Contribution of Root Hair Development to Sulfate Uptake in <i>Arabidopsis</i>

Root hairs often contribute to nutrient uptake from environments, but the contribution varies among nutrients. In Arabidopsis, two high-affinity sulfate transporters, SULTR1;1 and SULTR1;2, are responsible for sulfate uptake by roots. Their increased expression under sulfur deficiency (&#8722;S) stimulates sulfate uptake. Inspired by the higher and lower expression, respectively, of SULTR1;1 in mutants with more (werwolf [wer]) and fewer (caprice [cpc]) root hairs, we examined the contribution of root hairs to sulfate uptake. Sulfate uptake rates were similar among plant lines under both sulfur sufficiency (+S) and &#8722;S. Under &#8722;S, the expression of SULTR1;1 and SULTR1;2 was negatively correlated with the number of root hairs. These results suggest that both &#8722;S-induced SULTR expression and sulfate uptake rates were independent of the number of root hairs. In addition, we observed (1) a negative correlation between primary root lengths and number of root hairs and (2) a greater number of root hairs under &#8722;S than under +S. These observations suggested that under both +S and &#8722;S, sulfate uptake was influenced by the root biomass rather than the number of root hairs