Proteasome resides in and dismantles plant heat stress granules constitutively.

Stress granules (SGs) are conserved reversible cytoplasmic condensates enriched with aggregation-prone proteins assembled in response to various stresses. How plants regulate SG dynamics is unclear. Here, we show that 26S proteasome is a stable component of SGs, promoting the overall clearance of SGs without affecting the molecular mobility of SG components. Increase in either temperature or duration of heat stress reduces the molecular mobility of SG marker proteins and suppresses SG clearance. Heat stress induces dramatic ubiquitylation of SG components and enhances the activities of SG-resident proteasomes, allowing the degradation of SG components even during the assembly phase. Their proteolytic activities enable the timely disassembly of SGs and secure the survival of plant cells during the recovery from heat stress. Therefore, our findings identify the cellular process that de-couples macroscopic dynamics of SGs from the molecular dynamics of its constituents and highlights the significance of the proteasomes in SG disassembly.

Rational design of ROS scavenging and fluorescent gold nanoparticles to deliver siRNA to improve plant resistance to Pseudomonas syringae.

Bacterial diseases are one of the most common issues that result in crop loss worldwide, and the increasing usage of chemical pesticides has caused the occurrence of resistance in pathogenic bacteria and environmental pollution problems. Nanomaterial mediated gene silencing is starting to display powerful efficiency and environmental friendliness for improving plant disease resistance. However, the internalization of nanomaterials and the physiological mechanisms behind nano-improved plant disease resistance are still rarely understood. We engineered the polyethyleneimine (PEI) functionalized gold nanoparticles (PEI-AuNPs) with fluorescent properties and ROS scavenging activity to act as siRNA delivery platforms. Besides the loading, protection, and delivery of nucleic acid molecules in plant mature leaf cells by PEI-AuNPs, its fluorescent property further enables the traceability of the distribution of the loaded nucleic acid molecules in cells. Additionally, the PEI-AuNPs-based RNAi delivery system successfully mediated the silencing of defense-regulated gene AtWRKY1. Compared to control plants, the silenced plants performed better resistance to Pseudomonas syringae, showing a reduced bacterial number, decreased ROS content, increased antioxidant enzyme activities, and improved chlorophyll fluorescence performance. Our results showed the advantages of AuNP-based RNAi technology in improving plant disease resistance, as well as the potential of plant nanobiotechnology to protect agricultural production.

A Novel Method for Precision Measurement and Result Optimization of Detuning Angle for KDP Crystals.

In this paper, we investigate the theory of energy distribution when divergent light undergoes harmonic conversion in KDP crystals, and based on this theory, we design and construct a precision measuring instrument for the detuning angle of (KDP) Crystals (MIDC). The device can obtain the detuning angle of the crystal by a single measurement with an average measurement error of 72.78 urad. At the same time, it also has the function of scanning the full aperture of the crystals. Using the MIDC, it is possible to quickly measure the KDP crystal at a single point and quickly scan the crystal detuning angle at full aperture. In addition, we conduct a theoretical study on the variation of detuning angle caused by gravity-influencing factors under online conditions, propose an optimization formula for the offline measurement results of detuning angle, and calculate the optimized values of detuning angle for two kinds of crystals under 45° online conditions. We finally study the error source of the MIDC device, analyze the trend of the influence of positioning errors of the crystal and optical elements on the detuning angle measurement results, and provide theoretical support for the error monitoring and correction of MIDC.

Small particles, big effects: How nanoparticles can enhance plant growth in favorable and harsh conditions.

By 2050, the global population is projected to reach 9 billion, underscoring the imperative for innovative solutions to increase grain yield and enhance food security. Nanotechnology has emerged as a powerful tool, providing unique solutions to this challenge. Nanoparticles (NPs) can improve plant growth and nutrition under normal conditions through their high surface-to-volume ratio and unique physical and chemical properties. Moreover, they can be used to monitor crop health status and augment plant resilience against abiotic stresses (such as salinity, drought, heavy metals, and extreme temperatures) that endanger global agriculture. Application of NPs can enhance stress tolerance mechanisms in plants, minimizing potential yield losses and underscoring the potential of NPs to raise crop yield and quality. This review highlights the need for a comprehensive exploration of the environmental implications and safety of nanomaterials and provides valuable guidelines for researchers, policymakers, and agricultural practitioners. With thoughtful stewardship, nanotechnology holds immense promise in shaping environmentally sustainable agriculture amid escalating environmental challenges.

Abnormal [18F]FDG uptake in liver and adipose tissue: a potential imaging biomarker for cancer-associated cachexia.

OBJECTIVES: This study aims to investigate and develop imaging biomarkers for the diagnosis of cancer-associated cachexia based on the organ and tissue-specific abnormal metabolisms measured by fluorine-18-fluorodeoxyglucose (18F-FDG) PET/CT. METHODS: FDG PET/CT data from 390 cancer patients were analyzed retrospectively. Patients were divided into a development cohort and a validation cohort. Cachexia was defined as weight loss > 5% in 6 months or BMI < 20 and weight loss > 2%. According to the above definitions, patients were divided into cachexia and non-cachexia groups. Results of the clinical laboratory tests for metabolic levels and organ and tissue-specific FDG uptake obtained from the cachexia and non-cachexia groups were compared statistically. Logistic regression analysis was performed to identify independent variables associated with cachexia in the development cohort for generating the regression model. The performance of the model was tested using the data from a validation cohort and evaluated by area under the receiver operating characteristic curve (AUC). RESULTS: Based on the data from the development cohort of 286 patients and a validation cohort of 104 patients, it is found that age, white blood cell count, peak standardized uptake value (SUV) of the liver, and minimum SUV of lean body mass of visceral fat and subcutaneous fat were independently associated with cachexia. The model incorporating these variables reached an AUC of 0.777 (95% confidence interval (CI): 0.721, 0.833) in the development cohort and an AUC of 0.729 (95% CI: 0.629, 0.829) in the validation cohort. CONCLUSION: Organ and tissue-specific abnormal glucose metabolism as measured by PET/CT can be used as a biomarker for cancer-associated cachexia. KEY POINTS: • Patients with cancer-associated cachexia have reduced FDG uptake in the liver and increased FDG uptake in visceral fat and subcutaneous fat. • FDG uptake of the liver, visceral fat, and subcutaneous fat can be independent risk factors for identifying cancer-associated cachexia. • Cancer-associated cachexia can be classified using the model that incorporates age, white blood cell count, FDG uptake of the liver, and visceral and subcutaneous fat can diagnose with an AUC of 0.729.

Divergent beam-based method for measuring the detuning angles of a laser frequency converter.

We propose a method to obtain the detuning angles of a frequency converter by tripling the frequency of a divergent Gaussian beam. The frequency tripling process of the divergent beam was first simulated. It is found that the detuning angles of the frequency converter are linearly related to the position of the maximum light intensity point of the third harmonic laser. The corresponding experiment was conducted, and the results agreed well with the theoretical analysis. This method measures the detuning angles of the frequency converter in only one measurement and within 1 min. The detuning angle measurement errors of KDP and KD*P crystals are less than 10 µrad and 36.5-61.9 µrad, respectively.

Cerium oxide nanoparticles improve cotton salt tolerance by enabling better ability to maintain cytosolic K+/Na+ ratio.

BACKGROUND: Salinity is a worldwide factor limiting the agricultural production. Cotton is an important cash crop; however, its yield and product quality are negatively affected by soil salinity. Use of nanomaterials such as cerium oxide nanoparticles (nanoceria) to improve plant tolerance to stress conditions, e.g. salinity, is an emerged approach in agricultural production. Nevertheless, to date, our knowledge about the role of nanoceria in cotton salt response and the behind mechanisms is still rare. RESULTS: We found that PNC (poly acrylic acid coated nanoceria) helped to improve cotton tolerance to salinity, showing better phenotypic performance, higher chlorophyll content (up to 68% increase) and biomass (up to 38% increase), and better photosynthetic performance such as carbon assimilation rate (up to 144% increase) in PNC treated cotton plants than the NNP (non-nanoparticle control) group. Under salinity stress, in consistent to the results of the enhanced activities of antioxidant enzymes, PNC treated cotton plants showed significant lower MDA (malondialdehyde, up to 44% decrease) content and reactive oxygen species (ROS) level such as hydrogen peroxide (H2O2, up to 79% decrease) than the NNP control group, both in the first and second true leaves. Further experiments showed that under salinity stress, PNC treated cotton plants had significant higher cytosolic K+ (up to 84% increase) and lower cytosolic Na+ (up to 77% decrease) fluorescent intensity in both the first and second true leaves than the NNP control group. This is further confirmed by the leaf ion content analysis, showed that PNC treated cotton plants maintained significant higher leaf K+ (up to 84% increase) and lower leaf Na+ content (up to 63% decrease), and thus the higher K+/Na+ ratio than the NNP control plants under salinity stress. Whereas no significant increase of mesophyll cell vacuolar Na+ intensity was observed in PNC treated plants than the NNP control under salinity stress, suggesting that the enhanced leaf K+ retention and leaf Na+ exclusion, but not leaf vacuolar Na+ sequestration are the main mechanisms behind PNC improved cotton salt tolerance. qPCR results showed that under salinity stress, the modulation of HKT1 but not SOS1 refers more to the PNC improved cotton leaf Na+ exclusion than the NNP control. CONCLUSIONS: PNC enhanced leaf K+ retention and Na+ exclusion, but not vacuolar Na+ sequestration to enable better maintained cytosolic K+/Na+ homeostasis and thus to improve cotton salt tolerance. Our results add more knowledge for better understanding the complexity of plant-nanoceria interaction in terms of nano-enabled plant stress tolerance.

Nanoceria seed priming enhanced salt tolerance in rapeseed through modulating ROS homeostasis and α-amylase activities.

BACKGROUND: Salinity is a big threat to agriculture by limiting crop production. Nanopriming (seed priming with nanomaterials) is an emerged approach to improve plant stress tolerance; however, our knowledge about the underlying mechanisms is limited. RESULTS: Herein, we used cerium oxide nanoparticles (nanoceria) to prime rapeseeds and investigated the possible mechanisms behind nanoceria improved rapeseed salt tolerance. We synthesized and characterized polyacrylic acid coated nanoceria (PNC, 8.5 ± 0.2 nm, -43.3 ± 6.3 mV) and monitored its distribution in different tissues of the seed during the imbibition period (1, 3, 8 h priming). Our results showed that compared with the no nanoparticle control, PNC nanopriming improved germination rate (12%) and biomass (41%) in rapeseeds (Brassica napus) under salt stress (200 mM NaCl). During the priming hours, PNC were located mostly in the seed coat, nevertheless the intensity of PNC in cotyledon and radicle was increased alongside with the increase of priming hours. During the priming hours, the amount of the absorbed water (52%, 14%, 12% increase at 1, 3, 8 h priming, respectively) and the activities of α-amylase were significantly higher (175%, 309%, 295% increase at 1, 3, 8 h priming, respectively) in PNC treatment than the control. PNC primed rapeseeds showed significantly lower content of MDA, H2O2, and •O2- in both shoot and root than the control under salt stress. Also, under salt stress, PNC nanopriming enabled significantly higher K+ retention (29%) and significantly lower Na+ accumulation (18.5%) and Na+/K+ ratio (37%) than the control. CONCLUSIONS: Our results suggested that besides the more absorbed water and higher α-amylase activities, PNC nanopriming improves salt tolerance in rapeseeds through alleviating oxidative damage and maintaining Na+/K+ ratio. It adds more knowledge regarding the mechanisms underlying nanopriming improved plant salt tolerance.

Monitoring Plant Health with Near-Infrared Fluorescent H2O2 Nanosensors.

Near-infrared (nIR) fluorescent single-walled carbon nanotubes (SWCNTs) were designed and interfaced with leaves of Arabidopsis thaliana plants to report hydrogen peroxide (H2O2), a key signaling molecule associated with the onset of plant stress. The sensor nIR fluorescence response (>900 nm) is quenched by H2O2 with selectivity against other stress-associated signaling molecules and within the plant physiological range (10-100 H2O2 µM). In vivo remote nIR imaging of H2O2 sensors enabled optical monitoring of plant health in response to stresses including UV-B light (-11%), high light (-6%), and a pathogen-related peptide (flg22) (-10%), but not mechanical leaf wounding (<3%). The sensor's high biocompatibility was reflected on similar leaf cell death (<5%) and photosynthetic rates to controls without SWCNT. These optical nanosensors report early signs of stress and will improve our understanding of plant stress communication, provide novel tools for precision agriculture, and optimize the use of agrochemicals in the environment.

Scale-Up Preparation of Crocins I and II from Gardeniajasminoides by a Two-Step Chromatographic Approach and Their Inhibitory Activity Against ATP Citrate Lyase.

Crocins are highly valuable natural compounds for treating human disorders, and they are also high-end spices and colorants in the food industry. Due to the limitation of obtaining this type of highly polar compound, the commercial prices of crocins I and II are expensive. In this study, macroporous resin column chromatography combined with high-speed counter-current chromatography (HSCCC) was used to purify crocins I and II from natural sources. With only two chromatographic steps, both compounds were simultaneously isolated from the dry fruit of Gardenia jasminoides, which is a cheap herbal medicine distributed in a number of countries. In an effort to shorten the isolation time and reduce solvent usage, forward and reverse rotations were successively utilized in the HSCCC isolation procedure. Crocins I and II were simultaneously obtained from a herbal resource with high recoveries of 0.5% and 0.1%, respectively, and high purities of 98.7% and 99.1%, respectively, by HPLC analysis. The optimized preparation method was proven to be highly efficient, convenient, and cost-effective. Crocins I and II exhibited inhibitory activity against ATP citrate lyase, and their IC50 values were determined to be 36.3 ± 6.24 and 29.7 ± 7.41 µM, respectively.

Root vacuolar Na+ sequestration but not exclusion from uptake correlates with barley salt tolerance.

Soil salinity is a major constraint for the global agricultural production. For many decades, Na+ exclusion from uptake has been the key trait targeted in breeding programs; yet, no major breakthrough in creating salt-tolerant germplasm was achieved. In this work, we have combined the microelectrode ion flux estimation (MIFE) technique for non-invasive ion flux measurements with confocal fluorescence dye imaging technique to screen 45 accessions of barley to reveal the relative contribution of Na+ exclusion from the cytosol to the apoplast and its vacuolar sequestration in the root apex, for the overall salinity stress tolerance. We show that Na+ /H+ antiporter-mediated Na+ extrusion from the root plays a minor role in the overall salt tolerance in barley. At the same time, a strong and positive correlation was found between root vacuolar Na+ sequestration ability and the overall salt tolerance. The inability of salt-sensitive genotypes to sequester Na+ in root vacuoles was in contrast to significantly higher expression levels of both HvNHX1 tonoplast Na+ /H+ antiporters and HvVP1 H+ -pumps compared with tolerant genotypes. These data are interpreted as a failure of sensitive varieties to prevent Na+ back-leak into the cytosol and existence of a futile Na+ cycle at the tonoplast. Taken together, our results demonstrated that root vacuolar Na+ sequestration but not exclusion from uptake played the main role in barley salinity tolerance, and suggested that the focus of the breeding programs should be shifted from targeting genes mediating Na+ exclusion from uptake by roots to more efficient root vacuolar Na+ sequestration.

Efficient iron plaque formation on tea (Camellia sinensis) roots contributes to acidic stress tolerance.

Tea plants grow in acidic soil, but to date, their intrinsic mechanisms of acidic stress tolerance have not been elucidated. Here, we assessed the tea plant response to growth on NH4 + nutrient media having different pH and iron levels. When grown in standard NH4 + nutrient solution (iron insufficient, 0.35 mg L-1 Fe2+ ), tea roots exhibited significantly lower nitrogen accumulation, plasma membrane H+ -ATPase activity, and protein levels; net H+ efflux was lower at pH 4.0 and 5.0 than at pH 6.0. Addition of 30 mg L-1 Fe2+ (iron sufficient, mimicking normal soil Fe2+ concentrations) to the NH4 + nutrient solution led to more efficient iron plaque formation on roots and increased root plasma membrane H+ -ATPase levels and activities at pH 4.0 and 5.0, compared to the pH 6.0 condition. Furthermore, plants grown at pH 4.0 and 5.0, with sufficient iron, exhibited significantly higher nitrogen accumulation than those grown at pH 6.0. Together, these results support the hypothesis that efficient iron plaque formation, on tea roots, is important for acidic stress tolerance. Furthermore, our findings establish that efficient iron plaque formation is linked to increased levels and activities of the tea root plasma membrane H+ -ATPase, under low pH conditions.

Na+ extrusion from the cytosol and tissue-specific Na+ sequestration in roots confer differential salt stress tolerance between durum and bread wheat.

The progress in plant breeding for salinity stress tolerance is handicapped by the lack of understanding of the specificity of salt stress signalling and adaptation at the cellular and tissue levels. In this study, we used electrophysiological, fluorescence imaging, and real-time quantitative PCR tools to elucidate the essentiality of the cytosolic Na+ extrusion in functionally different root zones (elongation, meristem, and mature) in a large number of bread and durum wheat accessions. We show that the difference in the root's ability for vacuolar Na+ sequestration in the mature zone may explain differential salinity stress tolerance between salt-sensitive durum and salt-tolerant bread wheat species. Bread wheat genotypes also had on average 30% higher capacity for net Na+ efflux from the root elongation zone, providing the first direct evidence for the essentiality of the root salt exclusion trait at the cellular level. At the same time, cytosolic Na+ accumulation in the root meristem was significantly higher in bread wheat, leading to the suggestion that this tissue may harbour a putative salt sensor. This hypothesis was then tested by investigating patterns of Na+ distribution and the relative expression level of several key genes related to Na+ transport in leaves in plants with intact roots and in those in which the root meristems were removed. We show that tampering with this sensing mechanism has resulted in a salt-sensitive phenotype, largely due to compromising the plant's ability to sequester Na+ in mesophyll cell vacuoles. The implications of these findings for plant breeding for salinity stress tolerance are discussed.

Cell-Type-Specific H+-ATPase Activity in Root Tissues Enables K+ Retention and Mediates Acclimation of Barley (Hordeum vulgare) to Salinity Stress.

While the importance of cell type specificity in plant adaptive responses is widely accepted, only a limited number of studies have addressed this issue at the functional level. We have combined electrophysiological, imaging, and biochemical techniques to reveal the physiological mechanisms conferring higher sensitivity of apical root cells to salinity in barley (Hordeum vulgare). We show that salinity application to the root apex arrests root growth in a highly tissue- and treatment-specific manner. Although salinity-induced transient net Na+ uptake was about 4-fold higher in the root apex compared with the mature zone, mature root cells accumulated more cytosolic and vacuolar Na+, suggesting that the higher sensitivity of apical cells to salt is not related to either enhanced Na+ exclusion or sequestration inside the root. Rather, the above differential sensitivity between the two zones originates from a 10-fold difference in K+ efflux between the mature zone and the apical region (much poorer in the root apex) of the root. Major factors contributing to this poor K+ retention ability are (1) an intrinsically lower H+-ATPase activity in the root apex, (2) greater salt-induced membrane depolarization, and (3) a higher reactive oxygen species production under NaCl and a larger density of reactive oxygen species-activated cation currents in the apex. Salinity treatment increased (2- to 5-fold) the content of 10 (out of 25 detected) amino acids in the root apex but not in the mature zone and changed the organic acid and sugar contents. The causal link between the observed changes in the root metabolic profile and the regulation of transporter activity is discussed.

Targeting the middle region of CP4-EPSPS protein for its traceability in highly processed soy-related products.

Transgenic components in genetically modified organisms consist not only of the transgenic genes, but also the transgenic protein. However, compared with transgenic DNA, less attention has been paid to the detection of expressed protein, especially those degraded from genetically modified soybean after food processing. In this study, the full length 5-enolpyruvyl-shikimate-3-phosphate synthase (CP4-EPSPS, 47.6 kD) protein was probed with the SC-16 (S19-R33) and the DC-16 (D219-K233) polyclonal antibodies in immunoblots. Both antibodies were able to detect the full length CP4-EPSPS and its residues in soy powder made from Roundup-Ready soybeans after heating and microwaving treatments which also reduced the molecular weight of the protein to 45.8 and 38.7 kD, respectively. Taken together the immunoblot results suggest that the middle region of the CP4-EPSPS protein possessed better stability than its N-terminal during thermal processing. This deduction was further validated by autoclave treatment, where a 37.4 kD residue of the protein was recognized by DC-16. A similar result was obtained in processed smoked sausage containing Roundup Ready soybean protein isolate (as an extender). The additional use of a further polyclonal antibody CK-17 (C372-K388), showed that compared with only the one signal for CP4-EPSPS detected by the SC-16 and CK-17 antibodies, the DC-16 middle region antibody detected four signals for CP4-EPSPS from five market sourced soy protein concentrates. Taken together, the study suggested that the middle region of CP4-EPSPS was more useful than the N- and C-terminal for tracing transgenic CP4-EPSPS protein and its remnants in highly processed soy-related products.

Anion Channel Inhibitor NPPB-Inhibited Fluoride Accumulation in Tea Plant (Camellia sinensis) Is Related to the Regulation of Ca²âº, CaM and Depolarization of Plasma Membrane Potential.

Tea plant is known to be a hyper-accumulator of fluoride (F). Over-intake of F has been shown to have adverse effects on human health, e.g., dental fluorosis. Thus, understanding the mechanisms fluoride accumulation and developing potential approaches to decrease F uptake in tea plants might be beneficial for human health. In the present study, we found that pretreatment with the anion channel inhibitor NPPB reduced F accumulation in tea plants. Simultaneously, we observed that NPPB triggered Ca(2+) efflux from mature zone of tea root and significantly increased relative CaM in tea roots. Besides, pretreatment with the Ca(2+) chelator (EGTA) and CaM antagonists (CPZ and TFP) suppressed NPPB-elevated cytosolic Ca(2+) fluorescence intensity and CaM concentration in tea roots, respectively. Interestingly, NPPB-inhibited F accumulation was found to be significantly alleviated in tea plants pretreated with either Ca(2+) chelator (EGTA) or CaM antagonists (CPZ and TFP). In addition, NPPB significantly depolarized membrane potential transiently and we argue that the net Ca(2+) and H⁺ efflux across the plasma membrane contributed to the restoration of membrane potential. Overall, our results suggest that regulation of Ca(2+)-CaM and plasma membrane potential depolarization are involved in NPPB-inhibited F accumulation in tea plants.

Al(3+) -promoted fluoride accumulation in tea plants (Camellia sinensis) was inhibited by an anion channel inhibitor DIDS.

BACKGROUND: Generally, tea plants are grown in acid soil which is rich in aluminum (Al) and fluoride (F). A recent publication showed that pretreatment with Al(3+) promoted F accumulation in tea plants by increasing endogenous Ca(2+) and calmodulin (CaM). A high level of F in tea leaves not only impairs tea quality but also might pose a health risk for people drinking tea regularly. Therefore it is important to try to find some clues which might be beneficial in controlling F accumulation in tea plants grown in acid soil (Al(3+) ). RESULTS: It was found that diisothiocyanostilbene-2,2-disulfonic acid (DIDS) significantly reduced Al(3+) -promoted F accumulation in tea plants. Additionally, Al(3+) plus DIDS treatment stimulated significantly higher Ca(2+) efflux and decreased the CaM level in tea roots compared with Al(3+) treatment. Besides, significantly higher depolarization of membrane potential was shown in tea roots treated with Al(3+) plus DIDS than in those treated with Al(3+) , as well as higher net total H(+) efflux and plasma membrane H(+) -ATPase activity. CONCLUSION: Al(3+) -promoted F accumulation in tea plants was inhibited by an anion channel inhibitor DIDS. Ca(2+) /CaM and membrane potential depolarization may be the components involved in this process. © 2016 Society of Chemical Industry.

Developing and validating a high-throughput assay for salinity tissue tolerance in wheat and barley.

MAIN CONCLUSION: Leaf tissue tolerance was strongly and positively correlated with overall salt tolerance in barley, but not in wheat where the inability of sensitive varieties to exclude Na(+) is compensated by their better ability to handle Na(+) accumulated in the shoot via tissue tolerance mechanisms. A new high-throughput assay was developed to use the excised leaves to eliminate the confounding contribution of sodium exclusion mechanisms and evaluate genetic variability in salinity tissue tolerance in a large number of wheat (Triticum aestivum and Triticum turgidum ssp. durum) and barley (Hordeum vulgare) accessions. The changes in relative chlorophyll content (measured as chlorophyll content index, CCI) in excised leaves exposed to 50 mM NaCl for 48 h were found to be a reliable indicator of leaf tissue tolerance. In both wheat and barley, relative CCI correlated strongly with the overall plant salinity tolerance (evaluated in glasshouse experiments). To a large extent, this tissue tolerance was related to more efficient vacuolar Na(+) sequestration in leaf mesophyll, as revealed by fluorescent Na(+) dye imaging experiments. However, while in barley this correlation was positive, tissue tolerance in wheat correlated negatively with overall salinity tolerance. As a result, more salt-sensitive durum wheat genotypes possessed higher tissue tolerance than bread wheat plants, and this negative correlation was present within each of bread and durum wheat clusters as well. Overall, these results indicate that the lack of effective Na(+) exclusion ability in sensitive wheat varieties is compensated by their better ability to handle Na(+) accumulated in the shoot via tissue tolerance mechanisms. Implications of these findings for plant breeding for salinity tolerance are discussed.