Investigating pH Complexity in Living Roots with Noninvasive Fluorescence-Based Imaging Methods

FIGURE 26.1 Nutrient uptake in mature roots. (A) Schematic representation of the three pathways used for the radial transport of nutrients in roots. The symplastic pathway (green arrow) requires nutrient entry into the epidermal cell by a selective transporter to allow its transport through the plasmodesmata in the inner root layers. The coupled transcellular pathway (dark arrow) requires carriers for successive influx and efflux of nutrients from cell to cell. The apoplastic pathway (blue arrow) represents the passive diffusion through the apoplast until the Casparian strip, where ions and nutrients need the plasmodesmata or carriers to reach the pericycle. (B) Schematic of the exchanges at the plasma membrane of a root cell. The PM is energized by PM H + -ATPase, whose activity generates the proton motive force (PMF) with the cytosolic face of the negatively charged PM, whereas the apoplast is acidic. In the apoplast, H + and Ca 2+ can interact with de-esterified pectins in the cell wall. Ep: epidermis; Co