Fig. 10.

Cytokinin eliminates the altered hydrotropism of ahr1 and the no hydrotropic response phenotype of nhr1 in a diagonal NM→WSM test system for hydrotropism. In this system, the NM (top) and WSM (bottom) were obliquely split in a square Petri dish. Seeds of wt, ahr1, and nhr1 genotypes were sown in the NM portion of the oblique system in the absence (A, B) or presence of 0.3 μM kinetin (C, D). (A) ahr1 roots showed an altered hydrotropic response with longer roots that developed a hydrotropic curvature in the WSM towards the NM. (A, B) Wt roots developed a hydrotropic curvature in the NM and were shorter than those of ahr1 and nhr1. (B) nhr1 roots displayed a no hydrotropic response. (C) ahr1 roots supplied with kinetin were shorter and developed a hydrotropic curvature in the NM. (C, D) Root growth of the wt was reduced by kinetin. (D) nhr1 roots were shorter than those left untreated. Images were taken 7 d after germination. Arrows delimit the border between NM and WSM. NM, normal medium; WSM, water stress medium. Scale bar=13 mm.