflux of Rb+(86Rb+) and of K+(86Rb+) from 9-day-old roots of plants of barley (Hordeum vulgare L. cv. Salve). The efflux from high K+ and low K+ roots of intact and detopped plants were compared. After excision of the shoot of high K+ plants, a marked increase in efflux was observed after 2.5 h with a maximum at about 7 h. The increase in efflux was seen as a peak in plots of efflux versus time. Excision of the shoot from low K+ roots did not give rise to a consistent increase in efflux. Regular K+ ion efflux curves were observed from roots of intact plants of high or low K+ status. Furthermore, after a pulse treatment of 9-day-old roots of intact plants of high or low K+ status with a solution containing Rb+(86Rb+), the Rb+(86Rb+) transport to the shoots was not reduced during the following 3 h in unlabelled solution. It is suggested that both the peak appearing in the efflux plots and the maintained tracer transport to the shoots after transfer of the roots to an unlabelled solution indicate the existence of a K+/Rb+ transport system in the symplasm of the roots that has only a slow exchange with the bulk cytoplasm and vacuoles.

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