Fluxes of carbon dioxide and water vapour over a C4 pasture in southwestern Amazonia (Brazil)

1998 ◽  
Vol 25 (5) ◽  
pp. 519 ◽  
Author(s):  
John Grace ◽  
Jon Lloyd ◽  
Antonio Carlos Miranda ◽  
Heloisa Miranda ◽  
J.H.C. Gash
Keyword(s):  
Water Vapour ◽  
Intercellular Co2 Concentration ◽  
Nutrient Status ◽  
Co2 Concentration ◽  
Co2 Assimilation ◽  
Daily Basis ◽  
Photosynthetic Performance ◽  
Wet Season ◽  
Area Index ◽  
C4 Grass

In Brazil, pastures for cattle ranching are being established in areas that were previously forested. To investigate some consequences of this change in land use we measured fluxes of CO2 and water vapour over a typical pasture, dominated by the introduced C4 grass Brachiaria brizantha. In addition, we compared the CO2, water vapour fluxes and canopy stomatal conductances observed with those obtained simultaneously over a nearby undisturbed rain forest. Measurements were made near the end of the wet season under conditions of ample soil moisture. Leaf area index of the pasture was 3.9. The pasture had a lower canopy stomatal conductance than the forest (typically 0.2–0.3 mol m-2 s-1 versus 0.4–0.9 mol m-2 s-1 at high photon irradiance) and was less responsive to the canopy-to-air vapour pressure difference. As a consequence of these lower canopy stomatal conductances, the pasture used much less water than the forest with average values over the period examined being 153 mol H2O m-2 d-1 and 249 mol H2O m-2 d-1 for pasture and forest respectively (2.74 and 4.48 mm d-1 respectively). This was also reflected by differing fractions of the absorbed energy being dissipated as evaporation. This proportion was typically 0.56 for the pasture and 0.74 for the forest. After allowing for soil and plant respiration, average daily photosynthetic rates were 0.67 mol C m-2 d-1 for the pasture and 0.57 mol C m-2 d-1for the forest (8.0 and 6.8 g C m-2 d-1, respectively). Thus, despite an appreciably lower rate of water use the pasture assimilated more carbon on a daily basis. Nevertheless, Brachiaria displayed a somewhat lower rate of photosynthesis than expected for a C4 grass, perhaps because of a low nutrient status. Indeed, at low and medium photon irradiance the pasture and forest showed remarkably similar photosynthetic performance. There was, however, less tendency for CO2 assimilation rates of the pasture canopy to saturate at high photon irradiance. The respiratory fluxes from the two ecosystems at night were quite similar, 6–8 µmol m-2 s-1. The ratio of intercellular CO2 concentration to ambient CO2 concentration was usually 0.4 to 0.6 for the pasture, a range which is higher than that often reported for C4 plants but possibly not unusual for tropical grasses in their natural environment.

scholarly journals Spatial arrangement of maize plants aiming to maximize grain yield in the hybrid BRS-3046

2020 ◽  
pp. 1662-1669
Author(s):  
Marcus Willame Lopes Carvalho ◽  
Edson Alves Bastos ◽  
Milton José Cardoso ◽  
Aderson Soares de Andrade Junior ◽  
Carlos Antônio Ferreira de Sousa
Keyword(s):  
Grain Yield ◽  
Plant Density ◽  
Intercellular Co2 Concentration ◽  
Maximum Yield ◽  
Co2 Concentration ◽  
Spatial Arrangement ◽  
Co2 Assimilation ◽  
Linear Increase ◽  
Planting Density ◽  
Row Spacing

The objectives of this study were to: (i) evaluate the effect of different spatial arrangements on morpho-physiological characteristics and (ii) determine the optimal spatial arrangement to maximize grain yield of the maize hybrid BRS-3046 grown in the Mid-North region of Brazil. We tested two row spacings (0.5 and 1 m) and five plant densities (2, 4, 6, 8, 10 plants m-2), which corresponded to 10 different plant spatial arrangements. Different morphophysiological variables, gas exchange rates and grain yield were measured. The increased planting density led to a linear increase in LAI, regardless of row spacing, while the net CO2 assimilation rate increased until the density of 4 and 6 plants m-2, under a row spacing of 0.5 and 1.0 m, respectively. On the other hand, we found a linear reduction in the stomatal conductance with increasing planting density. The intercellular CO2 concentration and the transpiration rate were higher in the widest row spacing. The instantaneous efficiency of carboxylation, in turn, showed a slight increase up to the density of six plants m-2, then falling, regardless of row spacing. Increasing plant density resulted in a linear increase in plant height and ear insertion height, regardless of row spacing. However, it had an opposite effect on stem diameter. Grain yield, in turn, increased up to 7.3 plants m-2 at a row spacing of 0.5 m and 8 plants m-2 at a row spacing of 1.0 m. This spatial arrangement was considered as ideal for achieving maximum yield

scholarly journals The effect of rainfall amount and timing on annual transpiration in a grazed savanna grassland

2021 ◽  
Author(s):  
Matti Räsänen ◽  
Mika Aurela ◽  
Ville Vakkari ◽  
Johan P. Beukes ◽  
Juha-Pekka Tuovinen ◽  
...  
Keyword(s):  
Leaf Area ◽  
Gross Primary Production ◽  
Co2 Exchange ◽  
Wet Season ◽  
Area Index ◽  
C4 Grass ◽  
Precipitation Timing ◽  
Dry Spells ◽  
Annual Water

Abstract. The role of precipitation (P) variability on evapotranspiration (ET) and its two components, transpiration (T) and evaporation (E) from savannas, continues to draw significant research interest given its relevance to a number of eco-hydrological applications. Our study reports on six years of measured ET and estimated T and E from a grazed savanna grassland in Welgegund, South Africa. Annual P varied significantly in amount (508 to 672 mm yr−1), with dry years characterized by infrequent early-season rainfall. T was determined using annual water-use efficiency and gross primary production estimates derived from eddy covariance measurements of latent heat flux and net ecosystem CO2 exchange rates. The computed annual T was nearly constant, 331 ± 11 mm yr−1 (T/ET = 0.52), for the four wet years with frequent early wet-season rainfall, whereas annual T was 268 and 175 mm yr−1 during the dry years. Annual T/ET was linearly related to the early wet-season storm frequency. The constancy of annual T during wet years is explained by the moderate water stress of C4 grass and constant annual tree transpiration covering 15 % of the landscape. However, grass transpiration declines during dry spells. Moreover, grasses respond to water availability with a dieback-regrowth pattern, reducing leaf area and transpiration during drought. These changes lead to an anomalous monthly T/ET relation to leaf-area index (LAI). The results highlight the role of the C4 grass layer in the hydrological balance and suggest that the grass response to dry spells and drought is reasonably described by precipitation timing.

Growth and Physiology Vary Little Among North American, an Asian, and a North American x Asian Hybrid Ash in a Common Garden in Ohio, U.S.A

2019 ◽  
Vol 45 (3) ◽  
Author(s):  
Laurel Haavik ◽  
Daniel Herms
Keyword(s):  
Photosystem Ii ◽  
North American ◽  
Intercellular Co2 Concentration ◽  
Emerald Ash Borer ◽  
Common Garden ◽  
Co2 Concentration ◽  
Interspecific Variation ◽  
Co2 Assimilation ◽  
Agrilus Planipennis ◽  
White Ash

The emerald ash borer (EAB) (Agrilus planipennis Fairmaire) invasion of North America has increased interest in ash (Fraxinus, Oleaceae) phylogeny, ecology, and physiology. In a common garden in central Ohio, we compared the performance of three North American ash cultivars that are highly susceptible to EAB (F. pennsylvanica ‘Patmore,’ F. americana ‘Autumn Purple,’ and F. nigra ‘Fall Gold’), one North American species that is less susceptible to EAB (F. quadrangulata), and two taxa that are resistant to EAB (F. mandshurica and F. mandshurica × F. nigra ‘Northern Treasure’). During the 2015 growing season, we measured diameter growth, foliar N concentration, specific leaf area, and on four dates (two with adequate and two with low precipitation) we measured CO2 assimilation rate (A), stomatal conductance (gs), intercellular CO2 concentration (Ci), photosynthetic nitrogen use efficiency (PNUE), variable fluorescence (Fv’/Fm’: efficiency of energy harvested by open photosystem II reaction centers), and the fraction of photons absorbed by photosystem II that were used for photosynthesis (ɸPSII). F. pennsylvanica grew fastest and on most sampling dates was superior in physiological performance (A, gs, and ɸPSII). Generally, however, there was little interspecific variation in growth and physiology among the different ash taxa tested, as all performed well. This suggests that the EAB-resistant F. mandshurica and F. mandshurica × F. nigra hybrid, as well as the moderately resistant blue ash, are as physiologically well-suited to growing conditions in the Midwestern United States as green and white ash cultivars that had been widely planted prior to the EAB invasion.

scholarly journals PYRACLOSTROBIN PRESERVES PHOTOSYNTHESIS IN ARABICA COFFEE PLANTS SUBJECTED TO WATER DEFICIT

2020 ◽  
Vol 28 ◽  
pp. 109-119
Author(s):  
Anelisa Figueiredo Peloso ◽  
Sandro Dan Tatagiba ◽  
Francisco José Teixeira Amaral ◽  
Paulo César Cavatte ◽  
José Eduardo Macedo Pezzopane
Keyword(s):  
Quantum Yield ◽  
Water Deficit ◽  
Chlorophyll A ◽  
Co2 Concentration ◽  
Co2 Assimilation ◽  
Photosynthetic Performance ◽  
Effective Quantum Yield ◽  
Fluorescence Maximum ◽  
Common Strategy ◽  
Coffee Plants

The objective of this study was to investigate the effect of pyraclostrobin on the photosynthetic performance of rabica coffee plants subjected or not to a water deficit, using the parameter of gas exchange (net CO2 assimilation, stomatal conductance, transpiration rate, and internal CO2 concentration and nocturnal respiration), chlorophyll fluorescence a parameters (minimum fluorescence, maximum fluorescence, maximum quantum yield of photosystem II, effective quantum yield of PSII, quantum yield of regulated energy dissipation and quantum yield dissipation non-regulated) as well as the concentrations of chloroplast pigments. In the plants maintained without water deficit, pyraclostrobin did not cause any alteration on the parameters of chlorophyll a fluorescence; however, it contributed to an increase in the level of chlorophyll a + b, CO2 assimilation and CO2 influx for the carboxylation sites of the stroma. Decreases in nocturnal respiration in plants treated with pyraclostrobin, submitted or not to water deficit seems to be a common strategy in reducing energy waste in the maintenance metabolism. Under water deficit, pyraclostrobin contributed to increase the photochemical yield, enabling plants to effectively prevent the capture, use and dissipation of light energy.

scholarly journals Antioxidant Protection of Photosynthesis in Two Cashew Progenies Under Salt Stress

2018 ◽  
Vol 10 (10) ◽  
pp. 388
Author(s):  
Anselmo F. da Silva ◽  
Valéria F. de O. Sousa ◽  
Gisele L. dos Santos ◽  
Eugênio S. Araújo Júnior ◽  
Sérgio L. F. da Silva ◽  
...  
Keyword(s):  
Salt Stress ◽  
Quantum Efficiency ◽  
Salinity Stress ◽  
Intercellular Co2 Concentration ◽  
Co2 Concentration ◽  
Co2 Assimilation ◽  
Photochemical Activity ◽  
Photochemical Quenching ◽  
Tree Seedlings ◽  
Cashew Tree

The present work evaluated the indicators of photosynthetic efficiency and antioxidative protection in cashew tree seedlings subjected to salinity stress. The study was conducted with seedlings of two advanced dwarf cashew clones (CCP09 and CCP76) subjected to salt stress with increasing doses of NaCl (0, control; 25; 50; 75; 100 mM) in the nutrient solution for 30 days under greenhouse conditions. The variables of gas exchange, CO2 assimilation (PN), stomatal conductance (gS), transpiration (E), intercellular CO2 concentration (CI), photochemical activity, potential quantum efficiency (Fv/Fm), effective quantum efficiency (ΔF/Fm’) of photosystem II (PSII), photochemical quenching (qP), non-photochemical quenching (NPQ) electron transport rate (ETR) as well as the indicators of damage and oxidative protection were measured. Under these conditions, there was an intense accumulation Na+ associated with a reduction in the K+/Na+ ratio in the leaves of both clones in response to salt, with higher values for this ratio in clone CCP09 than in CCP76 the highest concentration of NaCl (100 mM). Salinity reduced PN, gS and E in the two clones evaluated, with lower reductions in CCP09 than in CCP76 at the highest salt dose. Instantaneous carboxylation (PN/CI) and water use (PN/E) efficiencies were strongly restricted by salinity but were less affected in CCP09 than in CCP76. Salinity stress also increased hydrogen peroxide (H2O2) levels in CCP09, whereas lipid peroxidation decreased in both progenies. The clones presented specific antioxidant responses due to greater enzymatic and non-enzymatic activity in CCP76, in addition to the activity of phenol peroxidase (POX) in CCP09.

scholarly journals Photosynthetic responses of young cashew plants to varying environmental conditions

2005 ◽  
Vol 40 (8) ◽  
pp. 735-744 ◽  
Author(s):  
Rogéria Pereira de Souza ◽  
Rafael Vasconcelos Ribeiro ◽  
Eduardo Caruso Machado ◽  
Ricardo Ferraz de Oliveira ◽  
Joaquim Albenísio Gomes da Silveira
Keyword(s):  
Gas Exchange ◽  
Intercellular Co2 Concentration ◽  
Co2 Concentration ◽  
Co2 Assimilation ◽  
Photon Flux ◽  
Photochemical Quenching ◽  
Photon Flux Density ◽  
Effective Quantum Yield ◽  
Water Losses ◽  
Controlled Conditions

The aim of this study was to characterize gas exchange responses of young cashew plants to varying photosynthetic photon flux density (PPFD), temperature, vapor-pressure deficit (VPD), and intercellular CO2 concentration (Ci), under controlled conditions. Daily courses of gas exchange and chlorophyll a fluorescence parameters were measured under natural conditions. Maximum CO2 assimilation rates, under optimal controlled conditions, were about 13 mmol m-2 s-1 , with light saturation around 1,000 mmol m-2 s-1. Leaf temperatures between 25ºC and 35ºC were optimal for photosynthesis. Stomata showed sensitivity to CO2, and a closing response with increasing Ci. Increasing VPD had a small effect on CO2 assimilation rates, with a small decrease above 2.5 kPa. Stomata, however, were strongly affected by VPD, exhibiting gradual closure above 1.5 kPa. The reduced stomatal conductances at high VPD were efficient in restricting water losses by transpiration, demonstrating the species adaptability to dry environments. Under natural irradiance, CO2 assimilation rates were saturated in early morning, following thereafter the PPFD changes. Transient Fv/Fm decreases were registered around 11h, indicating the occurrence of photoinhibition. Decreases of excitation capture efficiency, decreases of effective quantum yield of photosystem II, and increases in non-photochemical quenching were consistent with the occurrence of photoprotection under excessive irradiance levels.

Gas Exchange and Nitrogen Compartmentalization of Eggplant under Nitrogen and Silicon Doses

2019 ◽  
pp. 1-8
Author(s):  
Ewerton Gonçalves de Abrantes ◽  
Josinaldo Lopes Araujo Rocha ◽  
Kariolania Fortunato De Paiva ◽  
Railene Hérica Carlos Rocha ◽  
Alexandre Paiva da Silva ◽  
...  
Keyword(s):  
Gas Exchange ◽  
Leaf Area Index ◽  
Leaf Area ◽  
Photosynthetic Rate ◽  
Intercellular Co2 Concentration ◽  
Co2 Concentration ◽  
Dry Mass ◽  
Nitrogen Accumulation ◽  
Area Index ◽  
Associated Variables

To evaluate the effect of fertilization with N and Si on gaseous exchanges, dry mass, concentrations, accumulations and compartmentalization of nitrogen fractions in eggplant. The experimental design was a randomized entirely design, in a 5 x 4 factorial arrangement with four replications and one plant per plot, totaling 80 experimental units. The experiment was conducted in a protected environment at Center of Sciences and Agri-Food Technology of the Federal University of Campina Grande, Campus of Pombal, Paraiba, Brazil, between July and September 2016. The nitrogen doses applied was 25, 125, 250, 350 and 500 mg dm-3 and four silicon doses was 0, 75, 150 and 200 mg dm-3 both supplied by root. In pre-flowering stage were evaluated growth components; gas exchange, which are: photosynthesis, stomatal conductance, transpiration rate and intercellular CO2 concentration; levels and accumulation of fractions of nitrogen (NO3-, NH4+, and total), and the silicon concentration in the leaves. There was no significant interaction (p >0.05) between the factors nitrogen and silicon doses for any of the evaluated variables. Nitrogen and silicon doses influenced the variables evaluated only independently each other. The nitrogen doses promoted increases in the photosynthetic rate and associated variables, dry matter yield of stem leaves and roots and in the concentration and accumulations of nitric, ammoniacal and total nitrogen in leaf, stem e roots and decrease the concentration of silicon in leaves. The silicon doses increased the leaf area index, the nitrate levels and accumulation in the roots and the silicon content in the leaves. In conclusion, the nitrogen supply increased the photosynthetic rate, dry mass and nitrogen accumulation and decreased the concentrations of silicon in leaf. Silicon did not interfered with growth of eggplant, however increased leaf area index, decreased nitrate levels and accumulations in the roots at lower doses of this element.

scholarly journals GROWTH AND PHYSIOLOGICAL RESPONSE OF COFFEE SEEDLINGS TREATED WITH FUNGICIDES

2019 ◽  
Vol 14 (2) ◽  
pp. 138 ◽  
Author(s):  
Viviane Maria Ruela ◽  
Adriano Bortolotti da Silva ◽  
André Delly Veiga ◽  
Thiago Corrêa de Souza ◽  
Daniele Maria Marques ◽  
...  
Keyword(s):  
Water Use Efficiency ◽  
Water Use ◽  
Intercellular Co2 Concentration ◽  
Co2 Concentration ◽  
Co2 Assimilation ◽  
Fresh Matter ◽  
Fungicidal Action ◽  
Positive Effects ◽  
Use Efficiency ◽  
Intercellular Co2

Research has shown that, in addition to the fungicidal action already known, strobilurins have positive physiological effects on the yield of some crops. Boscalid has also shown positive effects on plants, applied together or associated with strobilurin. The objective in this study was to evaluate the effect of fungicide application on growth and physiological behavior of coffee seedlings. The experimental design was in randomized blocks, with five replicates. There were five treatments: T1-Control, T2-Boscalid, T3-Pyraclostrobin, T4- Boscalid+ Pyraclostrobin and T5- Azoxystrobin applied in coffee seedlings. The application was at the “orelha de onça” stage (two round-shaped leaves), repeated every 15 days, counting 5 applications in total. Were evaluated shoot length, root length, stem diameter, shoot and root fresh matter, shoot and root dry matter, leaf photosynthesis, stomatal conductance, transpiration, intercellular CO2 concentration, water use efficiency and carboxylation efficiency. The application of fungicides promotes greater vegetative growth of coffee seedlings due to increased CO2 assimilation rate, reduced transpiration rates and increased water use efficiency, associated to the increased levels of auxin and cytokinins in leaves

scholarly journals Gas exchange, growth, and quality of passion fruit seedlings cultivated with saline water

2021 ◽  
Vol 42 (1) ◽  
pp. 137-154
Author(s):  
Geovani Soares de Lima ◽  
◽  
José Nathanael Ferreira de Andrade ◽  
Mizael Nabor Vaz de Medeiros ◽  
Lauriane Almeida dos Anjos Soares ◽  
...  
Keyword(s):  
Gas Exchange ◽  
Saline Water ◽  
Block Design ◽  
Intercellular Co2 Concentration ◽  
Relative Yield ◽  
Co2 Concentration ◽  
Co2 Assimilation ◽  
Passion Fruit ◽  
Water Salinity

This study was conducted to evaluate the gas exchange, growth, and quality of passion fruit cultivars under irrigation with waters of different salinity levels. The experiment was conducted in a greenhouse, in Pombal-PB, Brazil, using a randomized block design in a 5 ? 2 factorial arrangement, with five levels of electrical conductivity of irrigation water (0.3, 1.1, 1.9, 2.7, and 3.5 dS m-1) and two passion fruit cultivars (BRS Sol do Cerrado and Guinezinho), with three plants per plot and four replicates. The reduction in transpiration, intercellular CO2 concentration and CO2 assimilation rate in passion fruit plants grown with saline water was related to factors of stomatal and non-stomatal origin. Gas exchange and growth of passion fruit cultivars were negatively affected by water salinity from 0.3 dS m-1 at 75 days after sowing. Despite the reduction in the growth of the passion fruit cultivars, irrigation with water of up to 3.5 dS m-1 could be used to obtain seedlings with acceptable quality. Based on the relative yield of total dry phytomass, the passion fruit cultivars BRS Sol do Cerrado and Guinezinho were classified as moderately sensitive to water salinity during the seedling phase.

scholarly journals Gas exchange, growth, and production of mini-watermelon under saline water irrigation and phosphate fertilization

2020 ◽  
Vol 41 (6supl2) ◽  
pp. 3039-3052
Author(s):  
Geovani Soares de Lima ◽  
◽  
Charles Macedo Félix ◽  
Saulo Soares da Silva ◽  
Lauriane Almeida dos Anjos Soares ◽  
...  
Keyword(s):  
Salt Stress ◽  
Gas Exchange ◽  
Saline Water ◽  
Block Design ◽  
Intercellular Co2 Concentration ◽  
Co2 Concentration ◽  
Co2 Assimilation ◽  
Northeastern Brazil ◽  
Randomized Block Design ◽  
Semi Arid Region

In the semi-arid region of Northeastern Brazil, due to the occurrence of excess salts, both in the water and soil, plants are constantly exposed to various conditions of abiotic stress. Thus, it is extremely important to identify methods capable of minimizing the effects of salt stress on plants as a way to ensure the expansion of irrigated areas. In this context, the objective of this study was to evaluate the gas exchange, growth, and production of mini-watermelon irrigated with saline waters and fertilized with phosphorus. The experiment was conducted in pots under greenhouse conditions in Pombal, PB, Brazil, using a randomized block design in a 5 x 4 factorial scheme, corresponding to five levels of electrical conductivity of irrigation water—ECw (0.3, 1.3, 2.3, 3.3, and 4.3 dS m-1), four phosphorus doses— PD (60, 80, 100, and 120% of the recommendation), and with three replicates. Watermelon plants cv. Sugar Baby were sensitive to water salinity greater than 0.3 dS m-1, with more pronounced inhibition of gas exchange, growth, and production. Reduction in the CO2 assimilation rate of watermelon plants cv. Sugar Baby was associated with factors of stomatal and non-stomatal origin. Phosphorous doses corresponding to 73 and 88% of the recommended values promoted an increase in the intercellular CO2 concentration and stem diameter of mini-watermelon plants. P2O5 doses ranging from 60 to 120% of the recommendation did not mitigate the effects of salt stress on the cultivation of watermelon cv. Sugar Baby.

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