Radial Transport of Nutrients: The Plant Root as a Polarized Epithelium

Abstract

In higher plants, roots acquire water and soil nutrients and transport them upward to their aerial parts. These functions are closely related to their anatomical structure; water and nutrients entering the root first move radially through several concentric layers of the epidermis, cortex, and endodermis before entering the central cylinder. The endodermis is the innermost cortical cell layer that features rings of hydrophobic cell wall material called the Casparian strips, which functionally resemble tight junctions in animal epithelia. Nutrient uptake from the soil can occur through three different routes that can be interconnected in various ways: the apoplastic route (through the cell wall), the symplastic route (through cellular connections), and a coupled trans-cellular route (involving polarized influx and efflux carriers). This Update presents recent advances in the radial transport of nutrients highlighting the coupled trans-cellular pathway and the roles played by the endodermis as a barrier.

Transpiration flow controls Zn transport in Brassica napus and Lolium multiflorum under toxic levels as evidenced from isotopic fractionation

“…(2) diffusion (Zn transport on relatively short distance under concentration gradient) (Barberon and Geldner, 2014;Caldelas et al, 2011;Moynier et al, 2009;Weiss et al, 2005 and references herein); and (3) convection (mass flow transport in plant controlled by transpiration) (Barberon and Geldner, 2014;Lorenz et al, 1994). So far, the two first processes were essentially the only ones explored with the isotopic tool: as previously described by Jouvin et al (2012), metal transport is carried out by the metal complexation with organic acids or amino acids or peptides produced by the plant.…”

“…In disagreement with Aucour et al (2011), who postulated that advection with transpiration stream does not fractionate the Zn isotopes, our results show higher D 66 Zn shoot-root when the transpiration volume per biomass unit increases. Active transport (through carrier proteins) is associated with plants in metal-deficient conditions (or low metal concentrations) (Barberon and Geldner, 2014), while passive transport (transpiration flow) is generally observed in plant-soil systems displaying high metal levels (Hopmans and Bristow, 2002). Along the same lines, diffusion processes in soil or in the rhizosphere may control Zn uptake under deficient conditions, whereas mass flow may control the flux of Zn from soil to plants under high Zn supply (Degryse et al, 2009).…”

HLB1 Is a Tetratricopeptide Repeat Domain-Containing Protein That Operates at the Intersection of the Exocytic and Endocytic Pathways at the TGN/EE in Arabidopsis

“…The endomembrane system is highly dynamic and consists of a network of functionally interconnected organelles beginning with the endoplasmic reticulum (ER) where proteins are synthesized and then trafficked to the plasma membrane (PM) and vacuole after processing and sorting in the Golgi apparatus and post-Golgi organelles (Richter et al, 2009;Brandizzi and Barlowe, 2013). Recycling and degradation of PM proteins, which also are facilitated by the endomembrane trafficking machinery, are essential for establishing and maintaining the polar localization of lipids and critical proteins, including auxin carriers, transmembrane receptors, channels, and ion transporters that regulate diverse physiological processes in plants (Geldner et al, 2007;Takano et al, 2010;Barberon and Geldner, 2014;Hachez et al, 2014;Doyle et al, 2015).…”

Cu isotopic compositions in Elsholtzia splendens: Influence of soil condition and growth period on Cu isotopic fractionation in plant tissue

“…As mineral elements are taken up by the plant root and translocated throughout the plant, Cu in the upper stems and branches is translocated upward from lower stems and branches. It is generally assumed that two main mechanisms are involved in the transport of Cu into stems and branches: diffusion of Cu over relatively short distances according to a concentration gradient (Moynier et al, 2009;Weinstein et al, 2011), and convective mass flow in the plant, controlled by transpiration (Barberon and Geldner, 2014;Couder et al, 2015;Lorenz et al, 1994).…”