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1.
Olive (Olea europaea L cv. Leccino and cv. Frantoio) plants grown in aeroponic cultivation system were supplied with Hoagland solutions containing 0 and 150 mM NaCl for 4 weeks. Sodium (Na+), chloride (Cl‐), and potassium (K+) concentration was measued on 15‐day‐old leaves and K+/Na+ selectivity ratio was calculated. Plant water relations were estimated on the same leaves by measuring leaf bulk water and osmotic potentials, and by calculating leaf turgor pressure. Root and leaf tissues were also analysed for lipid composition, estimating free sterol (FS), glycolipid (GL) and phospholipd (PL) content. The salt‐sensitive Leccino accumulated more Na+ and Cl‐ in the leaves and showed a lower K+/Na+ selectivity ratio than the salt‐tolerant Frantoio. The FS/PL ratio and the content of GL (namely mono‐galactosyldiglyceride, MGDG) in the roots were related to the salt accumulation in the shoot. Salinity‐induced changes on root lipids were more important in Frantoio than in Leccino, indicating the specific role of the roots in salt exclusion mechanisms. Conversely the effect of salinity on leaf lipid composition was more important in the leaves of the salt‐sensitive Leccino.  相似文献   

2.
To invertigate the relationship between salt tolerance and plant mineral status in celery (Apium graveolens L.) growth and the concentration of nitrogen (N), phosphorus (P), potassium (K), calcium (Ca), sodium (Na), and chloride (Cl) in different tissues were determined in plants grown in hydroculture with nutrient solutions containing 5 (control), 50,100, and 300 mM sodium chloride (NaCl) for four weeks. At salinity levels of 50 and 100 mM NaCl, there was a moderate, albeit significantly, reduction of growth, while a drastic decrease in both fresh and dry weight was obtained at 300 mM NaCl. Regardless of the salinity level, growth resumed promptly and completely once the stress was ceased. Sodium chloride stress reduced the accumulation of nitrate (NO3)‐N in all plant tissues, but there were no relevant effects on the concentration of reduced N and P. The concentration of K in roots and leaf petioles was unaffected by NaCl treatment, but it gradually declined with increasing salinity in leaf blades. This reduction was less pronounced in the young leaves as compared to the mature ones. Increasing the NaCl concentration decreased the concentration of Ca in all tissues, but it prevented the occurrence of black‐heart, a typical Ca‐related physiological disorder which affected severely the controls. Salt‐stressed plants absorbed large amounts of Na and Cl which accumulated in the mature leaves, particularly in the oldest leaves. These findings suggest that the relatively high salt tolerance of celery relies on the ability to maintain an adequate nutritional status and to protect the shoot meristem from salt toxicity.  相似文献   

3.
Olive trees (Olea europaea L.) are considered moderately tolerant to salinity, with clear differences found among cultivars. One‐year‐old self‐rooted olive plants of the Croatian cv. Oblica and Italian cv. Leccino were grown for 90 d in nutrient solutions containing 0, 66, or 166 mM NaCl, respectively. The shoot length and the number of nodes and leaves for both cultivars were not affected by salinity up to 66 mM NaCl. However, at 166 mM NaCl, growth of Leccino was reduced earlier and to a higher extent than growth of Oblica. After 10 d of exposure to 66 and 166 mM NaCl, increased activity of superoxide dismutase (SOD) was observed in Leccino, whereas there was almost no response in Oblica. Reduced SOD activity in Leccino at 166 mM NaCl was observed after prolonged stress (90 d), whereas in Oblica SOD was increased at 66 mM compared to control or 166 mM NaCl. Electrolyte and K+ leakage were increased and relative water content decreased as NaCl concentration increased with similar intensity of response measured in both cultivars. Oblica exhibited an ability to keep a higher K+ : Na+ ratio at all salinity levels compared to Leccino, but since no difference was found in leaf K+ concentration, this was mainly achieved by less Na+ ions reaching the younger leaves. The antioxidative system represents a component of the complex olive salt‐tolerance mechanism, and it seems that the role of SOD in protection from oxidative stress depends on sodium accumulation in leaves.  相似文献   

4.
Pepper (Capsicum annuum L.) plants grown in pots were irrigated with the nutrient solutions containing 50, 75, and 100 mM NaCl or a control solution. Salinity markedly decreased plant growth. Increasing salinity levels increased stomatal resistance and sodium (Na), chloride (Cl), proline contents of the plants. Potassium (K), total‐nitrogen (N), and chlorophyll content of the plants were decreased under high salinity conditions.  相似文献   

5.
Two pairs of contrasting rice genotypes, each pair having similar general characteristics but differing in their tolerance to salt, were compared in short‐term experiments of NaCl absorption and translocation in intact plants. At low external NaCl concentration (0.1 mM), the absorption of Na was passive with a constant net influx rate (In), while the absorption of Cl was an active process obeying Michaelis‐Menten kinetics. At both low and high external NaCl concentrations (0.1 and 50 mM), salt‐tolerant ‘Pokkali’ had significantly lower rates of Na and Cl absorption than did salt‐sensitive ‘Peta’, although another moderately salt‐tolerant genotype, ‘IR 29725–25–22–3‐3–3’, did not differ from its salt‐sensitive counterpart, ‘IR 5’. For both pairs of the plants, translocation rates of Na and Cl were significantly lower in the salt‐tolerant genotypes than in the salt‐sensitive ones. It was concluded that exclusion of Na and/or Cl from the shoots may involve both absorption and translocation components of regulation. For relatively salt‐tolerant genotypes, a better regulation of either or both of the two components results in lower Na and/or Cl contents in the shoots, leading to a higher degree of salt tolerance.  相似文献   

6.
Salinity is a major problem in a wide pomegranate-growing area of central Iran. Effects of four levels of salinity on leaf and root chlorine (Cl), sodium (Na), and potassium (K) partitioning and shoot growth in three major commercial cultivars of pomegranate (Punica granatum), namely ‘Alak Torsh,’ ‘Malas Torsh,’ and ‘Malas Shirin,’ under climatic conditions of central Iran were investigated. Pomegranate cuttings were rooted and planted in plastic pots containing 1:1 sand:perlite medium and irrigated immediately with complete Hoagland's solution immediately. Four salinity levels of irrigation water (0, 40, 80, and 120 mM NaCl) were used. Final concentrations of NaCl were achieved after three weeks and continued for 80 d. Growth characteristics (i.e., length of the main stem, length and number of internodes, and leaf surface) were measured during the experiment. At harvest, concentrations of Na, K, and Cl in root and apical and basal leaves of the three cultivars were determined separately. In ‘Malas Torsh’ and ‘Alak Torsh’ cultivars, increasing salinity was proportional to NaCl concentration and reduced the length of stem, the length and number of the internodes, and leaf surface. There was an increase in the growth rate of the ‘Malas Shirin’ cultivar with increasing salinity up to 40 mM, but a decline in growth rate occurred at salinity levels higher than 40 mM. With increasing salinity level, the tissue concentration of Na and Cl increased while the K/Na ratio decreased. No significant differences were observed among the three cultivars in Na, Cl, and K concentrations of roots or apical or basal leaves. These results show that ‘Malas Shirin’ grew better under saline conditions compared with the ‘Malas Torsh’ and ‘Alak Torsh’ cultivars.  相似文献   

7.
Results of several studies show interactive effects of salinity and macronutrients on the growth of wheat plants. These effects may be associated with the nutrient status in plant tissues. The objective of this study was to investigate interactive effects of salinity and macronutrients on mineral element concentrations in leaves, stems, and grain of spring wheat (Triticum aestivum L. cv. Lona), grown in hydroponics, and the relation of these effects to yield components. Eight salinity levels were established from 0 to 150 mM NaCl, and 1, 0.2, and 0.04 strength Hoagland macronutrient solution (x HS) were used as the macronutrient levels. Sodium (Na), potassium (K), calcium (Ca), magnesium (Mg), chlorine (Cl), and phosphorus (P) in leaves, stems, and grain, NO3 in leaves and stems, and total nitrogen (N) in grain were determined. Supplemental Ca, Mg, K, and NO3 added to 0.2 x HS increased mineral concentrations in leaves and stems, but did not improve growth or yield in salinized wheat plants except moderately at 100–150 mM NaCl. In contrast, growth or yield was improved significantly when the concentration of macronutrients was increased from 0.04 to 0.2 × HS. In contrast to leaves and stems, mineral concentrations in grain increased (Na, Cl) or decreased (Ca, Mg, K) only slightly or were not affected (K) by salinity except at high salinity and low macronutrient level. Nitrogen and P concentrations in grain were not affected by salinity. Sodium and Cl concentrations in leaves and stems increased significantly, whereas K and NO3 decreased significantly, with an increase in salinity regardless of the macronutrient level. The latter was also observed for Ca and Mg in leaves. Extreme Na/Ca ratios in plant tissues negatively affected grain yield production at high salinity with medium or high macronutrient levels and at low macronutrient level together with medium salinity. Even though strong and significant correlations between mineral concentration at grain maturity in leaves, stems, and grain and various yield parameters were observed, our results are inconclusive as to whether toxicity, nutrient imbalance, nutrient deficiency, or all of these factors had a strong influence on grain yield.  相似文献   

8.
The absorption and transport of Na and Cl from 0.1 mM and 10 mM 22Na labelled NaCl or 36Cl labelled KCl were examined in 15 days old seedlings of 3 cultivars of rice differing in their tolerance to salinity. Furthermore, the effects of 10, 100 and 1000 ppm (N)2S on their uptake were studied. It was found that in general, the salt‐tolerant cultivars BR and PNL‐1 absorbed more Na and translocated a lesser proportion of it to the shoot, compared to the salt‐sensitive IR‐8, from 0.1 mM NaCl. The presence of (N)2S reduced the uptake of Na in all the cultivars. It was also found that the presence of 100 ppm K, KN or NNreduced Na absorption from 0.1 mM NaCl significantly in all the cultivars, and the translocation to shoot in BR‐ Chloride transport from 0.1 mM NaCl was reduced by (N)2S in all the cultivars. The 3 cultivars differed significantly in the rates of absorption and transport of Na and Cl. The results indicate that PNL‐1 which is a cross of IR‐8 X BR, has inherited the salt tolerance trait from BR. Lower rates of Na translocation to the shoot can be used as an index of salt tolerance in rice.  相似文献   

9.
Abstract

Five tomato (Lycopersicon esculentum Mill) cultivars were grown in sand nutrient culture experiment in a greenhouse to investigate the effects of salinity on growth and yield. Nutrient solutions were made saline with 50 mM NaCl (EC = 5.5 mS/cm or supplemented with 2 mM KNO3 (EC = 6.8), 20 mM Ca(NO3)2 (EC = 7.5), and combination of potassium (K) and calcium (Ca) (EC = 8.0). Seedlings were irrigated with saline treatments commencing two weeks after transplanting. Determination of sodium (Na) and K in tomato leaves and fruits were by flame photometry. Accumulation of Na in tomato fruits was higher than in leaves under control or saline conditions for all tomato cultivars. The amount of K in the tomato leaves was higher in control than in saline‐grown plants. Addition of K and Ca to the nutrient solution resulted in a 3 to 7 fold increase in K accumulation in all cultivars tested. Stem and leaf growth were significantly reduced with salinity but growth was enhanced following irrigation when K was added to the nutrient solution. Flowering and fruit set were adversely affected by NaCl stress. Reduction of flower number was 44% relative to the control plants. Fresh fruit yield decreased by 78% when plants received 50 mM NaCl. Growth and development of tomatoes under saline conditions was enhanced in this study following the application of K to the saline nutrient solution. Amelioration in growth was also achieved when Ca was used but to a lesser extent. Our results suggest that ion accumulation and regulation of K and Ca contribute to salt tolerance and growth enhancement.  相似文献   

10.
Abstract

Salinity affects plants by interaction between sodium (Na) and calcium (Ca). Two sorghum (Sorghum bicolor) genotypes ('Hegari’ and ‘NB‐9040') were studied for the Na x Ca interaction in a soil amended with 2% calcium carbonate (CaCO3) and with 0, 12.3, 24.6, and 36.9 mmol sodium chloride (NaCl)/kg soil. The two genotypes were similar in their response to soil NaCl in their shoot and root growth but differed in response to lime. The salinity‐tolerant Hegari was suppressed by high Ca concentration in the soil, mainly in the low‐NaCl treatments, and responded by a lower concentration of potassium (K) and magnesium (Mg) in the leaves, which was associated with leaf‐chlorosis. Since Na uptake was reduced by Ca, the main effect of salinity on plant growth was by the accumulation of chloride (Cl) in the leaves.  相似文献   

11.
The influx and partitioning of sodium (Na) is controlled by potassium (K)/Na selectivity/exchange mechanisms. Since ammonium‐nitrogen (NH4‐N) has been shown to inhibit K absorption and K/Na selectivity/exchange mechanisms control Na influx and partitioning, our objective was to observe if NH4‐N affects Na influx and partitioning in muskmelon. Muskmelon (Cucumis melo L.) were grown in a pH controlled nutrient solution with 100 mM NaCl in a complete nutrient solution containing either 10 mM nitrate‐nitrogen (NO3‐N) or NH4‐N. With NH4‐N, Na accumulation and partitioning to the leaf blade increased while K absorption was almost completely inhibited. A second study omitted K to simulate the inhibition of K absorption by NH4‐N and monitored Na accumulation and partitioning as K was depleted in the plant. Sodium accumulation and partitioning to the leaf increased as K decreased in the plant, mirroring the effect of NH4‐N. Roots appeared healthy in both studies. Our work indicates that at a given level of NaCl stress, NO3‐N reduces the level of stress experienced by muskmelon plants through reducing the net rate of Na influx and transport to the sensitive leaf blade, not by reducing chloride (Cl) absorption, thereby permitting these plants to “avoid”; this stress.  相似文献   

12.
□ Growth and nutrient acquisition of tomato (Lycopersicon esculentum L.) cv ‘Amani’ were studied under induced salt stress in Hoagland's solution. The plants were treated for 37 days with salinity induced by incorporating different concentrations [0.0 (control), 50, 100, 150, or 200 mM] of sodium chloride (NaCl) to the nutrient solution. Slight reduction was obtained in growth represented by (shoot length and number, leaf number, and dry weight) when seedlings were directly exposed to NaCl stress from 0.0 to 100 mM. At higher concentrations (150 or 200 mM), growth parameters were adversely affected and seedlings died thereafter. Elevated salinity significantly reduced crude protein and fiber in shoots and roots. Tomato shoot and root contents of potassium (K), iron (Fe), and ash were reduced significantly in response to increased levels of salinity. Tissue contents of sodium (Na) and chloride (Cl) increased with elevated salinity treatments.  相似文献   

13.
The shoot and root growth response of three species of Sesbania to 0, 50 and 100 mM NaCl in a hydroponic culture was studied. Absorption and translocation of Na and Cl in 15 day old seedlings were studied using 22Na and 36Cl labelled NaCl. Shoot growth was significantly reduced at 100 mM NaCl in the nutrient solution for all three species. The salt tolerance of the three species was in the order S. rostrata > S. aculeata > S. speciosa. The transport of Na to stem and leaf was less compared to uptake in S. rostrata but greater proportion of the absorbed Cl was translocated to the shoot. Salinity reduced the nitrogen content in root and stem significantly.  相似文献   

14.
The element contents in the compartments of root and leaf cells of soybean and cucumber plants grown for 8 d in a nutrient solution containing 50 mM NaCl, 25 mM CaCl2 or 50 mM NaCl+4.75 mM CaSO4 were examined by X-ray microanalysis of freeze-substituted dry sections. Sodium accumulated in the vacuoles rather than in the cytoplasm and apoplastic space in the root cells of the soybean plants, leading to the difficulty in the transport of Na to leaves in soybean. Salt injury of soybean is considered to be caused by the accumulation of Cl at high concentrations in all the compartments of root and leaf cells. In contrast, the accumulation of Na in the cytoplasm of the root and leaf cells might disturb the metabolism and lead to the occurrence of salt toxicity in cucumber plants, which are tolerant to Cl due to the stimulation of Cl accumulation in vacuoles when the Ca concentration was high in nutrient media.  相似文献   

15.
The element contents in the compartments of root and leaf cells of soybean and cucumber plants grown for 8 d in a nutrient solution containing 50 mM NaCl, 25 mM CaCl2 or 50 mM NaCl+4.75 mM CaSO4 were examined by X-ray microanalysis of freeze-substituted dry sections. Sodium accumulated in the vacuoles rather than in the cytoplasm and apoplastic space in the root cells of the soybean plants, leading to the difficulty in the transport of Na to leaves in soybean. Salt injury of soybean is considered to be caused by the accumulation of Cl at high concentrations in all the compartments of root and leaf cells. In contrast, the accumulation of Na in the cytoplasm of the root and leaf cells might disturb the metabolism and lead to the occurrence of salt toxicity in cucumber plants, which are tolerant to Cl due to the stimulation of Cl accumulation in vacuoles when the Ca concentration was high in nutrient media.  相似文献   

16.
Two lines of alfalfa (Medicago sativa L.), a salt‐tolerant AZ‐Germ Salt II and a salt‐sensitive Mesa Sirsa, were grown for three weeks in solution culture containing 0 or 100 mol/m3 sodium chloride (NaCl) in half‐strength Hoagland nutrient solution. Distribution of cations and chloride (Cl) in the leaves of varying ages was determined. The older leaves (age‐dependent) of both lines contained more sodium (Na) in the laminae and petioles than the younger leaves at the salt treatment, whereas the reverse was true for potassium (K) in the laminae. Age‐dependent Cl distribution was only found in the laminae of AZ‐Germ Salt II. Distribution of calcium (Ca) in the lamina and petioles was strongly age‐dependent in both lines, but such a pattern was not found for magnesium (Mg) concentrations. AZ‐Germ Salt II accumulated considerably higher concen‐ trations of Na and Cl in the laminae compared with Mesa Sirsa. The lower Na and Cl concentrations in the laminae of Mesa Sirsa were due to relatively higher accumulation of these ions in the stems. It is concluded that distribution of Na, Cl, and Ca in the leaf laminae is age dependent. Salt tolerance in alfalfa is related to inclusion of Na and Cl in the leaf laminae.  相似文献   

17.
Salt toxicity comprises of osmotic and ionic components both of which can severely affect root and shoot growth. In many crop species, supplemental calcium (Ca) reduces the inhibition of growth typical of exposure to salt stress. The objective of this study was to compare whole plant growth and physiological responses to interactive effect of salinity and Ca level on three forage species [African millet (AM), tall wheat grass (TW), and perennial ryegrass (PR)] differing in tolerance to sodium chloride (NaCl) salinity. Plants were grown under glasshouse condition and supplied with nutrient solution containing 0, 100, and 250 mM NaCl supplemented with 0.5, 5, or 10 mM calcium chloride (CaCl2). Plant growth, ionic concentration, water relations, and solute (proline and glycinebetaine) concentrations of the plants were determined two weeks after the salinity treatments. At 100 mM NaCl, there was a moderate reduction in dry matter (DM) production of all three species. A drastic decrease in DM occurred at 250 mM NaCl. Supplemental Ca reduced the adverse effects of salinity on all three species. The TW showed higher shoot and root growth in 100 and 250 mM NaCl than AM and PR. It also showed the highest DM at 5 and 10 mM Ca supplement. The shoot and root DM of TW increased by about 45 and 15%, respectively compared to the control. Chemical analysis indicated that in TW, Ca restricted both uptake and transport of sodium (Na) from root to shoot. It also increased Ca and potassium (K) concentrations in both organs. The transport of K and Ca from root to shoot of AM and PR were decreased by NaCl, but were restored with increasing Ca in the medium. The opposite occurred for Na. In PR, more K uptake was observed in shoot at 250 mM NaCl with 10 mM Ca supplement. The sap osmotic potential (ΨS) was the highest in TW at 10 mM Ca in the presence of 250 mM NaCl. Contribution of various solutes to the difference in ΨS among the species from the control and 250 mM salt treatment differed greatly. Supplemental Ca induced decline in the leaf ΨS of TW which was predominately due to K, glycinebetaine, Na and proline accumulation. Addition of 10 mM Ca to the growth medium maintained a low Na and a high K level. Accumulation of glycinebetaine and proline in leaf contributed the NaCl tolerance of TW. The presented results suggest that supplement Ca, not only improved ionic relations but also induced plant ability in production of compatible solutes (glycinebetaine and proline) and osmotic adjustment. Accordingly, genotype dependent capacity could be found using supplemental Ca.  相似文献   

18.
Plant growth promoting effects of Bacillus subtilis EY2, Bacillus atrophaeus EY6, Bacillus spharicus GC subgroup B EY30, Staphylococcus kloosii EY37 and Kocuria erythromyxa EY43 were tested on strawberry cv. ‘Fern’ in terms of fruit yield, growth, chlorophyll reading value, leaf relative water content (LRWC), membrane permeability and ionic composition of leaves and roots under saline conditions. Compared with 0 mM sodium chloride (NaCl) treatment, the average decrease of yield and LRWC were 51.6% and 21.0%, respectively, when 35 mM NaCl was applied. However, EY30, EY37, and EY43 treatments under saline condition (35 mM NaCl) significantly increased fruit yield (54.4%, 51.7% and 94.9%) compared with 35 mM NaCl treatment without plant growth promoting bacteria (PGPB). The LRWC increased from 72.0% in 35 mM NaCl treatment to 88.4%, 86.6%, 84.2%, 83.5%, and 86.2% by EY2, EY6, EY30, EY37, and EY43 applications, respectively. The lowest membrane permeability among the bacterial strains was obtained from EY37 treatment (37) while it was 33 and 58 in 0 mM NaCl and 35 mM NaCl treatments, respectively. The concentration of all plant tissue nutrients investigated [nitrogen (N), phosphorus (P), potassium (K), calcium (Ca), and magnesium (Mg)] with the exception of root phosphorus (P) and Mg concentration significantly decreased with 35 mM salt treatment. Nitrogen content of leaves varied between 3.04 and 3.14% in bacterial treatments under saline conditions while it was 2.71% in 35 mM NaCl treatment. In contrast sodium (Na) and chloride (Cl) of leaves and Cl content of roots were significantly decreased by root inoculation with all bacterial treatments in comparison to 35 mM NaCl treatment with no inoculation. Treatment with Bacillus EY30, Staphylococcus EY37 and Kocuria EY43 to strawberry plants can ameliorative the deleterious effect of salt stress on fruit yield, growth and nutrition. These results demonstrate that PGPB treatment could be offer an economic and simple means to increased plant resistance for salinity stress.  相似文献   

19.
A sand culture experiment was conducted to study the effect of saline water on the growth and fruit quality of processing tomato (Lycopersicon esculentum Mill.) Seedlings of five tomato cultivars were transplanted in quartz‐sand pots in a greenhouse at the Agricultural Experiment Station of Sultan Qaboos University. There were four saline nutrient solutions and a control consisting of half‐strength Hoagland solution. Salinity treatments were: 50 raM NaCl + 3 mM K2SO4 (EC 6.75), 50 mM NaCl + 1.5 mM orthophosphoric acid (EC = 7.18), 50 mM NaCl + 1.5 mM orthophosphoric acid + 3 mM R2SO4 (EC 7.29), and 50 mM NaCL (EC = 5.6). Treatments were applied daily commencing two weeks after transplanting. Data were collected on growth, and fruit yield and quality. Partitioning of mineral elements was determined in the vegetative tissue. The results obtained clearly show that concentrations of total soluble solids were increased in fruits treated with saline nutrients. Dry matter content of fruits exposed to salinity were higher than those from the control plants. Fruit acidity was increased with salinity, possibly due to a lower water content and increased organic acid accumulation. In the saline treatments, sodium (Na) content was decreased when potassium (K) was applied with NaCl but Na was higher in stems followed by root and leaf tissues. The partitioning of K followed a trend opposite to that for Na but with higher content in leaves. A similar situation was observed for calcium (Ca) and magnesium (Mg). Accumulation of phosphorus (P) was the lowest among all the ions. These results indicated that survival under saline conditions was accompanied by high ion accumulation. The study confirmed that saline nutrients are important for improving fruit quality of processing tomatoes.  相似文献   

20.
Abstract

Due to the discrepancy in metabolic sodium (Na) requirements between plants and animals, cycling of Na between humans and plants is limited and critical to the proper functioning of bio‐regenerative life support systems, being considered for long‐term human habitats in space (e.g., Martian bases). This study was conducted to determine the effects of limited potassium (K) on growth, Na uptake, photosynthesis, ionic partitioning, and water relations of red‐beet (Beta vulgaris L. ssp. vulgaris) under moderate Na‐saline conditions. Two cultivars, Klein Bol, and Ruby Queen were grown for 42 days in a growth chamber using a re‐circulating nutrient film technique where the supplied K levels were 5.0, 1.25, 0.25, and 0.10 mM in a modified half‐strength Hoagland solution salinized with 50 mM NaCl. Reducing K levels from 5.0 to 0.10 mM quadrupled the Na uptake, and lamina Na levels reached ‐20 g kg?1 dwt. Lamina K levels decreased from ‐60 g kg?1 dwt at 5.0 mM K to ‐4.0 g kg?1 dwt at 0.10 mM K. Ruby Queen and Klein Bol responded differently to these changes in Na and K status. Klein Bol showed a linear decline in dry matter production with a decrease in available K, whereas for cv. Ruby Queen, growth was stimulated at 1.25 mM K and relatively insensitive to a further decreases of K down to 0.10 mM. Leaf glycinebetaine levels showed no significant response to the changing K treatments. Leaf relative water content and osmotic potential were significantly higher for both cultivars at low‐K treatments. Leaf chlorophyll levels were significantly decreased at low‐K treatments, but leaf photosynthetic rates showed no significant difference. No substantial changes were observed in the total cation concentration of plant tissues despite major shifts in the relative Na and K uptake at various K levels. Sodium accounted for 90% of the total cation uptake at the low K levels, and thus Na was likely replacing K in osmotic functions without negatively affecting the plant water status, or growth. Our results also suggest that cv. Ruby Queen can tolerate a much higher Na tissue concentration than cv. Klein Bol before there is any growth reduction.  相似文献   

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