Limited supply of mineral nutrients such as potassium increases the root-to-shoot ratio. This also increases the ratio between water-absorbing and -losing plant surface. Water uptake per unit surface has to either decrease (root) or increase (shoot). Coffey et al. test this on 2–3 week old barley plants grown with low supply of potassium (Low-K).
The data show that water flow through plants exposed to low K is adjusted at the root level, through a decrease in hydraulic conductivity at organ and cell level. Aquaporins assayed by qPCR analyses are involved in the response, while apoplastic barriers to water transport, visible in anatomical analyses, do not change.
Coffey, O., Bonfield, R., Corre, F., Althea Sirigiri, J., Meng, D., & Fricke, W. (2018). Root and cell hydraulic conductivity, apoplastic barriers and aquaporin gene expression in barley (Hordeum vulgare L.) grown with low supply of potassium. Annals of Botany, 122(7), 1131–1141. https://doi.org/10.1093/aob/mcy110