caa a22 4500 477111815 CHVBK 20180405111611.0 cr unu---uuuuu 170330e19961101xx s 000 0 eng 10.1007/BF00011653 doi (NATIONALLICENCE)springer-10.1007/BF00011653 Turgor-regulation during extension growth and osmotic stress of maize roots. An example of single-cell mapping [Elektronische Daten] [Jeremy Pritchard, Wieland Fricke, Deri Tomos] The growing cells of hydroponic maize roots expand at constant turgor pressure (0.48 MPa) both when grown in low-(0.5 mol m-3 CaCl2) or full-nutrient (Hoagland's) solution and also when seedlings are stressed osmotically (0.96 MPa mannitol). Cell osmotic pressure decreases by 0.1-0.2 MPa during expansion. Despite this, total solute influx largely matches the continuously-varying volume expansion-rate of each cell. K+ in the non-osmotically stressed roots is a significant exception-its concentration dropping by 50% regardless of the presence or absence of K+ in the nutrient medium. This corresponds to the drop in osmotic pressure. Nitrate appears to replace Cl- in the Hoagland-grown cells. Analogous insensitivity of solute gradients to external solutes is observed in the radial distribution of water and solutes in the cortex 12 mm from the tip. Uniform turgor and osmotic pressures are accompanied by opposite gradients of K+ and Cl-, outwards, and hexoses and amino acids, inwards, for plants grown in either 0.5 mol m-3 CaCl2 or Hoagland's solution (with negligible Cl-). K+ and Cl- levels within both gradients were slightly higher when the ions were available in the medium. The gradients themselves are independent of the direction of solute supply. In CaCl2 solution all other nutrients must come from the stele, in Hoagland's solution inorganic solutes are available in the medium. 24 h after osmotic stress, turgor pressure is recovered at all points in each gradient by osmotic adjustment using organic solutes. Remarkably, K+ and Cl- levels hardly change, despite their ready availability. Hexoses are responsible for some 50% of the adjustment with mannitol for a further 30%. Some 20% of the final osmotic pressure remains to be accounted for. Proline and sucrose are not significantly involved. Under all conditions a standing water potential step of 0.2 MPa between the rhizodermis and its hydroponic medium was found. We suggest that this is due to solute leakage. Kluwer Academic Publishers, 1996 extension growth nationallicence maize roots nationallicence osmotic adjustment nationallicence single-cell sampling nationallicence turgor regulation nationallicence vacuolar solutes nationallicence EDX : energy dispersive X-ray microanalysis nationallicence Ψ : water potential nationallicence 11-1 : cell osmotic pressure nationallicence P : turgor pressure nationallicence Pritchard Jeremy Ysgol Gwyddorau Bioleg, Prifysgol Cymru, LL57 2UW, Bangor, Gwynedd, Wales, UK aut Fricke Wieland Ysgol Gwyddorau Bioleg, Prifysgol Cymru, LL57 2UW, Bangor, Gwynedd, Wales, UK aut Tomos Deri Ysgol Gwyddorau Bioleg, Prifysgol Cymru, LL57 2UW, Bangor, Gwynedd, Wales, UK aut Plant and Soil Kluwer Academic Publishers; http://www.wkap.nl 187/1(1996-11-01), 11-21 0032-079X 187:1<11 1996 187 11104 https://doi.org/10.1007/BF00011653 text/html Onlinezugriff via DOI 1 research-article jats NATIONALLICENCE 856 40 https://doi.org/10.1007/BF00011653 text/html Onlinezugriff via DOI NATIONALLICENCE 700 1- Pritchard Jeremy Ysgol Gwyddorau Bioleg, Prifysgol Cymru, LL57 2UW, Bangor, Gwynedd, Wales, UK aut NATIONALLICENCE 700 1- Fricke Wieland Ysgol Gwyddorau Bioleg, Prifysgol Cymru, LL57 2UW, Bangor, Gwynedd, Wales, UK aut NATIONALLICENCE 700 1- Tomos Deri Ysgol Gwyddorau Bioleg, Prifysgol Cymru, LL57 2UW, Bangor, Gwynedd, Wales, UK aut NATIONALLICENCE 773 0- Plant and Soil Kluwer Academic Publishers; http://www.wkap.nl/ 187/1(1996-11-01), 11-21 0032-079X 187:1<11 1996 187 11104 Metadata rights reserved Springer special CC-BY-NC licence nationallicence BK010053 XK010053 XK010000 NATIONALLICENCE NATIONALLICENCE NL-springer