FIGURE 6.

Effects of Oshak8 knockout on K translocation under different K⁺-supply conditions. (A) K⁺ net uptake rate of WT and Oshak8 mutant (Oshak8-1, Oshak8-2) plants. The seeds of the WT and Oshak8 mutants were germinated in water for 5 days, transferred to the hydroponic solutions containing 10 mM of K⁺ for 14 days, and then transferred to the hydroponic solutions containing 0 mM of K⁺ for 5 days. For the K⁺ uptake assay, K⁺-starved plants were incubated in the medium containing 0.01 or 10 mM of K⁺ for 3 days and the roots and shoots were collected for K⁺ content measurements using inductively coupled plasma analysis. (B) The shoot/root ratios of K⁺ in various plant materials. Growth conditions were as described in Figure 2. The roots were collected for K⁺ content measurements using inductively coupled plasma analysis. (C) K⁺ export rate in the xylem. Seven-day-old rice seedlings were grown in the International Rice Research Institute (IRRI) solution for 2 weeks and then transferred to 10- or 0.01-mM K⁺ solutions for 2 weeks before the sampling. The detailed protocols for the shoot excision, collection of the xylem sap by cotton ball, determination of K⁺ concentration by ICP, and calculation of the xylem K⁺ export rate were described previously by Yang et al. (2014). K⁺ contents were determined by ICP-AES. Significant differences were found between WT and Oshak8 mutants (Oshak8-1, Oshak8-2) (*P < 0.01 by Student’s t-test). Data are means of three replicates of one experiment. The experiment was repeated three times with similar results. Error bars represent ± SD. Asterisks represent significant differences. DW, dry weight.