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A plant's ability to maintain an optimal cytosolic K+/Na+ ratio has long been cited as a key feature of salinity tolerance. As traditional whole-leaf nutrient analysis does not account for tissue and organelle-specific ion sequestration, the predictive value of this index at the whole-plant level is not always satisfactory. Consequently, suitable in situ methods for functionally assessing the activity of the key membrane transporters contributing to this trait at the cellular level need to be developed. The aim of this work was to investigate the extent to which plasma membrane transporter-mediated Na+ exclusion and KOR-mediated K+ retention traits, measured with the microelectrode ion flux measuring (MIFE) technique, are inheritable in wheat, and whether the MIFE technique has the potential to be used in combination with molecular markers to determine QTLs for these transporter proteins. Experiments involved two bread ( Triticum aestivum) and two durum ( Triticum turgidum) wheat lines contrasting in their salinity tolerance. Net Na+, K+ and H+ fluxes were measured from 6-day-old roots of parental lines and their F1 hybrids upon addition and removal of NaCl. These results were complemented by assessment of whole-plant physiological and agronomic characteristics. We show evidence for a strong heritability of plasma membrane transporter-mediated Na+ exclusion and K+ retention traits in wheat at the cellular level. This opens the prospect of using the MIFE technique to map the position of these transporters on particular loci of wheat chromosomes. The next obvious step would be to pyramid these traits in one ideotype with superior salinity tolerance. [ABSTRACT FROM AUTHOR]

Pak choi is a leafy vegetable with high economic value. Despite its importance, the information related to its metabolomics profile has still not been well-understood. This study aimed to determine the leaf metabolite composition of seven pak choi. In total, 513 metabolites belonging to 24 separate metabolite groups were detected. Pak choi leaves were rich in organic acids, amino acids, and flavonoids. There were ninety-two flavonoid compounds detected in pak choi leaves. Multivariate analysis revealed a distinct variation in the metabolite and flavonoid profile of green and purple leaved varieties. The flavonoid accumulation was comparatively greater in green leaved than purple leaf cultivar. This work provides novel insights into pak choi metabolomics profile, the flavonoids in particular, thus, to assess the nutritional value of this vegetable for humans., (Copyright © 2022 Elsevier Ltd. All rights reserved.)

Noninvasive microelectrode ion flux measurements (the MIFE™ technique) allow the concurrent quantification of net fluxes of several ions with high spatial (several μm) and temporal (ca 5 s) resolution. The MIFE technique has become a popular tool for studying the adaptive responses of plant cells and tissues to a large number of abiotic and biotic stresses. This chapter briefly summarizes some key findings on spatial and temporal organization of plant nutrient acquisition obtained by the MIFE technique, as well as the MIFE contribution towards elucidating the mechanisms behind a plant's perception and signaling of major abiotic stresses. The full protocols for microelectrode fabrication, calibration, and use are then given, and two basic routines for mapping root ion flux profiles and studying transient ion flux kinetics are given.

A plant's ability to maintain an optimal cytosolic K(+)/Na(+) ratio has long been cited as a key feature of salinity tolerance. As traditional whole-leaf nutrient analysis does not account for tissue and organelle-specific ion sequestration, the predictive value of this index at the whole-plant level is not always satisfactory. Consequently, suitable in situ methods for functionally assessing the activity of the key membrane transporters contributing to this trait at the cellular level need to be developed. The aim of this work was to investigate the extent to which plasma membrane transporter-mediated Na(+) exclusion and KOR-mediated K(+) retention traits, measured with the microelectrode ion flux measuring (MIFE) technique, are inheritable in wheat, and whether the MIFE technique has the potential to be used in combination with molecular markers to determine QTLs for these transporter proteins. Experiments involved two bread (Triticum aestivum) and two durum (Triticum turgidum) wheat lines contrasting in their salinity tolerance. Net Na(+), K(+) and H(+) fluxes were measured from 6-day-old roots of parental lines and their F(1) hybrids upon addition and removal of NaCl. These results were complemented by assessment of whole-plant physiological and agronomic characteristics. We show evidence for a strong heritability of plasma membrane transporter-mediated Na(+) exclusion and K(+) retention traits in wheat at the cellular level. This opens the prospect of using the MIFE technique to map the position of these transporters on particular loci of wheat chromosomes. The next obvious step would be to pyramid these traits in one ideotype with superior salinity tolerance., (© 2011 German Botanical Society and The Royal Botanical Society of the Netherlands.)

Polyamine (PA) levels in plants increase considerably under saline conditions. Because such an increase is believed to be beneficial for stress resistance, exogenous application of PAs has often been advocated as a means of ameliorating the detrimental effects of salinity. Results, however, are rather controversial, ranging from a significant amelioration to being ineffective or even toxic. The reasons for this controversy remain elusive. The ability of a root to retain K(+) in the presence of NaCl was used as a physiological indicator to evaluate the ameliorative effects of PA. Pre-treatment with 1 mM Spm(4+) (spermine), Spd(3+) (spermidine) or Put(2+) (putrescine) prevented salt-induced K(+) leak only in the mature root zone of hydroponically grown maize and Arabidopsis. In contrast, in the distal elongation root zone, PA pre-treatment resulted in an even larger NaCl-induced K(+) efflux, with the effect ranging from Spm(4+) >Spd(3+ )= Put(2+). A similar sequence has been also reported for H(+) pump inhibition, measured for both root zones. It appears that PAs affect cell membrane transporters in a highly specific way, with a relatively narrow 'window' in which amelioration is observed. We suggest that the ameliorative affect of PAs is the result of a complex combination of factors which might potentially include PA transport and accumulation in the cell cytosol, their metabolization and the functional expression of the specific target proteins or signaling elements.

The effects of secondary metabolites produced by waterlogged soils on net K(+), H(+), and Ca(2+) fluxes were studied in the mature zone of roots of two barley (Hordeum vulgare) cultivars contrasting in their waterlogging (WL) tolerance using the noninvasive microelectrode ion flux measuring technique. In WL-sensitive variety 'Naso Nijo', all three lower monocarboxylic acids (formic, acetic, and propionic acids) and three phenolic acids (benzoic, 2-hydroxybenzoic, 4-hydroxybenzoic acids) caused a substantial shift toward steady K(+) efflux, accompanied by an immediate net influx of H(+). Detrimental effects of secondary metabolites on K(+) homeostasis in root cells were absent in WL-tolerant 'TX' variety. Root treatment with Mn(2+) caused only a temporary K(+) loss that returned to the initial level 10 min after treatment. Phenolic acids slightly increased Ca(2+) influx immediately after treatment, while other metabolites tested resulted in transient Ca(2+) efflux from the root. In the long-term (24 h) treatment, all metabolites tested significantly reduced K(+) uptake and the adverse effects of phenolic acids were smaller than for monocarboxylic acids and Mn(2+). Treatment with monocarboxylic acids for 24 h shifted H(+) from net efflux to net influx, while all three phenolic acids did not cause significant effects compared with the control. Based on results of pharmacological experiments and membrane potential measurements, a model explaining the effects of secondary metabolites on membrane transport activity is proposed. We also suggest that plant tolerance to these secondary metabolites could be considered a useful trait in breeding programs.