Assimilate Transport in the Xylem Sap of Pedunculate Oak (Quercus robur) Saplings

Abstract

The rates of photosynthesis and transpiration, as well as the concentrations of organic compounds (total soluble non-protein N compounds [TSNN], soluble carbohydrates), in the xylem sap were determined during two growth seasons in one-year-old Quercus robur saplings. From the data, the total C gain of the leaves, by both photosynthesis and the transpiration stream, was calculated. Large amounts of C were allocated to the leaves by the transpiration stream; depending on the time of day and the environmental conditions the portion of C originating from xylem transport amounted to 8 to 91% of total C delivery to the leaves. Particularly under conditions of reduced photosynthesis, e.g., during midday depression of photosynthesis, a high percentage of the total C delivery was provided to the leaves by the transpiration stream (83 to 91 %). Apparently, attack by phloem-feeding aphids lowered the assimilate transport from roots to shoots; as a consequence the portion of C available to the leaves from xylem transport amounted to only 12 to 16 %. The most abundant organic compounds transported in the xylem sap were sugars (sucrose, glucose, fructose) with concentrations of ca. 50 to 500 μmol C ml^-1, whereas C from N compounds was of minor significance (3 to 20 μmol ml^-1 C). The results indicate a significant cycling of C in the plants because the daily transport of C with the transpiration stream exceeded the daily photosynthetic CO₂ fixation in several cases. This cycling pool of C may sustain delivery of photosynthate to heterotrophic tissues, independent of short time fluctuations in photosynthetic CO₂ fixation.

Organic carbon - carbon cycling - photosynthesis - transpiration - Quercus robur

References

• 01 Alaoui-Sosse,  B.,, Parmentier,  C.,, Dizengremel,  P.,, and Barnola,  P.. (1994);  Rhythmic growth and carbon allocation in Quercus robur. 1. Starch and sucrose.  Plant Physiol. Biochem.. 32 331-339
• 02 Candolfi-Vasconcelos,  M. C.,, Candolfi,  M. P.,, and Koblet,  W.. (1994);  Retranslocation of carbon reserves from the woody storage tissues into the fruit as a response to defoliation stress during the ripening period in Vitis vinifera L.  Planta. 192 567-573
• 03 Chapin,  F. S. III.,, Schulze,  E. D.,, and Mooney,  H. A.. (1990);  The ecology and economics of storage in plants.  Annu. Rev. Ecol. Syst.. 21 423-448
• 04 Cramer,  M. D., and Richards,  M. B.. (1999);  The effect of rhizosphere dissolved inorganic carbon on gas exchange characteristics and growth rates of tomato seedlings.  J. Exp. Bot.. 50 79-87
• 05 Ferguson,  A. R.. (1980);  Xylem sap from Actinia chinensis: Apparent differences in sap composition arising from the method of collection.  Ann. Bot.. 46 791-801
• 06 Geßler,  A.,, Schneider,  S.,, Weber,  P.,, Hanemann,  U.,, and Rennenberg,  H.. (1998);  Soluble N compounds in trees exposed to high loads of N: a comparison between the roots of Norway spruce (Picea abies [L.] Karst) and beech (Fagus sylvatica L.) trees grown under field conditions.  New Phytol.. 138 385-399
• 07 Glad,  C.,, Regnard,  J. L.,, Querou,  Y.,, Brun,  O.,, and Morot-Gaudry,  J. F.. (1992);  Flux and chemical composition of xylem exudates from Chardonnay grapevines temporal evolution and effect of recut.  Am. J. Enol. Viticult.. 43 275-282
• 08 Jeschke,  W. D., and Pate,  J. S.. (1991);  Modelling of the partitioning assimilation and storage of nitrate within root and shoot organs of Castor bean Ricinus communis L.  J. Exp. Bot.. 42 1091-1104
• 09 Kaakeh,  W.,, Pfeiffer,  D. G.,, and Marini,  R. P.. (1993);  Effect of Aphis spiraecola and Aphis pomi (Homoptera: Aphidiae) on the growth of young apple trees.  Crop Protection. 12 141-147
• 10 Kozlowski,  T. T.. (1992);  Carbohydrate sources and sinks in woody plants.  Botanical Rev.. 58 107-222
• 11 Kozlowski,  T. T., and Pallardy,  S. G.. (1996) Physiology of Woody Plants. Academic Press; ISBN: 012424162X pp. 411
• 12 Kühn,  C.,, Barker,  L.,, Bürkle,  L.,, and Frommer,  W.-B.. (1999);  Update on sucrose transport in higher plants.  J. Exp. Bot.. 50 935-953
• 13 Martin,  T.,, Frommer,  W.-B.,, Salanoubat,  M.,, and Willmitzer,  L.. (1993);  Expression of an Arabidopsis sucrose synthase gene indicates a role in metabolization of sucrose both during phloem loading and in sink organs.  Plant J.. 4 367-377
• 14 Meyer,  G. A., and Whitlow,  T. H.. (1992);  Effects of leaf and sap feeding insects on photosynthetic rates of goldenrod.  Oecologia. 92 480-489
• 15 Morselli,  M. F.,, Marvin,  J. W.,, and Laing,  F. M.. (1978);  Image-analysing computer in plant science: More and larger vascular rays in sugar maples of high sap and sugar yield.  Can. J. Bot.. 56 983-986
• 16 Nelson,  D. P.,, Pan,  W. L.,, and Franceschi,  V. R.. (1990);  Xylem and phloem transport of mineral nutrients from Solanum tuberosum roots.  J. Exp. Bot.. 41 1143-1148
• 17 Patonnier,  M. P.,, Peltier,  J. P.,, and Marigo,  G.. (1999);  Drought-induced increase in xylem malate and mannitol concentrations and closure of Fraxinus excelsior L. stomata.  J. Exp. Bot.. 50 1223-1229
• 18 Peuke,  A. D.. (2000) Xylem and phloem transport, assimilation and partitioning of nitrogen in Ricinus communis under several nutritional conditions. Nitrogen in a sustainable ecosystem: from cell to the plant. Martins-Loucao, M. A., Lips, S. H., eds. Leiden, The Netherlands; Backhuys Publishers in press
• 19 Raven,  J. A.. (1983);  Phytophages of xylem and phloem: a comparison of animal and plant sap-feeder.  Adv. Ecol. Res.. 13 135-234
• 20 Rennenberg,  H.,, Kreutzer,  K.,, Papen,  H.,, and Weber,  P.. (1998);  Consequences of high loads of nitrogen for spruce (Picea abies) and beech (Fagus sylvatica) forests.  New Phytol.. 139 71-86
• 21 Rennenberg,  H.,, Schneider,  S.,, and Weber,  P.. (1996);  Analysis of uptake and allocation of nitrogen and sulphur by trees in the field.  J. Exp. Bot.. 47 1491-1498
• 22 Rossing,  W. A. H.. (1992);  Simulation of damage in winter wheat caused by the grain aphid Sitobion avenae 2. Construction and evaluation of a simulation model.  Netherlands J. Plant Pathol.. 97 25-54
• 23 Satoh,  S.,, Lizuka,  C.,, Kikuchi,  A.,, Nakamura,  N.,, and Fujii,  T.. (1992);  Proteins and carbohydrates in xylem sap from squash root.  Plant Cell Physiol.. 33 841-847
• 24 Sauter,  J. J.. (1980);  Seasonal variation of sucrose content in the xylem sap of Salix. .  Z. Pflanzenphysiol.. 98 377-391
• 25 Schneider,  A.,, Schatten,  T.,, and Rennenberg,  H.. (1994);  Exchange between phloem and xylem during long distance transport of glutathione in spruce trees (Picea abies [Karst.] L.).  J. Exp. Bot.. 45 457-462
• 26 Schneider,  S.,, Geßler,  A.,, Weber,  P.,, von Sengbusch,  D.,, Hanemann,  U.,, and Rennenberg,  H.. (1996);  Soluble N compounds in trees exposed to high loads of N: a comparison of spruce (Picea abies) and beech (Fagus sylvatica) grown under field conditions.  New Phytol.. 134 103-114
• 27 Scholander,  P. F.,, Hammel,  T.,, Bradstreet,  E. D.,, and Hemmingsen,  E. A.. (1965);  Sap pressure in vascular plants.  Science. 148 339-345
• 28 Seegmüller,  S., and Rennenberg,  H.. (1994);  Interactive effects of mycorrhization and elevated carbon dioxide on growth of young pedunculate oak (Quercus robur L.) trees.  Plant Soil. 167 325-329
• 29 Siebrecht,  S., and Tischner,  R.. (1999);  Changes in the xylem exudate composition of poplar (Populus tremula x P. alba) - dependent on the nitrogen and potassium supply.  J. Exp. Bot.. 50 1797-1806
• 30 Taylor,  F. H.. (1956);  Variation in sugar content of maple sap.  Bull. Univ. Vt. Agric. Exp. Stn.. 587 1-39
• 31 Voitsekhovskaja,  O. V.,, Pakhomova,  M. V.,, Syutkina,  A. V.,, Gamalei,  Y. V.,, and Heber,  U.. (2000);  Compartmention of assimilate fluxes in leaves. II. Apoplastic sugar levels in leaves of plants with different companion cell types.  Plant Biol.. 2 107-112
• 32 Winter,  H.,, Lohaus,  G.,, and Heldt,  W.. (1992);  Phloem transport of amino acids in relation to their cytosolic levels in barley leaves.  Plant Physiol.. 99 996-1004
• 33 Wyka,  T.. (1999);  Carbohydrate storage and use in an alpine population of the perennial herb, Oxytropis sericea. .  Oecologia. 120 198-208
• 34 Yu,  S.-M.. (1999);  Cellular and genetic responses of plants to sugar starvation.  Plant Physiol.. 121 687-693
• 35 Zimmer,  W.,, Brüggemann,  N.,, Emeis,  S.,, Giersch,  C.,, Lehning,  A.,, Steinbrecher,  R.,, and Schnitzler,  J.-P.. (2000);  Process-based modelling of isoprene emission by oak leaves.  Plant Cell Environ.. 23 585-597

Section Editor: U. Lüttge