Salinity tolerance of citrus rootstocks: Effects of salt on root and leaf mineral concentrations

The effects of three concentrations of sodium chloride (NaCl) on seven citrus rootstocks were studied under greenhouse conditions. Leaf and root mineral concentrations and seedling growth were measured. Sodium chloride was added to the nutrient solution to achieve final osmotic potentials of –0.10, –0.20, and –0.35 MPa. Increasing the concentration of NaCl in the nutrition solution reduced growth proportionally and altered leaf and root mineral concentrations of all rootstocks. Significant differences in leaf and root mineral concentration among rootstocks were also found under stressed and non-stressed conditions. Salinity caused the greatest growth reduction in Milam lemon and trifoliate orange and the least reduction in sour orange and Cleopatra mandarin. No specific nutrient deficiency was the sole factor reducing growth and causing injury to citrus rootstocks. Sodium chloride sensitivity of citrus rootstocks in terms of leaf burn symptoms and growth reduction could be attributed more to Cl than to Na. Sodium and Cl concentrations were greater in the leaves than in the roots, particularly at the medium and high salinity levels. Root Cl was not useful for assessing injury because no differences were found in root Cl concentrations among rootstocks. Increasing salinity level did not affect the level of N and Ca in the roots but did reduce N and Ca levels in the leaves. No relationship in mineral concentration or accumulation seemed to exist between citrus leaves and roots. At the –0.10 MPa salinity level, sour orange, rough lemon, and Milam were not able to exclude either Na or Cl from their leaves. Trifoliate orange and its two hybrids (Swingle citrumelo and Carrizo citrange) excluded Na at the lowest salt level used, but were unable to exclude Na at the higher salinity levels. Similarly, Cleopatra mandarin excluded Cl at the lowest salt level, but was not able to exclude Cl at higher salt concentrations. Hence, the ability of citrus rootstocks to exclude Na or Cl breaks down at higher salt concentrations.Florida Agricultural Experiment Station Journal Series No. R-02276.     

叶片淋洗对NaCl胁迫下玉米生长和矿质营养的影响

研究了叶片淋洗对NaCl胁迫下玉米生长和体内矿质营养含量的影响 .结果表明 ,无盐或低盐浓度下(0、5 0mmol·L-1) ,淋洗处理与对照的生物量没有差异 ,高盐浓度下 (10 0、2 0 0mmol·L-1) ,淋洗处理的生物量提高 ,pH3 .5淋洗液的淋洗效果好于 pH 7.0 .无盐胁迫时 ,淋洗处理的茎叶K含量高于对照 ,2 0 0mmol·L-1盐胁迫时则低于对照 ;在高盐胁迫时 ,淋洗处理的茎叶Na含量低于对照 ;无盐胁迫时 ,淋洗处理茎叶中Ca、Mg含量高于对照 .根系K、Na、Ca、Mg含量以及植株相对水分含量在淋洗和对照之间基本无明显差别 ,说明淋洗可以减轻中高度盐胁迫下玉米植株的受害程度 ,其原因与淋洗降低茎叶中Na含量有关 .     

Effect of salinity on growth, ion content and CO2 assimilation rate in lemon varieties on different rootstocks

Citrus rootstocks as well as lemon scions differ in their ability to restrict sodium and chloride ions and in their sensitivity to saline stress. To determine the behaviour of different rootstock-scion combinations, 3 lemon cultivars on 3 different rootstocks were grown in containers in a greenhouse and irrigated with 5, 25 and 50 m M NaCl. Growth of the plants and foliar contents of sodium and chloride as well as physiological parameters including transpiration rate, gas exchange, stomatal conductance and chlorophyll content were evaluated. Shoot length of the plants on sour orange and on C. volkameriana showed a greater reduction with salinity than those on C. macrophylla . Accumulation of salt in the leaves was also scion dependent, cv. 'Eureka' having higher concentrations of sodium and chloride than the others. Assimilation rate of CO₂ and stomatal conductance were greatly reduced by salinity in the leaves of Verna and Eureka on sour orange. Gas exchange in the leaves was highly correlated with chloride and sodium contents in all lemon-rootstock combinations. C. macrophylla showed a higher resistance to salinity than C. volkameriana and sour orange. Inferences on the mechanisms of action of salt on lemon trees are discussed.     

Comparing morphological plasticity of root orders in slow- and fast-growing citrus rootstocks supplied with different nitrate levels

BACKGROUND AND AIMS: Studies of the plasticity of functional root traits involved in resource acquisition have focused mainly on root length without considering such 'morphological components' as biomass allocation, specific root length, root fineness, and tissue density that affect root length. The plasticity of the above components in response to nitrate supply was studied in each root order of two co-generic citrus rootstocks, namely the fast-growing Citrus jambhiri 'Rough Lemon' (RL) and the slow-growing Citrus reshni 'Cleopatra Mandarin' (CM). METHODS: Morphological traits of individual root orders of CM and RL, grown at different nitrate levels (NO(3)-N at 0.1, 0.5, 1 and 10 mm) were examined by using an image-specific analysis system. KEY RESULTS: At high nitrate levels, the root length ratio, root mass ratio and, to a lesser degree, specific root length, root fineness and tissue density of tap and 1st-order laterals in both CM and RL were reduced. In 2nd-order laterals, however, the same treatment led to increased values of each morphological trait in CM but decreased values of the same traits in RL. At low nitrate supply, CM exhibited longer tap roots whereas RL developed longer 2nd-order laterals. These effects were due to root mass ratio and, to a lesser extent, specific root length. CONCLUSIONS: Biomass allocation was the main component of nitrate-induced changes in root length ratio. The 2nd-order laterals were more sensitive to nitrate availability than the tap root and 1st-order laterals. At low nitrate availability, RL displayed longer 2nd-order lateral roots and lower root plasticity than CM. This suggests a different root growth strategy among citrus rootstocks for adapting to nitrate availability: RL invests in 2nd-order laterals, the preferred zone for acquiring the nutrient, whereas CM responds with longer tap roots.     

不同铁源对哺乳仔猪生长、代谢和环境的影响

为了探索不同铁源对哺乳仔猪生长、代谢和环境的影响,选用15窝共158头哺乳仔猪随机分为Ⅰ、Ⅱ、Ⅲ组,分别饲喂含硫酸亚铁、柠檬酸铁和蛋氨酸铁的3种饲粮(饲粮铁含量为146mg·kg-1)进行补铁效果试验.结果表明,Ⅱ、Ⅲ组仔猪在35日龄试验结束时的体重、日增重、体况行为等级、血液血红蛋白值、血浆转铁蛋白含量、血浆和肝脏铁含量等指标均显著(P<005或P<001)高于Ⅰ组;饲料消耗、腹泻发生率、排粪量、粪中含铁量和排铁量则显著(P<005或P<001)低于Ⅰ组.Ⅲ组35日龄体重和日增重也显著(P<005)高于Ⅱ组,但其余指标在Ⅱ组和Ⅲ组之间无显著差异(P>005),说明蛋氨酸铁和柠檬酸铁可明显改善仔猪的健康状况、生长发育、饲料报酬和血液生理生化指标,促进铁在猪体内的吸收和利用,降低排粪量和粪中排铁量,不失为给哺乳仔猪补铁的高效而安全的铁源     

Effect of salinity stress on organic and mineral constituents in the leaves of pigeonpea (Cajanus cajan L. Var. C-11)

Summary Effects of sodium chloride and sodium sulphate on the content of some organic and inorganic constituents in the leaves of pigeonpea (Cajanus cajan L. Var. C-11) were studied. Increased water content under saline conditions made the leaves succulent. The concentration of reducing sugars appeared to be higher while that of total sugars and starch was lower. The plants also failed to accumulate proline at higher salinity levels. Phosphorus and potassium content were lowered while those of calcium, magnesium, sodium, chloride and sulphate were increase under both salinities. This indicates that there is no regulation on the uptake of latter elements under saline conditions.     

Effect of NaCl salinity on photosynthetic rate,transpiration rate,and oxidative stress tolerance in contrasting wheat genotypes

Wheat (Triticum aestivum L.) genotypes K-65 (salt tolerant) and HD 2329 (salt sensitive) were grown in pots under natural conditions and irrigated with NaCl solutions of electrical conductivity (ECe) 4.0, 6.0, and 8.0 dS m⁻¹. Control plants were irrigated without saline water. Observations were made on the top most fully expanded leaf at tillering, anthesis, and grain filling stages. The net photosynthetic rate (P _N), stomatal conductance (g _s), and transpiration rate (E) were reduced with the addition of NaCl. The reduction was higher in HD 2329 than in K-65. Salinity enhanced leaf to air temperature gradient (ΔT) in both the genotypes. NaCl increased the activities of superoxide dismutase (SOD) and peroxidase (POX); the percent increment was higher in K-65. The sodium and potassium contents were higher in the roots and leaves of K-65 over HD 2329. Thus at cellular level K-65 has imparted salt tolerance by manipulating P _N, E, g _s, and K accumulation in leaves along with overproduction of antioxidative enzyme activities (SOD and POX).     

Effect of NaCl salinity on growth and mineral partitioning in Quercus robur L., a rhythmically growing species

 Sodium salt sensitivity of common oak (Quercus robur L.) was evaluated in hydroponic culture using INRA-Morizet solution. Addition of NaCl to the nutrient solution reduced only length and weight of roots and first flush stems. In contrast, the second flush was properly expanded even in the presence of 40 mM of NaCl in culture medium. Both leaf number and leaf area were not affected by increasing salt concentration in medium culture while this increase induced significant leaf damage especially in first flush leaves. Stem starch storage was reduced only at 40 mM NaCl treatment. Common oak seedlings seemed to be able to better compartmentalize sodium than chloride when the NaCl concentration increased in the medium culture. Chloride presented a lower uptake than sodium. Sodium was preferentially accumulated in roots and this accumulation occurred at the expense of potassium uptake. The decrease of ATP content in leaves of common oak seedlings submitted to NaCl treatments could indicate that it was used for sodium exclusion out of the leaves, especially in second flush leaves. Relationships between growth responses, starch and mineral element distribution in common oak seedlings will be discussed. Received: 20 November 1997 / Accepted: 3 March 1998     

Effects of 4-month Fe deficiency exposure on Fe reduction mechanism, photosynthetic gas exchange, chlorophyll fluorescence and antioxidant defense in two peach rootstocks differing in Fe deficiency tolerance

Fe deficiency was imposed by omission of Fe (-Fe), or by inclusion of bicarbonate (supplied as 20 mM NaHCO3) in the nutrient solution in two contrasting peach rootstocks (GF-677; tolerant to Fe deficiency and Cadaman; sensitive to Fe deficiency) for 4 months. In the Fe-deprived leaves and roots, and especially in those treated with bicarbonate, a decrease in Fe concentrations was recorded. Omission of Fe resulted in an increase of the activity of root Fe(III)-chelate reductase (FCR) in both rootstocks, whereas FCR activity decreased in the bicarbonate-treated roots of Cadaman. The results obtained from the FCR assay were confirmed by an agarose-based staining technique used to localize FCR activity. Also, an agar-pH-test revealed that the roots of GF-677 exposed to (-Fe) treatment induced a strong H+ extrusion. In addition, Fe deficiency resulted in reduction of the total chlorophyll (CHL) content. Apart from the (-Fe)-treated leaves of GF-677, Fe deficiency caused a decline in the photosynthetic rate (P(n)) and stomatal conductance (g(s)), without changes of the intercellular CO2 concentration (C(i)), as well as a reduction in the maximum quantum yield of PSII (F(v)/F(m)) and the ratio between variable to initial fluorescence F(v)/F0. The above changes were particularly evident for the bicarbonate-treated leaves of Cadaman. On the other hand, Fe deficiency resulted in an increase of leaf superoxide dismutase (SOD) activity and a depression of catalase (CAT) activity in the leaves and roots, irrespective of the rootstock. Although the non-enzymatic antioxidant activity (FRAP values) was increased in the roots of both rootstocks exposed to -Fe treatment, however, FRAP values were stimulated in the (-Fe)-treated leaves of GF-677 and decreased in the bicarbonate-treated leaves of Cadaman. The H2O2 content was increased in Fe-deprived tissues except for the (-Fe)-treated leaves and roots of GF-677. As a result of Fe deficiency, peroxidase (POD) activity and isoform expression were diminished in the tissues of Cadaman. However, in the tissues of GF-677 subjected to -Fe treatment POD activity was increased whereas an additional POD isoform was detected in the roots suggesting that expression of POD isoforms might be an important attribute linked to the tolerance to Fe deficiency.     

Mineral nutrient imbalances and arginine concentrations in needles of Picea abies (L.) Karst. from two areas with different levels of airborne deposition

Summary This study evaluated the utility of free arginine concentrations as a possible alternative to mineral nutrient concentrations as an indicator of mineral nutrient imbalances in Norway spruce [Picea abies (L.) Karst.]. The concentrations of mineral nutrients and arginine were measured in the needles of spruce trees from two areas in Sweden, one with high (15–30 kg ha^–1 year^–1) airborne N deposition, and one with lower (1–4 kg ha^–1 year^–1) deposition. The spruce needles from the area with high deposition in southern Sweden had elevated concentrations of free arginine, especially on peat sites. No increase in concentrations was found in the low deposition area in northern Sweden. The arginine concentrations on different sampling occasions were consistent for each site and for individual trees. Trees on peat sites in the south seemed to suffer from P deficiency in relation to N availability. A tendency for K deficiency in needles from peat sites was also found. Needles from trees on mor plots showed acceptable levels of these nutrient elements. Sites in the northern area showed low N concentrations, but the ratios between the different mineral elements analyzed in this study and N were within ranges normally found. A low P/N ratio correlated to high free arginine concentration. The threshold for elevated arginine concentrations is crossed when P/N ratios drop below 0.07–0.08. A tendency for increased arginine levels when ratios between N and the other mineral elements are low was also found, although it was not as strong as that for the P/N ratio. The results are discussed in relation to mineral nutrient imbalances in spruce stands caused by airborne deposition.     

Effect of different water salinity levels and organic matter application on the composition of water soluble and exchangeable bases in a brackishwater fish pond soil

Behaviour of different water soluble and exchangeable bases in a brackishwater fish pond soil was studied under four levels of water salinity, in combination with and without organic matter application. The results showed average content of water soluble bases to increase with increase in water salinity. The bases were dominated by Na⁺ followed by Mg⁺⁺, Ca⁺⁺ and K⁺ in decreasing order. SAR values of water increased with increase in water salinity and decreased slightly on organic matter treatment.Total content of exchangeable bases in soils was fairly high and was dominated by Ca⁺⁺ and Mg⁺⁺, followed by Na⁺ and K⁺ respectively. Amount of exchangeable Ca⁺⁺ + Mg⁺⁺ decreased while that of Na⁺ increased with increase in water salinity levels. Amount of exchangeable K⁺ did not show any appreciable change. Application of organic matter tended to increase the exchangeable Ca⁺⁺ + Mg⁺⁺ content and decrease the amount of exchangeable Na⁺ in the soil, while exchangeable K⁺ content remained practically unaffected due to organic matter treatment.Formed part of a Ph.D. thesis submitted to Bidhan Chandra Agricultural University, India in 1978Formed part of a Ph.D. thesis submitted to Bidhan Chandra Agricultural University, India in 1978     

Effect of water temperature,salinity, and their interaction on growth,plasma osmolality,and gill Na,K-ATPase activity in juvenile GIFT tilapia Oreochromis niloticus (L.)

We used a central composite rotatable experimental design and response surface methodology to evaluate the effects of temperature (18–37 °C), salinity (0–20‰), and their interaction on specific growth rate (SGR), feed efficiency (FE), plasma osmolality, and gill Na⁺, K⁺-ATPase activity in GIFT tilapia juveniles. The linear and quadratic effects of temperature and salinity on SGR, plasma osmolality, and gill Na⁺, K⁺-ATPase activity were statistically significant (P<0.05). The interactive effects of temperature and salinity on plasma osmolality were significant (P<0.05). In contrast, the interaction term was not significant for SGR, FE, and gill Na⁺, K⁺-ATPase activity ⁽P>0.05). The regression equations for SGR, FE, plasma osmolality, and gill Na⁺, K⁺-ATPase activity against the two factors of interest had coefficients of determination of 0.944, 0.984, 0.966, and 0.960, respectively (P<0.01). The optimal temperature/salinity combination was 28.9 °C/7.8‰ at which SGR (2.26% d¹) and FE (0.82) were highest. These values correspond to the optimal temperature/salinity combination (29.1 °C/7.5‰) and the lowest plasma osmolality (348.38 mOsmol kg⁻¹) and gill Na⁺, K⁺-ATPase activity (1.31 µmol Pi. h⁻¹ g⁻¹ protein), and resulted in an energy-saving effect on osmoregulation, which promoted growth.     

Effect of saline irrigation on plant water traits,photosynthesis and ionic balance in durum wheat genotypes

In the era of climate change, decreased precipitation and increased evapo-transpiration hampers the yield of several cereal crops along with the soil salinity and poor ground water resource. Wheat being the moderately tolerant crop face many challenges in the arid and semi-arid regions under irrigated agriculture. In view of this, the study was planned to explore the potential of durum wheat genotypes under salinity on the basis of physiological traits. Experiment was designed as RBD in three replications to evaluate 15 wheat genotypes with moderate saline irrigation (EC_iw – 6 dS m⁻¹) and extreme saline irrigation (EC_iw – 10 dS m⁻¹) along with one set of control (Best available water). Different physiological traits such as water potential (ψ_p), osmotic potential (ψ_s), relative water content (RWC), Na⁺ and K⁺ content were recorded in roots as well as shoots at the reproductive stage whereas photosynthetic rate and chlorophyll content were measured in the flag leaves. A significant variability (p < 0.001) was noted among the genotypes under different stress environments and it was observed that durum genotype HI 8728 and HI 8737 showed less reduction in plant water traits (RWC, ψ_p and ψ_s) than the salinity tolerant checks of bread wheat KRL 99 and KRL 3–4. HD 4728 and HI 8708 maintained higher photosynthetic rate as well as higher chlorophyll content under the extreme salinity level of EC_iw – 10 dSm⁻¹. No significant differences were found in root Na⁺ in genotypes KRL 99 (3.17^g), KRL 3–4 (3.34^g) and HI 8737 (3.41^g) while in shoots, lowest accumulation was seen in KRL 99, MACS 3949 and KRL 3–4 at EC_iw – 10 dSm⁻¹. The mean range of K⁺ content was 7.60–9.74% in roots and 4.21–6.61% in shoots under control environment which decreased to 50.77% in roots and 46.05% in shoots under extreme salinity condition of EC_iw – 10 dSm⁻¹. At EC_iw – 10 dSm⁻¹, KRL 99 maintained highest K^+/Na⁺ in both root and shoot followed by KRL 3–4, HI 8737, MACS 3949, HD 4728 in roots and MACS 3949, KRL 3–4, MACS 4020, HD 4758, MACS 3972 and HI 8713 in shoots. The differential response of durum wheat genotypes under salinity particularly for physiological traits, confer their adaptability towards stress environments and exhibit their potential as genetic sources in breeding programs for improving salt stress tolerance.     

Effects of different nitrogen forms and combination with foliar spraying with 6-benzylaminopurine on growth,transpiration, and water and potassium uptake and flow in tobacco

NH₄ ⁺-N can have inhibitory effects on plant growth. However, the mechanisms of these inhibitory effects are still poorly understood. In this study, effects of different N forms and a combination of ammonium + 6-benzylaminopurine (6-BA, a synthetic cytokinin) on growth, transpiration, uptake and flow of water and potassium in 88-days-old tobacco (Nicotiana tabacum L. K 326) plants were studied over a period of 12 days. Plants were supplied with equal amounts of N in different forms: NO₃ ^–, NH₄NO₃, NH₄ ⁺ or NH₄ ⁺+6-BA (foliar spraying every 2 days after onset of the treatments). For determining flows and partitioning upper, middle and lower strata of three leaves each were analysed. During the 12 days study period, 50% replacement of NO₃ ^–-N by NH₄ ⁺-N (NH₄NO₃) did not change growth, transpiration, uptake and flow of water and K⁺ compared with the NO₃ ^–-N treatment. However, NH₄ ⁺-N as the sole N-source caused: (i) a substantial decrease in dry weight gain to 42% and 46% of the NO₃ ^–-N and NH₄NO₃ treatments, respectively; (ii) a marked reduction in transpiration rate, due to reduced stomatal conductance, illustrated by more negative leaf carbon-isotope discrimination (¹³C) compared with the NO₃ ^– treatment, especially in upper leaves; (iii) a strong reduction both in total water uptake, and in the rate of water uptake by roots, likely due to a decrease in root hydraulic conductivity; (iv) a marked reduction of K⁺ uptake to 10%. Under NH₄ ⁺ nutrition the middle leaves accumulated 143%, and together with upper leaves 206% and the stem 227% of the K⁺ currently taken up, indicating massive mobilisation of K⁺ from lower leaves and even the roots. Phloem retranslocation of K⁺ from the shoot and cycling through the root contributed 67% to the xylem transport of K⁺, and this was 2.2 times more than concurrent uptake. Foliar 6-BA application could not suppress or reverse the inhibitory effects on growth, transpiration, uptake and flow of water and ions (K⁺) caused by NH₄ ⁺-N treatment, although positive effects by 6-BA application were observed, even when 6-BA (10^–8 M) was supplied in nutrient solution daily with watering. Possible roles of cytokinin to regulate growth and development of NH₄ ⁺-fed plants are discussed.