Time-dependent kinetics of xylem Na⁺ loading was investigated using a large number of barley genotypes contrasting in their salinity tolerance. Salt-sensitive varieties were less efficient in controlling xylem Na⁺ loading and showed a gradual increase in the xylem Na⁺ content over the time. To understand underlying ionic and molecular mechanisms, net fluxes of Ca²⁺, K⁺ and Na⁺ were measured from the xylem parenchyma tissue in response to H₂O₂ and ABA; both of them associated with salinity stress signalling. Our results indicate that NADPH oxidase-mediated apoplastic H₂O₂ production acts upstream of the xylem Na⁺ loading and is causally related to ROS-inducible Ca²⁺ uptake systems in the root stelar tissue. It was also found that ABA regulates (directly or indirectly) the process of Na⁺ retrieval from the xylem and the significant reduction of Na⁺ and K⁺ fluxes induced by bumetanide are indicative of a major role of chloride cation co-transporter (CCC) on xylem ion loading. Transcript levels of HvHKT1;5_like and HvSOS1_like genes in the root stele were observed to decrease after salt stress, while there was an increase in HvSKOR_like gene, indicating that these ion transporters are involved in primary Na⁺/K⁺ movement into/out of xylem.

Item Type:	Refereed Article
Keywords:	ABA; CCC transporter; H2O2; NADPH oxidase; SKOR; SOS1; xylem sodium loading
Research Division:	Biological Sciences
Research Group:	Plant biology
Research Field:	Plant physiology
Objective Division:	Plant Production and Plant Primary Products
Objective Group:	Grains and seeds
Objective Field:	Barley
UTAS Author:	Zhu, M (Ms Min Zhu)
UTAS Author:	Zhiu, M (Professor Meixue Zhou)
UTAS Author:	Shabala, L (Associate Professor Lana Shabala)
UTAS Author:	Shabala, S (Professor Sergey Shabala)
ID Code:	117709
Year Published:	2017 (online first 2016)
Web of Science® Times Cited:	69
Deposited By:	Tasmanian Institute of Agriculture
Deposited On:	2017-06-26
Last Modified:	2017-11-02
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