caa a22 4500 477101690 CHVBK 20180405111543.0 cr unu---uuuuu 170330e19960801xx s 000 0 eng 10.1007/BF00195177 doi (NATIONALLICENCE)springer-10.1007/BF00195177 Characterization of the uptake of sucrose and glucose by isolated seed coat halves of developing pea seeds. Evidence that a sugar facilitator with diffusional kinetics is involved in seed coat unloading [Elektronische Daten] [A. De Jong, J. Koerselman-Kooij, J. Schuurmans, A. Borstlap] Uptake of 14C-labelled sucrose and glucose by isolated seed coat halves of pea (Pisum sativum L. cv. Marzia) seeds was measured in the concentration range <0.1 μM to 100 mM. The initial influx of sucrose was strictly proportional to the external concentration, with a coefficient of proportionality (k) of 6.2 μmol·(g FW)−1·min−1·M−1. Sucrose influx was not affected by 10 μM carbonylcyanide m-chlorophenylhydrazone (CCCP), but it was inhibited by 40% in the presence of 2.5 mM p-chloromercuribenzenesulfonic acid (PCMBS). Influx with diffusional kinetics was also observed for glucose (k = 4.8 μmol·(g FW)−1·min −1·M −1) and mannitol (k = 5.1 μmol·(g FW)−1·min−1·M−1). For glucose an additional saturable system was found (Km = 0.26 mM, V max = 4.2 nmol·(g FW)−1·min−1), which appeared to be completely inhibited by CCCP and partly by PCMBS. In contrast to the diffusional pathway, uptake by this saturable system was slightly pH-dependent, with an optimum at pH 5.5. The influx of sucrose appears to be by the same pathway as the efflux of endogenous sucrose, which was inhibited by 36% in the presence of 2.5 mM PCMBS (De Jong A, Wolswinkel P, 1995, Physiol Plant 94: 78-86). It is argued that passive transport may be the only mechanism for sucrose transport through the plasma membrane of seed coat parenchyma cells. The estimated permeability coefficient of the plasma membrane for sucrose (P = 3.5·10−7 cm·s−1) is more than 1 × 106-fold higher than that reported for artificial lipid membranes. This relatively high permeability is hypothesized to result from pore-forming proteins that allow the diffusion of sucrose. Furthermore, it is shown that a sucrose gradient across the plasma membrane of the seed coat parenchyma of only 22 mM will suffice to result in the net efflux of sucrose which is required to feed the embryo. Springer-Verlag, 1996 Glucose nationallicence Membrane transport nationallicence Phloem unloading nationallicence Pisum (seed coat, sugar) nationallicence Sucrose nationallicence Uptake (kinetics, sugar) nationallicence CCCP : carbonylcyanide m-chlorophenylhydrazone nationallicence PCMBS : p-chloromercuribenzenesulfonic acid nationallicence RWC : relative water content nationallicence De Jong A. Transport Physiology Research Group, Department of Plant Ecology and Evolutionary Biology, University of Utrecht, P.O. Box 800.84, 3508 TB, Utrecht, The Netherlands aut Koerselman-Kooij J. Transport Physiology Research Group, Department of Plant Ecology and Evolutionary Biology, University of Utrecht, P.O. Box 800.84, 3508 TB, Utrecht, The Netherlands aut Schuurmans J. Transport Physiology Research Group, Department of Plant Ecology and Evolutionary Biology, University of Utrecht, P.O. Box 800.84, 3508 TB, Utrecht, The Netherlands aut Borstlap A. Transport Physiology Research Group, Department of Plant Ecology and Evolutionary Biology, University of Utrecht, P.O. Box 800.84, 3508 TB, Utrecht, The Netherlands aut Planta Springer-Verlag 199/4(1996-08-01), 486-492 0032-0935 199:4<486 1996 199 425 https://doi.org/10.1007/BF00195177 text/html Onlinezugriff via DOI 1 research-article jats NATIONALLICENCE 856 40 https://doi.org/10.1007/BF00195177 text/html Onlinezugriff via DOI NATIONALLICENCE 700 1- De Jong A. Transport Physiology Research Group, Department of Plant Ecology and Evolutionary Biology, University of Utrecht, P.O. Box 800.84, 3508 TB, Utrecht, The Netherlands aut NATIONALLICENCE 700 1- Koerselman-Kooij J. Transport Physiology Research Group, Department of Plant Ecology and Evolutionary Biology, University of Utrecht, P.O. Box 800.84, 3508 TB, Utrecht, The Netherlands aut NATIONALLICENCE 700 1- Schuurmans J. Transport Physiology Research Group, Department of Plant Ecology and Evolutionary Biology, University of Utrecht, P.O. Box 800.84, 3508 TB, Utrecht, The Netherlands aut NATIONALLICENCE 700 1- Borstlap A. Transport Physiology Research Group, Department of Plant Ecology and Evolutionary Biology, University of Utrecht, P.O. Box 800.84, 3508 TB, Utrecht, The Netherlands aut NATIONALLICENCE 773 0- Planta Springer-Verlag 199/4(1996-08-01), 486-492 0032-0935 199:4<486 1996 199 425 Metadata rights reserved Springer special CC-BY-NC licence nationallicence BK010053 XK010053 XK010000 NATIONALLICENCE NATIONALLICENCE NL-springer