Abstract
Analyses of vascular saps supplying source and sink organs havedemonstrated the presence of major endogenous hormones and/or theirprecursors. Indol-3yl-acetic acid, a number of gibberellins, cytokininsand abscisic acid, as well as the precursor for ethylene production havebeen found in these vascular saps, allowing the sites of hormonalsynthesis and putative target tissues to be deduced. Exogenously appliedhormones are also readily loaded into these vascular pathways and may betranslocated over considerable distances from a point of application.Observations such as these indicate a possible co-ordination systembetween source and sink regulated by the synthesis and transport ofendogenous hormones. It is widely accepted that the partitioning ofassimilates between photosynthetic source organs and utilising sinkorgans is regulated by endogenous plant hormones. The key intermediatesteps involved in assimilate transport, such as phloem loading andunloading, have been shown to be responsive to applied hormones,although the role of endogenous hormones in these processes remainsessentially unresolved. Results of the analyses of vascular saps fromRicinus communis, which have been obtained using a range ofphysicochemical methods, are compared and contrasted with those obtainedby the application of exogenous hormones or their precursors. Theseresults are evaluated critically and interpreted in the light of currentmodels of source:sink regulatory processes and the long-distancetransport of auxins and cytokinins in higher plants.
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Allen JRF and Baker DA (1980) Free tryptophan and indole-3-acetic acid levels in the leaves and vascular pathways of Ricinus communis L. Planta 148: 69-74
Allen JRF, Greenway AM and Baker DA (1979) Determinations of indole-3-acetic acid in xylem sap of Ricinus communis L. using mass fragmentography. Planta 144: 299-303
Baker DA and Allen JRF (1988) Auxin transport in the vascular system. In: Kutacek M, Bandurski RS and Krekule J (eds) Physiology and Biochemistry of Auxins in Plants. Prague: Academia, pp 21-32
Baker DA and Allen JRF (1992) Cytokinin transport in the vascular system. In: Kaminek M, Mok DWS and Zazimalova E (eds) Physiology and Biochemistry of Cytokinins in Plants. SBP Academic Publishing, pp 225-228
Borkovec V, Didehvar F and Baker DA (1994) The biosynthesis and translocation of 14C-IAA in Ricinus communis. Plant Growth Regulation 15: 137-141
Chen C-M, Ertl JR, Leisner SM and Chang C-C (1985) Localisation of cytokinin biosynthetic sites in pea plants and carrot roots. Plant Physiol 78: 510-513
Chino M, Hayashi H, Nakamura S, Oshima T, Turner H, Sabnis D, Borkovec V, Baker DA, Bonnemain JL and Delrot S (1991) Phloem sap, composition. In: Bonnemain JL, Delrot S, Lucas WJ and Dainty J (eds) Recent Advances in Phloem Transport and Assimilate Compartmentation, Ouest Editions. Nantes Cedex, France: Presses Académiques
Ehness R and Roitsch T (1997) Co-ordinated induction of mRNAs for extracellular invertase and a glucose transporter in C. rubrum by cytokinins. Plant J 11: 539-548
Girousse C, Bonnemain J-L, Delrot S and Bournoville R (1991) Sugar and amino acid composition of Medicago sativa: A comparative study of two collecting methods. Plant Physiol Biochem 29: 41-48
Hall SM and Baker DA (1972) The chemical composition of Ricinus phloem exudate. Planta 106: 131-140
Hall SM and Medlow GC (1974) Identification of IAA in phloem and root pressure saps of Ricinus communis L., by mass spectrometry. Planta 119: 257-261
Hoad GV (1995) Transport of hormones in the phloem of higher plants. Plant Growth Regulation 16: 173-182
Kamboj JS, Blake PS and Baker DA (1998) Cytokinins in the vascular saps of Ricinus communis. Plant Growth Regulation 25: 123-126
Kawabe S, Bukomorita T and Chino M (1980) Collection of rice phloem sap from stylets of homopterous insect severed by YAG laser. Plant Cell Physiol 21: 1319-1327
Komor E, Liegl I and Schobert C (1993) Loading and translocation of various cytokinins in the phloem and xylem of the seedlings of Ricinus communis L. Planta 191: 252-255
Kuiper D, Kuiper PJC, Lambers H, Schuit J and Stall M (1989) Effects of internal and external cytokinin concentration on root growth and shoot to root ratio of Plantago major sp. Pleiosperma at different nutrient concentrations. Plant and Soil 111: 231-237
Kuiper D (1993) Sink strength: established and regulated by plant growth regulators. Plant, Cell and Environment 16: 1025-1026
Letham DS (1978) Cytokinins. In: Letham DS, Goodwin PB and Higgins TJV (eds) Phytohormones and Related Compounds: A Comprehensive Treatise, Volume 1. Amsterdam: Elsevier, pp 205-263
Phillips DA and Cleland DF (1972) Cytokinin activity from the phloem sap of Xanthium strumarium L. Planta 102: 173-178
Sheldrake AR (1973) The production of hormones in higher plants. Biol Rev 48: 509-559
Van Staden J and Davey JE (1979) The synthesis, transport and metabolism of endogenous cytokinins. Plant Cell Environ 2: 93-106
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Baker, D. Vascular transport of auxins and cytokinins in Ricinus. Plant Growth Regulation 32, 157–160 (2000). https://doi.org/10.1023/A:1010749411009
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DOI: https://doi.org/10.1023/A:1010749411009