Effect of OsHAK5 expression level on rice growth and K accumulation under conditions of low K supply. Ten-day-old seedlings were grown in IRRI solution containing 1 mm  K for 2 weeks, then transferred to a solution containing 0.3 mm  K and allowed to grow for 2 weeks (A–D) or 20 d (E and F). A, C, and E, OX lines and their respective wild-type lines. B, D, and F, KO lines and their respective wild-type lines. A and B, Accumulation of dry biomass (dry weight) in root (R), basal node plus sheath (BN.S), and leaf blades (L.B). C and D, Accumulation of K (K concentration and total K content per plant [inset]). E and F, Net K uptake rates during days 1 to 10 and 11 to 20 of growth in solution containing 0.3 mm  K. WT(NB), The wild type of cv Nipponbare; OX1 to OX3, three independent lines of OsHAK5-overexpressing plants of cv Nipponbare; WT(DJ), the wild type of the cv DJ; KO(DJ), OsHAK5 knockout mutant line of cv DJ; WT(HY), the wild type of cv HY; KO(HY), OsHAK5 knockout mutant line of cv HY. Error bars indicate se (n = 5 plants); pl, plant. Significant differences from the wild type in each group (NB, DJ, or HY) are indicated by different letters (P < 0.05, one-way ANOVA).