Leaf Concentrations Of Na Research Articles

Leaf production and quality of sea beet (Beta vulgaris subsp. maritima) grown with saline drainage water from recirculating hydroponic or aquaculture systems

The application of greenhouse soilless culture (or hydroponics) and recirculating aquaculture system (RAS) is rapidly growing worldwide as these technologies provide controlled growing conditions for crop plants and aquatic organisms, thus enhancing productivity. The wastewater from RAS and hydroponics is generally rich in many essential plant nutrients and could be reused for crop irrigation, thus reducing the costs for both wastewater treatment and fertilizers. Many wild edible plant species are salt-tolerant glycophytes or halophytes and hence are suitable for cultivation with saline wastewater in cascade cropping systems or decoupled aquaponic systems.The goal of this work was to investigate the effects of drainage water from semi-closed substrate plant culture or saltwater RAS on leaf production and quality of sea beet plants (Beta vulgaris subsp. maritima) grown hydroponically in a greenhouse. Two experiments were conducted in autumn with plants cultivated in a floating raft system to compare five different nutrient solutions: standard nutrient solution (CNS, control; EC 2.80 dS m−1, Na 0.7 mM); the effluent from a semi-closed substrate culture of tomato used as such (tomato effluent 100%, TE100; EC 6.49 dS m−1, Na 34.9 mM) or diluted (50:50) with CNS (tomato effluent 50%, TE50; EC 4.50 dS m−1, Na 17.8 mM); the effluent from a saltwater RAS with gilthead sea bream, used as such (aquaculture effluent 100%, AE100; EC 42.00 dS m−1, Na 408.6 mM) or diluted (50:50) with CNS (aquaculture effluent 50%, AE50; EC 25.40 dS m−1, Na 204.6 mM).In both experiments, leaf production was significantly reduced in plants grown with AE50 (−46.8%, on average) and AE100 (−70.4%, on average) compared to CNS; on the contrary, no or minor differences were found between CNS, TE50 and TE100 plants. The reduction of crop yield was due to the higher salinity and not to abnormal concentration of some mineral nutrients in AE. In the first experiment, the use of TE and AE also resulted in higher leaf antioxidant capacity and concentration (both expressed on a fresh weight basis) of total chlorophylls, carotenoids, flavonoids, and phenols. In both experiments, leaf concentration of Na and oxalate (both total and soluble) significantly increased with the salinity of the nutrient solution. Due to the less favourable light conditions, leaf nitrate concentration was much higher in the second experiment than in the first one, regardless of the nutrient solution.In conclusion, sea beet could be grown using hydroponic wastewater with moderate salinity with no or minor effect on leaf production and quality. In contrast, the use of highly saline aquaculture effluents markedly reduced crop yield and negatively affected leaf quality due to increased concentration of sodium, oxalate, and nitrate. In general, sea beet leaves were high in oxalate and their consumption should be limited.

Porta-enxerto de cajueiro anão tolerante à salinidade tem melhor homeostase iônica e desempenho morfofisiológico de mudas

ABSTRACT Considering the cashew tree’s relevance and the limitations imposed by salinity stress in semi-arid regions, the use of alternatives capable of mitigating the harmful effects due to salinity is of great importance to the production sector. The use of grafted plants, especially with rootstock made of tolerant materials, influences the accumulation of toxic ions in leaves of grafted seedlings. Thus, the objective of this work was to evaluate morphophysiological characteristics and leaf concentrations of Na+, K+ and Ca+2 of combinations of scion and rootstock of early dwarf cashew, contrasting in terms of salinity tolerance. The experiment was carried out in a completely randomized design with five replicates, in a 4 × 3 factorial arrangement, corresponding to four dwarf cashew scion/rootstock combinations (self-graft CCP 09, CCP 09/CCP 76, self-graft CCP 76, and CCP 76/CCP 09) and three NaCl concentrations (0, 50, and 100 mM L-1). Height, number of leaves, leaf area, dry matter, tolerance index and leaf concentrations of Na+, K+ and Ca+2 were evaluated after 30 days of application of NaCl concentrations. The scion/rootstock combination CCP 76/09 showed tolerance to 50 mM L-1, due to the increase of leaf area and number of leaves. The scion/rootstock combination CCP 76/09 was more suitable, as it kept the leaf K+ concentration and had the lowest Na+ concentration.

Physiological, epigenetic and genetic regulation in some olive cultivars under salt stress

Cultivated olive, a typical fruit crop species of the semi-arid regions, could successfully face the new scenarios driven by the climate change through the selection of tolerant varieties to salt and drought stresses. In the present work, multidisciplinary approaches, including physiological, epigenetic and genetic studies, have been applied to clarify the salt tolerance mechanisms in olive. Four varieties (Koroneiki, Royal de Cazorla, Arbequina and Picual) and a related form (O. europaea subsp. cuspidata) were grown in a hydroponic system under different salt concentrations from zero to 200 mM. In order to verify the plant response under salt stress, photosynthesis, gas exchange and relative water content were measured at different time points, whereas chlorophyll and leaf concentration of Na+, K+ and Ca2+ ions, were quantified at 43 and 60 days after treatment, when stress symptoms became prominent. Methylation sensitive amplification polymorphism (MSAP) technique was used to assess the effects of salt stress on plant DNA methylation. Several fragments resulted differentially methylated among genotypes, treatments and time points. Real time quantitative PCR (RT-qPCR) analysis revealed significant expression changes related to plant response to salinity. Four genes (OePIP1.1, OePetD, OePI4Kg4 and OeXyla) were identified, as well as multiple retrotransposon elements usually targeted by methylation under stress conditions.

Nutrient deficiencies in olives grown on typical Mediterranean soils (Terra rossa, Rendzina, Lithosol)

ABSTRACTAn important part of agriculture in the European Mediterranean area is olive (Olea europaea L.) production. Characterising the relationships between properties of different soils where olive is grown and nutrient status in olive leaves can enhance our understanding of soil-plant interactions. Three different soils (Terra rossa, Rendzina, Lithosol) were characterized for their physical and chemical characteristics; plant-available nutrients were extracted with ammonium nitrate. Soils, soil extracts and leaf digests were analysed for nutrients and for nitrogen in soils and leaf. A redundancy analysis (RDA) was applied to elucidate relationships between soil properties and leaf nutrients. As revealed by RDA, leaf concentrations of Mg, K, Ca and micronutrients were explained by available Mg, total carbonates and soil organic carbon in topsoil. Leaf concentration of Na was associated with total Na in topsoil. Copper and Mo deficiencies were detected in plants grown in Lithosol, and Mg, P, Mn and Zn deficiencies were noted in all plants. Through appropriate agronomic techniques, Lithosols can be used for olive groves, but they have significant limitation regarding nutrient availability. Our results support the relevance of using soil nutrient variability to provide a basis for optimisation of measures for olive groves.

Genotypic variation in tolerance to salinity of common beans cultivated in Western Cameroon as assessed at germination and during early seedling growth

Abstract This study was carried out to determine effects of salinity on germination and seedling development of commercially important common bean genotypes in Cameroon. The seeds of eight genotypes were used for both trials. The germination experiments were carried out on petri dishes in the laboratory while early growth trials continued in plastic pots in the screenhouse. Both stages were setup using a randomized complete block design with three replications. Germination and early growth trials of the different genotypes were studied using distilled water as control or osmotic potentials of 50, 100, 150 and 200mM NaCl to study the effects of salinity on germination and seedling growth characteristics. Leaf concentrations of Na+ and K+ were determined. At the germination level, germination percentage, germination index and the coefficient of velocity of germination decreased with increasing salinity while the mean germination time and time to 50% germination increased with increasing level of salt. All the growth variables decreased with increasing salinity with the exception of the root length which was not affected by salinity. It was observed that increasing salinity induced a significant increase in leaf Na+ and substantial reduction in the accumulation of K+ in the leaves. For ions accumulation, germination variables and growth parameters, significant differences at 0.001 probability levels were found among salinity treatments, common bean genotypes and most of their interactions. Significant correlations were found between all germination variables and between most growth parameters. From the effect of salt application, the common bean genotypes namely KEBCB049, KEB-CB053 and Mac-33 were the most tolerant while KEB-CB055 and KEB-CB050 were the most sensitive. The results confirm that there is genotypic variation in salinity tolerance and that the most tolerant genotypes should be further explored in selection programs, with the aim that they should be promoted for cultivation in tropical zones affected by salinity.

Potential and constraints of different seawater and freshwater blends as growing media for three vegetable crops

Alternative water sources for irrigation are needed to be found, as agriculture is currently using the 70% of total freshwater. Seawater use for growing crops has long been studied; while an agriculture based on pure seawater is currently impossible, seawater hydroponics may be viable, not aggravating salinization problems in soils. This work aimed at assessing the possibility of growing lettuce, chard and chicory with 3 seawater and freshwater blends (i.e. 5%–10%–15% of seawater). We investigated: i) crops growth, water consumptions, water use efficiency (WUE), water productivity (WP); ii) photosynthetic parameters; iii) principal mineral elements, soluble sugars and phenolics concentration. Lettuce productivity was negatively affected by 10% and 15% of seawater, whereas chard and chicory’s growth were not affected by any blend. Interestingly, water consumptions dropped and WUE significantly upturned in every tested crop accordingly with increased seawater concentrations. Leaf concentration of Na+ and of some other ions increased. We concluded that certain amounts of seawater can be practically used in hydroponics, allowing freshwater saving and increasing certain mineral nutrients concentrations.

Evaluating the Contribution of Ionic and Agronomic Components toward Salinity Tolerance in Safflower

Safflower (Carthamus tinctorius L.) is a versatile crop species that is well adapted to arid and semiarid conditions. Limited information is available on the response of safflower genotypes to salinity stress under field conditions. The objective of this study was to investigate the effects of field salinity on seed yield, yield components, and leaf ionic concentrations in different safflower genotypes. A 2‐yr field experiment was conducted in normal (E1) and saline (E2) field conditions using 64 safflower genotypes. Plant height, number of capitula per plant, number of seeds per capitulum, 1000‐seed weight, seed yield, biological yield, and harvest index were determined in this study. Leaf concentrations of Na+ and K+ were also measured and the K+/Na+ ratio calculated. Results indicated that under salinity all the traits significantly decreased except tissue Na+ content and harvest index. Linear regression and genotype‐by‐traits analyses revealed a strong inverse association between leaf Na+ concentration and salinity tolerance. Results of stepwise multiple regression analysis showed that plant height, number of capitula per plant, biological yield, harvest index, and leaf Na+ content were the strongest predictors of seed yield, collectively explaining 97% of the variation in seed yield under saline conditions. Therefore, the only ionic predictor of salinity tolerance in the regression model, leaf Na+ concentration, can be suggested as an effective indirect screening criterion for salinity tolerance in safflower. The mechanisms of Na+ homoeostasis, including Na+‐specific transport or K+/Na+ co‐transport, could also be explored using the most contrasting genotypes with respect to salinity stress.

Production, water consumption and nutrient content of Chinese cabbage grown hydroponically in brackish water

Underground water reserves in the semi-arid region of Brazil are stored in the crystal formations that in large part have high concentrations of salt. However, the scarcity of this resource makes the use of this water necessary for various activities, including agriculture. The aim of this study was to evaluate the use of brackish water on the electrical conductivity and pH of the nutrient solution, and on the production, water consumption and the uptake of nutrients in Chinese cabbage (Brassica pekinensis L.) under a hydroponic system. The experimental design was completely randomised, with four replications and six levels of water salinity (0.2, 1.2, 2.2, 3.2, 4.2 and 5.2 dS m-1), obtained by adding NaCl to the local water supply, with this water being used to prepare the nutrient solution and to make up the volume lost through evapotranspiration. The results showed that with the exception of the treatment at the lowest salinity, there was a tendency to increased electrical conductivity of the nutrient solution with the increasing salinity of the water; that the pH of the nutrient solution remained within the normal range throughout the cycle; that with the increasing salinity of the solution there was a reduction in all growth and production variables under analysis, in water consumption, and in leaf N, K, Ca and Mg, and an increase in leaf concentrations of Na and Cl. It is possible to use brackish water for the production of Chinese cabbage when grown hydroponically as an alternative for those producers who have an available supply of brackish water and a restricted supply of fresh water, however with a reduction in productivity.

STIMULATION GROWTH AND PRODUCTIVITY OF Cucurbita moschata UNDER RECLAIMED SALINE SOIL CONDITION BY USING SULPHUR SOIL APPLICATION AND ASCORBIC ACID FOLIAR SPRAY

The effects of soil application with sulphur (SAS) at a rate of 200 kg fed–1 and/or foliar application with 0, 1 or 2 mM of ascorbic acid (FAA) on the growth, fruit yield and yield components, the concentrations of potassium (K), sodium (Na), sulphur (S) and ascorbic acid (AsA), and the ratio of K/Na of pumpkin (Cucurbita moschata Duchesne) plants grown on a newly-reclaimed saline soil were investigated. Two field experiments (2012 and 2013) were performed on a newly-reclaimed saline soil using a design of completely randomized blocks with six treatments, each with four replicates. Results indicated that SAS and/or FAA increased growth traits (i.e., stem length, canopy dry weight plant–1, number of leaves plant–1, average leaf area and total leaf area plant–1), fruit yield and yield quality (i.e., fruit length and diameter, flesh thickness, TSS, average fruit weight and fruit yield fed–1), leaf concentrations of N, P, K, S and AsA, and K/Na ratio. In contrast, leaf concentration of Na was reduced as a result of SAS and/or FAA. SAS and FAA, therefore, have the potential to be used as a soil and foliar applications, respectively for pumpkin to overcome the adverse effects of the newly-reclaimed saline soils.

Salinity-Induced Changes in Ion Concentrations of ‘Hass’ Avocado Trees on Three Rootstocks

ABSTRACT The effect of salinity (1.5, 3.0, 4.5, or 6.0 dS m− 1) on ion concentrations [magnesium (Mg), calcium (Ca), potassium (K), sodium (Na), and chloride (Cl)] of one-year-old ‘Hass’ avocado (Persea americana Mill.) trees on one of three rootstocks [‘Duke 7’ (D7), ‘Toro Canyon’ (TC), or ‘Thomas’ (TH)] was investigated. Concentrations of Mg decreased in roots, stems, and older leaves with increasing substrate salinity. Salinity had no effect on Ca concentration of the trees. Potassium concentrations decreased in roots of all trees and stems of trees on TH. Potassium concentrations either remained unchanged or increased at salinity levels of 3.0 dS m− 1 and above in leaves and buds of all trees. Sodium increased in roots and woody organs in trees on all rootstocks. Leaf Na concentrations increased with salinity in trees on D7 and TH, but not TC. Chloride increased in all organs of all trees with increasing salinity, but to the greatest extent in trees on TH and to the least extent in trees on TC. At high substrate salinity concentrations, leaves of trees on TH rootstock had the highest leaf concentrations of Na and Cl, and the highest Na:K ratios. Sodium and chloride concentrations were correlated with necrosis in older leaves of TH, but less so in leaves of trees on TC or D7. Based on percent necrosis in older leaves with increased salinity, trees on TH performed poorest, whereas trees on TC exhibited the greatest salt tolerance. Leaf necrosis was consistently observed at Cl concentrations of 4 mg g− 1 or more, and at Na:K ratios of 0.01 or more in older leaves. Chloride concentration and Na:K ratio in older leaves appears to be a useful marker for salinity tolerance screening in avocado rootstocks. The relative tolerance of the various rootstocks appeared to be due primarily to their ability to exclude Na and Cl from the leaves.

Morpho-physiological responses of cowpea leaves to salt stress

The effect of salt stress of known intensity and duration on morpho-physiological changes in leaves of different ages from cowpea [Vigna unguiculata (L.) Walp.] plants was studied, aiming for a better understanding of the acclimation process of the whole-plant. Seeds were sown in vermiculite and seedlings were transferred to plastic trays containing aerated nutrient solution, and kept in a greenhouse. When the first trifoliate leaf emerged the seedlings were transplanted into 3 L plastic pots containing aerated nutrient solution. Salt additions started 5 d later, and the salt-treated plants received 25 mmol L-1 per day until reaching a final concentration of 75 mmol L-1. During the experimental period primary leaves and the 1st, 2nd, and 3rd trifoliate leaves were used for measurements of net photosynthesis, leaf area, leaf succulence, specific leaf mass, ions and chlorophyll concentrations. Growth analysis of the whole-plant was performed at the end of the experimental period. Salinity did not affect net photosynthesis, but reduced dry mass production and the number of lateral branches. Leaf concentrations of Na+, Cl-, K+ and P increased in salt-stressed plants, but these responses were dependent upon stress duration and leaf age. The higher concentration of potentially toxic ions (Na+ and Cl-) in older leaves could contribute to the reduced ion accumulation in growing tissues, but the tendency of K and P accumulation in leaves appeared to be the result of reduced re-translocation, i.e., not related to plant acclimation. Salinity also increased the source/sink ratio, leaf succulence, specific leaf mass, and chlorophyll accumulation per unit of leaf area, suggesting that the observed changes could be part of an integrated mechanism of whole-plant acclimation to salt stress.

Cotton Leaf Curl Virus: Ionic Status of Leaves and Symptom Development

In the present study, the relationship between the nutritional status of leaves and the development of symptoms of cotton leaf curl virus (CLCuV) in two cotton (Gossypium hirsutum L.) cultivars (i.e. CIM-240 and S-12) was investigated. The incidence of disease attack was found to be 100% in the S-12 cultivar and 16% in the CIM-240 cultivar. Geminivirus particles in infected leaves were confirmed by transmission electron microscope examination of highly specific geminivirus coat protein antisera-treated cell sap. The CLCuV impaired the accumulation of different nutrients in both cultivars. A marked decrease in the accumulation of Ca2+ and K+ was observed in infected leaves. However, the disease had no effect on leaf concentrations of Na+, N, and P. It was observed that the curling of leaf margins in CLCuV-infected plants was associated with the leaf Ca2+ content; leaf curling was severe in plants with a significant reduction in Ca2+ content. Moreover, leaf K+ content was found to be associated with resistance/susceptibility to CLCuV infection. (Managing editor: Ping He)

Functional analysis of CHX21: a putative sodium transporter in Arabidopsis

The functional role of CHX21, a member of the Arabidopsis thaliana CHX cation transporter family, has been investigated in plants growing under "ideal" conditions and in the presence of elevated NaCl levels. In public databases, AtCHX21 (At2g31910) is annotated as a putative Na+/H+ antiporter. In this study, Southern analysis was used to identify a genotype that contained a single transposon insertion within its genome; using PCR, this insertion was shown to be within the CHX21 locus. No CHX21 transcript was detectable in Atchx21 (mutant) plants using RT-PCR. In the absence of salt stress, Atchx21 showed significant quantitative differences from the wild type (AtCHX21) in development with respect to characters such as rosette width and flowering time. In the presence of 50 mM NaCl, (i) roots of Atchx21 elongated more slowly than the wild type, (ii) the leaf sap Na+ concentration was significantly lower in Atchx21 compared with the wild type, and (iii) the concentra) in the xylem was lower compared with the wild type. The concentration of Na+ exported from the leaf in the phloem was unchanged. Thus, loading of Na+ into the root xylem could explain changes in leaf concentration of Na+. This hypothesis was supported by immunolocalization which demonstrated that the AtCHX21 transporter could only be detected in root endodermal cells. Immunogold labelling of ultra-thin sections, followed by transmission electron microscopy, demonstrated the localization of the protein in the plasma membrane. The data demonstrate that the CHX21 transporter may play a role in regulation of xylem Na+ concentration and, consequently, Na+ accumulation in the leaf.

Response to sodium chloride in different species and clones of genus Populus L.

A greenhouse study was undertaken to evaluate the response to sodium chloride (control, 68 mM and 137 mM) of different species and genotypes of genus Populus L. (P. × euramericana (Dode) Guinier clones: ‘I-214’, ‘Flevo’, ‘I-MC’ and ‘Triplo’; P. deltoides × P. alba clones: ‘M30’ and ‘M31’; P. alba L. clones: ‘Jalón-F-1–22’, ‘Jalón F-1–4’, ‘Guadalquivir F-21–38’,‘Guadalquivir F-21–39’, ‘Guadalquivir F-21–40’ and ‘Montañana F-2–9’; and P. euphratica Oliv.). Survival, visual symptomatology, height growth, dry weight both in shoots and roots, photosynthesis rate and leaf concentrations of Na+, K+ and Ca2+ were evaluated. There were differences in survival between clones (0 per cent for the most sensitive and 100 per cent for the most tolerant) but growth was significantly reduced in all cases except for dry weight of P. euphratica at 68 mM. The photosynthesis rate was significantly reduced in all clones at the end of the experiment (60 days) but not in the same way in the middle (30 days). The leaf levels of Na+, K+ and Ca2+ were also significantly different between clones. Intra- and interspecific variability have been detected in the genus, especially in P. alba.

Crape Myrtle (Lagerstroemia sp.) Growth and Quality as Affected by Cultivar and Salt Stress

Rooted liners of the crape myrtle cultivars `Pink Lace', `Natchez' and `Basham's Party Pink' (`BPP') were grown in 20-L containers filled with a 2 peat: 1 pine bark: 1 sand (v/v) medium and irrigated for 15 weeks with irrigation water containing 0, 3, 6, 12, and 24 mm NaCl. Cultivar selection and salinity significantly affected plant growth and quality. Regardless of salinity level, `Natchez' plants had higher leaf area, total and shoot (top) dry weights and growth indices, whereas `Pink Lace' had the lowest. `BPP' had the highest average root dry weights across salt treatments. The vigorous shoot (top) growth of `Natchez' was also evident with an average shoot to root ratio of 4.1, compared to 2.7 and 2.4 for `BPP' and Pink Lace', respectively. Salinity significantly decreased plant growth and quality in the three cultivars, but the rate at which these parameters were reduced with increases in salinity differed among the cultivars. The rate of reduction in plant growth parameters was lower in `Pink Lace' plants compared to `Natchez' and `BPP'. However, foliage burn symptoms due to salt stress increased at significantly higher rate for `Pink Lace' plants compared to the other two cultivars. `BPP' plants had in general the lowest salt burn ratings at each salinity level. Leaf concentrations of Na and Cl increased with salt stress in all cultivars, but significantly lower concentrations were found in `BPP' plants. `Pink Lace' plants had better correlations with the recorded salt burn symptoms as compared to the other two cultivars.

Changes in gas exchange and chlorophyll fluorescence characteristics of two mangroves and a mangrove associate in response to salinity in the natural environment

Photosynthetic responses of two mangroves and a mangrove associate were investigated in a low salinity site at Beachwood (<12‰) and a high salinity site at Durban Bay (35‰). Measurements were made of CO2 exchange, chlorophyll fluorescence, ion and water relations of Avicennia marina, Bruguiera gymnorrhiza and Hibiscus tiliaceus at the two sites. At Beachwood, CO2 exchange was highest in H. tiliaceus (9.12 µmol m–2s–1) and least in A. marina (3.27 µmol m–2s–1). At the Durban Bay site, CO2 exchange in A. marina was greater than that at Beachwood by 79%, that in H. tiliaceus decreased by 59% while that in B. gymnorrhiza remained unchanged. In all species, photosystem II (PSII) quantum yield decreased with increase in photon flux density (PFD) up to 2,000 µmol m–2s–1. Electron transport rate (ETR) through PSII increased with increase in PFD, reaching saturation at 1000 µmol m–2s–1. At saturating PFD, PSII quantum yield and ETR were higher in the mangroves but lower in H. tiliaceus at the high salinity site. Photochemical and non-photochemical quenching were, however, lower in the mangroves but higher in H. tiliaceus at the high salinity site. Predawn and midday leaf water potential were higher at Beachwood and significantly reduced at Durban Bay, values being highest in H. tiliaceus (–0.4 and –1.8 MPa) and least in A. marina (–2.5 and –3.8 MPa). Leaf concentrations of Na+, Cl–, Ca2+ and Mg2+ in mangroves were significantly higher at Durban Bay than at Beachwood. In H. tiliaceus there were no differences in ion concentrations between sites except for K+, which was significantly higher at Durban Bay.

Low salinities adversely affect photosynthetic performance of the mangrove, Avicennia marina

Photosynthetic performance of the highly salt tolerant mangrove, Avicennia marina, was compared at two sites differing insubstrate soil salinities. Carbon dioxide exchange and chlorophyll fluorescence weremonitored at a high salinity site in Durban Bay (35‰) and at a low salinitysite in Beachwood (< 12‰). Mean CO2 exchange, conductanceand transpiration were consistently higher at the high salinity site. Carbondioxide response curves indicated that carboxylation efficiency was higherand stomatal limitation lower at the Durban Bay site. PSII quantum yield,electron transport rates (ETR) and intrinsic PSII efficiency(Fv/Fm) were significantly higher at the high salinity site.Quenching analysis indicated a higher degree ofphotoinhibition/photoprotection in leaves at the low salinity site. Predawnand midday leaf water potentials were –1.6 and –3.1 MPa at Beachwood,compared to –2.6 and –3.8 MPa, respectively, at Durban Bay. Leafconcentrations of Na+, K+, Ca2+, Mg2+,Cl- and N were significantly higher at Durban Bay. Photosyntheticperformance is apparently impaired at the low salinity site in Beachwood asa result of K+ and N deficiencies in the leaves.

Effects of salinity on baldcypress seedlings: Physiological responses and their relation to salinity tolerance

Growth and physiological responses of 15 open-pollinated families of baldcypress (Taxodium distichum var.distichum) subjected to flooding with saline water were evaluated in this study. Ten of the families were from coastal sites in Louisiana and Alabama, USA that have elevated levels of soil-water salinity. The other five families were from inland, freshwater sites in Louisiana. Seedlings from all families tolerated flooding with water of low (2 g 1−1) salinity. Differences in biomass among families became most apparent at the highest salinity levels (6 and 8 g 1−1). Overall, increasing salinity reduced leaf biomass more than root biomass, which in turn was reduced more than stem biomass. A subset of seedlings from the main greenhouse experiment was periodically placed indoors under artificial light, and measurements were made of gas exchange and leaf water potential. Also, tissue concentrations of Cl−, Na+, K+, and Ca2+ were determined at the end of the greenhouse experiment. Significant intraspecific variation was found for nearly all the physiological parameters evaluated, but only leaf concentrations of Na+ and Cl− were correlated with an index of family-level differences in salt tolerance.

Calcium, magnesium, and sodium uptake in Rabbit‐eye blueberries

Abstract In a sand culture study with rabbiteye blueberries (Vaccinium ashei Reade), increasing Na fertilization levels increased leaf concentrations of Na, Mg, Ca, Mn, and Zn, and reduced leaf K plus plant growth. Magnesium fertilization did not affect leaf concentration of K, Ca, Mn, Fe, or Zn. High Ca fertilization increased leaf Ca and Mg. Calcium and Mg fertilization did not independently influence plant vigor, chlorosis, or growth of leaves and stems. Higher Na fertilization levels decreased plant vigor plus leaf production and increased chlorosis. With low Na fertilization levels, high Mg fertilization reduced leaf production. At the highest levels of Na fertilization, Ca fertilization had a synergistic influence and Mg had an antagonistic effect on Na uptake.

Effect of Salinity on Leaf Ionic Content and Photosynthesis of Taxodium distichum L.

Bald cypress (Taxodium distichum L.) seedlings were subjected to flooding with salinity levels ranging from 0-140 moles m-3 NaCl. Imposition of salinity was designed to simulate the increase in salinity level which some of Louisiana's extensive cypress forests are currently experiencing due to rapid subsidence in the Mississippi River Deltaic Plain. The effect of salt water on leaf tissue ion concentrations and subsequent changes in net photosynthesis were measured. Leaf concentrations of Na, K, Ca and Mg increased substantially as salinity of floodwater increased. Net photosynthesis declined from 7.6 ,umol.m-2s-1 to 0.9 ,umol.m-2s-1 when salinity increased from 0-140 moles m-3 NaCl. Despite the parallel reduction in both stomatal conductance and net photosynthesis, the leaf internal CO2 concentrations remained relatively constant over the entire range of salt concentrations. These results suggest that elevated floodwater salinity causes excess accumulation of several ions in the bald cypress leaf tissue. Consequently, increase in leaf ionic content is primarily the cause of reductions in photosynthesis which is accompanied by simultaneous diffusional limitations caused by stomatal closure. INTRODUCTION Significant parts of coastal forests including bald cypress (Taxodium distichum L.) stands are currently being subjected to saltwater intrusion caused by rapid subsidence and compaction of recent Mississippi River alluvial sediment. Salinity in streams flowing through the extensive cypress forests bordering Lake Pontchartrain has been reported as high as 50 moles m-3 NaCl (Salinas et al., 1986). The continuous land subsidence in wetland coastal areas and the projection indicating faster sea level rises in the future (Hoffman et al., 1983) may result in elimination of many salt-sensitive, but otherwise flood-tolerant species by exposing them to high salinity. Despite the potential impact of saltwater intrusion on survival, productivity and species composition of coastal vegetation, there is little information on the extent of salt tolerance and the physiological characteristics of these species. Assessment of physiological response of bald cypress seedlings to salt stress is important in order to identify the level of tolerance and possible adaptation/acclimation to salinity conditions. Salt stress reduces growth through several effects including water stress, excess ion and biochemical relations (Greenway and Munns, 1980). Presumably, plants can survive sublethal salt stress as long as they are able to photosynthesize positively. The photosynthetic rates of glycophytes, however, declines in response to salinity. Such response has been attributed to stomatal closure as well as direct effect of excess ion content on photosynthetic processes (Seemann and Critchley, 1985). Reports of photosynthetic response of bald cypress to salinity is limited to those of Pezeshki et al., (1986) and Pezeshki et al., (1987). The former studied the photosynthetic response of different leaf age group under salinity and the latter reported photosynthetic responses to a wide range of floodwater salinity. Generally, significant declines in net photosynthesis have been observed as a result of both flood and salt stresses in bald cypress. In our continuous efforts to further investigate the response of this key wetland tree species to increased inundation and salinity, this study was conducted to examine the effects of floodwater salinity on leaf ionic contents and the subsequent effects on photosynthesis.