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Contrasting dynamics of water and mineral nutrients in stems shown by stable isotope tracers and cryo‐SIMS
Author(s) -
METZNER RALF,
THORPE MICHAEL R.,
BREUER UWE,
BLÜMLER PETER,
SCHURR ULRICH,
SCHNEIDER HEIKE U.,
SCHROEDER WALTER H.
Publication year - 2010
Publication title -
plant, cell and environment
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.646
H-Index - 200
eISSN - 1365-3040
pISSN - 0140-7791
DOI - 10.1111/j.1365-3040.2010.02157.x
Subject(s) - xylem , transpiration stream , potassium , nutrient , chemistry , tracer , transpiration , shoot , botany , phaseolus , phloem , biology , photosynthesis , biochemistry , physics , organic chemistry , nuclear physics
Lateral exchange of water and nutrients between xylem and surrounding tissues helps to de‐couple uptake from utilization in all parts of a plant. We studied the dynamics of these exchanges, using stable isotope tracers for water (H 2 18 O), magnesium ( 26 Mg), potassium ( 41 K) and calcium ( 44 Ca) delivered via a cut stem for various periods to the transpiration stream of bean shoots ( Phaseolus vulgaris cv. Fardenlosa Shiny). Tracers were subsequently mapped in stem cross‐sections with cryo‐secondary ion mass spectrometry. The water tracer equilibrated within minutes across the entire cross‐section. In contrast, the nutrient tracers showed a very heterogeneous exchange between xylem vessels and the different stem tissues, even after 4 h. Dynamics of nutrients in the tissues revealed a fast and extensive exchange of nutrients in the xylem parenchyma, with, for example, calcium being completely replaced by tracer in less than 5 min. Dilution of potassium tracer during its 30 s transit in xylem sap through the stem showed that potassium concentration was up‐regulated over many hours, to the extent that some of it was probably supplied by phloem recirculation from the shoot.