Abstract
Short day length-induced alteration of potassium (K) localization in perennial trees is believed to be a mechanism for surviving and adapting to severe winters. To investigate the relationship between cesium (Cs) and K localizations, a model tree poplar, hybrid aspen T89, was employed. Under short day length conditions, the amount of 137Cs absorbed through the root and translocated to the root was drastically reduced, but 42K was not. Potassium uptake from the rhizosphere is mediated mainly by KUP/HAK/KT and CNGC transporters. In poplar, however, these genes were constantly expressed under short-day conditions except for a slight increase in the expression a KUP/HAK/KT gene six weeks after the onset of the short-day treatment. These results indicated that the suppression of 137Cs uptake was triggered by short day length but not regulated by competitive Cs+ and K+ transport. We hypothesize that there are separately regulated Cs+ and K+ transport systems in poplar.
Highlights
IntroductionAn increase in K+ concentration in xylem sap was observed during the winter season in field-grown Populus nigra[20]
We investigated the relationship between the change in K localization induced by short day length and the behavior of Cs absorbed from the rhizosphere
Furukawa et al indicated Ca2+ transport from root to shoot in Populus maximowiczii is regulated by the shift from LD to SD19
Summary
An increase in K+ concentration in xylem sap was observed during the winter season in field-grown Populus nigra[20] These behaviors imply the existence of re-translocation mechanisms for K, and it is assumed that the potassium is transported to the organs that require it once it is resorbed. Potassium ion uptake by the root symplast via HATS is mediated by the KUP/HAK/KT transporter family. There are thirteen such transporters in Arabidopsis[24,25] and twenty-seven in rice[26]. We investigated the relationship between the change in K localization induced by short day length and the behavior of Cs absorbed from the rhizosphere To this end, 137Cs and 42K accumulations and gene expression patterns of major K+ transporters were analyzed using a model tree poplar, hybrid aspen T89
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