caa a22 4500 47710133X CHVBK 20180405111542.0 cr unu---uuuuu 170330e19960501xx s 000 0 eng 10.1007/BF00196877 doi (NATIONALLICENCE)springer-10.1007/BF00196877 Turgor-dependent efflux of assimilates from coats of developing seed of Phaseolus vulgaris L.: water relations of the cells involved in efflux [Elektronische Daten] [Wenhao Zhang, Brian Atwell, John Patrick, N. Walker] The turgor-homeostat model of assimilate efflux from coats of developing seed of Phaseolus vulgaris L. was further characterised. The turgor pressure (P), the volumetric elastic modulus (ɛ) and hydraulic conductivity (Lp) of the seed coat cells responsible for assimilate efflux and cotyledon storage parenchyma cells were determined with a pressure probe. In addition, turgor of the seed coat and cotyledons was estimated by measuring the osmolalities of symplastic and apoplastic fluids extracted by centrifugation. Osmolality of symplastic and apoplastic saps collected from the seed coat declined significantly over the period of seed development from a cotyledon water content of 80% to 50%. However, the difference in osmolalities of the apoplastic and symplastic saps remained relatively constant. For cotyledons, osmolality of the apoplastic sap exhibited a significant decline during seed development, while the osmolality of symplastic sap did not change significantly. Hence cotyledon P increased as the water content dropped from 80% to 50%. For both detached and attached ‘empty' seed coats, a small decrease (ca. 40mOsmol·kg−1) in the osmolality of the bathing solution, led to a rapid increase in P of cells involved in assimilate efflux (efflux cells) by about 0.07 MPa. Thereafter, cell P exhibited a rapid decline to the original value within some 20-30 min. When P of the ‘efflux cells' was reduced by increasing the osmolality of the bathing solution, P exhibited a comparable rate of recovery for attached ‘empty' seed coats but there was no P recovery to its original value in the case of detached seed coats. In contrast, the cotyledon storage parenchyma cells did not exhibit P regulation when the osmolality of the bathing solution was changed. The observations that the ‘efflux cells' of P. vulgaris seed coats can rapidly adjust their P homeostatically in response to small changes in apoplastic osmolality are consistent with the operation of a turgor-homeostat mechanism. The volumetric elastic modulus (ɛ) of the seed coat ‘efflux cells' exhibited a mean value of 7.3±0.8 MPa at P=0.15 MPa and was found to be linearly dependent on cell P. The e of the cotyledon storage parenchyma cells was estimated to be 6.1±1.0 MPa at P=0.41 MPa. Hydraulic conductivity (Lp) of the seed coat cells and the cotyledon cells was (8.2±1.5) × 10−8m·s−1·MPa−1and (12.8±1.0) × 10−8 m·s−1·MPa−1, respectively. The relatively high ɛ, i.e., low elasticity, for the seed coat cell walls would ensure that small changes in water potential of the seed apoplast will be reflected in large changes in cell P. The high Lp values for both the seed coat and the cotyledon cells is consistent with the rapid changes in P in response to changes in water potential of the seed apoplast. Springer-Verlag, 1996 Cell water relations nationallicence Cotyledon nationallicence Phaseolus (water relations) nationallicence Pressure probe nationallicence Seed coat nationallicence Turgorhomeostat nationallicence LYCH : Lucifer Yellow CH nationallicence ɛ : volumetric elastic modulus nationallicence Lp : hydraulic conductivity nationallicence P : turgor pressure nationallicence π : osmotic pressure nationallicence t1/2 : half-time for water exchange nationallicence Zhang Wenhao Department of Biological Sciences, The University of Newcastle, 2308, Newcastle, NSW, Australia aut Atwell Brian School of Biological Sciences, Macquarie University, 2109, NSW, Australia aut Patrick John Department of Biological Sciences, The University of Newcastle, 2308, Newcastle, NSW, Australia aut Walker N. Centre for Plant Membrane Biology, Department of Botany, University of Adelaide, 5005, S.A., Australia aut Planta Springer-Verlag 199/1(1996-05-01), 25-33 0032-0935 199:1<25 1996 199 425 https://doi.org/10.1007/BF00196877 text/html Onlinezugriff via DOI 1 research-article jats NATIONALLICENCE 856 40 https://doi.org/10.1007/BF00196877 text/html Onlinezugriff via DOI NATIONALLICENCE 700 1- Zhang Wenhao Department of Biological Sciences, The University of Newcastle, 2308, Newcastle, NSW, Australia aut NATIONALLICENCE 700 1- Atwell Brian School of Biological Sciences, Macquarie University, 2109, NSW, Australia aut NATIONALLICENCE 700 1- Patrick John Department of Biological Sciences, The University of Newcastle, 2308, Newcastle, NSW, Australia aut NATIONALLICENCE 700 1- Walker N. Centre for Plant Membrane Biology, Department of Botany, University of Adelaide, 5005, S.A., Australia aut NATIONALLICENCE 773 0- Planta Springer-Verlag 199/1(1996-05-01), 25-33 0032-0935 199:1<25 1996 199 425 Metadata rights reserved Springer special CC-BY-NC licence nationallicence BK010053 XK010053 XK010000 NATIONALLICENCE NATIONALLICENCE NL-springer