Exploring the potential of Δ17O in CO2 for determining mesophyll conductance.

Mesophyll conductance to CO2 from the intercellular air space to the CO2-H2O exchange site has been estimated using δ18O measurements (gm18). However, the gm18 estimates are affected by the uncertainties in the δ18O of leaf water where the CO2-H2O exchange takes place and the degree of equilibration between CO2 and H2O. We show that measurements of Δ17O (i.

Paired analysis of tree ring width and carbon isotopes indicates when controls on tropical tree growth change from light to water limitations.

Light and water availability are likely to vary over the lifespan of closed-canopy forest trees, with understory trees experiencing greater limitations to growth by light and canopy trees greater limitation due to drought. As drought and shade have opposing effects on isotope discrimination (Δ13C), paired measurement of ring width and Δ13C can potentially be used to differentiate between water and light limitations on tree growth. We tested this approach for Cedrela trees from three tropical forests in Bolivia and Mexico that differ in rainfall and canopy structure.

A meta-analysis of responses of C plants to atmospheric CO : dose-response curves for 85 traits ranging from the molecular to the whole-plant level.

Generalised dose-response curves are essential to understand how plants acclimate to atmospheric CO . We carried out a meta-analysis of 630 experiments in which C plants were experimentally grown at different [CO ] under relatively benign conditions, and derived dose-response curves for 85 phenotypic traits. These curves were characterised by form, plasticity, consistency and reliability.

Leaf scale quantification of the effect of photosynthetic gas exchange on Δ of CO.

The clumped isotope composition (Δ, the anomaly of the mass 47 isotopologue relative to the abundance expected from a random isotope distribution) of CO has been suggested as an additional tracer for gross CO fluxes. However, the effect of photosynthetic gas exchange on Δ has not been directly determined and two indirect/conceptual studies reported contradicting results. In this study, we quantify the effect of photosynthetic gas exchange on Δ of CO using leaf cuvette experiments with one C and two C plants.

Dividing the pie: A quantitative review on plant density responses.

Plant population density is an important variable in agronomy and forestry and offers an experimental way to better understand plant-plant competition. We made a meta-analysis of responses of even-aged mono-specific stands to population density by quantifying for 3 stand and 33 individual plant variables in 334 experiments how much both plant biomass and phenotypic traits change with a doubling in density. Increasing density increases standing crop per area, but decreases the mean size of its individuals, mostly through reduced tillering and branching.

Evolution of Increased Photosynthetic Capacity and Its Underlying Traits in Invasive .

The evolution of increased competitive ability (EICA) hypothesis and the shifting defense hypothesis (SDH) predict that evolutionary changes occur in a suite of traits related to defense and growth in invasive plant species as result of the absence of specialist herbivores. We tested how this suite of traits changed due to the absence of specialist herbivores in multiple invasive regions that differ in climatic conditions with native and invasive in a controlled environment. We hypothesized that invasive in all invasive regions have i) a higher plant growth and underlying traits, such as photosynthetic capacity, ii) lower regrowth-related traits, such as carbohydrate storage, and iii) an increased plant qualitative defense, such as pyrrolizidine alkaloids (PAs).

(15)N in tree rings as a bio-indicator of changing nitrogen cycling in tropical forests: an evaluation at three sites using two sampling methods.

Anthropogenic nitrogen deposition is currently causing a more than twofold increase of reactive nitrogen input over large areas in the tropics. Elevated (15)N abundance (δ(15)N) in the growth rings of some tropical trees has been hypothesized to reflect an increased leaching of (15)N-depleted nitrate from the soil, following anthropogenic nitrogen deposition over the last decades. To find further evidence for altered nitrogen cycling in tropical forests, we measured long-term δ(15)N values in trees from Bolivia, Cameroon, and Thailand.

The effect of irradiance on the carbon balance and tissue characteristics of five herbaceous species differing in shade-tolerance.

The carbon balance is defined here as the partitioning of daily whole-plant gross CO2 assimilation (A) in C available for growth and C required for respiration (R). A scales positively with growth irradiance and there is evidence for an irradiance dependence of R as well. Here we ask if R as a fraction of A is also irradiance dependent, whether there are systematic differences in C-balance between shade-tolerant and shade-intolerant species, and what the causes could be.

Gap effects on leaf traits of tropical rainforest trees differing in juvenile light requirement.

The relationships of 16 leaf traits and their plasticity with the dependence of tree species on gaps for regeneration (gap association index; GAI) were examined in a Neotropical rainforest. Young saplings of 24 species with varying GAI were grown under a closed canopy, in a medium-sized and in a large gap, thus capturing the full range of plasticity with respect to canopy openness. Structural, biomechanical, chemical and photosynthetic traits were measured.

The art of growing plants for experimental purposes: a practical guide for the plant biologist.

Every year thousands of experiments are conducted using plants grown under more-or-less controlled environmental conditions. The aim of many such experiments is to compare the phenotype of different species or genotypes in a specific environment, or to study plant performance under a range of suboptimal conditions. Our paper aims to bring together the minimum knowledge necessary for a plant biologist to set up such experiments and apply the environmental conditions that are appropriate to answer the questions of interest.

Oxygen isotopes in tree rings are a good proxy for Amazon precipitation and El Nino-Southern Oscillation variability.

We present a unique proxy for the reconstruction of variation in precipitation over the Amazon: oxygen isotope ratios in annual rings in tropical cedar (Cedrela odorata). A century-long record from northern Bolivia shows that tree rings preserve the signal of oxygen isotopes in precipitation during the wet season, with weaker influences of temperature and vapor pressure. Tree ring δ(18)O correlates strongly with δ(18)O in precipitation from distant stations in the center and west of the basin, and with Andean ice core δ(18)O showing that the signal is coherent over large areas.

Interaction of temperature and irradiance effects on photosynthetic acclimation in two accessions of Arabidopsis thaliana.

The effect of temperature and irradiance during growth on photosynthetic traits of two accessions of Arabidopsis thaliana was investigated. Plants were grown at 10 and 22 °C, and at 50 and 300 μmol photons m(-2) s(-1) in a factorial design. As known from other cold-tolerant herbaceous species, growth of Arabidopsis at low temperature resulted in increases in photosynthetic capacity per unit leaf area and chlorophyll.

Estimating mesophyll conductance to CO2: methodology, potential errors, and recommendations.

The three most commonly used methods for estimating mesophyll conductance (g(m)) are described. They are based on gas exchange measurements either (i) by themselves; (ii) in combination with chlorophyll fluorescence quenching analysis; or (iii) in combination with discrimination against (13)CO(2). To obtain reliable estimates of g(m), the highest possible accuracy of gas exchange is required, particularly when using small leaf chambers.

Xeml Lab: a tool that supports the design of experiments at a graphical interface and generates computer-readable metadata files, which capture information about genotypes, growth conditions, environmental perturbations and sampling strategy.

Data mining depends on the ability to access machine-readable metadata that describe genotypes, environmental conditions, and sampling times and strategy. This article presents Xeml Lab. The Xeml Interactive Designer provides an interactive graphical interface at which complex experiments can be designed, and concomitantly generates machine-readable metadata files.

The role of ethylene perception in the control of photosynthesis.

The process of photosynthesis is under the control by several internal factors. Apart from the effect of abscisic acid on stomatal conductance, little is known about the interaction between hormonal signals and photosynthesis in fully-developed, nonsenescing leaves. Recently, we found that the ethylene transduction pathway is involved in the regulation of photosynthesis.

Canopy light gradient perception by cytokinin.

We have recently identified cytokinin as an important xylem-carried signal involved in the photosynthetic acclimation of plants to light gradients in dense canopies. Lower leaves become shaded in a dense canopy and consequently have reduced transpiration rates. our measurements have shown that this results in a reduced delivery of cytokinins carried in the transpiration stream to shaded leaves, as compared to light-exposed leaves.

Ethylene insensitivity results in down-regulation of rubisco expression and photosynthetic capacity in tobacco.

Little is known about the effect of hormones on the photosynthetic process. Therefore, we studied Rubisco content and expression along with gas exchange parameters in transgenic tobacco (Nicotiana tabacum) plants that are not able to sense ethylene. We also tested for a possible interaction between ethylene insensitivity, abscisic acid (ABA), and sugar feedback on photosynthesis.

Cytokinin import rate as a signal for photosynthetic acclimation to canopy light gradients.

Plants growing in dense canopies are exposed to vertical light gradients and show photosynthetic acclimation at the whole-plant level, resulting in efficient photosynthetic carbon gain. We studied the role of cytokinins transported through the transpiration stream as one of probably multiple signals for photosynthetic acclimation to light gradients using both tobacco (Nicotiana tabacum) and Arabidopsis (Arabidopsis thaliana). We show that substantial variation in leaf transpiration parallels the light gradient in tobacco canopies and experimental reduction of the transpiration rate of a leaf, independent of light, is sufficient to reduce photosynthetic capacity in both species, as well as transcript levels of the small subunit of Rubisco (rbcS) gene in Arabidopsis.

Symbiotic nitrogen fixation in a tropical rainforest: 15N natural abundance measurements supported by experimental isotopic enrichment.

* Leguminous trees are very common in the tropical rainforests of Guyana. Here, species-specific differences in N(2) fixation capability among nodulating legumes growing on different soils and a possible limitation of N(2) fixation by a relatively high nitrogen (N) and low phosphorus (P) availability in the forest were investigated. * Leaves of 17 nodulating species and 17 non-nodulating reference trees were sampled and their delta(15)N values measured.

Functional significance of shade-induced leaf senescence in dense canopies: an experimental test using transgenic tobacco.

Canopy photosynthesis models have predicted an optimal leaf area index (LAI; leaf area per unit surface area) and leaf nitrogen distribution at which whole-plant carbon gain per unit N is maximized. In this study we experimentally tested these models, using transgenic P(SAG12)-IPT tobacco (SAG; Nicotiana tabacum L.) plants with delayed leaf senescence and therefore a greater LAI and more uniform N distribution than the wild type (WT).

Submergence-induced morphological, anatomical, and biochemical responses in a terrestrial species affect gas diffusion resistance and photosynthetic performance.

Gas exchange between the plant and the environment is severely hampered when plants are submerged, leading to oxygen and energy deficits. A straightforward way to reduce these shortages of oxygen and carbohydrates would be continued photosynthesis under water, but this possibility has received only little attention. Here, we combine several techniques to investigate the consequences of anatomical and biochemical responses of the terrestrial species Rumex palustris to submergence for different aspects of photosynthesis under water.

Species-specific variation in the importance of the spectral quality gradient in canopies as a signal for photosynthetic resource partitioning.

Background And Aims: Plants adjust the distribution of photosynthetic capacity and chlorophyll to canopy density. The importance of the gradient in the red : far-red ratio (R : FR) relative to the irradiance gradient was studied for its perception with respect to this partitioning of photosynthetic resources. Whether the relative importance of these two signals varied between six species of different growth habit (Phaseolus vulgaris, Lysimachia vulgaris, Hedera helix, Ficus benjamina, Carex acutiformis and Brachypodium pinnatum) was investigated further.

Midday depression of net photosynthesis in the tropical rainforest tree Eperua grandiflora: contributions of stomatal and internal conductances, respiration and Rubisco functioning.

High midday temperatures can depress net photosynthesis. We investigated possible mechanisms underlying this phenomenon in leaves of Eperua grandiflora (Aubl.) Benth.

Photosynthetic induction in saplings of three shade-tolerant tree species: comparing understorey and gap habitats in a French Guiana rain forest.

The photosynthetic induction response under constant and fluctuating light was examined in naturally occurring saplings (about 0.5-2 m in height) of three shade-tolerant tree species, Pourouma bicolor spp digitata, Dicorynia guianensis, and Vouacapoua americana, growing in bright gaps and in the shaded understorey in a Neotropical rain forest. Light availability to saplings was estimated by hemispherical photography.