bluuebunny/crossref_metadata_2025_split huggingface dataset:
Accumulation and excretion of sodium, potassium and chloride from leaves of two accessions of Diplachne fusca (L.) Beauv.
Authors: WARWICK N. W. M. , HALLORAN G. M. 
Published: April 2006

summaryWhen two accessions of brown beetle grass [Diplachne fusca (L.) Beauv. syn. Leptochloa fusca (L.) Kunth], differing in tolerance to salinity, were exposed to NaCl over 15 d, Na concentrations were constant in the shoot. However, there were differences in shoot Na concentration between the two accessions which were manifest after 5 d exposure to 100 mol m−3 NaCl. Na and Cl concentrations in the shoot were found to be controlled within a narrow range and did not increase any further after 5 d exposure to NaCl. Leaves of differing maturity and growth rate of both accessions did not differ in their Na concentrations. Na concentrations remained stable in leaves of differing ages after the first 6 d of exposure to NaCl whereas K declined with time, possibly due to remobilization to younger leaves. Avoidance of high concentrations of Na in younger leaves by its sequestration in older tissue does not appear to be a salt‐tolerance mechanism in D. fusca. The primary mechanism of exclusion of Na and Cl from the plant is in the root, with secondary control of leaf Na and Cl concentration by excretion of excess Na and Cl through leaf salt‐glands. Total Na uptake for the relatively salt‐tolerant accession of D. fusca. M1, was similar to that for the relatively intolerant accession F3, although M1 had a lower Na concentration in its leaves than F3 after 5d exposure to NaCl. This suggests a possible mechanism for the higher tolerance of M1 to NaCl. Leaf Na concentration was significantly higher in F3 than M1, but M1 had significantly higher Na excretion rates than F3. The leaf salt‐glands of both accessions of D. fusca were found to be capable of excreting approximately 50–80 % of the Na entering the leaf.
Selection of donors for salt‐tolerance in tomato using physiological traits
Authors: CUARTERO J. , YEO A. R. , FLOWERS T. J. 
Published: April 2006

summaryAttempts to enhance the salt‐tolerance of the cultivated tomato using the tolerance of related wild species of Lycopersicon Mill, have been unsuccessful commercially. An alternative approach is to attempt to accumulate physiological characters that contribute to tolerance within a genotype. We have investigated the relationships between tolerance and certain physiological characteristics in accessions of L. esculentum Mill., L. cheesmanii (Hook) C. H. Mull., L. pennellii (Correll) D'Arcy, L. peruvianum (L.) Mill, and L. pimpinellifolium Mill, with this aim in view.At a salinity equivalent to 40% of that in an artificial seawater, the growth of young plants was ranked both in absolute terms (fresh weight, dry weight or the growth in area of a leaf that developed during the salt treatment) and relative to growth in a salinity 2% of that of seawater. In absolute terms, two cultivars of L. esculentum (‘Moneymaker’ and ‘Edkawy’) performed about as well as L. pimpinellifolium and better than L. pennellii and L. cheesmanii: L. peruvianum showed the poorest tolerance. In relative terms, L. pimpinellifolium remained the most tolerant of the species, and L. peruvianum the most sensitive. L. cheesmanii was little more tolerant than L. peruvianum.The five species differed in their succulence and the Na: K ratio in leaves that developed during the treatment with salinity. Succulence was higher at low salinity in L. pennellii and L. cheesmanii than in the other species, but increased less on salinization. L. pimpinellifolium showed the greatest increase in succulence on salinization, a consequence of its low water content in 2% seawater. Sodium concentrations increased dramatically in all five species on salinization: L. pimpinellifolium had the highest and L. esculentum the lowest values. L. peruvianum was notable for maintaining a Na: K ratio of less than 3 throughout the period of the experiment.
Effects of salinity on root growth and death dynamics of tomato, Lycopersicon esculentum Mill.
Authors: SNAPP S. S. , Shennan C. 
Published: April 2006

summaryNumerous hydroponic studies have shown that root growth of tomato (Lycopersicon esculentum Mill.) is little affected by salinity. In contrast, data from soil‐grown plants show salinity may induce reductions of up to 50% in root length density. In this study, root growth of two tomato cultivars exposed to salinity (NaCl and CaCl2, 4:1) was examined in the field, in large soil‐filled containers, and in hydroponics. The two cultivars, UC82B and CX8303, differed in susceptibility to a common root rot organism (Phytophthora parasitica Dast.), and were hypothesized to differ in root growth response to environmental stress. In agreement with the literature, root weight of young, hydroponically‐grown plants (as determined by multiple, destructive harvests) was unaffected by salinity in both cultivars. In contrast, root length density of cv. UC82B was reduced 40% by salinity in the field, whereas root length density of root rot‐tolerant cv. CX8303 was unaffected. Similar responses to salinity were observed in the containers, with root counts from horizontal minirhizotron tubes reduced in cv. UC82B, but not in cv. CX8303. Observations from windows in the sides of the containers showed that reduction in net root growth in cv. UC82B was primarily due to an increased rate of root death at high salinity. Root turnover remained low in cv. CX8303 under both low and high salinity. Differential effects of salinity on root growth of the two cultivars in containers were not evident until about 60 d after transplanting. This suggests that the discrepancy between salinity responses of hydroponic and soil‐grown plants was primarily due to differences in phenology. Enhanced rates of root death during the reproductive growth stage may represent an important, previously undocumented carbon cost to some genotypes exposed to salinity.
Field studies on Norway spruce trees at high altitudes
Authors: POLLE ANDREA , MÖSSNANG MICHAEL , VON SCHÖNBORN ALEXANDER , SLADKOVIC RUDOLF , RENNENBERG HEINZ 
Published: April 2006

summaryThe present study was performed on mature Norway spruce trees (Picea abies L.) with needle losses in the range of 25–35 %. The trees were growing at three altitudes (870, 1270, and 1700 m above sea level) in a mountain forest in the Calcareous Alps of Bavaria. The objectives were to assess the role of climate and pollution in addition to nutrient disorders for damage to spruce trees. During the growing season the average temperature was up to 5 °C lower and the average ozone concentration was about twofold higher at the high altitude in comparison to the low altitude (13 and 18 °C, and 60 and 35 nl I−1 ozone, respectively); the average NOx and SO2 concentrations did not exceed 5 nl I−1. Foliar analysis of pollutants did not indicate critical levels of Pb, Cd, Cl, F and S. Biometrical parameters, foliar element composition, pigment and protein content of the needles were determined during four seasons. Average dry:fresh weight ratios, specific needle weights, projected needle areas, soluble protein and carotenoid contents were similar within the 20 % range for needles from all three altitudes. Foliar analysis of nutrients indicated a low nutrient status especially for nitrogen, and showed a phosphorus deficiency in needles from the three sites. The chlorophyll content of the needles decreased with increasing altitude. Since nutrient imbalances were greatest in needles from the lowest site, it was concluded that the greater damage to spruce trees and lower chlorophyll content of the needles at altitudes > 1000 m above sea level were not caused by nutrient disorders.
The late Quaternary vegetational history of northwest Greece
Authors: WILLIS K.J. 
Published: April 2006

summaryRezina marsh, a small basin at a height of 1800 m, in the Pindus mountain range, is both the smallest and highest site yet to be studied in Greece. Techniques of pollen and plant macrofossil analysis, sediment chemistry, mineral magnetics and radiocarbon dating have been employed to reconstruct both vegetational and sedimentary history of the basin. The sequence extending back to c. 10000 bp, provides the first evidence for the possible location of full glacial refugia for temperate tree taxa in Greece. In the early postglacial a dense mixed woodland containing at least sixteen different tree taxa was present around the Rezina basin. This woodland persisted throughout the early postglacial although dominance of tree types in the woodlands changed several times. These changes are thought to be closely related to climatic changes during the early postglacial. At c. 6000 bp both the density and diversity of the woodland became greatly reduced. Although there was some recovery of the woodland at c. 5000 BP, anthropogenic intervention at c. 4000 BP led to total destruction of this montane forest and the development of open grassland similar to the present day situation.
The response of spring wheat (Triticum aestivum L.) to ozone at higher elevations
Authors: GRANDJEAN GRIMM A. , FUHRER J. 
Published: April 2006

summaryThe flux of O3 was determined in open‐top chambers (OTC) used to investigate its effect on spring wheat (Triticum aestivum L., cv. Albis) in 1989 and 1990. The experimental site was located at 900 m above sea level at Zimmerwald, near Bern (Switzerland). The aims were to evaluate the use of OTCs for O3 flux measurements under field conditions, to assess the role of stomata in controlling the O3 fluxes, and to establish a quantitative relationship between radiation‐weighted O3 concentrations and O3 flux. Measurements were carried out from full expansion of flag leaves until the onset of senescence. Ozone flux was determined by mass balance using the concentrations of O3 measured at the inlet and outlet of the OTC. The CO2 exchange rate was corrected for soil‐borne COO and used as a reference. Measurements of temperature, photosynthetically active radiation (PAR), saturated water vapour pressure deficit (SVPD), and boundary layer conductance were used to describe the microclimate inside OTCs.In the warmer microclimate in 1989, the plant canopy was characterized by a smaller leaf area index (LAI) than in 1990, while the fluxes of O3 and CO2 during daytime were generally larger in 1989. The diurnal patterns of fluxes of O2 and CO2, in OTCs supplied with unfiltered air were similar. It is estimated that O3 absorption via the stomata contributed 50–70% of its total flux. Identical relationships between leaf conductance for O2, measured by porometry and leaf conductance calculated from O3 flux were found in both years, but measured leaf conductance during daytime was generally smaller in 1990 than in 1989. The results indicate that stomatal conductance largely controlled O3 flux, and that the canopy structure has an influence on the overall conductance of the canopy.Different linear functions were obtained for the relationship between radiation‐weighted O3 concentration and O3 flux, using data from OTCs supplied with either charcoal‐filtered air, unfiltered air or unfiltered air enriched with O. (two levels). These relationships form the basis for the calculation of mean O3 fluxes which can be used as an exposure index in the exposure‐response analysis.
The response of spring wheat (Triticum aestivum L.) to ozone at higher elevations
Authors: FUHRER J. , GRIMM A. GRANDJEAN , TSCHANNEN W. , SHARIAT‐MADARI H. 
Published: April 2006

summaryThe effect of ozone on the yield, yield components and grain composition of spring wheat (Triticum aestivum L., cv. Albis) was investigated in 1989 and 1990 at 900 m above sea level. Plants were grown from the three‐leaf stage until harvest in open‐top chambers ventilated with charcoal‐filtered air (CF), unfiltered air (UF) or unfiltered air with one of two levels of O3., added when global radiation exceeded 400 J m−2s−1(O3– 1, O3– 2). Ambient plots (AA) without chambers were used as a reference. Mean 7‐h d−1(09.00–16.00 h) O3 concentrations in the CF, O3– 1 and O3– 2 treatment, respectively, was approximately 0.5, 1.4 and 1.8 times the concentration in the UF treatment, which was 70μgm−3in 1989 and 76μg m−3in 1990. The OTC environment was characterized by a warmer, more humid microclimate and reduced soil moisture, compared with the open field. In 1989, this effect of the chambers was more pronounced than in 1990. When compared with A A plots, chamber enclosure significantly reduced grain and straw yield in 1989, while in 1990 no difference was observed. Grain yield decreased with increasing seasonal mean O3 concentration as a result of reductions in the weight of individual grains and in the number of grains per head. A small decrease in the ratio between grain weight and total above‐ground biomass (harvest index) indicated a shift in biomass allocation. With increasing O3, small or no changes were observed in protein, starch and K concentrations, and in protein quality (Zeleny value) of the grain. Relationships between different measures of O3 exposure and relative grain yield were constructed with a quadratic model. With mean concentrations (7‐h d−1mean or radiation‐weighted mean) or with a cumulative index (SUMO6 = sum of concentrations above 60 μl1−1) to describe exposure, the response of grain yield to increasing O3 was smaller in 1990 than in 1989. Nearly identical exposure‐response functions were obtained for both seasons, with the mean O3 flux used to estimate the absorbed dose of O3. Quadratic exposure‐response functions suggest that ambient levels of O3, reduced grain yield by 9‐5% and 11.6% in 1989 and 1990, respectively. Using Weibull exposure‐response functions, a comparison with results from an earlier study at 485 m above sea level indicates reduced sensitivity at the higher elevation.
Effects of nitrogen source on growth, nutrition, photosynthetic rate and nitrogen metabolism of mycorrhizal and phosphorus‐fertilized plants of Lactuca sativa L.
Authors: AZCÓN R. , GOMEZ M. , TOBAR R. 
Published: April 2006

summaryPlants of Lactuca sativa L. cv. Romana were inoculated with two vesicular‐arbuscular (VA) mycorrhizal fungi, Glomus mosseae (Nicol. & Gerd.) Gerd. & Trappe and Glomus fasciculatum (Thaxter sensu Gerd.) Gerd. & Trappe, or provided with phosphorus. These three treatments plus a control were supplemented with 3.0 mM nitrogen as nitrate or ammonium in 1 of 5 NO3−/NH4+ ratios. Leaf and root weights, N, P, K, Ca and Mg absorption, as well as the percentage of root length colonized, were evaluated. Physiological parameters such as leaf area, photosynthetic rate, glutamine synthetase (EC 6.3.1.2) and nitrate reductase (EC 1.6.6.1) activity and leaf proline accumulation were also determined. Mycorrhizal lettuce and P‐fertilized plants derived significantly more benefit from N fertilization regardless of the N‐source than did controls. Ammonium was a better N‐source for non‐mycorrhizal plants and nitrate for mycorrhizal plants. P‐fertilized lettuce reached maximum growth when N was supplied as 50% NO3−/ 50% NH4+ so that mycorrhizal status particularly affected the plant response to the form of N provided. Growth of mycorrhizal plants was comparable to non‐mycorrhizal P‐fertilized plants when N was provided as 100% NH4+ or 25 % NO3−/75 % NH4+. When N applications were as 50% NO3−7 50% NH4+ or 75% NO3−/25% NH4+, growth of P‐fertilized plants was greater than mycorrhizal ones. Lettuce colonized by G. mosseae grew fastest when fed nitrate only. Separation of NO3− and NH4+assimilation into shoot and root compartments may account for the differential effects of such ions into symbiotic and non‐symbiotic plants. Uptake or metabolism of nitrogenous forms was particularly affected in G. mosseae‐colonized plants, independent of P nutrition. P fertilization increased activities of nitrate reductase (NR) by 29 % and glutamine synthetase (GS) by 24% compared with activities in control plants. In the case of G. fasciculatum‐colonized plants, NR and GS were increased 54% and 117 %, respectively, over control activities. In general, concentration of minerals, except Ca, were increased in mycorrhizal and P‐fertilized plants compared with controls. Assimilation of CO2 and accumulation of proline were increased in G. fasciculatum‐colonized lettuce under all N regimes.
Genecological studies of groundsel (Senecio vulgaris L.)
Authors: BRIGGS D. , BLOCK M. 
Published: April 2006

summaryIn a well‐weeded site, selection is likely to favour quick‐maturing variants of annual weeds. Variation in rate of development ‐ from sowing, with synchronous germination, to first flowering and fruiting‐was studied in experiments with Senecio vulgaris L. from the Botanic Garden of Cambridge University, England. Experiments revealed that the number of nodes on the main axis could not be used a ‘genetic marker’ for rate of development.From a large random sample of seed‐parents, progenies were raised from open‐pollinated capitula. Family lines differed significantly in rate of development, with markedly different degrees of variation within families. Twenty family lines, representing the extremes of variation, were chosen for further study. In cultivated selfed derivatives, the majority of the seed‐parents appeared to be behaving as inbred lines for rate of development. Evidence of genetic segregation was detected in only two out of 20 cases. Using the radiate locus as a marker, there was also evidence for a very small amount of outcrossing, with greater values for radiate than non‐radiate seed‐parents. In an experiment in which six inbred lines, derived from the original seed‐parents, were grown out‐of‐doors on fertile and infertile soils and on fertile soil in a glasshouse, there was considerable developmental flexibility in a number of heritable traits including rate of development.Although the methods of weed control in the Botanic Garden would seem to exert a powerful directional selective force favouring only the quickest‐maturing variants of groundsel, a certain amount of variation was nevertheless detected. Many factors are likely to be important in the maintenance of population variation in rate of development in groundsels in the Garden. Several statistically significant lines x soils and lines x places of cultivation were discovered. Thus, the lines did not all behave in the same way in the inside and outside treatments and the rank order of date of maturity of the different lines was not the same in the two soils. This suggests that, in the Garden proper, relative fitness, in the face of weeding pressures, is not fixed but may vary seasonally and in soils of different fertility. This behaviour, in a species which is able to reproduce at all seasons of the year, could be a major factor in the maintenance of population variation. Other contributory factors are of great importance, namely, spatial and seasonal variation in the intensity of weeding, developmental flexibility and the effects of predators, pests and diseases.
Genecological studies of groundsel (Senecio vulgar is L.)
Authors: BRIGGS D. , BLOCK M. , FULTON E. , VINSON S. 
Published: April 2006

summaryPlants of groundsel (Senecio vulgaris L.) in the very well‐kept University Botanic Garden, Cambridge are quicker in their rate of development than those from sites subject to less regular or no weeding pressure. However, the directional selection pressure favouring precocity has not resulted in population uniformity. In order to generate hypotheses about the development and maintenance of population variation in this annual weed, we have studied the origin and patterns of migration of two genetic variants. Also, we have investigated the history of the oldest established flowerbeds in the Garden, with particular reference to continuity of use and garden practices.The Systematic Beds have been in existence for more than 140 years and, despite periods of difficulty, have been subject to regular and frequent weeding.Evidence suggests that the radiate variant of groundsel was most likely introduced into the Garden in the late 1890s from plants collected at Bandon Station, County Cork, Ireland. Subsequently, this plant ‐ var. hibernicus Syme ‐ spread to many parts of the Garden but it did not establish itself on the Systematic Beds until 1985. Using the radiate capitulum locus as a marker, our results reveal a consistently very low level of outcrossing in non‐radiate plants and a more variable and seasonally higher frequency in radiate plants. In 1987, simazine resistant plants were detected in the Systematic Beds, an area which has never been treated with triazine herbicides. It seems likely that these resistant plants originated from a population of resistant plants on treated ground just outside the western border of the Garden.Two models have been devised to explain our findings. The first model postulates that weeding has been too efficient on the Systematic Beds to permit the slower developing radiate plant to establish itself there. A second model, which appears to fit the facts more closely than the first, postulates that the migration of the radiate variant has been restricted by gene flow.
Ecological segregation between closely related species in the flooded forests of the upper Rhine plain
Authors: SCHNITZLER ANNIK , CARBIENER ROLAND , TRÉMOLIÈRES MICHÈLE 
Published: April 2006

summaryIn the large European river floodplains, closely related species segregate between habitats within numerous forest communities whose structure and dynamics are shaped by the river and its tributaries. Factors of segregation are mainly geochemistry (lime content and texture), water stress and fluvial dynamics. When sympatric, the closely related species coexist by niche differentiation (life‐form, place in the successional stages, phenology and abundance).We have made a comparative study of the niches of 70 species belonging to 24 genera in the alluvial forest communities of the upper Rhine valley (France), using a descriptive and qualitative approach. Results were compared with the literature on European biogeography. Particular attention was paid to seven woody genera (Populus, Salix, Ulmus, AInus, Acer, Crataegus and Primus) and to the behaviour of hybrids along the environmental gradients of the study area.
Palynological variation in primula L. subgenus Sphondylia (Duby) Rupr., and the relationship of this group to Dionysia Fenzl.
Authors: WADI HUSSEN AL , RICHARDS A. J. 
Published: April 2006

summary Primula subgenus Sphondylia is composed of eight localized and probably relictual taxa distributed from Ethiopia to the west Himalaya. It is considered to occupy an ancestral position in the genus, and to demonstrate stages in the evolution of dimorphic heterostyly. Previous authors have suggested that the heterostylous genus Dionysia evolved from forerunners of this group.It has previously been reported that, in five of the species, only prolate 3‐colporoidate pollen is found, dimorphic in size for heterostylous species. However, the pollen of the heterostylous species P. edelbergii, P. gauheana and P. darisii is dimorphic for shape and colpus number, as well as for size. Thus, our study reports for the first time, a major morphological pollen dimorphism, and 1‐ and 2‐colpor(oid)ate pollen in the Primulaceae.We found that three distinct trends in the development of pollen dimorphism can be traced in this group, two of which appear to have no major phyletic implication. However, it is possible that P. floribunda represents phyletic links between subgenus Sphondylia and later heterostylous developments in Primula.Pollen in Dionysia is said to be weakly dimorphic for shape and colpus number, and our findings agree with this. We suggest that Dionysia is not closely related to Primula subgenus Sphondylia and that strong superficial resemblances between certain taxa in these groups may have resulted from parallel evolution.