Does Leaf Position within a Canopy Affect Acclimation of Photosynthesis to Elevated CO2? . Analysis of a Wheat Crop under Free-Air CO2 Enrichment

Previous studies of photosynthetic acclimation to elevated CO2 have focused on the most recently expanded, sunlit leaves in the canopy. We examined acclimation in a vertical profile of leaves through a canopy of wheat (Triticum aestivum L.). The crop was grown at an elevated CO2 partial pressure of 55 Pa within a replicated field experiment using free-air CO2 enrichment. Gas exchange was used to estimate in vivo carboxylation capacity and the maximum rate of ribulose-1,5-bisphosphate-limited photosynthesis. Net photosynthetic CO2 uptake was measured for leaves in situ within the canopy. Leaf contents of ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco), light-harvesting-complex (LHC) proteins, and total N were determined. Elevated CO2 did not affect carboxylation capacity in the most recently expanded leaves but led to a decrease in lower, shaded leaves during grain development. Despite this acclimation, in situ photosynthetic CO2 uptake remained higher under elevated CO2. Acclimation at elevated CO2 was accompanied by decreases in both Rubisco and total leaf N contents and an increase in LHC content. Elevated CO2 led to a larger increase in LHC/Rubisco in lower canopy leaves than in the uppermost leaf. Acclimation of leaf photosynthesis to elevated CO2 therefore depended on both vertical position within the canopy and the developmental stage

Regioselectivity in Electrophilic Aromatic Substitution: Insights from Interaction Energy Decomposition Potentials

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Crop water relations under different CO2 and irrigation: testing of ecosys with free air CO2 enrichment (FACE) experiment.

Increases in crop growth under elevated atmospheric C

Soil Organic Carbon Isotope Tracing in Sorghum under Ambient CO2 and Free-Air CO2 Enrichment (FACE)

As atmospheric carbon dioxide concentrations, [CO2Air ], continue their uncontrolled rise, the capacity of soils to accumulate or retain carbon is uncertain. Free-air CO2 enrichment (FACE) experiments have been conducted to better understand the plant, soil and ecosystem response to elevated [CO2 ], frequently employing commercial CO2 that imparts a distinct isotopic signal to the system for tracing carbon. We conducted a FACE experiment in 1998 and 1999, whereby sorghum (C4 photosynthetic pathway) was grown in four replicates of four treatments using a split-strip plot design: (i) ambient CO2 /ample water (365 µmol mol−1, “Control–Wet”), (ii) ambient CO2 /water stress (“Control–Dry”), (iii) CO2-enriched (560 µmol mol−1, “FACE–Wet”), and (iv) CO2-enriched/water stressed (“FACE–Dry”). The stable-carbon isotope composition of the added CO2 (in FACE treatments) was close to that of free atmosphere background values, so the subsequent similar13 C-enriched carbon signal photosynthetically fixed by C4 sorghum plants could be used to trace the fate of carbon in both FACE and control treatments. Measurement of soil organic carbon content (SOC (%) = gC/ gdry soil × 100%) and δ13 C at three depths (0–15, 15–30, and 30–60 cm) were made on soils from the beginning and end of the two experimental growing seasons. A progressive ca. 0.5‰–1.0‰ δ13 C increase in the upper soil SOC in all treatments over the course of the experiment indicated common entry of new sorghum carbon into the SOC pools. The 0–15 cm SOC in FACE treatments was13 C-enriched relative to the Control by ca. 1‰, and according to isotopic mass balance, the fraction of the new sorghum-derived SOC in the Control–Wet treatment at the end of the second season was 8.4%, 14.2% in FACE–Wet, 6.5% in Control–Dry, and 14.2% in FACE–Dry. The net SOC enhancement resulting from CO2 enrichment was therefore 5.8% (or 2.9% y−1 of experiment) under ample water and 7.7% (3.8% y−1 of experiment) under limited water, which matches the pattern of greater aboveground biomass increase with elevated [CO2Air ] under the Dry treatment, but no parallel isotopic shifts were found in deeper soils. However, these increased fractions of new carbon in SOC at the end of the experiment do not necessarily mean an increase in total SOC content, because gravimetric measurements of SOC did not reveal a significant increase under elevated [CO2Air ], at least within the limits of SOC-content error bars. Thus, new carbon gains might be offset by pre-experiment carbon losses. The results demonstrate successful isotopic tracing of carbon from plants to soils in this sorghum FACE experiment showing differences between FACE and Control treatments, which suggest more dynamic cycling of SOC under elevated [CO2Air ] than in the Control treatment. © 2022 by the authors. Licensee MDPI, Basel, Switzerland.Open access journalThis item from the UA Faculty Publications collection is made available by the University of Arizona with support from the University of Arizona Libraries. If you have questions, please contact us at [email protected]

Free-air CO2 enrichment (FACE): blower effects on wheat canopy microclimate and plant development.

Free-air carbon dioxide enrichment (FACE) provides a realistic, cost-effective method for evaluating the effects of supra-ambient C

Photosynthesis and conductance of spring-wheat leaves: field response to continuous free-air atmospheric CO2 enrichment. Plant, Cell Environ

ABSTRACT Spring wheat was grown from emergence to grain maturity in two partial pressures of CO 2 (pCO 2 ): ambient air of nominally 37 Pa and air enriched with CO 2 to 55 Pa using a free-air CO 2 enrichment (FACE) apparatus. This experiment was the first of its kind to be conducted within a cereal field without the modifications or disturbance of microclimate and rooting environment that accompanied previous studies. It provided a unique opportunity to examine the hypothesis that continuous exposure of wheat to elevated pCO 2 will lead to acclimatory loss of photosynthetic capacity. The diurnal courses of photosynthesis and conductance for upper canopy leaves were followed throughout the development of the crop and compared to model-predicted rates of photosynthesis. The seasonal average of midday photosynthesis rates was 28% greater in plants exposed to elevated pCO 2 than in contols and the seasonal average of the daily integrals of photosynthesis was 21% greater in elevated pCO 2 than in ambient air. The mean conductance at midday was reduced by 36%. The observed enhancement of photosynthesis in elevated pCO 2 agreed closely with that predicted from a mechanistic biochemical model that assumed no acclimation of photosynthetic capacity. Measured values fell below predicted only in the flag leaves in the mid afternoon before the onset of grain-filling and over the whole diurnal course at the end of grain-filling. The loss of enhancement at this final stage was attributed to the earlier senescence of flag leaves in elevated pCO 2 . In contrast to some controlled-environment and field-enclosure studies, this field-scale study of wheat using free-air CO 2 enrichment found little evidence of acclimatory loss of photosynthetic capacity with growth in elevated pCO 2 and a significant and substantial increase in leaf photosynthesis throughout the life of the crop

Orbital spectral variables, growth analysis and sugarcane yield Variáveis espectrais orbitais, indicadoras de desenvolvimento e produtividade da cana-de-açúcar

Temporal analysis of crop development in commercial fields requires tools for large area monitoring, such as remote sensing. This paper describes the temporal evolution of sugar cane biophysical parameters such as total biomass (BMT), yield (TSS), leaf area index (LAI), and number of plants per linear meter (NPM) correlated to Landsat data. During the 2000 and 2001 cropping seasons, a commercial sugarcane field in Araras, São Paulo state, Brazil, planted with the SP80-1842 sugarcane variety in the 4th and 5th cuts, was monitored using nine Landsat images. Spectral data were correlated with agronomic data, obtained simultaneously to the imagery acquisition. Two methodologies were used to collect spectral data from the images: four pixels (2 &#215; 2) window and average of total pixels in the field. Linear and multiple regression analysis was used to study the spectral behavior of the plants and to correlate with agronomic variables (days after harvest-DAC, LAI, NPM, BMT and TSS). No difference was observed between the methodologies to collect spectral data. The best models to describe the spectral crop development in relation to DAC were the quadratic and cubic models. Ratio vegetation index and normalized difference vegetation index demonstrated correlation with DAC, band 3 (B3) was correlated with LAI, and NDVI was well correlated with TSS and BMT. The best fit curves to estimate TSS and BMT presented r² between 0.68 and 0.97, suggesting good potential in using orbital spectral data to monitor sugarcane fields.<br>Dados de satélites são tradicionalmente utilizados em monitoramento de culturas. O presente trabalho busca contribuir no entendimento da evolução temporal de indicadores de crescimento da cana-de-açúcar como a biomassa total (BMT), produtividade (TSS), índice de área foliar (LAI) e número de plantas por metro (NPM) por meio de dados orbitais dos satélites Landsat 5 e 7, e verificar o seu potencial para o monitoramento desta. Durante as safras 2000 e 2001, uma área comercial em Araras, SP, cultivada com a variedade SP80-1842 no 4º e 5º cortes, foi acompanhada por imagens, buscando-se correlacionar dados espectrais com dados agronômicos. Os dados espectrais foram coletados de duas formas: uma com janelas de quatro pixels e outra com dados médios do talhão (DMt). Regressão linear e múltipla foram usadas para a análise temporal das bandas 3 e 4 e de índices de vegetação. As correlações e ajuste de modelos entre os dados espectrais orbitais e as variáveis agronômicas não apresentaram diferenças estatísticas. Os modelos quadráticos e cúbicos melhor descreveram o desenvolvimento temporal das variáveis espectrais, em função dos dias após o corte e apresentaram significância com os índices de vegetação da razão e por diferença normalizada (NDVI). As correlações entre os dados espectrais médios do talhão e as variáveis agronômicas foram significativas para banda3 e LAI, e entre NDVI e TSS/BMT. Os dados médios do talhão (DMt), para primeira safra (1ªS), para a segunda safra (2ªS) e ambas juntas geraram regressões múltiplas, com coeficientes determinação (r²) variando de 0,68 a 0,97 para a TSS e a BMT, mostrando que os dados espectrais orbitais estudados podem ser empregados no monitoramento da cultura da cana-de-açúcar