Scarce population genetic differentiation but substantial spatiotemporal phenotypic variation of water‑use efficiency in Pinus sylvestris at its western distribution range

Water and carbon fluxes in forests are largely related to leaf gas exchange physiology varying across spatiotemporal scales and modulated by plant responses to environmental cues. We quantified the relevance of genetic and phenotypic variation of intrinsic water-use efficiency (WUEi, ratio of net photosynthesis to stomatal conductance of water) in Pinus sylvestris L. growing in the Iberian Peninsula as inferred from tree-ring carbon isotopes. Inter-population genetic variation, evaluated in a provenance trial comprising Spanish and German populations, was low and relevant only at continental scale. In contrast, phenotypic variation, evaluated in natural stands (at spatial level) and by tree-ring chronologies (at temporal inter-annual level), was important and ten- and threefold larger than the population genetic variance, respectively. These results points to preponderance of plastic responses dominating variability in WUEi for this species. Spatial phenotypic variation in WUEi correlated negatively with soil depth (r = − 0.66; p < 0.01), while temporal phenotypic variation was mainly driven by summer precipitation. At the spatial level, WUEi could be scaled-up to ecosystem-level WUE derived from remote sensing data by accounting for soil water-holding capacity (r = 0.63; p < 0.01). This outcome demonstrates a direct influence of the variation of leaf-level WUEi on ecosystem water and carbon balance differentiation. Our findings highlight the contrasting importance of genetic variation (negligible) and plastic responses in WUEi (large, with changes of up to 33% among sites) on determining carbon and water budgets at stand and ecosystem scales in a widespread conifer such as Pinus sylvestris.This work was supported by the Spanish Government [MINECO Grant Number AGL2015-68274-C3-3-R] and the Russian Science Foundation (Project Number 14-14-00219-P, mathematical approach). We acknowledge P. Sopeña and M.J. Pau for technical assistance and V. Muñoz, M. Sala and A. Teixidó for field sampling

Mesophyll diffusion conductance to CO 2: An unappreciated central player in photosynthesis

Mesophyll diffusion conductance to CO 2 is a key photosynthetic trait that has been studied intensively in the past years. The intention of the present review is to update knowledge of g m, and highlight the important unknown and controversial aspects that require future work. The photosynthetic limitation imposed by mesophyll conductance is large, and under certain conditions can be the most significant photosynthetic limitation. New evidence shows that anatomical traits, such as cell wall thickness and chloroplast distribution are amongst the stronger determinants of mesophyll conductance, although rapid variations in response to environmental changes might be regulated by other factors such as aquaporin conductance.Gaps in knowledge that should be research priorities for the near future include: how different is mesophyll conductance among phylogenetically distant groups and how has it evolved? Can mesophyll conductance be uncoupled from regulation of the water path? What are the main drivers of mesophyll conductance? The need for mechanistic and phenomenological models of mesophyll conductance and its incorporation in process-based photosynthesis models is also highlighted.The study was financially supported by the Estonian Ministry of Science and Education (grant SF1090065s07), the Spanish Ministry of Science and Innovation through projects BFU2008-01072 (MEFORE), AGL2009-11310/AGR, BFU2011-23294 (MECOME) and CGL2009-13079-C02-01 (PALEOISOTREE), and the European Commission through European Regional Fund (the Estonian Center of Excellence in Environmental Adaptation), and the Marie Curie project MC-ERG-246725 (FP7). J.P.F. is supported by the Ramón y Cajal program (RYC-2008-02050). A.G. had a Swiss National Science Fellowship (PA00P3_126259). M.M.B. and C.R.W are supported by Future Fellowships from the Australian Research Council (FT0992063 and FT100100024). C.D. was supported by a grant from the French government and by the cooperation project Tranzfor (Transferring Research between EU and Australia–New Zealand on Forestry and Climate Change, PIRSES-GA-2008-230793) funded by the European Union

The stable isotope ecology of terrestrial plant succession

We review the relevance and use of stable isotopes for the study of plant community succession. Stable isotope measurements provide information on the origin of resources acquired by plants, the processes governing resource uptake and transformation, and the physiological and environmental conditions of plant growth. When combined with measurements of the stable isotope ratio values of soil microbial biomass, soil organic matter and plant litter, isotope measurements of plants can indicate effects of successional changes on ecosystem processes. However, their application to questions of plant succession and ecosystem change is limited by the degree to which the underlying assumptions are met in each study, and complementary measures may be required, depending upon the question of interest. First, we discuss the changes that occur in the stable isotope composition of plants and ecosystems with ontogeny and species replacements, as well as their potential evolutionary significance. Second, we discuss the imprints of plant competition and facilitation on leaf and wood tissue, as well as how stable isotopes can provide novel insights on the mechanisms underlying plant interactions. Finally, we discuss the capacity for stable isotope measurements to serve as a proxy record for past disturbances such as fire, logging and cyclones

Agronomic conditions and crop evolution in ancient Near East agriculture

The appearance of agriculture in the Fertile Crescent propelled the development of Western civilization. Here we investigate the evolution of agronomic conditions in this region by reconstructing cereal kernel weight and using stable carbon and nitrogen isotope signatures of kernels and charcoal from a set of 11 Upper Mesopotamia archaeological sites, with chronologies spanning from the onset of agriculture to the turn of the era. We show that water availability for crops, inferred from carbon isotope discrimination (Δ13C), was two- to fourfold higher in the past than at present, with a maximum between 10,000 and 8,000 cal BP. Nitrogen isotope composition (δ15N) decreased over time, which suggests cultivation occurring under gradually less-fertile soil conditions. Domesticated cereals showed a progressive increase in kernel weight over several millennia following domestication. Our results provide a first comprehensive view of agricultural evolution in the Near East inferred directly from archaeobotanical remains

Processes driving nocturnal transpiration and implications for estimating land evapotranspiration

Evapotranspiration is a major component of the water cycle, yet only daytime transpiration is currently considered in Earth system and agricultural sciences. This contrasts with physiological studies where 25% or more of water losses have been reported to occur occurring overnight at leaf and plant scales. This gap probably arose from limitations in techniques to measure nocturnal water fluxes at ecosystem scales, a gap we bridge here by using lysimeters under controlled environmental conditions. The magnitude of the nocturnal water losses (12-23% of daytime water losses) in row-crop monocultures of bean (annual herb) and cotton (woody shrub) would be globally an order of magnitude higher than documented responses of global evapotranspiration to climate change (51-98 vs. 7-8 mm yr-1). Contrary to daytime responses and to conventional wisdom, nocturnal transpiration was not affected by previous radiation loads or carbon uptake, and showed a temporal pattern independent of vapour pressure deficit or temperature, because of endogenous controls on stomatal conductance via circadian regulation. Our results have important implications from large-scale ecosystem modelling to crop production: homeostatic water losses justify simple empirical predictive functions, and circadian controls show a fine-tune control that minimizes water loss while potentially increasing posterior carbon uptake

Plasticidad fenotípica y variación genética en eficiencia en uso del agua en Pinus sylvestris

En poblaciones forestales la importancia de la plasticidad fenotípica y la adaptación genética como mecanismos de respuesta intra-específica frente a cambios ambientales resulta de compleja cuantificación. Se ha estudiado dicha relevancia en Pinus sylvestris para una característica funcional de trascendencia en ambientes con limitación hídrica: la eficiencia en el uso del agua (EUA, carbono fijado por unidad de agua transpirada). La plasticidad fenotípica se determinó mediante muestreo de 28 rodales próximos al límite meridional de distribución de la especie (Pirineos) característicos de la variabilidad edafoclimática presente en la zona y supuestamente similares en propiedades adaptativas. La variación adaptativa se evaluó en un ensayo de procedencias con poblaciones españolas y alemanas (Aragüés, Huesca). EUA se estimó mediante isótopos (δ13C). En el primer caso se detectaron diferencias en δ13C entre rodales cercanas al 3‰, lo que sugiere una plasticidad en EUA superior al 25%. En el segundo, se observaron diferencias genéticas únicamente entre los dos grupos de poblaciones, con valores ligeramente superiores de EUA en los orígenes alemanes (~5%). Estos resultados sugieren que la plasticidad en la regulación del carbono fijado respecto al agua transpirada supera ampliamente a la variación intra-específica como estrategia de respuesta en Pinus sylvestris frente a fluctuaciones ambientales.Este trabajo se ha desarrollado en el marco del proyecto FUTURPIN (AGL2015-68274-C3-3-R). Los autores agradecen la asistencia técnica de M.J. Pau, M. Sala, P. Sopeña y A. Teixidó.Variación intra-específicaPino silvestreAdaptaciónEconomía del carbonoIsótopos estable

Mesophyll diffusion conductance to CO 2: An unappreciated central player in photosynthesis

Flexas, Jaume et al.-- 14 páginas, 9 figuras, 157 referencias.-- [email protected] diffusion conductance to CO 2 is a key photosynthetic trait that has been studied intensively in the past years. The intention of the present review is to update knowledge of g m, and highlight the important unknown and controversial aspects that require future work. The photosynthetic limitation imposed by mesophyll conductance is large, and under certain conditions can be the most significant photosynthetic limitation. New evidence shows that anatomical traits, such as cell wall thickness and chloroplast distribution are amongst the stronger determinants of mesophyll conductance, although rapid variations in response to environmental changes might be regulated by other factors such as aquaporin conductance.Gaps in knowledge that should be research priorities for the near future include: how different is mesophyll conductance among phylogenetically distant groups and how has it evolved? Can mesophyll conductance be uncoupled from regulation of the water path? What are the main drivers of mesophyll conductance? The need for mechanistic and phenomenological models of mesophyll conductance and its incorporation in process-based photosynthesis models is also highlighted.The study was financially supported by the Estonian Ministry of Science and Education (grant SF1090065s07), the Spanish Ministry of Science and Innovation through projects BFU2008-01072 (MEFORE), AGL2009-11310/AGR, BFU2011-23294 (MECOME) and CGL2009- 13079-C02-01 (PALEOISOTREE), and the European Commission through European Regional Fund (the Estonian Center of Excellence in Environmental Adaptation), and the Marie Curie project MCERG- 246725 (FP7). J.P.F. is supported by the Ramón y Cajal program (RYC-2008-02050). A.G. had a Swiss National Science Fellowship (PA00P3 126259). M.M.B. and C.R.W are supported by Future Fellowships from the Australian Research Council (FT0992063 and FT100100024). C.D. was supported by a grant from the French government and by the cooperation project Tranzfor (Transferring Research between EU and Australia–New Zealand on Forestry and Climate Change, PIRSES-GA-2008-230793) funded by the European Union.Peer Reviewe

Circadian rhythms have significant effects on leaf-to-canopy scale gas exchange under field conditions

Molecular clocks drive oscillations in leaf photosynthesis, stomatal conductance, and other cell and leaf-level processes over ~24 h under controlled laboratory conditions. The influence of such circadian regulation over whole-canopy fluxes remains uncertain; diurnal CO2 and H2O vapor flux dynamics in the field are currently interpreted as resulting almost exclusively from direct physiological responses to variations in light, temperature and other environmental factors. We tested whether circadian regulation would affect plant and canopy gas exchange at the Montpellier European Ecotron. Canopy and leaf-level fluxes were constantly monitored under field-like environmental conditions, and under constant environmental conditions (no variation in temperature, radiation, or other environmental cues)

Scarce population genetic differentiation but substantial spatiotemporal phenotypic variation of water‑use efficiency in Pinus sylvestris at its western distribution range

Water and carbon fluxes in forests are largely related to leaf gas exchange physiology varying across spatiotemporal scales and modulated by plant responses to environmental cues. We quantified the relevance of genetic and phenotypic variation of intrinsic water-use efficiency (WUEi, ratio of net photosynthesis to stomatal conductance of water) in Pinus sylvestris L. growing in the Iberian Peninsula as inferred from tree-ring carbon isotopes. Inter-population genetic variation, evaluated in a provenance trial comprising Spanish and German populations, was low and relevant only at continental scale. In contrast, phenotypic variation, evaluated in natural stands (at spatial level) and by tree-ring chronologies (at temporal inter-annual level), was important and ten- and threefold larger than the population genetic variance, respectively. These results points to preponderance of plastic responses dominating variability in WUEi for this species. Spatial phenotypic variation in WUEi correlated negatively with soil depth (r = − 0.66; p < 0.01), while temporal phenotypic variation was mainly driven by summer precipitation. At the spatial level, WUEi could be scaled-up to ecosystem-level WUE derived from remote sensing data by accounting for soil water-holding capacity (r = 0.63; p < 0.01). This outcome demonstrates a direct influence of the variation of leaf-level WUEi on ecosystem water and carbon balance differentiation. Our findings highlight the contrasting importance of genetic variation (negligible) and plastic responses in WUEi (large, with changes of up to 33% among sites) on determining carbon and water budgets at stand and ecosystem scales in a widespread conifer such as Pinus sylvestris

Molecular Cloning and Characterization of Full-Length cDNA of Calmodulin Gene from Pacific Oyster Crassostrea gigas

The shell of the pearl oyster (Pinctada fucata) mainly comprises aragonite whereas that of the Pacific oyster (Crassostrea gigas) is mainly calcite, thereby suggesting the different mechanisms of shell formation between above two mollusks. Calmodulin (CaM) is an important gene for regulating the uptake, transport, and secretion of calcium during the process of shell formation in pearl oyster. It is interesting to characterize the CaM in oysters, which could facilitate the understanding of the different shell formation mechanisms among mollusks. We cloned the full-length cDNA of Pacific oyster CaM (cgCaM) and found that the cgCaM ORF encoded a peptide of 113 amino acids containing three EF-hand calcium-binding domains, its expression level was highest in the mantle, hinting that the cgCaM gene is probably involved in shell formation of Pacific oyster, and the common ancestor of Gastropoda and Bivalvia may possess at least three CaM genes. We also found that the numbers of some EF hand family members in highly calcified species were higher than those in lowly calcified species and the numbers of these motifs in oyster genome were the highest among the mollusk species with whole genome sequence, further hinting the correlation between CaM and biomineralization