Clonal Variability in Photosynthetic and Growth Characteristics of Populus Deltoides Under Saline Irrigation

Fifty-d-old poplar (Populus deltoides L.) plants were irrigated with 50-200 mM NaCl. 100 and 200 mM NaCl significantly reduced net photosynthetic rate, chlorophyll and carotenoid contents, leaf area, dry matter accumulation, and harvest index (HI) in all tested poplar clones (Bahar, S7C15, and WSL22). Clone S7C15 was more tolerant to salinity than the other clones.     

Seed Germination in Relation to Salinity and Temperature in Sarcobatus Vermiculatus

Sarcobatus vermiculatus (Hook) Torrey is a leaf succulent, sodium-accumulating shrub usually found in saline substrates of the Great Basin desert, Utah, USA. Laboratory experiments were conducted to determine the effect of salinity (0, 200, 400, 600, 800 and 1000 mM NaCl) and temperature (day/night: 5/15, 10/20, 15/25, 20/30, and 25/35°C) on seed germination. S. vermiculatus showed 100% germination in non-saline controls, at all thermoperiods. Percentage and rate of germination decreased with increases in salinity and few seeds germinated at even 1000 mM NaCl. High salinity exposure caused the loss of viability at higher temperature regimes, while some recovery was recorded in low salinity treatments.     

Effects of sodium chloride on growth of ectomycorrhizal fungal isolates in culture

We studied the tolerance of ectomycorrhizal (ECM) fungi to sodium chloride (NaCl) to find the best fungus to aid growth of Pinus thunbergii. Four ECM fungi, Cenococcum geophilum, Pisolithus tinctorius, Rhizopogon rubescens, and Suillus luteus, were grown in liquid MMN media with five different concentrations of NaCl for 30 days, and their mycelial weights were determined. Mycelial weights of P. tinctorius and R. rubescens were not significantly different between 0 mM and 200 mM, whereas those of C. geophilum and S. luteus decreased with increasing NaCl concentration, indicating that the former two species were more tolerant to higher NaCl concentrations than the latter species. We further studied the intraspecific differences in NaCl tolerance of nine P. tinctorius isolates. They were grown on MMN agar media with six different concentrations of NaCl for 21 days, and their radial growth was measured. In total, the hyphal growth at 25 mM NaCl was significantly higher than those at the other NaCl concentrations, and EC₅₀ values were confirmed at between 50 mM and 200 mM. Among the isolates, Pt03 and Pt21 showed measurable growth at 200 mM; the growth of Pt03 was not significantly different between 0 mM and 200 mM. The results indicate that there are intraspecific variations in NaCl tolerance of Pisolithus species.     

Antioxidative Defense Potential to Salinity in the Euhalophyte Salicornia brachiata

The antioxidative defense mechanism to salinity was assessed by monitoring the activities of some antioxidative enzymes and levels of antioxidants in an obligate halophyte, Salicornia brachiata, subjected to varying levels of NaCl (0, 200, 400, and 600 mM) under hydroponic culture. In the shoots of S. brachiata, salt treatment preferentially enhanced the activities of ascorbate peroxidase (APX), guaiacol peroxidase (POX), glutathione reductase (GR), and superoxide dismutase (SOD), whereas it induced the decrease of catalase (CAT) activity. Similarly, salinity caused an increase in total glutathione content (GSH + GSSG) and a decrease in total ascorbate content. Growth of S. brachiata was optimum at 200 mM NaCl and decreased with further increase in salinity. Salinity caused an increase in Na⁺ content and a decrease in K⁺ content of shoots. Proline levels did not change at low (0-200 mM NaCl) or moderate (400 mM NaCl) salinities, whereas a significant increase in proline level was observed at high salinity (600 mM NaCl). Accumulation of Na⁺ may have a certain role in osmotic homeostasis under low and moderate salinities in S. brachiata. Parameters of oxidative stress such as malondialdehyde (MDA), a product of lipid peroxidation, and H₂O₂ concentrations decreased at low salinity (200 mM NaCl) and increased at moderate (400 mM NaCl) and high salinities (600 mM NaCl). As a whole, our results suggest that the capacity to limit ionic and oxidative damage by the elevated levels of certain antioxidative enzymes and antioxidant molecules is important for salt tolerance of S. brachiata.     

Germination responses of Diplotaxis harra to temperature and salinity

Diplotaxis harra (Forssk.) Boiss, an annual herb in the family of Brassicaceae, is widely distributed in many sandy and gypseous areas in southern Tunisia. Laboratory experiments were carried out to assess the effects of temperature and salinity on seed germination and recovery responses after seed transfer to distilled water. The germination responses of the seeds in complete darkness were determined over a wide range of temperatures (5, 10, 15, 20, 25 and 30 °C) and salinities (0, 50, 100, 150 and 200 mM NaCl). Germination was inhibited by either an increase or decrease in temperature from the optimal temperature (15 °C). Highest germination percentages were obtained under non-saline conditions and an increase in NaCl concentrations progressively inhibited seed germination. Rate of germination decreased with an increase in salinity at all temperatures but comparatively higher rates were obtained at 15 °C. Salt stress decreased both the percentage and the rate of germination. An interaction between salinity and temperature yielded no germination at 200 mM NaCl. Seeds were transferred from salt solution to distilled water after 20 days, and those from low salinities recovered at all temperatures. At NaCl concentration of 200 mM, the recovery of germination was completely inhibited.     

Hot water and dilute acid pretreatment of high and low specific gravity <Emphasis Type="Italic">Populus</Emphasis><Emphasis Type="Italic">deltoides</Emphasis> clones

Populus sp. are hardwood feedstocks that grow in forest management areas that are logged for softwoods; however, they are also being considered as an energy-destined feedstock. The objective of this work was to determine the effect of xylose yield from dilute acid and hot water pretreatments performed in unstirred batch stainless steel reactors at temperatures ranging from 140 to 200°C. Populus deltoides clones S13C20 and S7C15 used in this study originated from Eastern Texas and were cultivated for 14 years in Pine Tree, AR. P. deltoides clones S13C20 and S7C15 had specific gravities of 0.48 and 0.40, respectively. Bark and wood were examined separately. As expected, hot water pretreatments, in the tested temperature range, resulted in very little direct xylose recovery. However, the 140°C dilute acid pretreatment of the lower specific gravity clone, S7C15, wood yielded the highest average xylose recovery of 56%. This condition also yielded the highest concentration of furfural, 9 mg/g sample, which can be inhibitory to the fermentation step. The highest xylose recovery from bark samples, 31%, was obtained with clone S7C15, using the 160°C dilute acid pretreatment for 60 min.     

Salt stress effects on growth,pigments, proteins and lipid peroxidation in <Emphasis Type="Italic">Salicornia persica</Emphasis> and <Emphasis Type="Italic">S. europaea</Emphasis>

The effects of NaCl stress on growth, water status, contents of protein, proline, malondialdehyde (MDA), various sugars and photosynthetic pigments were investigated in seedlings of Salicornia persica and S. europaea grown in vitro. Seeds were germinated under NaCl (0, 100, 200, 300, 400, 500 and 600 mM) on Murashige and Skoog medium for 45 d. The shoot growth of both species increased under low NaCl concentration (100 mM) and then decreased with increasing NaCl concentrations. In contrast to S. persica, root length in S. europaea reduced steadily with an increase in salinity. Proline content in S. persica was higher than in S. europaea at most NaCl concentrations. Proline, reducing saccharide, oligosaccharide and soluble saccharide contents increased under salinity in both species. In contrast, contents of proteins and polysaccharides reduced in both species under salt stress. MDA content remained close to control at moderate NaCl concentrations (100 and 200 mM) and increased at higher salinities. MDA content in S. europaea was significantly higher than S. persica at higher salinities. Salt treatments decreased K⁺ and P contents in seedlings of both species. Significant reduction in contents of chlorophylls and carotenoids due to NaCl stress was also observed in seedlings of both species. Some differences appeared between S. persica and S. europaea concerning proteins profile. On the basis of the data obtained, S. persica is more salt-tolerant than S. europaea.     

Paxillus involutus mycorrhiza attenuate NaCl-stress responses in the salt-sensitive hybrid poplar Populus×canescens

In order to characterise the effect of ectomycorrhiza on Na⁺-responses of the salt-sensitive poplar hybrid Populus × canescens, growth and stress responses of Paxillus involutus (strain MAJ) were tested in liquid cultures in the presence of 20 to 500 mM NaCl, and the effects of mycorrhization on mineral nutrient accumulation and oxidative stress were characterised in mycorrhizal and non-mycorrhizal poplar seedlings exposed to 150 mM NaCl. Paxillus involutus was salt tolerant, showing biomass increases in media containing up to 500 mM NaCl after 4 weeks growth. Mycorrhizal mantle formation on poplar roots was not affected by 150 mM NaCl. Whole plant performance was positively affected by the fungus because total biomass was greater and leaves accumulated less Na⁺ than non-mycorrhizal plants. Energy dispersive X-ray microanalysis using transmission electron microscopy analysis of the influence of mycorrhization on the subcellular localisation of Na⁺ and Cl⁻ in roots showed that the hyphal mantle did not diminish salt accumulation in root cell walls, indicating that mycorrhization did not provide a physical barrier against excess salinity. In the absence of salt stress, mycorrhizal poplar roots contained higher Na⁺ and Cl⁻ concentrations than non-mycorrhizal poplar roots. Paxillus involutus hyphae produced H₂O₂ in the mantle but not in the Hartig net or in pure culture. Salt exposure resulted in H₂O₂ formation in cortical cells of both non-mycorrhizal and mycorrhizal poplar and stimulated peroxidase but not superoxide dismutase activities. This shows that mature ectomycorrhiza was unable to suppress salt-induced oxidative stress. Element analyses suggest that improved performance of mycorrhizal poplar under salt stress may result from diminished xylem loading of Na⁺ and increased supply with K⁺.     

Stimulation of intermolecular ligation with E. coli DNA ligase by high concentrations of monovalent cations in polyethylene glycol solutions.

In the presence of high concentrations of the nonspecific polymer polyethylene glycol (PEG), intermolecular cohesive-end ligation with the DNA ligase from Escherichia coli was stimulated by high salt concentrations: 200 mM NaCl or 300 mM KCl in 10% (w/v) PEG 6000 solutions, and 100-200 mM NaCl or 150-300 mM KCl in 15% PEG 6000 solutions. Intermolecular blunt-end ligation with this ligase was also stimulated at 100-150 mM NaCl or 150-250 mM KCl in 15% PEG 6000 solutions. The extent of such intermolecular ligation increased and the salt concentrations at which ligation was stimulated extended to lower concentrations when we raised the temperature from 10 to 37 degrees C.     

Stability of Biopolymer Particles Formed by Heat Treatment of β-lactoglobulin/Beet Pectin Electrostatic Complexes

The purpose of this study was to examine the stability of biopolymer particles formed by heating electrostatic complexes of β-lactoglobulin and sugar beet pectin together (pH 5, 80 °C for 15 min). The effects of electrostatic interactions on the formation and stability of the particles were investigated by incorporation of different salt levels (0 to 200 mM NaCl) during the preparation procedure. Biopolymer particles were characterized by turbidity, electrophoretic mobility, dynamic light scattering, and visual observance. Salt inclusion (≥25 mM) prior to heating β-lactoglobulin/pectin complexes led to the formation of large biopolymer particles (d > 1,000 nm) that rapidly sedimented, but salt inclusion after heating (0 to 200 mM) led to the formation of biopolymer particles that remained relatively small (d < 350 nm) and were stable to sedimentation. The biopolymer particles formed in the absence of salt remained stable over a wide range of pH values (e.g., pH 3 to 7 in the presence of 200 mM NaCl). These biopolymer particles may therefore be suitable for application in a number of food products as delivery systems, clouding agents, or texture modifiers.     

Ultrastructural characterization of somatic embryos regenerated from NaCl selected and nonselected calli ofDactylis glomerata

Summary Calli were induced from leaf expiants of aDactylis glomerata L. (orchardgrass) genotype which has a high capacity for somatic embryogenesis. After 7 months culture on SH medium containing NaCl, a line was selected which was tolerant to 200 mM NaCl. When both selected and nonselected calli were maintained for 56 days on media containing 0 to 300 mM NaCl, the selected line showed significantly higher regeneration capacity than nonselected calli when placed on media containing more than 50 mM NaCl. Ultrastructural features of control somatic embryos not exposed to the salt were compared to those from nonselected and selected embryos cultured on 200 mM NaCl medium. In the presence of NaCl there were changes in the appearance of cell walls and mitochondria, accumulation of lipids and a higher degree of vacuolation in cells of nonselected embryos compared to control and selected embryos.     

6-Oxocytidine a novel protonated C-base analogue for stable triple helix formation.

2'-O-Methyl-3'-O-phosphoramidite building blocks of 6-oxocytidine 6 and its 5-methyl derivative 7, respectively, were synthesized and incorporated via phosphoramidite chemistry in 15 mer oligodeoxynucleotides [d(T72T7), S2; d(T73T7), S3] to obtain potential Py.Pu.Py triplex forming homopyrimidine strands. UV thermal denaturation studies and CD spectroscopy of 1:1 mixtures of these oligomers and a 21 mer target duplex [d(C3A7GA7C3)-d(G3T7CT7G3), D1] with a complementary purine tract showed a nearly pH-independent (6.0-8.0) triple helix formation with melting temperatures of 21-19 degrees C and 18.5-17.5 degrees C, respectively (buffer system: 50 mM sodium cacodylate, 100 mM NaCl, 20 mM MgCl2). In contrast, with the corresponding 15mer deoxy-C-containing oligonucleotide [d(T(7)1T7), S1] triplex formation was observed only below pH 6.6. Specificity for the recognition of Watson-Crick GC-base pairs was observed by pairing the modified C-bases of the 15mers with all other possible Watson-Crick-base compositions in the target duplex [d(C3A7XA7C3)-d(G3T7YT7G3), X = A,C,T; Y = T,G,A, D2-4]. Additionally, the Watson-Crick-pairing of the modified oligomers S2 and S3 was studied.     

Comparative Anatomical,Morphological, and Physiological Parameters Controlling Photosynthesis in Two Populusxeuramericana Clones During Short-Term Osmotic Treatment

The relationships between drought response and anatomical/physiological properties were assessed in two poplar clones belonging to the Aigeros section: Populusxeuramericana clone Dorskamp (drought-tolerant) and clone Luisa Avanzo (drought-sensitive). Cuttings of both clones were exposed for 12 h to 0 mM (control). 50 mM (osmotic potential −0.112 MPa), and 150 mM (−0.336 MPa) mannitol. In control, Dorskamp had smaller stomata than Luisa Avanzo, one or two layers of palisade cells, a spongy mesophyll, and high concentrations of antioxidative compounds (ascorbate, glutathione). After exposure to 50 or 150 mM mannitol, both clones closed their stomata: leaf conductance and opening of stomata decreased. When exposed to 50 mM mannitol, net photosynthetic rate (P _N) and chlorophyll (Chl) and total solute contents remained stable; ribulose-1,5-bisphosphate carboxylase/-oxygenase activity, Chl synthesis and turn-over, ascorbate peroxidase and glutathione reductase activities were less affected in Dorskamp than in Luisa Avanzo. Following an exposure to 150 mM mannitol, Dorskamp exhibited higher P _N and higher contents of antioxidants (ascorbate, glutathione) and antioxidative enzymes (ascorbate peroxidase, glutathione reductase) than Luisa Avanzo. Hence the drought-tolerant poplar was able to better avoid and tolerate osmotic stress. This revised version was published online in June 2006 with corrections to the Cover Date.     

Effects of NaCl salinity on growth, morphology, photosynthesis and proline accumulation of Salvinia natans

The effects of NaCl salinity on growth, morphology and photosynthesis of Salvinia natans (L.) All. were investigated by growing plants in a growth chamber at NaCl concentrations of 0, 50, 100 and 150 mM. The relative growth rates were high (ca. 0.3 d⁻¹) at salinities up to 50 mM and decreased to less than 0.2 d⁻¹ at higher salinities, but plants produced smaller and thicker leaves and had shorter stems and roots, probably imposed by the osmotic stress and lowered turgor pressure restricting cell expansion. Na⁺ concentrations in the plant tissue only increased three-fold, but uptake of K⁺ was reduced, resulting in very high Na⁺/K⁺ ratios at high salinities, indicating that S. natans lacks mechanisms to maintain ionic homeostasis in the cells. The contents of proline in the plant tissue increased at high salinity, but concentrations were very low (<0.1 μmol g⁻¹ FW), indicating a limited capacity of S. natans to synthesize proline as a compatible compound. The potential photochemical efficiency of PSII (F_v/F_m) of S. natans remained unchanged at 50 mM NaCl but was reduced at higher salinities, and the photosynthetic capacity (ETR_max) was significantly reduced at 50 mM NaCl and higher. It is concluded that S. natans is a salt-sensitive species lacking physiological measures to cope with exposure to high NaCl salinity. At low salinities salts are taken up and accumulate in old leaves, and high growth rates are maintained because new leaves are produced at a higher rate than for plants not exposed to salt.     

Comparison of growth, biomass and nutrient distribution in five promising clones of Populus deltoides under an agrisilviculture system

Variations in growth, above- and below-ground biomass and nutrient distribution were examined in five clones (G3, G48, 65/27, D121 and S7C1) of Populus deltoides grown under agrisilviculture system in sub-humid tropics of Central India. The monoclonal blocks were planted at 4x5 m in a randomized block design with three replications. Diameter at breast height (dbh) and tree height were consistently higher in clone 65/27 and lowest in clone S7C1. Mean annual increments (MAI) in dbh and height were 1.6 and 1.3 times higher in clone 65/27 compared to clone S7C1. Total biomass varied from 48.5 to 62.2 Mg ha(-1) in six-year-old clones. In rank order, the total biomass of clones was: 65/27>D121>G48>G3>S7C1. Stem wood accounted 60.4-68.9% to total biomass followed by coarse roots (12.2-18.9%), branches (12.3-15%), leaves (3.02-6.9%) and fine roots (1.5-2.7%). Root-shoot ratio ranged from 0.2 to 0.35. It was highest in clone G48 and lowest in clone S7C1. In six-year-old clones, total N ranged from 184.3 to 266.3 kg ha(-1), P from 16.8 to 31.1 kg ha(-1) and K from 81.9 to 128.7 kg ha(-1). Total N and P were highest in clone 65/27, while K in clone G48. Nutrients were lowest in clone S7C1. In general, maximum nutrients (N, P and K) were allocated to above-ground components (leaves>stem>branches) than below-ground components. Available N, P and K in the soil improved significantly after six years of planting. It was higher in 0-20 cm and decreased with soil depth. At 0-20 cm soil depth, N increased from 14.9% to 24.1%, P from 17.2% to 23.3% and K from 3.1% to 5.1% under different clones. The yield of both soybean and wheat reduced under poplar clones. Yield losses in soybean ranged from 10.1% to 33% and wheat from 15% to 30.3% under different clones. The management strategies for reducing tree-crop competition and nutrient export from the site under P. deltoides based agrisilviculture system for achieving sustainable production are discussed.     

Solution structure of the complex formed between human complement C3d and full-length complement receptor type 2

Complement receptor type 2 (CR2, CD21) is a cell surface protein that links the innate and adaptive immune response during the activation of B-cells through its binding to C3d, a cleavage fragment of the major complement component C3. The extracellular portion of CR2 comprises 15 or 16 short complement regulator (SCR) domains in a partially folded-back but flexible structure. Here, the effect of C3d binding to CR2 was determined by analytical ultracentrifugation and X-ray scattering. The sedimentation coefficient of unbound CR2 is 4.03 S in 50 mM NaCl. Because this agrees well with a value of 3.93 S in 137 mM NaCl, the overall CR2 structure is unaffected by change in ionic strength. Unbound C3d exists in monomer-dimer and monomer-trimer equilibria in 50 mM NaCl, but as a monomer only in 137 mM NaCl. In c(s) size-distribution analyses, an equimolar mixture of the CR2-C3d complex in 50 mM NaCl revealed a single peak shifted to 4.52 S when compared to unbound CR2 at 4.03 S to show that the complex had formed. The CR2-C3d complex in 137 mM NaCl showed two peaks at 2.52 S and 4.07 S to show that this had dissociated. Solution structural models for the CR2 SCR-1/2 complex with C3d and CR2 SCR-1/15 were superimposed. These gave an average sedimentation coefficient of 4.57 S for the complex, in good agreement with the observed value of 4.52 S. It is concluded that CR2 does not detectably change conformation when C3d is bound to it. Consistent with previous analyses, its C3d complex is not formed in physiological salt conditions. The implications of these solution results for its immune role are discussed. To our knowledge, this is the first solution structural study of a large multidomain SCR protein CR2 bound to its physiological ligand C3d.     

Genotypic variability and stability of poplars and willows grown onnitrate-contaminated soils

Abstract

Phyto-recurrent selection is an established method for selecting tree genotypes for phytoremediation. To identify promising Populus (poplar) and Salix (willow) genotypes for phytotechnologies, our objectives were to (1) evaluate the genotypic variability in survival, height, and diameter of poplar and willow clones established on soils heavily contaminated with nitrates; and (2) assess the genotypic stability in survival and diameter of selected poplar clones after one and eleven growing seasons. We tested 27 poplar and 10 willow clones planted as unrooted cuttings, along with 15 poplar genotypes planted as rooted cuttings. The trees were tested at an agricultural production facility in the Midwestern, United States. After 11 growing seasons, using phyto-recurrent selection, we surveyed survival and measured the diameter of 27 poplar clones (14 unrooted, 13 rooted) that were selected based on superior survival and growth throughout plantation development. Overall, willow exhibited the greatest survival, while poplar had the greatest height and diameter. At 11 years after planting, superior clones were identified that exhibited above-average diameter growth at the establishment- and rotation-age, most of which had stable genotypic performance over time. Selection of specific clones was favorable to genomic groups, based on the geographic location and soil conditions of the site.     

Alleviation of Salinity-Induced Dormancy in Perennial Grasses

All seeds of Aeluropus lagopoides and Urochondra setulosa germinated under non-saline conditions except for Sporobolus ioclados which showed only 40 % germination. Increase in salinity substantially inhibited germination and few seeds germinated at 400 mM NaCl. Germination at 200 mM NaCl was alleviated in U. setulosa by the application of gibberellic acid and fusicoccin, in A. lagopoides by thiourea, betaine, kinetin, fusicoccin and ethephon, and in S. ioclados by gibberellin and ethephon. High salinity (400 mM NaCl) induced germination inhibition was alleviated by proline, kinetin, fusicoccin and ethephon only in A. lagopoides.     

The response of CO2 exchange rate to photosynthetic photon flux density for several Populus clones under laboratory conditions

No significant differences were found between four mathematical equations describing the response of CO₂ exchange rate to photosynthetic photon flux density in seven poplar clones under laboratory conditions. Choice of an optimal equation for poplar may be based on the contemplated aims. High significant differences (at p<0.001) were found among the clones.Research was supported by the Instituut tot Aanmoediging van het Wetenschappelijk Onderzoek in Nijverheid en Landbouw (I.W.O.N.L.), Brussels.     

Germination responses of <Emphasis Type="Italic">Cymbopogon schoenanthus</Emphasis> to salinity

Germination studies of Cymbopogon schoenanthus (Poaceae) distributed along southern Tunisia were carried out to assess the effects of salinity. A preliminary experiment showed 30°C as the optimum germination temperature for seeds of this species. After that, seed germination was studied at different salinity levels. Our results revealed a decrease in germination percentage with increasing salinity. Germination rate, however, was maintained up to 200 mM NaCl and drastically declined at 300 mM NaCl.