Author:
Dannel Frank,Pfeffer Heidrun,Römheld Volker
Abstract
The B pools in the roots and the
characteristics of B uptake and its loading into the xylem were investi-gated
in sunflower (Helianthus annuus L.) plants precultured
with high (100 M) or low (1 M) 11 B supply. In order to
study B fluxes and their dependence on root metabolic activity, short-term
treatments with differential 10 B supply in combination
with metabolic inhibition treatments (50 M 2,4-dinitrophenol; root zone
temperature of 7˚C) or with no further treatment (control) were carried
out. Subsequently, xylem exudate was collected, and roots were harvested and
fractionated into two B pools that differed in their water-solubility as well
as in their exchangeability. The exchange or release of
11 B initially present during the 3 h treatment was
maximal at 18% in the cell wall pool, whilst it was up to 94% in
the symplasmic pool. All observed alterations in the cell wall-bound B can be
explained by passive processes. Control plants precultured with high B supply
showed a linear response of the 10 B concentrations in
the root cell sap and in the xylem exudate to the differential short-term
10B supply, and this was not affected by the metabolic
inhibition treatments. In the control plants precultured with low B supply,
the response of the 10 B concentrations in the root cell
sap and xylem exudate to the differential short-term 10
B supply appeared to be a com-bination of a saturable and a linear component.
The metabolic inhibition treatments turned off the saturable compo-nent and
the response became linear. In summary, the results suggest that B uptake into
the root symplasm, as well as xylem loading, are performed by two transport
mechanisms, with the linear components representing B transport by passive
diffusion. The saturable components may represent unknown carrier- or
channel-mediated transport of B, which is dependent on metabolic energy.
Subject
Plant Science,Agronomy and Crop Science
Cited by
15 articles.
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