In situ localization of glucose and sucrose in dehydrating leaves of Sporobolus stapfianus

Accumulation of soluble carbohydrates during dehydration stress is thought to be a very important mechanism for the acquisition of desiccation tolerance. Despite the proposed importance of soluble carbohydrate accumulation (especially sucrose), nothing is known about the cellular localization of carbohydrates in desiccation-tolerant plants. The present study proposes a novel and selective method for the in situ localization of sucrose and glucose in the desiccation-tolerant plant Sporobolus stapfianus. The detection of sucrose and glucose is based on a series of coupled enzymatic reactions leading to the formation of NADH. Iodonitrotetrazolium (INT) reacts with NADH, thereby providing the red-colored insoluble INT-formazan. Stained tissue sections were immediately visualized using light microscopy. Localization of the respective sugars was site specific. Sucrose was visualized in all leaf cell types during dehydration: vascular bundles, bundle sheath cells, mesophyll cells and epidermal cells. Similarly, glucose was shown to be localized in the same leaf compartments as reported for sucrose. This is the first report that describes sucrose localization in dehydrating leaf tissues of a "resurrection" plant. We conclude that, during dehydration stress, sucrose accumulates in all viable tissues; these results are in agreement with the previously proposed theories about its function as a cellular protectant.     

Salinity and temperature tolerance of juvenileMesopodopsis orientalis: laboratory studies

Separate and combined effects of changes in salinity and water temperature on the survival of laboratory hatched juvenileMesopodsis orientalis were investifated. Full strength seawater (35) was not favorable to juvenile survival. Salinities down to 10% seawater were tolerated when subjected to sudden exposure, but salinity acclimation increased juvenile ability to tolerate even fresh water. Water temperatures tolerated by the animals ranged from 12°C to 33°C. Salinities of 30% to 60% seawater and water temperatures of 22°C to 28°C were most favorable to the juveniles. Experimental results were compared with field observations and a relationship between the salinity and temperature of seawater and abundance of juveniles in May to June, and November to January in Bombay coastal waters (west coast of India) was established. Seawater of reduced salinity was found to be a major factor for occurrence of juvenileM. orientalis in abundance.     

The presence of the enhanced K/Na discrimination trait in diploid Triticum species

Summary A number of accessions of the three species of diploid wheat, Triticum boeoticum, T. monococcum, and T. urartu, were grown in 50 mol m^-3 NaCl+2.5 mol m^-3 CaCl₂. Sodium accumulation in the leaves was low and potassium concentrations remained high. This was not the case in T. durum grown under the same conditions, and indicates the presence in diploid wheats of the enhanced K/Na discrimination character which has previously been found in Aegilops squarrosa and hexaploid wheat. None of the accessions of diploid wheat showed poor K/Na discrimination, which suggests that if the A genome of modern tetraploid wheats was derived from a diploid Triticum species, then the enhanced K/Na discrimination character became altered after the formation of the original allopolyploid. Another possibility is that a diploid wheat that did not have the enhanced K/Na discrimination character was involved in the hybridization event which produced tetraploid wheat, and that this diploid is now extinct or has not yet been discovered.     

Filamentous fungi quiescent in seeds and culm nodes of weedy and forage grass species endemic to the Palouse Region of Washington and Idaho

Asymptomatic seeds of forage and weedy grasses from germplasm accessions and from uncultivated sites in eastern Washington and western Idaho were assayed for the presence of quiescent filamentous fungi. Asymptomatic culm nodes of the same species were similarly assayed. The predominant taxa isolated were strains of dematiaceous hyphomycetes, principally strains of Alternaria and Cladosporium. A. infectoria was the species most frequently isolated from seed. A. tenuissima was common and A. alternata was rare. Aspergillus, Penicillium and Fusarium were very rare or absent in stored germplasm. Pathogenic coelomycetes were common in asymptomatic node samples, occasionally present in asymptomatic field seed, but were not detected in germplasm accessions. Previous reports of frequent occurrence of A. alternata in grass seed are probably the results of misidentification of various small-spored Alternarias, especially A. infectoria, as A. alternata.This revised version was published online in October 2005 with corrections to the Cover Date.     

Salt tolerance in Lycopersicon species. II. Genetic effects and a search for associated traits

Eleven quantitative traits, mostly related to tomato plant growth and fruit set, and their association with salt tolerance in terms of fruit yield under a 171.1 mM NaCl treatment have been investigated in 206 progeny derived from an interspecific hybrid, L. esculentum x L. pimpinellifolium, by self-pollination. None of the traits were highly correlated phenotypically to salt tolerance; however, the immunologically-detected presence of peptide 2 was significantly associated with high total fruit weight (TW) and number (FN) under saline treatment. Broad-sense heritability was estimated for these two salt-tolerance components as 53.44 and 72.59 %, respectively. Non-additive gene effects, which have to be considered in a breeding program for salt tolerance, have been detected in TW, FN and in average fruit weight (FW). Given that different types of gene action have been found depending on the presence or absence of a high NaCl concentration in the nutrient solution, a different set of genes, or genes, differently regulated, must be involved in the expression of TW, FN and other fruit-related characters depending on this environmental condition.     

Improved growth of salinity-stressed soybean after inoculation with salt pre-treated mycorrhizal fungi

Two sets of experiments to determine the effect of mycorrhiza on soybean (Glycine max) growth under saline conditions and to investigate the salt acclimation of mycorrhizal fungi were conducted. In the first experiment, the effect of an arbuscular mycorrhizal (AM) fungus Glomus etunicatum on mineral nutrient, proline and carbohydrate concentrations and growth of soybean. Under different NaCl concentrations (0, 50, 100, 150 and 200mM) was evaluated. Salinity decreased AM colonization. In both the M and nonAM plants shoot and root proline and shoot Na and Zn concentrations were increased under salinity. Soybean plants inoculated with the AM fungus had significantly higher fresh and dry weight, root proline, P, K and Zn but lower shoot proline and Na concentrations compared to the non inoculated plants. In the second experiment, the AM fungus was pre-treated with NaCl (salt acclimation) then was used as inoculum for soybean plants subjected to 100mM NaCl. Root colonization, fresh and dry weight, root proline, P, K and Zn concentrations were greater in soybean plants inoculated with the salt pre-treated fungus, compared to those inoculated with the nonsalt pre-treated fungus. However, for Na, the situation was the opposite. Based on these results, the AM inoculation helps the growth of soybean plants grown in saline conditions. When the AM fungus was pre-treated with NaCl with a gradual increase of concentration, and then exposed to a sudden salt stress, their efficiency was increased. This may be due to the acclimation of the AM fungus to salinity.     

Salinity tolerance in some mangrove species from Pakistan

Growth, ionic and water relations of three mangrove species viz. Avicennia marina, Ceriops tagal and Rhizophora mucronata werestudied in different seawater concentrations (0, 25, 50, 75 and 100%).All mangrove species showed optimal growth at 50% seawater. Relativelymore biomass was accumulated by R. mucronata while C. tagalhad the tallest individuals. Tissue water potential became more negativewith the increase in salinity and stomatal conductance was decreased in allplants. Higher stomatal conductance was noted in R. mucronata,followed by A. marina and C. tagal. Sodium and chloride ionsincreased with the increase in salinity and this accumulation was muchhigher in A. marina.     

Meiotic studies ofElymus nutans andE. jacquemontii (Poaceae,Triticeae) and their hybrids withPseudoroegneria spicata and seventeenElymus species

Hybridizations ofElymus nutans andE. jacquemontii were carried out with one species ofPseudoroegneria (S genome), and 20Elymus species, each containing either of the SH, SY, SYH, or SYW genomes. Chromosome configurations were analysed at metaphase I of the two target taxa and their interspecific hybrids. It is concluded that (i)E. nutans is an allohexaploid containing the SYH genomes, andE. jacquemontii is an allotetraploid having the SY genomes; (ii) the genomic affinity is associated with the geographic distance between the species studied; (iii) minor genomic structural rearrangements have occurred within the hexaploid taxon ofE. nutans.     

Genetic variability in Lycopersicon species and their genetic relationships

Summary Genetic diversity has to be described and measured in order to establish breeding strategies and manage genetic resources. It is also fundamental to develop a comparative intraspecific study before attempting to discuss and conclude any phylogenetic relationship. The genetic variability of Lycopersicon species was studied using starch gel electrophoresis of 11 enzymatic systems in a hierarchical fashion. The species with the greatest genetic variability are L. chilense, L. peruvianum and L. pennellii, mainly due to the within-line component. L. chmielewskii, L. parviflorum and L. pimpinellifolium show an intermediate total variability and their between-component clearly predominates over the within-component. The least variable species are L. cheesmanii and L. esculentum. Cluster analysis resulted in three main groups: one formed by the cultigen, L. pimpinellifolium, L. cheesmanii and L. peruvianum;another by two species with self-incompatibility systems, L. pennelli and L. chilense; and another by two autogamous species L. chmielewskii and L. parviflorum. With respect to L. esculentum the farthest related species is Solanum rickii and the closest, L. pimpinellifolium.     

Salinity stress proteins in Eurytemora affinis

Seasonal densities of Eurytemora affinis, a calanoid copepod in the Chesapeake Bay, seem to be controlled by temperature and salinity. To examine the role of osmotic stress we analyzed protein synthesis under various conditions of temperature and osmotic stress. Adult females were exposed in groups for 5 hours to different temperature and salinity regimes in the presence of isotope-labelled amino acid. Newly synthesized (stress) proteins could be separated and identified using polyacrylamide gel electrophoresis and autoradiography. The protein profiles occurring in copepods experiencing osmotic shock alone were different from those of control animals. Copepods transferred to lower (2 and 5) and higher (15 and 20) salinities showed differences in the up- and down-regulation of specific proteins. Concurrent heat stress changed these protein patterns. Animals experiencing osmotic and heat shock at the same time exhibited enhanced expression of another set of proteins. Variation in induced proteins occurred among individuals.     

The interaction of defoliation and nutrient uptake in Sporobolus kentrophyllus,a short-grass species from the serengeti plains

Summary Sporobolus kentrophyllus, a grazing-tolerant C₄ grass from the southeastern Serengeti Plains, was grown in solution culture to examine the effects of clipping on the uptake, preference and subsequent transport of varying nitrogen forms. Clipping reduced offtake mass, crown mass ane root mass, resulting in a 58% decline in plant mass. Proportional biomass allocation to roots decreased with clipping, while tillering rates increased. Clipping also increased the nitrogen concentrations of all tissues, and plant nitrogen uptake (nitrogen accumulated throughout the experiment per gram root). The ¹⁵N concentrations (% atom excess) of all tissues were higher in clipped compared with unclipped plants, and the average ¹⁵N uptake rate of clipped plants was twice that of unclipped plants. The relative ¹⁵N allocation to aboveground mass, a measure of canopy sink strength, was higher in clipped plants. Plants fed ¹⁵N-ammonium or ¹⁵N-nitrate during the ¹⁵N pulse experiment had greater ¹⁵N tissue concentrations compared with urea-fed plants, and ¹⁵N uptake rates were higher in ammonium-fed and nitrate-fed plants, compared with urea-fed plants. The relative magnitudes of these differences were higher when plants were clipped. Clipped plants had higher uptake rates for potassium, phosphorus and sodium, while differences between clipping treatments for calcium, iron, and magnesium were indistinguishable. Rapid uptake rates for species on the southeastern Serengeti plains, particularly during grazing periods, have important implications for nutrient cycling in this system.     

盐雾胁迫对极小种群植物日本荚蒾光合生理的影响

为评价日本荚蒾(Viburnum japonicum)的耐盐雾能力,对4 a生实生苗用不同盐雾浓度处理(盐雾NaCl质量浓度分别为0%、1%、2%、3%),测定叶片净光合速率、最大光化学效率(F_v/F_m)和叶绿素含量(Chl)等指标的变化。结果表明,1%盐雾处理的日本荚蒾植株能够存活,但生长不良,大于2%的盐雾处理的植株全部死亡。随着浓度的升高,日本荚蒾叶片的最大光合速率、F_v/F_m及Chl含量下降,而光饱和点及光补偿点总体呈上升趋势。这说明盐雾胁迫通过伤害光系统Ⅱ反应中心、改变植物可利用光能范围及降低叶绿素含量影响植物的光合作用。     

Ion measurements by X-ray microanalysis in unfixed,frozen, hydrated plant cells of species differing in salt tolerance

A technique is described for X-ray microanalysis of unfixed, frozen, hydrated higher plant cells using a scanning electron microscope in conjunction with a cryostage. Freezing in liquid N₂ is the only preparative step required. Using this method, ion distribution was compared in the roots of Zea mays L. (termed a salt excluder) and Hordeum vulgare L. (which is rather more tolerant), both grown in the presence of NaCl. Distinct differences were observed between the two species in Na, K and Cl distribution. Evidence is presented to support the hypothesis that reabsorption of Na from the xylem sap in the mature regions of the root may occur in salt-sensitive glycophytes such as Z. mays.     

Evolutionary change at the5S Dna loci of species in theTriticeae

Previous studies have shown that two separate loci for 5S DNA sequences may exist within a species. Two size classes have been tentatively assigned in the ranges 327–468 bp (chromosome 1), and 469–500 bp (chromosome 5) and the entire data-base was subjected to various numerical taxonomic analyses. The results confirm the existence of two lineages of 5S DNA sequences represented by the two size classes.Hordeum vulgare is separate from the species known also asCritesion and, together withDasypyrum, occupy an intermediate position between the two size classes. The 5S DNA units fromTriticum spp. that have also been namedAegilops spp. in other classifications appear as a distinct group withinTriticum spp. at both loci. The consensus 5S DNA sequence fromPsathyrostachys is remote fromHordeum s.l. in contrast to opinions based on morphology. Other aspects are detailed and discussed, including the inadequacy of the computing methods used as well as the need for more data in view of the large amount of homoplasy. The merit of using the spacer for phylogenetic inference is also discussed.     

Influence of host cultivars and Rhizobium species on the growth and symbiotic performance of Phaseolus vulgaris under salt stress

In order to study the effect of salt stress on the Rhizobium-common bean symbiosis, we investigated the response of both partners, separately and in symbiosis. The comparison of the behaviour of five cultivars of Phaseolus vulgaris differing in seed colour, growing on nitrates and different concentrations of NaCl, showed genotypic variation with respect to salt tolerance. Coco Blanc was the most sensitive cultivar, whereas SMV 29-21 was the most tolerant one. At the Rhizobium level, two strains previously selected for their salt tolerance were used: Rhizobium tropici strain RP163 and Rhizobium giardinii strain RP161. Their relative growth was moderately decreased at 250mM NaCl, but they were able to grow at a low rate in the presence of 342 mM NaCl. Their viability at the minimal inhibitory concentration was slightly affected. The effect of salinity on Rhizobium-plant association was studied by using the tolerant variety SMV 29-21 and the sensitive one Coco Blanc inoculated separately with both strains. In the absence of salinity, the strains induced a significantly higher number of nodules on the roots of the cultivar SMV 29-21 compared to those of Coco Blanc. Concerning effectiveness, both strains were similarly effective with SMV 29-21, but not with Coco Blanc. In the presence of salinity, Coco Blanc was more severely affected when associated with RP163 than with RP161. Salinity affected the nodulation development more than it affected the infection steps. Neither of the two strains was able to nodulate SMV 29-21 under saline conditions, in spite of the fact that this was considered the most salt-tolerant variety. The unsuccessful nodulation of SMV 29-21 could be related to the inhibition by salt of one or more steps of the early events of the infection process. In conclusion, N-fixing plants were found to be more sensitive to salt stress than those depending on mineral nitrogen. Evidence presented here suggests that a best symbiotic N2 fixation under salinity conditions could be achieved if both symbiotic partners, as well as the different steps of their interaction (early events, nodule formation, activity, etc.), are all tolerant to this stress.     

Relationships between five species ofLolium (Poaceae)

Morphological analysis and electrophoresis of seed proteins of fiveLolium species disclosed that they form two distinct groups corresponding to those recognized from compatibility data.Lolium temulentum andL. remotum of the self-pollinated group were shown to be distinct but closely related species. Morphological intergradation and high similarities between protein profiles ofL. perenne, L. multiflorum andL. rigidum (cross-pollinated species) suggest little genetic differentiation between these taxa. This implies that treatment at the infraspecific level might better accomodate the data.     

Cytogenetic and genomic relationships ofThinopyrum elongatum with twoPsathyrostachys species and withLeymus secalinus (Poaceae)

Intergeneric hybridizations were made betweenT. elongatum, and twoPsathyrostachys and fiveLeymus species. The seed set obtained onT. elongatum ×Leymus hybrids ranged from 5.65% to 20.00%, depending onLeymus species. The seed set obtained onT. elongatum ×Psathyrostachys hybrids ranged from 16.07% to 19.70%. Meiotic pairing at metaphase-I in JN diploid hybrids ofT. elongatum ×Psathyrostachys species revealed a very low level homology between the basic J and N genomes, and further demonstrated that the two genomes are quite diverged. Chromosome pairing in theT. elongatum ×Leymus secalinus hybrid averaged 15.19 univalents + 2.62 rod bivalents + 0.26 ring bivalents + 0.02 trivalents, suggesting that the partial J^e chromosomes ofT. elongatum has homology withLeymus secalinus genomes.L. secalinus might have 3–4 chromosomes originating from J^e genome.     

CHy-banding patterns and chromatin organization inAegilops andTriticum species (Poaceae)

The distribution of CHy-banded heterochromatin was studied in the chromosomes ofAegilops longissima, Ae. speltoides, Triticum monococcum, andT. turgidum. Interphase nuclei were measured after Feulgen staining at different thresholds of optical density; the curves so obtained indicated the relationship among the species with respect to the different fractions of the genomic DNA. The karyological and cytophotometric analyses indicate differences betweenAe. speltoides andAe. longissima, the latter species being enriched in heterochromatin. Similar results were demonstrated for the genusTriticum, in whichT. turgidum showed more heterochromatin when compared withT. monococcum. The results suggest that the B genome of the cultivated wheats possesses a type of heterochromatin that resembles the type present inAe. longissima.