Zhizhong Song and Yanhua Su. Distinctive potassium accumulation capability of Alternanthera philoxeroides links to high-affinity potassium transport facilitated by K+-uptake systems. Weed Science 2012 http://dx.doi.org-10.1614-WS-D-12-00100.1.
Abstract
Alternanthera philoxeroides (A. philoxeroides) is well known for its potassium (K+)-accumulating capabilities and its strong resistance to undesired growth conditions. The results of this study revealed properties of K+ accumulation and its contribution to drought stress in A. philoxeroides. In addition we attempted to characterise the molecular mechanisms of K+ accumulation in this plant. A. philoxeroides plants showed a consistent increase in biomass in response to external K+ concentrations ranging from micromolar to up to 50 mmol L-1; K+ was also accumulated accordingly in the plants. The stem was the most K+-accumulating organ accumulating up to 13% K+. Moreover this K+ super-accumulation resulted in an improved resistance to drought stress. The apparent K+ uptake by roots showed a typical high affinity property and the Km increased at higher plant K+ contents of the starting materials. Furthermore we isolated 3 putative K+ uptake transporter cDNAs from A. philoxeroides (ApKUP1 2 and 3 respectively) using degenerated primers and RACE techniques. The expression of ApKUP1 and 3 was predominately localised to the leaves whereas ApKUP2 was expressed throughout the entire plant. The expression of ApKUP1 and 3 was stimulated in the stems and roots when K+ was depleted from the external medium. Moreover ApKUP3 expression was enhanced in the stem in response to ABA treatment and drought stress. In conclusion our findings provide further insight into the mechanisms of K+ accumulation linked to K+ uptake in A. philoxeroides.
