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The physiological effects of high CO2 concentrations, i.e., [CO2], on plant stomatal responses may be of major importance in understanding the consequences of climate change, by causing increases in runoff through suppression of plant transpiration. Radiative forcing by high [CO2] has been the main consideration in models of global change to the exclusion of plant physiological forcing, but this potentially underestimates the effects on the hydrological cycle, and the consequences for ecosystems. We tested the physiological responses of fossil plants from the Triassic--Jurassic boundary transition (Tr--J) succession of East Greenland. This interval marks a major high CO2-driven environmental upheaval, with faunal mass extinctions and significant floral turnover. Our results show that both stomatal size (expressed in fossil material as SL, the length of the stomatal complex opening) and stomatal density (SD, the number of stomata per mm²) decreased significantly during the Tr--J. We estimate, using a leaf gas-exchange model, that the decreases in SD and SL resulted in a 50%--60% drop in stomatal and canopy transpiration at the Tr--J. We also present new field evidence indicating simultaneous increases in runoff and erosion rates. We propose that the consequences of stomatal responses to elevated [CO2] may lead to locally increased runoff and erosion, and may link terrestrial and marine biodiversity loss via the hydrological cycle. [ABSTRACT FROM AUTHOR]

Aim To determine how the distribution of species richness is associated with environmental factors for the four major C4 grass lineages in South Africa, as a means to explore the mechanisms responsible. Location South Africa, Lesotho and Swaziland. Methods The geographical distributions of species richness for four major C4 grass lineages (Aristidoideae, Chloridoideae, Andropogoneae and Paniceae) were sourced from a recently published flora that divided the study region into different vegetation types. Mean values of potential environmental correlates were calculated for each vegetation type, and the relative importances of these were determined using single- and multiple-predictor generalized linear models, with and without control for spatial autocorrelation. Model selection of the multiple-predictor generalized linear models was conducted using an Akaike's information criterion-information theoretic approach. Association with wet, intermediate or dry, shady or open, and disturbed or undisturbed habitats was also determined for each C4 grass clade using habitat data for all the grass species, and analysed using chi-square tests of independence. Results Andropogoneae and Paniceae are most species-rich in areas of high precipitation and in mesic habitats. Andropogoneae are associated with high fire frequencies. Species richness in Andropogoneae decreases and in Paniceae increases in relation to livestock density. Chloridoideae species richness is relatively constant across South Africa, but is highest where there are infrequent fires, high temperatures and basic soils, and in mesic and disturbed habitats. Aristidoideae are most species-rich in arid regions and in habitats with high temperatures, and are associated with disturbed habitats. Main conclusions Environmental variables other than precipitation, including temperature, fire frequency and grazing pressure, are strongly associated with the contrasting distributions of species richness for the various C4 grass clades in South Africa. Our results suggest that ecological sorting is an important determinant of phylogenetic patterns in the species richness of these C4 grass lineages. [ABSTRACT FROM AUTHOR]

An introduction to the journal is presented in which the editor discusses an article on the impact of natural drought in Amazon, the quality of various global circulation models (GCMs) climate situations which are employed to drive dynamic global vegetation models (DGVMs), and the mechanisms involve in DGVM processes.

• The recent discovery of a strong positive relationship between angiosperm genome size and stomatal guard cell length (GCL) opens the possibility of using plant fossil guard cell size as a proxy for changes in angiosperm genome size over periods of environmental change. • The responses of GCL to environmental stimuli are currently unknown and may obscure this predictive relationship. • Here, we investigated the effects of environmental variables (atmospheric CO2, drought, relative humidity, irradiance, ultraviolet radiation and pathogen attack) on GCL in the model plant Arabidopsis thaliana to quantify environmentally induced variation. • GCL responded to all variables tested, but the changes incurred did not significantly impinge on the predictive capability of the relationship. [ABSTRACT FROM AUTHOR]

We model plant species diversity globally by country to show that future plant diversity capacity has a strong dependence on changing climate and carbon dioxide concentration. CO2 increase, through its impact on net primary production and warming is predicted to increase regional diversity capacity, while warming with constant CO2 leads to decreases in diversity capacity. Increased CO2 concentrations are unlikely to counter projected extinctions of endemic species, shown in earlier studies to be more strongly dependent on changing land use patterns than climate per se. Model predictions were tested against (1) contemporary observations of tree species diversity in different biomes, (2) an independent global map of contemporary species diversity and (3) time sequences of plant naturalisation for different locations. Good agreements between model, observations and naturalisation patterns support the suggestion that future diversity capacity increases are likely to be filled from a ‘cosmopolitan weed pool’ for which migration appears to be an insignificant barrier. [ABSTRACT FROM AUTHOR]

• The observation that stomatal density (number mm−2) on herbarium leaves had decreased over the last century represents clear evidence that plants have responded to anthropogenic increases in CO2 concentration. The mechanism of the response has proved elusive but here it is shown that density responses to both CO2 concentration and humidity are correlated with changes in whole-plant transpiration and leaf abscisic acid (ABA) concentration. • The transpiration rate of a range of accessions of Arabidopsis thaliana was manipulated by changing CO2 concentration, humidity and by exogenous application of ABA. Stomatal density increased with transpiration and leaf ABA concentration. • A common property of signal transduction systems is that they rapidly lose their ability to respond to the co-associated stimulus. Pathways of water movement within the plant are connected and so variations in supply and demand can be signalled throughout the plant directly, modifying stomatal aperture of mature leaves and stomatal density of developing leaves. Furthermore, the system identified here does not conform to the loss of ability to respond. • A putative mechanism is proposed for the control of stomatal density by transpiration rate and leaf ABA concentration. [ABSTRACT FROM AUTHOR]

We report on the syntheses, crystal structures, and magnetic susceptibilities of a family of copper pyrazine (pz)-based antiferromagnets with moderate in-plane magnetic exchange. These materials fall into two classes: monoclinic complexes [Cu(pz)2]A2 for A = ClO4 (1) or BF4 (2) and the tetragonal complex [Cu(pz)2(NO3)]PF6 (3). Compound 1 and its deuterated version [Cu(pz-d4)2](ClO4)2 (1a) crystallize in the space group C2/m at room temperature with disordered perchlorate anions. For both 1 and 2, the C centering of the Cu(II), S = 1/2, site yields four equivalent nearest neighbors, producing layers of Cu(II) ions bridged by the pz molecules, which map onto a square magnetic lattice. The layers are offset such that Cu(II) ions lie above and below the holes of adjacent layers. Compound 3 crystallizes in the space group I4/mcm with a layer structure similar to those of 1 and 2 but with Cu(II) ions of adjacent layers stacked above each other and bridged by semicoordinate NO3- ions. The variable-temperature susceptibilities in these compounds approximate a two-dimensional Heisenberg antiferromagnet with J values within the layers of 17.5(3) K (1), 15.3(3) K (2), and 10.8(3) K (3). Ordering transitions are observed in the magnetic data at 4.2(3) and 4,3(5) K for 1 and 2, respectively. [ABSTRACT FROM AUTHOR]

• This paper is the first global study of the extent to which fire determines global vegetation patterns by preventing ecosystems from achieving the potential height, biomass and dominant functional types expected under the ambient climate (climate potential).• To determine climate potential, we simulated vegetation without fire using a dynamic global-vegetation model. Model results were tested against fire exclusion studies from different parts of the world. Simulated dominant growth forms and tree cover were compared with satellite-derived land- and tree-cover maps.• Simulations were generally consistent with results of fire exclusion studies in southern Africa and elsewhere. Comparison of global‘fire off’ simulations with landcover and treecover maps show that vast areas of humid C4 grasslands and savannas, especially in South America and Africa, have the climate potential to form forests. These are the most frequently burnt ecosystems in the world. Without fire, closed forests would double from 27% to 56% of vegetated grid cells, mostly at the expense of C4 plants but also of C3 shrubs and grasses in cooler climates.• C4 grasses began spreading 6–8 Ma, long before human influence on fire regimes. Our results suggest that fire was a major factor in their spread into forested regions, splitting biotas into fire tolerant and intolerant taxa.New Phytologist(2004)doi: 10.1111/j.1469-8137.2004.01252.x© New Phytologist(2004) [ABSTRACT FROM AUTHOR]

A modeling approach to simulating vegetation dynamics is described, incorporating critical processes of carbon sequestration, growth, mortality and distribution. The model has been developed to investigate the response of vegetation to environmental change, at time scales, from days to centuries and from the local to the global scale. The model is outlined and subsequent tests, against independent data sources, are relatively successful, from the small scale to the global scale. Tests against eddy covariance observations of carbon exchange by vegetation indicated significant differences between measured and simulated net ecosystem production (NEP). NEP is the net of large fluxes due to gross primary production and respiration, which are not directly measured and so there is some uncertainty in explaining differences between observations and simulations. In addition it was noted that closer agreement of fluxes was achieved for natural, or long-lived managed vegetation than for recently managed vegetation. The discrepancies appear to be most closely related to respiratory carbon losses from the soil, but this area needs further exploration. The differences do not scale up to the global scale, where simulated and measured global net biome production were similar, indicating that fluxes measured at the managed observed sites are not typical globally. The model (the Sheffield Dynamic Global Vegetation Model, SDGVM) has been applied to contemporary vegetation dynamics and indicates a significant CO2 fertilization effect on the sequestration of atmospheric CO2. The terrestrial carbon sink for the 20th century is simulated to be widespread between latitudes 40° S and 65° N, but is greatest between 10° S and 6° N, excluding the effects of human deforestation. The mean maximum sink capacity over the 20th century is small, at 25 gC m-2 year -1, or approximately 1% of gross primary production... [ABSTRACT FROM AUTHOR]

• We report the influence of a systemic irradiance signal, from mature leaves, on the anatomical characteristics of developing leaves. • A systemic signal of reduced irradiance was induced by growing tobacco ( Nicotiana tabaccum) plants at high irradiance and then measuring the effect of shading mature leaves on the development of new leaves. The reverse, a systemic signal of increased irradiance was induced by growing plants at low irradiance and then measuring the effect of increasing the irradiance of mature leaves. • Stomatal pore length, stomatal density and index, epidermal cell shape, epidermal cell size and developing leaf size were all influenced by the irradiance signal. These responses were reversible with changing irradiance, except for stomatal pore length. [ABSTRACT FROM AUTHOR]

Examines the patterns of population density and abundance of Cirsium species approaching the range edge in Great Britain. Decline in seed production; Persistence of species through clonal reproduction.

Assesses the patterns of genetic variance of Cirsium acaule and Cirsium heterophyllum in Great Britain using microsatellite markers. Similarity of seed production and population isolation; Genetic drift; Decline of population density approaching the range edge.

Stomata, the small pores on the surfaces of leaves and stalks, regulate the flow of gases in and out of leaves and thus plants as a whole. They adapt to local and global changes on all timescales from minutes to millennia. Recent data from diverse fields are establishing their central importance to plant physiology, evolution and global ecology. Stomatal morphology, distribution and behaviour respond to a spectrum of signals, from intracellular signalling to global climatic change. Such concerted adaptation results from a web of control systems, reminiscent of a ‘scale-free’ network, whose untangling requires integrated approaches beyond those currently used. [ABSTRACT FROM AUTHOR]

Early experiments investigating the effects of CO2 enrichment on plants frequently showed photosynthetic stimulation and reduced stomatal aperture over short time periods. Work on the effects of elevated CO2 has advanced in two major areas: by the extension of long-term and field experiments, and through investigations on the wide range of negative feedbacks affecting plant responses to CO2. Downward photosynthetic acclimation in response to CO2 enrichment is frequently observed over the short and long term, and indicates the activity of diverse feedback mechanisms. CO2 is generally viewed as a limiting photosynthetic resource. However, recent work on stomatal development has shown that this view is simplistic: long- and short-distance signalling of CO2 concentration are necessary components of normal plant development. [ABSTRACT FROM AUTHOR]

Examines the interaction between chemistry of neutral radicals and radical anion. Identification of electrolyte solutions; Observation of biochemical processes; Formation of the cyclopropyl ketones.

Summary • Stomatal density responses by 48 accessions of Arabidopsis , to CO2 enrichment, broadly parallel interspecific observations. • Accessions differing in the degree of stomatal response to both CO2 and drought differed in flower production. Under well watered conditions flowering benefits from a small reduction in stomatal density with CO2 enrichment, but benefits from a large reduction under drought. • Stomatal density increases with altitude in Vaccinium myrtillus but is also strongly influenced by exposure. Exposed plants had higher stomatal densities than plants at the same altitude but in a community of individuals. This difference might be explained by systemic signalling within the plant as mature leaves detect both irradiance and [CO2 ], subsequently controlling the response of stomatal development in developing leaves. • Plants with the highest stomatal densities also had the highest stomatal conductances and photosynthetic rates. This suggests that signalling from mature to developing leaves predetermines the potential of the developing leaf to maximize its photosynthetic potential, including associated features such as nitrogen allocation, during early stages of development in the enclosed bud. [ABSTRACT FROM AUTHOR]

Stomatal numbers are tightly controlled by environmental signals including light intensity and atmospheric CO2 partial pressure. This requires control of epidermal cell development during the early phase of leaf growth and involves changes in both the density of cells on the leaf surface and the proportion of cells that adopt a stomatal fate. This paper reviews the current understanding of how stomata develop and describes recent advances that have given insights into the regulatory mechanisms involved using mutant Arabidopsis plants that implicates a role for long-chain fatty acids in cell-to-cell communication. Evidence is presented which indicates that long-distance signalling from mature to newly developing leaves forms part of the mechanism by which stomatal development responds to environmental cues. Analysis of mutant plants suggests that the plant hormones abscisic acid, ethylene and jasmonates are implicated in the long-distance signalling pathway and that the action may be mediated by reactive oxygen species. [ABSTRACT FROM AUTHOR]

AbstractThe vegetated landscape of Europe has been strongly impacted by human management to produce a heterogeneous patchwork of semi-natural and agricultural vegetation varying over a wide range of spatial scales. A model is described for averaging vegetation fluxes from a landscape of forest and grassland into the planetary boundary layer (PBL). At a scale of 1 km, model simulations indicate that vegetation heterogeneity exerts little effect on the PBL and regional fluxes will be simple areal averages of the different vegetation types. Above 5 km the model simulates significant effects of different vegetation types on the whole PBL. Averaging fluxes to the regional scale will therefore need to consider explicitly the nature, extent and behaviour of different vegetation types. [ABSTRACT FROM AUTHOR]

Long-term satellite observations of normalized difference vegetation index (NDVI) for Mediterranean shrublands suggest an increase in vegetation activity during the 1980s, caused by climatic warming. However, whether this was due to artificial trends in the satellite data remains in question. We used a mechanistic model of vegetation growth and a database of observed climate to test whether the observed increase in NDVI could have been caused by changes in canopy structure driven by changes in climate. The model reproduced the longterm upward trend in maximum seasonal NDVI between 1981 and 1991, indicating that a change in vegetation structure could feasibly explain the satellite observations. The model indicated that the NDVI trend was caused by a 12% increase in leaf area index (LAI), mainly owing to changes in precipitation and rising atmospheric CO[sub 2]. By contrast, climatic warming during the 1980s exerted little control over this variation in LAI. Simulated trends in canopy structure exerted significant impacts on canopy function, being associated with a 15% rise in net primary productivity and a 30% increase in transpiration. From this analysis, we conclude that trends in historical satellite observations of NDVI have a plausible biological basis. [ABSTRACT FROM AUTHOR]

Examines the capacity of Sinapis alba plants to compensate for wind and density stress through responses in growth and fecundity traits. Leaf expansion in high-wind plants; Delay of flowering time by wind; Decrease of dry mass by plants with long exposure time to stresses.

The representation of root activity in models is here confined to considerations of applications assessing the impacts of changes in climate or atmospheric [CO2]. Approaches to modelling roots can be classified into four major types: models in which roots are not considered, models in which there is an interplay between only selected above-ground and below-ground processes, models in which growth allocation to all parts of the plants depends on the availability and matching of the capture of external resources, and models with explicit treatments of root growth, architecture and resource capture. All models seem effective in describing the major root activities of water and nutrient uptake, because these processes are highly correlated, particularly at large scales and with slow or equilibrium dynamics. Allocation models can be effective in providing a deeper, perhaps contrary, understanding of the dynamic underpinning to observations made only above ground. The complex and explicit treatment of roots can be achieved only in small-scale highly studied systems because of the requirements for many initialized variables to run the models. [ABSTRACT FROM AUTHOR]

A survey of 100 species and 122 observations has shown an average reduction in stomatal density of 143% (SE ± 2.2%) with CO2 enrichment, with 74% of the cases exhibiting a reduction in stomatal density. A sign test demonstrated that stomata! density decreases, in response to CO2, significantly more often than expected by chance. Repeated observations on the same species indicated a significant repeatability in the direction of the stomatal response. Analyses which removed the potential effect of taxonomy on this data set showed no significant patterns in the dependency of the degree of stomatal change on growth form (woodiness vs. non-woodiness; trees vs. shrubs), habitat (cool VS. warm) or stomatal distribution on the leaf (amphi- vs. hypostomatous). Forty-three of the observations had been made in controlled environments and under a typical range in CO2 enrichment of 350-700 μmol mol-1. For these cases the average stomata! density declined by 9% (SE ± 3.3%) and 60% of the cases showed reductions in stomatal density. When analyses were restricted to these 43 observations, amphistomatous samples more frequently had greater changes in stomatal density than did hypostomatous samples. The degree of reduction in stomatal density with increasing CO2 increases with initial stomatal density, after the influence of taxonomy is removed using analyses of independent contrasts. When the data were examined for patterns that might be due explicitly to the effects of relatedness, the subclasses of the Hamamelidae and the Rosidae showed highly significant reductions in stomatal density with CO2 (87% of the specks studied in the Hamamelidae and 80% of the species in the Rosidae showed reduction with CO2 enrichment) and correlations between initial stomatal density and degree of reduction in stomatal density. [ABSTRACT FROM AUTHOR]

Rising levels of atmospheric CO2, climate change, and fertilizer pollution provide the ecological imperative for investigating the interaction between plant responses to atmospheric CO2 concentration, temperature and nutrient supply. In this study spring wheat (Triticum aestivum L, cv. Wemhley) was grown at 40, 50, 60 and 70 Pa atmospheric CO2 pressure and three experiments were conducted to investigate interactions between growth responses to the CO2 treatment and: (i) temperature (24/16 °C vs. 18/10 °C day/night), (ii) nutrient solution nitrate concentration (2.5, 5, 10 and 15 mM Ca(NO3,)2. 4H2O). and (iii) phosphate concentration (0.025 and 0.5 mM KH2PO4. Dry mass and root/shoot ratio increased with CO2, level at the higher temperature. These responses were reversed at the lower temperature. The increase in yield with CO2 enhancement was limited by low rates of nutrient supply in both absolute and relative terms. In the elevated CO2 treatments, the shoot nitrogen concentration was reduced, as was the proportional allocation to the uppermost leaves. These results are discussed with respect to possible physiological mechanisms and physiological for improved crop performance in a future, elevated CO2 World. [ABSTRACT FROM AUTHOR]

Ecophysiological information on the responses of plants to past global environment changes may be obtained from quaternary fossil leaves by measurements of (i) stomatal density, (ii) stomatal dimensions and (iii) 13C discrimination (Δ 13C) The stomata! density and stomatal dimensions of leaves can be used to calculate stomatal conductance, while leaf Δ 13C values provide independent information on stomata! conductance and plant water use efficiency In this paper, stomatal conductance is calculated for a sequence of radiocarbon dated fossil leaves of Salix herbacea L which, together with herbarium and fresh material, represents a time-series spanning from the Last Glacial Maximum (LGM) (16500 yr BP) to the present day The calculated values were then tested against leaf Δ 13C values previously reported for the same material. Our calculations show that stomatal conductance is negatively correlated with increases in atmospheric CO2 concentration over the last 16500 yr. This represents the first evidence of long-term response of stomata! conductance to increases in atmospheric CO2 concentration and confirms the response observed in experimental systems exposing plants to lower-than-present CO2 concentrations in controlled environments, The calculated decrease in conductance was positively correlated with leaf δ 13C values, supporting this interpretation The mean leaf δ 13C value for the 18th and 19th centuries was significantly (P < 005) lower than the mean for the interval LGM--Holocene (10000 yr BP) implying an increase in plant water-use-efficiency over this time. These two lines of evidence, together with the stomatal density record horn a glacial cycle, and experimental studies growing C3 plants in glacial-to-present CO2 concentrations, strongly imply that the water use efficiency of vegetation during the LGM was lower than at present and that it has increased since that time Further evidence in support of this conclusion comes from the pattern of world vegetation types present during the LGM previously reconstructed using palaeoecological data, This evidence demonstrates that the distribution of vegetation types during the LGM was significantly different from that of the present day and showed a contraction in the area of rain forest and a major expansion of desert areas. [ABSTRACT FROM AUTHOR]

Predicting the future responses of plants and ecosystems to further changes in the CO2 concentration of the atmosphere and to the possibility of global warming are important current concerns. Predictions have been most frequently attempted using short-term, single-factor experiments in controlled environments. However, these experiments have failed to indicate the outcome of field experiments at larger spatial and temporal scales. Some of this failure is due to ignorance of environmental conditions and interactions while some is due to the use of inappropriate short-cuts, such as the addition of fertilizers for simulating enhanced mineralization, and some is due to ignorance of the processes involved in scaling-up from individual plants to populations. Long-term observations on plants in ecosystems nevertheless indicate that community-scale experiments may provide a useful but imperfect capacity to predict ecosystem responses. Although difficult to implement in practice, it is concluded that catchment-scale experiments offer the best opportunity to predict plant, community and ecosystem responses to environmental change. [ABSTRACT FROM AUTHOR]

Field measurements of selected upland and lowland species have demonstrated a decline in specific leaf area with altitude, probably due to changes in both air temperature and wind-speed. Both field and controlled environment experiments have demonstrated that the upland species have lower specific leaf areas than the lowland species, under similar environmental conditions. Leaf growth and turgor of the upland species, Phleum alpinum, are insensitive to changes in wind-speed in the range of 0.2 to 3 m s[SUP-1], while both growth and turgor decline with wind-speed for the lowland P. pratense. Leaf turgor of P. pratense declined with increasing specific leaf area but no such relationship was found for P. alpinum. [ABSTRACT FROM AUTHOR]

Independent temperature control of separate organs of seedling plants of Phleum bertolonii and P. alpinum indicates that the temperature of the first leaf and coleoptile exert the dominant temperature control of specific leaf area (SLA). Rates of leaf extension in the upland species P. alpinum are slower than in the lowland species P. bertolonii. This difference is related in the main to the significantly greater number of cell generations involved in the expansion of the leaf and not to the cell generation time, which does not differ between the species. Experiments with the growth of callus cultures suggest that interspecific differences in the potential for cell growth do not account for the observed differences in leaf extension. In both species the response of SLA to temperature is mainly a consequence of its influence on cell diameter, As a result it is the temperature in the region of cell expansion, within the leaf sheath, that will control SLA. [ABSTRACT FROM AUTHOR]

The growth rates of Dactylis glomerata L. and phleum bertolonii D.C., which are essentially lowland species in Britain, show a large response to an increase in day temperature from 10 to 20 °C, while those of Sesleria albicans Kit. which occurs from sea-level to 900 m, and Phleum alpinum L. (600 to 1200 m) show little response. These differences can be attributed to the greater leaf-area ratio, and to the increased rates of both leaf-initiation and leaf-expansion of the lowland species at higher temperatures. Net assimilation rates are scarcely affected by temperature. The differences are therefore due to morphogenetic effects and not to differences in the rates of physiological processes. [ABSTRACT FROM AUTHOR]

It has been demonstrated that the decrease of temperature associated with an increase in altitude of 250 m is sufficient to reverse the outcome of competition between Sedum rosea (L) Scop. and S. telephium L. ssp. fabaria Syme. Growth analyses of S. rosea and S. telephium in a range of temperature conditions have shown that the change in the outcome of competition is due to the marked increase in growth of S. telephium and the insensitivity of S. rosea to an increase in temperature over the range recorded in the field. [ABSTRACT FROM AUTHOR]

When plants of Sedum rosea (L.) Scop. and S. telephium L. ssp. fabaria Syme are grown in competition at different altitudes it is found that the growth of the species is affected differentially. This effect is such that at low altitudes S. telephium is a larger plant than S. rosea, while the reverse is the case at high attitudes. The observed differences are caused by a marked sensitivity of the growth of S. telephium to differences in altitude, whileS. rosea is very insensitive. The most probable cause of these responses would appear to be differences of climate. The influence of altitude in northern England on air temperature, saturation deficit and irradiance has been investigated in order to establish the magnitude of the differences which may cause these responses. [ABSTRACT FROM AUTHOR]

Abstract Evaluating the role of terrestrial ecosystems in the global carbon cycle requires a detailed understanding of carbon exchange between vegetation, soil, and the atmosphere. Global climatic change may modify the net carbon balance of terrestrial ecosystems, causing feedbacks on atmospheric CO2 and climate. We describe a model for investigating terrestrial carbon exchange and its response to climatic variation based on the processes of plant photosynthesis, carbon allocation, litter production, and soil organic carbon decomposition. The model is used to produce geographical patterns of net primary production (NPP), carbon stocks in vegetation and soils, and the seasonal variations in net ecosystem production (NEP) under both contemporary and future climates. For contemporary climate, the estimated global NPP is 57.0 Gt C y–1 , carbon stocks in vegetation and soils are 640 Gt C and 1358 Gt C, respectively, and NEP varies from –0.5 Gt C in October to 1.6 Gt C in July. For a doubled atmospheric CO2 concentration and the corresponding climate, we predict that global NPP will rise to 69.6 Gt C y–1 , carbon stocks in vegetation and soils will increase by, respectively, 133 Gt C and 160 Gt C, and the seasonal amplitude of NEP will increase by 76%. A doubling of atmospheric CO2 without climate change may enhance NPP by 25% and result in a substantial increase in carbon stocks in vegetation and soils. Climate change without CO2 elevation will reduce the global NPP and soil carbon stocks, but leads to an increase in vegetation carbon because of a forest extension and NPP enhancement in the north. By combining the effects of CO2 doubling, climate change, and the consequent redistribution of vegetation, we predict a strong enhancement in NPP and carbon stocks of terrestrial ecosystems. This study simulates the possible variation in the carbon exchange at equilibrium... [ABSTRACT FROM AUTHOR]

This paper describes experiments carried out to investigate the causes of high leaf nitrogen concentrations and high δ13C values in Alchemilla alpina L. growing at high altitudes. We investigated whether genetic adaptation, high levels of nitrogen input or low temperatures could account for these trends. In a field experiment, plants from two altitudes in the Scottish Highlands were transplanted to Great Dun Fell, a site in the Pennines of northern England. The experimental design was fully factorial : two altitudinal origins × two altitudes of growth × two nitrogen levels. A second experiment used a controlled environment to test the effects of temperature alone. The effects of altitude in the field transplant experiment were very similar to those in naturally growing plants. Leaf nitrogen concentration and δ13C were both higher at the high altitude, whilst growth declined and nitrogen per leaf was unaffected. An increase in potassium concentration with altitude was also found, Nitrogen addition caused increased leaf nitrogen concentrations but also increased nitrogen per leaf; δ13C was not affected and potassium and phosphorus concentrations decreased. The addition of nitrogen also increased mortality. Altitude of origin had relatively few effects but the population from the higher altitude did have a higher specific leaf area. Low temperature in the controlled environment caused increased δ13C, decreased leaf size and increased nitrogen and carbon contents, although the effect was less clear than the effects of altitude in the field. Gas exchange measurements suggested that the δ13C effect was caused by a reduction in stomatal conductance. We conclude that the effects of altitude on this species are principally the result of direct environmental modifications to growth rather than genetic adaptation. Of the various factors that change with altitude, temperature and a short growing season are particularly important; enhanced nitrogen supply through atmospheric deposition promotes increasing leaf nitrogen concentrations but must be considered in conjunction with other variables. [ABSTRACT FROM AUTHOR]

Presents research which quantified the dynamic variations in ecosystem carbon fluxes induced by changes in atmospheric CO2 and climate from 1861 to 2070. Use of a terrestrial biogeochemical model; Coupling of terrestrial ecosystems and the climate system; Carbon cycling; Prior research; Predictions about global net CO2 production; Response and influence of terrestrial ecosystem carbon fluxes.

Rising levels of atmospheric CO2 will have profound, direct effects on plant carbon metabolism. In this study we used gas exchange measurements, models describing the instantaneous response of leaf net CO2 assimilation rate (A) to intercellular CO2 partial pressure (Ci), in vitro enzyme activity assay, and carbohydrate assay in order to investigate the photosynthetic responses of wheat (Triticum aestivum L., cv. Wembley) to growth under elevated partial pressures of atmospheric CO2 (Ca). At flag leaf ligule emergence, the modelled, in vivo, maximum carboxylation velocity for RuBisCO was significantly lower in plants grown at elevated Ca than in plants grown at ambient Ca (70 Pa compared with 40 Pa). By 12 d after ligule emergence, no significant difference in this parameter was detectable. At ligule emergence, plants grown at elevated Ca exhibited reduced in vitro initial activities and activation states of RuBisCO. At their respective growth Ci values, the photosynthesis of 40-Pa-grown plants was sensitive to p(O2) and top(CO2), whereas that of 70-Pagrown plants was insensitive. Both sucrose and starch accumulated more rapidly in the leaves of plants grown at 70 Pa. At flag leaf ligule emergence, modelled non-photorespiratory respiration in the light (Rd) was significantly higher in 70-Pa-grown plants than in 40-Pa-grown plants. By 12 d after ligule emergence no significant differences in Rd were detectable. [ABSTRACT FROM AUTHOR]

The use of the light-induced absorbance change at 820 nm (ΔA 820) to monitor the oxidation and reduction of P-700 in irradiated leaves is examined. Results obtained from leaves irradiated with a range of wavelengths of light, poisoned with DCMU, or lacking PS I, are consistent with the proposition that the light-induced ΔA 820 can be used to monitor P-700 oxidation in leaves. [ABSTRACT FROM AUTHOR]

1. An electronic instrument is described which integrates temperature and photosyn- thetically active radiation (PAR) to provide measurements of 24-h, day and night temperatures, PAR and day length, averaged for the period between readings. The day/ night threshold was set at 0.1-10 μmol m-2 s-1 PAR. 2. Measurements were made in chestnut (Gastanea sativa Mill.) coppice in Sussex on five sites covering the firs! to tenth seasons of regrowth. Coppices are important sites for nature conservation and microclimatic measurements will aid experimental work on the ground flora. 3. Under a complete leaf canopy in summer, daylength was up to IS b shorter than in the open and about 02 h shorter in winter. The night length for photoperiodism and the length of the respiring period are therefore extended! for woodland plants in summer. 4. The sites with incomplete canopies were warmer (by 2-3°C, May-July) arid had greater day/night temperature amplitudes than the sites with closed canopies. [ABSTRACT FROM AUTHOR]

(1) The design of an instrument for the simultaneous measurement of photosynthetically active, radiation and red, far-red and blue light is described. The optical responses of the instrument closely match the action spectra of photosynthesis and some important photomorphogenic responses within the waveband of 400 to 800 nm. (2) The design of a single Instrument for the measurement of the quantum irradiance at 660 and 730 nm is also shown. (3) The application of these instruments to measurements in the field and the controlled environment is described. [ABSTRACT FROM AUTHOR]

Designs are described for sensors, integrators and a readout device which together measure temperature (or day-degrees) and photosynthetically active radiation (or short-wave radiation in the 300 to 3000 nm waveband). The equipment is cheap to produce (£15 to £18) and has a low electrical power requirement (3 mW at 20 °C). The integrators may be adjusted to measure temperature or irradiance above set thresholds. [ABSTRACT FROM AUTHOR]

Re-examines previously published data using information on taxonomic relationships to eliminate possible effects of relatedness on associations between carbon isotope composition and altitudinal and latitudinal distributions of plant species. Effect of plant life-form on carbon isotope composition; Altitude and observed differences in carbon isotope composition.

The author offers information on the topics discussed in the journal "Tansley Reviews." He states that the journal addresses a wide range of organizational scales within each process, from plant organelles to ecosystems. He also cites several physiological studies of plants, including evolution and development.

The author reflects regarding the conservation of biodiversity. He various factors that contributes to the biodiversity destruction which include the global scale travel of plants and people and intervention of human for the replacement of natural vegetation. He mentions that the result for the molecular approaches application to diversity which provided qualified and quantified hypotheses in geographical locations and species variety can help to give clarity for biodiversity conservation.

The author discusses the carbon dioxide (CO2) wherein it is viewed as the bête noire of the future climatic changes. The author mentions that shifting from fossil sources of energy is the most certain way to reduce carbon emissions. Moreover, the author says that the increasing concentrations of atmospheric carbon dioxide could induce the growth and productivity of plants.

The authors reflect on the identifiable levels of study related with plant science, and the factors that affect scientists in choosing the research topics and levels of their studies. They examine the levels of study of 21 selected papers that were published in the periodical "New Phytologist" in 2007 and 2008. They also provide information on the three new Editors of "New Phytologist" which include Amy Austin, Richard Abbott, and Marinus Pilon.

The article introduces research on the variety of mechanisms by which plants adjust to variations in water supply, including one on aquaporins and another on the role of stomatal responses in rapid drought responses.

The author comments on the significant research on trees published by the "New Phytologist" journal. Changes in tree ring width offer a composite picture of environmental influences on tree growth over extended periods. Periodic phenomena need long-term data to extract the characteristic periodicities and environmental impacts on masting. Meanwhile, papers in the unlabelled part of the relationship between time and space are characterized by relatively large areas of study and are basically field-based.

The article discusses various reports published within the issue including a research on the capacity of native plant species to tolerate the joint environmental problems of salinity and waterlogging.

Introduction: In contrast to other medical specialties, trainees in Geriatrics have historically provided an increased contribution to clinical workload in General Internal Medicine and a reduced output of academic achievements. More recently, development of non-clinical skills has been recognised to have similar importance to clinical skills and the South East (SE) London Geriatrics Training Programme has thus supported trainees in applications for Out of Programme (OOP) opportunities to optimise career progression. Methods: Doctors who had undertaken specialist registrar training in the SE London Geriatrics Training Programme at any time between 2011 and 2019 were sent a questionnaire to assess whether they had completed time OOP and whether they had been awarded research grants, published papers in peer-reviewed journals, had abstracts accepted for presentation at conferences, and/or published book chapters during their training programme. Chisquared and Wilcoxon rank-sum tests were used to compare data between registrars who had completed time OOP and those who had not taken time OOP. Results: 77 (24 male; 53 female) registrars completed training in the SE London Geriatrics Training Programme between 2011 and 2019. 71 registrars (92%) completed the questionnaire, of whom 31 (44%) completed time OOP. In total, registrars were awarded 15 research grants, published 86 papers in peer-reviewed journals, had abstracts accepted for 184 conference presentations and published 20 book chapters. A notably increased proportion of registrars who took time OOP had an output of research grants, papers published in peer reviewed journals, abstracts accepted for presentation at conferences and/or book chapters respectively compared with registrars who had not taken time OOP (23% vs 5% ; 61% vs 23%; 84% vs 33%; 45% vs 5%). This equated to a combined academic output in 94% of registrars who completed time OOP compared with 48% who did not (p <0.001). Conclusions: A very strong association existed between registrars in Geriatrics taking time OOP and academic achievement substantiating the training programme’s aspiration to support development of non-clinical skills that may be helpful to trainees in their future careers. It would be worthwhile further work being undertaken in this area in other regions. [ABSTRACT FROM AUTHOR]