Phenotype analyses of sitl1 mutant
For the seed germination assays, seeds of the sitl1 and WT were placed on moistened filter paper in a growth chamber under 16-h photoperiod. Seeds germination rates were scored every day for a week after sowing. To analyze phenotypic difference of the sitl1 and WT, plants were grown in the half-strength NS or double distilled water (DW). Plants were used to quantify the length and fresh weight of the coleoptile, root, leaf sheath, and leaf blade. To observe detailed root morphology, detached roots of the sitl1 and WT grown in NS or DW were scanned at 7 d after germination, and primary root lengths and widths, lateral root lengths, widths, numbers, and density in mature root zone (3~4 cm away from root tip) were quantified using ImageJ software (http://imagej.nih.gov/ij/).