Der Einfluß von Ca- und H-Ionen bei unterschiedlichen Stoffwechselbedingungen auf die Membranpermeabilität junger Gerstenwurzeln

Transport across plant roots

The plant root is a complex system that has evolved under the constraints of a number of functions. It is a pressure-probe that can penetrate the soil; it is a scavenger of nutrients that may be either tightly bound to soil particles or in low concentrations in the soil solution; it is an absorber of water from the soil. The tip of the root contains the region of dividing cells from which the root is formed, and is pushed through the soil by the extension of these cells some 10–20 times as they develop and differentiate.

Evidence for an electrogenic ion transport pump in cells of higher plants

Cyanide (CN) and dinitrophenol (DNP) rapidly depolarize the cells of oat coleoptiles (Avena sativa L., cultivar Victory) and of pea epicotyls (Pisum sativum L., cultivar Alaska); the effect is reversible. This indicates that electrogenesis is metabolic in origin, and, since active transport is blocked in the presence of CN and DNP, perhaps caused by interference with ATP synthesis, that development of cell potential may be associated with active ion transport. Additional evidence for an electrogenic pump is as follows. (1) Cell electropotentials are higher than can be accounted for by ionic diffusion. (2) Inhibition of potential, respiration, andactive ion transport is nearly maximal, but a potential of -40 to -80 mV remains. This is probably a passive diffusion potential since, under these conditions, a fairly close fit to the Goldman constant-field equation is found in oat coleoptile cells.