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Generalised dose-response curves are essential to understand how plants acclimate to atmospheric CO 2 . We carried out a meta-analysis of 630 experiments in which C 3 plants were experimentally grown at different [CO 2 ] under relatively benign conditions, and derived dose-response curves for 85 phenotypic traits. These curves were characterised by form, plasticity, consistency and reliability. Considered over a range of 200-1200 µmol mol -1 CO 2 , some traits more than doubled (e.g. area-based photosynthesis; intrinsic water-use efficiency), whereas others more than halved (area-based transpiration). At current atmospheric [CO 2 ], 64% of the total stimulation in biomass over the 200-1200 µmol mol -1 range has already been realised. We also mapped the trait responses of plants to [CO 2 ] against those we have quantified before for light intensity. For most traits, CO 2 and light responses were of similar direction. However, some traits (such as reproductive effort) only responded to light, others (such as plant height) only to [CO 2 ], and some traits (such as area-based transpiration) responded in opposite directions. This synthesis provides a comprehensive picture of plant responses to [CO 2 ] at different integration levels and offers the quantitative dose-response curves that can be used to improve global change simulation models., (© 2021 The Authors. New Phytologist © 2021 New Phytologist Foundation.)

The leaf economics spectrum (LES) represents a suite of intercorrelated leaf traits concerning construction costs per unit leaf area, nutrient concentrations, and rates of carbon fixation and tissue turnover. Although broad trade-offs among leaf structural and physiological traits have been demonstrated, we still do not have a comprehensive view of the fundamental constraints underlying the LES trade-offs. Here, we investigated physiological and structural mechanisms underpinning the LES by analysing a novel data compilation incorporating rarely considered traits such as the dry mass fraction in cell walls, nitrogen allocation, mesophyll CO 2 diffusion and associated anatomical traits for hundreds of species covering major growth forms. The analysis demonstrates that cell wall constituents are major components of leaf dry mass (18-70%), especially in leaves with high leaf mass per unit area (LMA) and long lifespan. A greater fraction of leaf mass in cell walls is typically associated with a lower fraction of leaf nitrogen (N) invested in photosynthetic proteins; and lower within-leaf CO 2 diffusion rates, as a result of thicker mesophyll cell walls. The costs associated with greater investments in cell walls underpin the LES: long leaf lifespans are achieved via higher LMA and in turn by higher cell wall mass fraction, but this inevitably reduces the efficiency of photosynthesis., (© 2017 The Authors. New Phytologist © 2017 New Phytologist Trust.)

Leaf dry mass per unit leaf area (LMA) is a central trait in ecology, but its anatomical and compositional basis has been unclear. An explicit mathematical and physical framework for quantifying the cell and tissue determinants of LMA will enable tests of their influence on species, communities and ecosystems. We present an approach to explaining LMA from the numbers, dimensions and mass densities of leaf cells and tissues, which provided unprecedented explanatory power for 11 broadleaved woody angiosperm species diverse in LMA (33-262 g m -2 ; R 2  = 0.94; P < 0.001). Across these diverse species, and in a larger comparison of evergreen vs. deciduous angiosperms, high LMA resulted principally from larger cell sizes, greater major vein allocation, greater numbers of mesophyll cell layers and higher cell mass densities. This explicit approach enables relating leaf anatomy and composition to a wide range of processes in physiological, evolutionary, community and macroecology., (© 2017 John Wiley & Sons Ltd/CNRS.)

Leaf mass per area (LMA) is a morphological trait widely used as a good indicator of plant functioning (i.e. photosynthetic and respiratory rates, chemical composition, resistance to herbivory, etc.). The LMA can be broken down into the leaf density (LD) and leaf volume to area ratio (LVA or thickness), which in turn are determined by anatomical tissues and chemical composition. The aim of this study is to understand the anatomical and chemical characteristics related to LMA variation in species growing in the field along a water availability gradient. We determined LMA and its components (LD, LVA and anatomical tissues) for 34 Mediterranean (20 evergreen and 14 deciduous) woody species. Variation in LMA was due to variation in both LD and LVA. For both deciduous and evergreen species LVA variation was strongly and positively related with mesophyll volume per area (VA or thickness), but for evergreen species positive relationships of LVA with the VA of epidermis, vascular plus sclerenchyma tissues and air spaces were found as well. The leaf carbon concentration was positively related with mesophyll VA in deciduous species, and with VA of vascular plus sclerenchymatic tissues in evergreens. Species occurring at the sites with lower water availability were generally characterised by a high LMA and LD.

Whether the fraction of total forest biomass distributed in roots, stems, or leaves varies systematically across geographic gradients remains unknown despite its importance for understanding forest ecology and modeling global carbon cycles. It has been hypothesized that plants should maintain proportionally more biomass in the organ that acquires the most limiting resource. Accordingly, we hypothesize greater biomass distribution in roots and less in stems and foliage in increasingly arid climates and in colder environments at high latitudes. Such a strategy would increase uptake of soil water in dry conditions and of soil nutrients in cold soils, where they are at low supply and are less mobile. We use a large global biomass dataset (>6,200 forests from 61 countries, across a 40 °C gradient in mean annual temperature) to address these questions. Climate metrics involving temperature were better predictors of biomass partitioning than those involving moisture availability, because, surprisingly, fractional distribution of biomass to roots or foliage was unrelated to aridity. In contrast, in increasingly cold climates, the proportion of total forest biomass in roots was greater and in foliage was smaller for both angiosperm and gymnosperm forests. These findings support hypotheses about adaptive strategies of forest trees to temperature and provide biogeographically explicit relationships to improve ecosystem and earth system models. They also will allow, for the first time to our knowledge, representations of root carbon pools that consider biogeographic differences, which are useful for quantifying whole-ecosystem carbon stocks and cycles and for assessing the impact of climate change on forest carbon dynamics.

Premise of the Study: Plant species differ widely in the leaf biomass invested per unit area (LMA). LMA can be explained by variation in leaf thickness and/or density, both of which are influenced by anatomical tissue composition. The aim of this study is to quantify the anatomical characteristics that underlie variation in LMA in a range of woody species. •, Methods: Twenty-six woody species, forming 13 species pairs with a deciduous and evergreen species from the same genus or family, were grown in a glasshouse. The youngest full-grown leaves were analyzed for LMA and morpho-anatomical characteristics at leaf, tissue, and cell level. •, Key Results: Considered over all species studied, leaf thickness and density were equally important to explain the variation in LMA, but the class difference between deciduous and evergreen species was mainly determined by thickness, whereas variation within each group was largely due to density. Evergreens had thicker leaves, predominantly caused by a larger volume of mesophyll and air spaces, whereas the higher leaf density within each group was due to a lower proportion of epidermis and air spaces, and overall smaller cells. •, Conclusions: The anatomical basis for variation in LMA in woody species depends on the contrast made. Higher LMA in evergreens is mainly due to a greater leaf thickness, caused by a larger volume of mesophyll and air spaces. Within deciduous species and evergreens, higher LMA is caused by a higher density, due to higher volumetric fractions of mesophyll and lower fractions of air spaces and epidermis.

Plants may experience different environmental cues throughout their development which interact in determining their phenotype. This paper tests the hypothesis that environmental conditions experienced early during ontogeny affect the phenotypic response to subsequent environmental cues. This hypothesis was tested by exposing different accessions of Rumex palustris to different light and nutrient conditions, followed by subsequent complete submergence. Final leaf length and submergence-induced plasticity were affected by the environmental conditions experienced at early developmental stages. In developmentally older leaves, submergence-induced elongation was lower in plants previously subjected to high-light conditions. Submergence-induced elongation of developmentally younger leaves, however, was larger when pregrown in high light. High-light and low-nutrient conditions led to an increase of nonstructural carbohydrates in the plants. There was a positive correlation between submergence-induced leaf elongation and carbohydrate concentration and content in roots and shoots, but not with root and shoot biomass before submergence. These results show that conditions experienced by young plants modulate the responses to subsequent environmental conditions, in both magnitude and direction. Internal resource status interacts with cues perceived at different developmental stages in determining plastic responses to the environment., (© 2012 The Authors. New Phytologist © 2012 New Phytologist Trust.)

We quantified the biomass allocation patterns to leaves, stems and roots in vegetative plants, and how this is influenced by the growth environment, plant size, evolutionary history and competition. Dose-response curves of allocation were constructed by means of a meta-analysis from a wide array of experimental data. They show that the fraction of whole-plant mass represented by leaves (LMF) increases most strongly with nutrients and decreases most strongly with light. Correction for size-induced allocation patterns diminishes the LMF-response to light, but makes the effect of temperature on LMF more apparent. There is a clear phylogenetic effect on allocation, as eudicots invest relatively more than monocots in leaves, as do gymnosperms compared with woody angiosperms. Plants grown at high densities show a clear increase in the stem fraction. However, in most comparisons across species groups or environmental factors, the variation in LMF is smaller than the variation in one of the other components of the growth analysis equation: the leaf area : leaf mass ratio (SLA). In competitive situations, the stem mass fraction increases to a smaller extent than the specific stem length (stem length : stem mass). Thus, we conclude that plants generally are less able to adjust allocation than to alter organ morphology., (© 2011 The Authors. New Phytologist © 2011 New Phytologist Trust.)

Plant growth response to salinity on a scale of years has not been studied in terms of growth analysis. To gain insights into this topic, 2-year-old Mediterranean Fan Palm (Chamaerops humilis L.) and Mexican Fan Palm (Washingtonia robusta H. Wendl) seedlings, each with its own distinct plant morphology, were grown for 2 years in a peat soil and irrigated with water of 2 dS m(-1) (control) or 8 dS m(-1) (saline). Plants were harvested on seven occasions and the time trends in relative growth rate (RGR, the rate of increase of biomass per unit of biomass already existing) and its components were analysed. In the long term, salinity produced a slight reduction in the mean RGR, values in both species. In the short term, salinity caused a reduction in RGR. However, during the second year, plants irrigated with 8 dS m(-1) grew somewhat more quickly than the control plants, probably as a result of delay in the growth kinetics due to salinity. Regarding RGR components, leaf nitrogen productivity (the rate of biomass gain per unit leaf N and time) was the major factor causing the differences in RGR resulting from salinity. Washingtonia robusta showed a relatively high plasticity in plant morphology by increasing root and decreasing stem biomass allocation in the presence of salinity. However, the long-term response of W. robusta to salinity, based to a great extent, on this morphological plasticity, was less effective than that of C. humilis, which is based mainly on the contribution of leaf N to RGR values.

In the past, biologists have characterized the responses of a wide range of plant species to their environment. As a result, phenotypic data from hundreds of experiments are publicly available now. Unfortunately, this information is not structured in a way that enables quantitative and comparative analyses. We aim to fill this gap by building a large database which currently contains data on 1000 experiments and 800 species. This paper presents methodology to generalize across different experiments and species, taking the response of specific leaf area (SLA; leaf area:leaf mass ratio) to irradiance as an example. We show how to construct and quantify a normalized mean light-response curve, and subsequently test whether there are systematic differences in the form of the curve between contrasting subgroups of species. This meta-analysis is then extended to a range of other environmental factors important for plant growth as well as other phenotypic traits, using >5300 mean values. The present approach, which we refer to as 'meta-phenomics', represents a valuable tool in understanding the integrated response of plants to their environment and could serve as a benchmark for future phenotyping efforts as well as for modelling global change effects on both wild species and crops.

Here, we analysed a wide range of literature data on the leaf dry mass per unit area (LMA). In nature, LMA varies more than 100-fold among species. Part of this variation (c. 35%) can be ascribed to differences between functional groups, with evergreen species having the highest LMA, but most of the variation is within groups or biomes. When grown in the same controlled environment, leaf succulents and woody evergreen, perennial or slow-growing species have inherently high LMA. Within most of the functional groups studied, high-LMA species show higher leaf tissue densities. However, differences between evergreen and deciduous species result from larger volumes per area (thickness). Response curves constructed from experiments under controlled conditions showed that LMA varied strongly with light, temperature and submergence, moderately with CO2 concentration and nutrient and water stress, and marginally under most other conditions. Functional groups differed in the plasticity of LMA to these gradients. The physiological regulation is still unclear, but the consequences of variation in LMA and the suite of traits interconnected with it are strong. This trait complex is an important factor determining the fitness of species in their environment and affects various ecosystem processes.

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. We measured Rubisco content in seedlings grown in agar with or without added sugar and fluridone, and Rubisco expression in hydroponically grown vegetative plants grown at low and high CO(2). Furthermore, we analyzed gas exchange and the photosynthetic machinery of transformants and wild-type plants grown under standard conditions. In the presence of exogenous glucose (Glc), agar-grown seedlings of the ethylene-insensitive genotype had lower amounts of Rubisco per unit leaf area than the wild type. No differences in Rubisco content were found between ethylene-insensitive and wild-type seedlings treated with fluridone, suggesting that inhibition of ABA production nullified the effect of Glc application. When larger, vegetative plants were grown at different atmospheric CO(2) concentrations, a negative correlation was found between Glc concentration in the leaves and Rubisco gene expression, with stronger repression by high Glc concentrations in ethylene-insensitive plants. Ethylene insensitivity resulted in plants with comparable fractions of nitrogen invested in light harvesting, but lower amounts in electron transport and Rubisco. Consequently, photosynthetic capacity of the insensitive genotype was clearly lower compared with the wild type. We conclude that the inability to perceive ethylene results in increased sensitivity to Glc, which may be mediated by a higher ABA concentration. This increased sensitivity to endogenous Glc has negative consequences for Rubisco content and photosynthetic capacity of these plants.

The effect of irradiance on leaf construction costs, chemical composition, and on the payback time of leaves was investigated. To enable more generalized conclusions, three different systems were studied: top and the most-shaded leaves of 10 adult tree species in a European mixed forest, top leaves of sub-dominant trees of two evergreen species growing in small gaps or below the canopy in an Amazonian rainforest, and plants of six herbaceous and four woody species grown hydroponically at low or high irradiance in growth cabinets. Daily photon irradiance varied 3-6-fold between low- and high-light leaves. Specific leaf area (SLA) was 30-130% higher at low light. Construction costs, on the other hand, were 1-5% lower for low-irradiance leaves, mainly because low-irradiance leaves had lower concentrations of soluble phenolics. Photosynthetic capacity and respiration, expressed per unit leaf mass, were hardly different for the low- and high-light leaves. Estimates of payback times of the high-irradiance leaves ranged from 2-4 d in the growth cabinets, to 15-20 d for the adult tree species in the European forest. Low-irradiance leaves had payback times that were 2-3 times larger, ranging from 4 d in the growth cabinets to 20-80 d at the most shaded part of the canopy of the mixed forest. In all cases, estimated payback times were less than half the life span of the leaves, suggesting that even at time-integrated irradiances lower than 5% of the total seasonal value, investment in leaves is still fruitful from a carbon-economy point of view. A sensitivity analysis showed that increased SLA of low-irradiance leaves was the main factor constraining payback times. Acclimation in the other five factors determining payback time, namely construction costs, photosynthetic capacity per unit leaf mass, respiration per unit leaf mass, apparent quantum yield, and curvature of the photosynthetic light-response-curve, were unimportant when the observed variation in each factor was examined.

Background and Aims: Leaf thickness plays an important role in leaf and plant functioning, and relates to a species' strategy of resource acquisition and use. As such, it has been widely used for screening purposes in crop science and community ecology. However, since its measurement is not straightforward, a number of estimates have been proposed. Here, the validity of the (SLA x LDMC)(-1) product is tested to estimate leaf thickness, where SLA is the specific leaf area (leaf area/dry mass) and LDMC is the leaf dry matter content (leaf dry mass/fresh mass). SLA and LDMC are two leaf traits that are both more easily measurable and often reported in the literature., Methods: The relationship between leaf thickness (LT) and (SLA x LDMC)(-1) was tested in two analyses of covariance using 11 datasets (three original and eight published) for a total number of 1039 data points, corresponding to a wide range of growth forms growing in contrasted environments in four continents., Key Results and Conclusions: The overall slope and intercept of the relationship were not significantly different from one and zero, respectively, and the residual standard error was 0.11. Only two of the eight datasets displayed a significant difference in the intercepts, and the only significant difference among the most represented growth forms was for trees. LT can therefore be estimated by (SLA x LDMC)(-1), allowing leaf thickness to be derived from easily and widely measured leaf traits.

Global-scale quantification of relationships between plant traits gives insight into the evolution of the world's vegetation, and is crucial for parameterizing vegetation-climate models. A database was compiled, comprising data for hundreds to thousands of species for the core 'leaf economics' traits leaf lifespan, leaf mass per area, photosynthetic capacity, dark respiration, and leaf nitrogen and phosphorus concentrations, as well as leaf potassium, photosynthetic N-use efficiency (PNUE), and leaf N : P ratio. While mean trait values differed between plant functional types, the range found within groups was often larger than differences among them. Future vegetation-climate models could incorporate this knowledge. The core leaf traits were intercorrelated, both globally and within plant functional types, forming a 'leaf economics spectrum'. While these relationships are very general, they are not universal, as significant heterogeneity exists between relationships fitted to individual sites. Much, but not all, heterogeneity can be explained by variation in sample size alone. PNUE can also be considered as part of this trait spectrum, whereas leaf K and N : P ratios are only loosely related.

Bringing together leaf trait data spanning 2,548 species and 175 sites we describe, for the first time at global scale, a universal spectrum of leaf economics consisting of key chemical, structural and physiological properties. The spectrum runs from quick to slow return on investments of nutrients and dry mass in leaves, and operates largely independently of growth form, plant functional type or biome. Categories along the spectrum would, in general, describe leaf economic variation at the global scale better than plant functional types, because functional types overlap substantially in their leaf traits. Overall, modulation of leaf traits and trait relationships by climate is surprisingly modest, although some striking and significant patterns can be seen. Reliable quantification of the leaf economics spectrum and its interaction with climate will prove valuable for modelling nutrient fluxes and vegetation boundaries under changing land-use and climate.

The plant hormone ethylene plays a role in various growth related processes. In this detailed study of the vegetative growth of Arabidopsis, Nicotiana tabacum, and Petunia x hybrida plants, we show that ethylene insensitivity does not result in an increased total leaf area or relative growth rate (RGR) under optimal growth conditions. When grown in semiclosed containers, leaf area of ethylene-insensitive plants was larger compared to the wild type. This effect was caused by a buildup of ethylene inside these containers, which inhibited the growth of wild-type plants. Ethylene-insensitive Arabidopsis and N. tabacum plants had a lower biomass, which was mainly the result of a smaller seed mass. RGR of vegetative plants was not affected by ethylene insensitivity, but the underlying components of RGR differed; specific leaf area (leaf area per unit leaf mass) was higher, and unit leaf rate (growth rate per unit leaf area) was lower. The latter was a result of a slower rate of photosynthesis per unit leaf area in the ethylene-insensitive plants.