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Electrical signalling and cytokinins mediate effects of light and root cutting on ion uptake in intact plants
Author(s) -
SHABALA SERGEY,
PANG JIAYIN,
ZHOU MEIXUE,
SHABALA LANA,
CUIN TRACEY A.,
NICK PETER,
WEGNER LARS H.
Publication year - 2009
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.1365-3040.2008.01914.x
Subject(s) - xylem , shoot , chemistry , efflux , ion transporter , cytokinin , biophysics , horticulture , botany , root hair , kinetin , biology , ion , biochemistry , auxin , tissue culture , in vitro , organic chemistry , gene
Nutrient acquisition in the mature root zone is under systemic control by the shoot and the root tip. In maize, exposure of the shoot to light induces short‐term (within 1–2 min) effects on net K + and H + transport at the root surface. H + efflux decreased (from −18 to −12 nmol m −2 s −1 ) and K + uptake (∼2 nmol m −2 s −1 ) reverted to efflux (∼−3 nmol m −2 s −1 ). Xylem probing revealed that the trans‐root (electrical) potential drop between xylem vessels and an external electrode responded within seconds to a stepwise increase in light intensity; xylem pressure started to decrease after a ∼3 min delay, favouring electrical as opposed to hydraulic signalling. Cutting of maize and barley roots at the base reduced H + efflux and stopped K + influx in low‐salt medium; xylem pressure rapidly increased to atmospheric levels. With 100 m m NaCl added to the bath, the pressure jump upon cutting was more dramatic, but fluxes remained unaffected, providing further evidence against hydraulic regulation of ion uptake. Following excision of the apical part of barley roots, influx changed to large efflux (−50 nmol m −2 s −1 ). Kinetin (2–4 µ m ), a synthetic cytokinin, reversed this effect. Regulation of ion transport by root‐tip‐synthesized cytokinins is discussed.