Rice cultivars with differing salt tolerance contain similar cation channels in their root cells

Salinity poses a major threat for agriculture worldwide. Rice is one of the major crops where most of the high-yielding cultivars are highly sensitive to salinity. Several studies on the genetic variability across rice cultivars suggest that the activity and composition of root plasma membrane transporters could underlie the observed cultivar-specific salinity tolerance in rice. In the current study, it was found that the salt-tolerant cultivar Pokkali maintains a higher K+/Na+ ratio compared with the salt-sensitive IR20 in roots as well as in shoots. Using Na+ reporter dyes, IR20 root protoplasts showed a much faster Na+ accumulation than Pokkali protoplasts. Membrane potential measurements showed that root cells exposed to Na+ in IR20 depolarized considerably further than those of Pokkali. These results suggest that IR20 has a larger plasma membrane Na+ conductance. To assess whether this could be due to different ion channel properties, root protoplasts from both Pokkali and IR20 rice cultivars were patch-clamped. Voltage-dependent K+ inward rectifiers, K+ outward rectifiers, and voltage-independent, non-selective channels with unitary conductances of around 35, 40, and 10 pS, respectively, were identified. Only the non-selective channel showed significant Na+ permeability. Intriguingly, in both cultivars, the activity of the K+ inward rectifier was drastically down-regulated after plant growth in salt but gating, conductance, and activity of all channel types were very similar for the two cultivars.     

Salinity tolerance in different cultivars of barley (Hordeum vulgare L.)

Seven barley(Hordeum vulgäre L.) cultivars tested varied greatly in their responses to root medium salinity (electrical conductivity of 3, 5, 10, 15 and 20 dS nr^-1)-lant growth was relatively more adversely affected than seed germination. Dry/fresh mass ratio increased at higher salinity levels in all barley cultivars indicating reduced water uptake. Higher K/Na ratio in plant shoots compared to that in the root medium solution indicated selective uptake of K that seems to be among processes involved in tolerance of cultivars to salinity stress.     

Effects of sodium chloride stress and calcium supply on growth, potassium uptake, and internal chloride and sodium levels of winter wheat seedlings

The effects of saline conditions on the K+ (86Rb), Na+ and Cl- uptake and growth of 6-day-old wheat (Triticum aestivum L. cv. GK Szeged) seedlings were studied in the absence and presence of Ca2+. It was found that on direct NaCl treatment the K+ uptake of the roots in the absence of Ca2+ declined significantly with increasing salinity. The reverse was true, however, in the case of NaCl pretreatment: seedlings grown under highly saline conditions (50 mM NaCl) absorbed more K+ than those pretreated with low levels of NaCl (1 or 10 mM NaCl). The data indicate a definite Na(+)-induced K+ uptake inhibition and/or feed-back regulation in the K+ uptake of roots under the above-mentioned growth conditions. As regards the Ca2+ effect, it was established that supplemental Ca2+ counteracts the unfavourable effect of saline conditions as concerns both the K+ uptake of the roots and the dry matter yield of the seedlings. The internal concentrations of Na+ and Cl- in the seedlings increased in proportion to increasing salinity. Marked differences were experienced, however, in the internal concentrations of Na+ and Cl- in the roots and shoots, respectively. It was concluded that under these experimental conditions the salt tolerance of wheat could be related to its capability of restricting the transport of Na+ at low and moderate levels to the shoots, where it is highly toxic.     

Proline accumulation by tomato leaf tissue in response to salinity

The capacity of tomato leaf tissues to accumulate proline in response to a salt shock (150 mM NaCl) applied to excised shoots, leaves, leaflets or leaf discs was determined and compared to that of whole plants grown at the same salinity. The associated changes in free amino acids, Na+, K+ and Cl- contents were also investigated. In excised organs treated for 80 h, up to 200 mumol g-1 DW of proline were accumulated, whereas the amount of proline in leaf discs did not exceed a value ten-fold lower. In the whole plants subjected to salinity the Na+, Cl- and K+ contents remained low in comparison to that observed in excised organs. Proline and other amino acids increased more slowly in whole plants than in excised shoots. The contribution of roots and vascular tissues to the control of Na+ and Cl- accumulation and to the regulation of proline metabolism are discussed.     

盐胁迫下柚和橘幼苗体内矿质元素变化的比较研究

采用沙培法,对盐胁迫下坪山柚和福橘幼苗体内矿质元素的变化进行了研究。结果表明,随着NaCl浓度的增加,坪山柚和福橘幼苗根部及地上部Na^＋、Cl-含量增加,且相同浓度下,福橘比坪山柚高。40mmol／L NaCI胁迫下,坪山柚和福橘幼苗地上部的K^＋、Fe含量,根部的Ca^2＋、Mg^2＋、Zn含量显著下降,而根部Fe含量及地上部Zn含量显著增加。随NaCl浓度增大,坪山柚根部K^＋含量,地上部Ca^2＋、Mg^2＋含量变化不明显,而福橘根部、地上部上述离子含量在NaCl浓度≥160mmol／L时均显著下降。因此,根部K^＋含量,地上部Ca^2＋、Mg^2＋含量存在品种问差异,或许可作为耐盐性鉴定指标。NaCl胁迫降低坪山柚和福橘幼苗根部及地上部P、Mn含量,而Cu含量在较高浓度NaCl胁迫下显著增加。NaCl胁迫明显降低坪山柚和福橘幼苗地上部K^＋／Na^＋、Ca^2＋／Na^＋和Mg^2＋／Na^＋值,其中K^＋／Na^＋值的变化可考虑作为柑橘耐盐性鉴定的指标。     

盐胁迫对弗吉尼亚栎生长及矿质离子吸收、运输和分配的影响

以低浓度(50 mmol.L-1)和高浓度(150 mmol.L-1)NaC l处理弗吉尼亚栎(Quercus virginiana)2年生扦插苗,研究了弗吉尼亚栎生长和根系形态学参数变化以及Na+、K+、Ca2+、Mg2+、NO3-等矿质离子在不同器官的吸收、运输和分配。结果表明,盐胁迫不同程度促进了地上部和根系生长,地上部和根系干重、根长、表面积和体积在低浓度盐胁迫下明显增加(P0.05),而在高浓度盐胁迫下变化不大。随着根系对Na+和C l-吸收的增加,K+、Ca2+、Mg2+在根部和茎部的积累明显降低,矿质离子由根部向茎部运输的能力在低浓度盐胁迫增加而高浓度下受到抑制。叶片在低浓度和高浓度盐胁迫下对K+、NO3-具有很强的选择吸收能力,这对于维持叶片离子平衡和正常的光合作用及代谢过程具有重要意义。Na+和C l-在根部的浓度远远大于地上部,说明弗吉尼亚栎根系对盐离子具有较高的耐受性,而减少盐离子在地上部的积累,对于维持地上部的正常生长具有重要意义,这也是弗吉尼亚栎对盐胁迫的适应机制之一。     

Salt tolerance in Aster tripolium L. II. Ionic regulation

Abstract Measurements of tissue ion contents (Na, K and Cl) were carried out at frequent intervals on plants of Aster tripolium L. grown at a range of salinities for 36 d. Aster tripolium behaved as a typical halophyte showing high levels of inorganic ion accumulation even at low salinities. As salinity increased Na replaced K to a large extent in the shoot but root K was unaffected up to 500 mol m^?3 external NaCl. Shoot (Na + K) concentration on a tissue water basis was maintained constant in all treatments throughout the experiment, whereas shoot (Na + K) on a dry weight basis showed marked fluctuations in some treatments. An increase in (Na + K) per gram dry weight was, however, accompanied by a parallel increase in fresh weight: dry weight (FW : DW) ratio. Transport of (Na + K) to the shoot per unit root weight changed during the experiment in the manner expected, given the observed changes in shoot relative growth rate and FW : DW to result in a constant shoot (Na + K) concentration on a water basis. Chloride was the major balancing anion in the shoot at high salinity, but never accounted for more than 38% of the (Na + K) found in the root tissue. At all salinities (Na + K) salts accounted for the majority of the measured shoot sap osmotic potential. The interactions between salinity, growth, ion transport and osmotic adjustment are discussed.     

Salinity tolerance of 'Valencia' orange trees on rootstocks with contrasting salt tolerance is not improved by moderate shade

The effects of shading in combination with salinity treatments were studied in citrus trees on two rootstocks with contrasting salt tolerance to determine if shading could reduce the negative effects of salinity stress. Well-nourished 2-year-old 'Valencia' orange trees grafted on Cleopatra mandarin (Cleo, relatively salt tolerant) or Carrizo citrange (Carr, relatively salt sensitive), were grown either under a 50% shade cloth or left unshaded in full sunlight. Half the trees received no salinity treatment and half were salinized with 50 mM Cl- during two 9 week salinity periods in the spring and autumn interrupted by an 11 week rainy period. The shade treatment reduced midday leaf temperature and leaf-to-air vapour pressure deficit regardless of salinity treatments. In non-salinized trees, shade increased midday CO2 assimilation rate (A(CO2)) and stomatal conductance, but had no effect on leaf transpiration (E(lf)). Shade also increased leaf chlorophyll and photosynthetic water use efficiency (A(CO2)/E(lf)) in leaves on both rootstocks and increased total plant dry weight in Cleo. The salinity treatment reduced leaf growth and leaf gas exchange parameters. Shade decreased Cl- concentrations in leaves of salinized Carr trees, but had no effect on leaf or root Cl- of trees on Cleo. There were no significant differences in leaf gas exchange parameters of shaded and unshaded salinized plants but the growth reduction from salinity stress was actually greater for shaded than for unshaded trees. Shaded trees on both rootstocks had higher leaf Na+ than unshaded trees after the first salinity period, and this shade-induced elevated leaf Na+ persisted after the second salinity period in trees on Carr. Thus, shading did not alleviate the negative effects of salinity on growth and Na+ accumulation.     

Response of tomato cultivars to salinity

The responses of five tomato cultivars (L. esculentum Mill) of different degrees of salt tolerance were examined over a range of 0 to 140 mM NaCl applied for 3 and 10 weeks. Judged by both Na and Cl accumulations and maintenance of K, Ca and Mg contents with increasing salinity, the most tolerant cultivars (Pera and GC-72) showed different responses. The greater salt tolerance of cv Pera was associated with a higher Cl and Na accumulation and a lower K content in the shoot than those found in the other cultivars, typical of a halophytic response to salinity. However, the greater salt tolerance of cv GC-72 was associated with a retention of Na and Cl in the root, restriction of their translocation to the shoot and maintenance of potassium selectivity under saline conditions. The salt tolerance mechanisms that operated in the remaining cultivars were similar to that of cv GC-72, as at first they excluded Na and Cl from the shoots, accumulating them in the roots; with longer treatment, the ability to regulate Na and Cl concentrations in the plant was lost only in the most salt sensitive cultivar (Volgogradskij), resulting in a massive influx of both ions into the shoot.The salt sensitivity of some tomato cultivars to salinity could be due to both the toxic effect of Na and Cl ions and nutritional imbalance induced by salinity, as plant growth was inversely correlated with Na and Cl contents and directly correlated with K and Ca contents. This study displays that there is not a single salt tolerance mechanism, since different physiological responses among tomato cultivars have been found.     

Lisianthus response to salinity stress

The effect of salinity on some morpho-physiological characteristics in lisianthus cultivars was investigated. Cultivars namely, Blue Picotee (C1), Champagne (C₂), Lime Green (C₃), and Pure White (C₄), were subjected to salt stress (0–60 mM NaCl) in a sand culture and their responses were measured. Our results showed that as a salinity level increased, growth parameters, relative water content, photosynthetic pigments, and gas-exchange characteristics decreased in all cultivars, while root fresh mass, root/shoot length ratio, electrolyte leakage, and a malondialdehyde content increased. However, the changes were less pronounced in C₃ and C₄ compared to C1 and C₂. The regression analysis of the relationship between salinity levels and seedling height or root/shoot length ratio defined two groups with different slope coefficients: C1 and C₂ as salt-sensitive cultivars and C₃ and C₄ as salt-tolerant cultivars. Shoot dry mass and leaf area tolerance indices were less affected by salinity in C₃ and C₄ compared to those in C1 and C₂. Further, C₃ and C₄ showed higher photosynthetic rates, greater stomatal conductances, and accumulated greater K+ and Ca2+ contents and K+/Na+ ratios in roots and shoots compared to those in C1 and C₂. The results suggests that C₃ and C₄ could be recommended as resistant cultivars due to maintaining higher growth, water balance, leaf gas exchange, ion compartmentalization, and lower lipid peroxidation in response to salinity compared to C1 and C₂.     

Relationship between xylem ion concentration and bean growth responses to short-term salinisation in spring and summer

Bean plants, Phaseolus vulgaris L. cv. Contender, were grown in the spring and summer seasons to study the relationship between xylem Na+/Cl-, transpiration rate, and salt tolerance. Eight-day-old seedlings were transplanted to 50% modified Hoagland solution with 1 mM NaCl. Four days after transfer, one of two treatments was applied: a control of 1 mM NaCl or a treatment of 25 mM NaCl every two days to reach a final treatment concentration of 75 mM NaCl. Plants were sampled on the fourth day after the final salt concentration was reached, eight days after the salinisation treatment began. Relative growth rate was 2.6-fold greater in summer than in spring. However, while no differences were found between treatments in spring, summer salt-treated plants had growth rates that were 31% lower than those of controls. In summer, CO2 assimilation, stomatal conductance, and transpiration rate of salinised plants declined with respect to controls. Leaf Na+ and trifoliolate leaf Cl- were higher in salt-treated plants in summer, although root Na+ was significantly higher in spring. Moreover, in summer salinity inhibited Ca2+ and K+ uptake and changed its distribution. Summer salt-treated plants had an average of 17-fold higher xylem Na+ during the daily cycle, while xylem Cl-, only in the afternoon, showed higher values (1.5-fold) compared to spring-grown plants. Our results suggest that the faster growth response to salt in summer-grown bean was at least partly due to an increase in xylem Na+ independent of the transpiration rate and possibly related to an increase in xylem Na+ influx or/and Na+ recirculation.     

Root structure and cellular chloride,sodium and potassium distribution in salinized grapevines

X-ray microanalysis was used to study the patterns of K+, Na+ and Cl- accumulation in salinized (25 mm NaCl) and non-salinized grapevine (Vitis) roots. The aim was to determine whether NaCl affects patterns of Cl- accumulation differentially in the roots of a Cl--excluding genotype and a non-excluding genotype. Two regions of fibrous roots were analysed: (1) a region 2-3 mm basipetal to the root tip; and (2) a region of the root 10-12 mm basipetal to the root tip where the outermost layer is the hypodermis. The ion contents of the hypodermis, cortex, endodermis and pericycle vacuoles were analysed. Data were also collected from the cytoplasm of the endodermal and pericycle cells. The analyses showed that the ion profiles of the hypodermis and the endodermis were significantly different from those of the cortex and pericycle. The hypodermis and endodermis had higher K+ and lower Na+ and Cl- than surrounding cells. Some changes due to salinity such as increased K+ concentrations in the hypodermis were also noted. Chloride concentrations did not differ between the genotypes in the hypodermis, across the cortex or in the endodermis, but were higher in the pericycle of the excluder in comparison with the non-excluding genotype. However, K+/Na+ ratios of the cortex and endodermis were higher in the excluder. The pericycle cells exhibited the greatest ability to sequester Na+ and Cl- in vacuoles. Overall the data show cell-type-specific ion accumulation patterns and small but significant differences were found between genotypes. The possibility that these accumulation patterns arise from differences in uptake properties of cell types and/or result from the spatial distribution of the cell types along the competing symplastic and apoplastic ion transport pathways across the root is discussed.     

Effect of salinity and temperature on germination, growth and ion relations of Panicum turgidum Forssk

Seed germination of Panicum turgidum was significantly affected by salinity levels, temperature and their interaction. Maximum germination was noted in the lowest saline media (25-50 mM) and distilled water at the temperature of 15-25 degrees C and 20-30 degrees C. Seeds germination was substantially delayed and reduced with an increase in NaCl to levels above 50mM. This trend was much pronounced under high levels of NaCl and incubation temperature. Low levels of NaCl (25-50 mM) stimulated shoot and root dry weights of P. turgidum seedlings. However, the highest NaCl levels (>100 mM) resulted in a significant decrease in shoot, root and total dry weights of seedlings. Intermediate degrees of temperature, 15-25 and 20-30 degrees C, resulted in a significant increase in biomass accumulation. The Na+ concentration in shoots and roots significantly increased as NaCl concentration increased. The K+ concentration in roots and K/Na ratio in shoots and roots was significantly reduced as salinity concentration increased. The K/Na ratio was greatly affected by higher NaCl concentration and incubation temperatures.     

Presowing Seed Treatment with Cytokinins and Its Effect on Growth, Photosynthetic Rate, Ionic Levels and Yield of Two Wheat Cultivars Differing in Salt Tolerance

The effects of presowing seed treatment with different concentrations of cytokinins （kinetin and benzylaminopurine; 100, 150, and 200 mg/L） on growth, photosynthetic capacity, and ion homeostasis were investigated in two spring wheat （Triticum aestivum L.） cultivars, namely MH-97 （salt sensitive） and Inqlab- 91 （salt tolerant）. Primed and non-primed seeds were sown in a field in which NaC1 salinity of 15 dS/m was developed. Of the different concentrations of priming agents tested, the effect of a moderate concentration of kinetin （150 mg/L） was very pronounced, particularly in improving growth and grain yield, in both cultivars. In addition, priming with kinetin alleviated the adverse effect of salt stress on gaseous exchange characteristics （net CO2 assimilation rate and water use efficiency） in both cultivars. Seed priming with a moderate concentration of kinetin also altered the pattern of accumulation of Na^＋ and Clˉ in the shoots, irrespective of the wheat cultivar, under conditions of salt stress. However, all other priming agents at the different concentrations tested did not show any consistent effect on ion levels, except hydropriming, which increased K^＋ levels in the shoots of both cultivars under salt stress. In conclusion, a moderate concentration of kinetin showed a consistent effect in altering the growth and grain yield of both wheat cultivars, which was related to the beneficial effects of kinetin priming on water use efficiency and photosynthetic rate under conditions of salt stress.     

NaCl胁迫对黄瓜幼苗体内K+、Na+和Cl-分布的影响

采用营养液水培,以2个耐盐性不同的黄瓜品种为材料,研究了不同浓度NaCl处理下幼苗植株体内K 、Na 和Cl-在器官间的区域化分布及其吸收和运输特性的变化。结果表明:NaCl胁迫下,黄瓜植株体内K 含量下降,Na 和Cl-含量升高,变化幅度随NaCl浓度的升高而增大;不同器官间,茎中Na 和Cl-含量最高,上位叶中Na 和Cl-含量最低、K 含量下降幅度最小。与耐盐性较弱的“津春2号”相比,耐盐性较强的“长春密刺”根向茎运输的SK,Na值较高,根系对Na 的截留作用较强,茎向上位叶运输的SK,Na和SCl,Na值均较高,叶片中K 含量下降幅度较小,K/Na和Cl/Na比值均较高,功能叶中盐分离子尤其是Na 积累较少,植株生物量较高。说明根系对Na 的截留能力较强且向上位叶运输Na 的选择性较低,是“长春密刺”耐盐性较强的主要原因之一。     

Colonization with arbuscular mycorrhizal fungi improves salinity tolerance of tomato (Solanum lycopersicum L.) plants

The purpose of this study was to investigate the mechanisms underlying alleviation of salt stress by mycorrhization. Solanum lycopersicum L. cultivars Behta and Piazar with different salinity tolerance were cultivated in soil without salt (EC?=?0.63 dSm^?1), with low (EC?=?5 dSm^?1), or high (EC?=?10 dSm^?1) salinity. Plants inoculated with the arbuscular mycorrhizal fungi Glomus intraradices (+AMF) were compared to non-inoculated plants (?AMF). Under salinity, AMF-mediated growth stimulation was higher in more salt tolerant Piazar than in sensitive Behta. Mycorrhization alleviated salt-induced reduction of P, Ca, and K uptake. Ca/Na and K/Na ratios were also better in +AMF. However, growth improvement by AMF was independent from plant P nutrition under high salinity. Mycorrhization improved the net assimilation rates through both elevating stomatal conductance and protecting photochemical processes of PSII against salinity. Higher activity of ROS scavenging enzymes was concomitant with lowering of H₂O_2, less lipid peroxidation, and higher proline in +AMF. Cultivar differences in growth responses to salinity and mycorrhization could be well explained by differences in ion balance, photochemistry, and gas exchange of leaves. Function of antioxidant defenses seemed responsible for different AMF-responsiveness of cultivars under salinity. In conclusion, AMF may protect plants against salinity by alleviating the salt-induced oxidative stress.     

Photosynthetic capacity is related to the cellular and subcellular partitioning of Na+, K+ and Cl- in salt-affected barley and durum wheat

The capacity of plants to tolerate high levels of salinity depends on the ability to exclude salt from the shoot, or to tolerate high concentrations of salt in the leaf (tissue tolerance). It is widely held that a major component of tissue tolerance is the capacity to compartmentalize salt into safe storage places such as vacuoles. This mechanism would avoid toxic effects of salt on photosynthesis and other key metabolic processes. To test this, the relationship between photosynthetic capacity and the cellular and subcellular distribution of Na+, K+ and Cl- was studied in salt-sensitive durum wheat (cv. Wollaroi) and salt-tolerant barley (cv. Franklin) seedlings grown in a range of salinity treatments. Photosynthetic capacity parameters (Vcmax, Jmax) of salt-stressed Wollaroi decreased at a lower leaf Na+ concentration than in Franklin. Vacuolar concentrations of Na+, K+ and Cl- in mesophyll and epidermal cells were measured using cryo-scanning electron microscopy (SEM) X-ray microanalysis. In both species, the vacuolar Na+ concentration was similar in mesophyll and epidermal cells, whereas K+ was at higher concentrations in the mesophyll, and Cl- higher in the epidermis. The calculated cytoplasmic Na+ concentration increased to higher concentrations with increasing bulk leaf Na+ concentration in Wollaroi compared to Franklin. Vacuolar K+ concentration was lower in the epidermal cells of Franklin than Wollaroi, resulting in higher cytoplasmic K+ concentrations and a higher K+ : Na+ ratio. This study indicated that the maintenance of photosynthetic capacity (and the resulting greater salt tolerance) at higher leaf Na+ levels of barley compared to durum wheat was associated with the maintenance of higher K+, lower Na+ and the resulting higher K+ : Na+ in the cytoplasm of mesophyll cells of barley.     

The Combined Effects of Salinity and Root Anoxia on Growth and Net Na+ and K+-accumulation in Zea mays Grown in Solution Culture

The effects of excess salinity and oxygen deficiency on growthand solute relations in Zea mays L. cv. Pioneer 3906 were examinedin greenhouse experiments. The roots of plants 14 d old growingin nutrient solution containing additions of NaCl in the range1.0–200 mol m^–3 were either exposed to a severedeficiency of O₂ by bubbling with nitrogen gas (N₂ treatment),or maintained with a supply of air (controls), for a periodof 1–7 d. The threshold NaCl concentration resulting inappreciable inhibition of leaf extension, and shoot f. wt gainin controls was between 10 and 25 mol m^–3. At 25 mol m^–3NaCl the ratio of Na+/K+ transported to shoots was about 20times greater than in plants in 1.0 mol m^–3 NaCl. Theeffect of addition of NaCl to the nutrient solution was to enhanceNa+ movement but simultaneously depress the rate of K+ transportto shoots (per g f. wt roots). Interactions between NaCl levels and aeration treatment wereshown by analyses of variance to be statistically significantfor leaf extension, shoot and root f. wt gains, Na+ and K+ concentrationsin shoots and roots. When roots were N₂-treated, shoot and rootgrowth were depressed, the effect of aeration treatment beinggreatest at NaCl concentrations of 50 mol m^–3 or less.Additionally, N₂-treatment greatly accelerated Na- transportto shoots while depressing K+ transport still further, so thatat 10 mol m^–3 NaCl the ratio Na+/K+ acquired by the shootswas 230 times greater than in controls. Over the concentrationrange 1.0 to 50 mol m^–3 NaCl, the ratio Na+/K+ transportedto shoots by anoxic roots increased by a factor of 860. Mechanisms controlling changes in solute flux to the shoot,and the significance in relation to plant tolerance of excesssalts or oxygen deficiency are discussed. Anaerobic, corn, flooding, maize, oxygen-deficiency, salinity     

The cyclic nucleotide-gated channel, AtCNGC10, influences salt tolerance in Arabidopsis

Cyclic nucleotide-gated channels (CNGCs) in the plasma membrane transport K+ and other cations; however, their roles in the response and adaptation of plants to environmental salinity are unclear. Growth, cation contents, salt tolerance and K+ fluxes were assessed in wild-type and two AtCNGC10 antisense lines (A2 and A3) of Arabidopsis thaliana (L.) Heynh. Compared with the wild-type, mature plants of both antisense lines had altered K+ and Na+ concentrations in shoots and were more sensitive to salt stress, as assessed by biomass and Chl fluorescence. The shoots of A2 and A3 plants contained higher Na+ concentrations and significantly higher Na+/K+ ratios compared with wild-type, whereas roots contained higher K+ concentrations and lower Na+/K+ ratios. Four-day-old seedlings of both antisense lines exposed to salt stress had smaller Na+/K+ ratios and longer roots than the wild-type. Under sudden salt treatment, the Na+ efflux was higher and the K+ efflux was smaller in the antisense lines, indicating that AtCNGC10 might function as a channel providing Na+ influx and K+ efflux at the root/soil interface. We conclude that the AtCNGC10 channel is involved in Na+ and K+ transport during cation uptake in roots and in long-distance transport, such as phloem loading and/or xylem retrieval. Mature A2 and A3 plants became more salt sensitive than wild-type plants because of impaired photosynthesis induced by a higher Na+ concentration in the leaves.