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The seasonal stem water isotopes of E ..

Permeability is dependent on the of the medium the water is flowing through.

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the seasonal variations of photosynthesis with ..

Specific leaf area (SLA; m2 leaf kg_1 leaf) is a key ecophysiological parameter influencing leaf physiology, photosynthesis, and whole plant carbon gain. Both individual tree-based models and other forest process-based models are generally highly sensitive to this parameter, but information on its temporal or within-stand variability is still scarce. In a 2-4-year-old Eucalyptus plantation in Congo, prone to seasonal drought, the within-stand and seasonal variability in SLA were investigated by means of destructive sampling carried out at 2-month intervals, over a 2-year period. Within-crown vertical gradients of SLA were small. Highly significant relationships were found between tree-average SLA (SLAt) and tree size (tree height, Ht, or diameter at breast height, DBH): SLAt ranged from about 9 m2 kg_1 for dominant trees to about 14-15 m2 kg_1 for the smallest trees. The decrease in SLAt with increasing tree size was accurately predicted from DBH using power functions. Stand-average SLA varied by about 20% during the year, with lowest values at the end of the 5-month dry season, and highest values about 2-3 months after the onset of the wet season. Variability in leaf water status according to tree size and season is discussed as a possible determinant of both the within-stand and seasonal variations in SLA. (Résumé d'auteur)

They form at high temperatures with very little water in the crystallization environment.

Summary:
Plants develop mechanisms of adaptations at multiple levels to track and cope with fluctuations in the light environment. At molecular level, the correct matching of circadian variation of gene expression with environmental rhythms allows plants to optimize the utilization of environmental light and to prevent damages due to light excess. Several studies highlighted that a correct matching of endogenous rhythms and external rhythms increases organismal fitness over a board geographic range. Indeed, latitudinal clines in circadian clock gene expression levels (and polymorphism in clock genes) were found in plants, suggesting that natural variation in clock parameters are required to synchronize organisms with their specific environment. Understanding the genetic and physiological mechanisms that plants develop for the seasonal and daily response to environmental conditions, could allow to predict their response to unexpected changes in environmental conditions that could happen in the future due to anthropogenic and climatic changes. Here we explore variations existing, in the daily phase, along a bathymetrical cline in the marine angiosperm Posidonia oceanica (L.) Delile, a key species in costal Mediterranean ecosystems. To do that, we measured modulation of genes expression, by RT-qPCR, at six time points during the day, in several genes related to photosynthesis and circadian rhythms regulation in plants growing at three target depths during the daily cycle along a bathymetrical cline (5 to 30 meter depth). Sampling was performed in a continuous meadow located in the Bay of Calvi, Corsica (thanks to the ESF Cost Action 0906). We analyze the effects of the distinct environmental light conditions on the circadian fluctuation of gene expression. Further, we assess the phenotypic variation among and between genotypes and we discuss its potential adaptive relevance on P. oceanica fitness and survival.

Seasonal variations of photosynthetic capacities of …

We suspect this is due to low CO2 production in the soil when water is limiting, in which case the invasion (abiotic) effect is more significant.

These data, when combined with surfaceirradiance measurements, allow to determine the water columnphotosynthetic cross section, which characterizes the efficiency of thewater column for fixing carbon per unit Chla and per mole of quanta.

Inthis study, we analyze the seasonal and local variability of thisefficiency with a particular emphasize on how its variations are drivenby the composition of the phytoplankton communities and their associatedphotophysiological properties derived from photosynthesis-irradiancemeasurements (P vs E curves).

It is found that the hydrochemical compositions of river water ..

The DIC concentrations and δ 13 C DIC are within the ranges measured for the most isotopically evolved groundwater in this region.

In this study, we measured temporal changes in plant and soil water and N relations during the growing season to compare species and evaluate the effects of changing resource availability on photosynthesis. We hypothesized that as soil moisture declines during the growing season, soil inorganic N availability will decline, with different consequences for N uptake and photosynthesis among grass and shrub species. We expected that the halophytic shrub Atriplex torreyi would have relatively constant leaf N throughout the season, since this species appears to have a competitive advantage in N uptake in saline soils. In contrast, we expected that leaf N in the halophytic grass, Distichlis spicata, and glycophytic shrub species, Ericameria nauseosa, would decline over the season. Consequently, we hypothesized that leaf N and carbon uptake would remain constant throughout the season for Atriplex torreyi, but would decrease for Distichlis spicata and Ericameria nauseosa. An overall goal of this study is to add an understanding of plant N relations to the growing understanding of the role of water availability in influencing plant distributions and community structure in this hydrologically and ecologically important region.

Model simulations also showed that nighttime δ18O values of aboveground respiration were variable, often becoming very positive in water-stressed conditions primarily because of the low relative humidity and resultant elevated δ18O values of leaf water.

Seasonal and local variations of the water column photosynthetic cross section in the ..
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  • Glossary of Terms: P - Physical Geography

    22/12/2003 · Annual and seasonal variations of phytoplankton, chlorophyll, and photosynthesis in ..

  • Lake Access -- Dissolved Oxygen in Lakes

    27/12/2017 · Chlorophyll fluorescence tracks seasonal variations of photosynthesis from ..

  • Stream Ecology, Temperature Impacts on - Water

    02/12/2005 · Water Quality Gradients across Albemarle-Pamlico Estuarine System: Seasonal Variations ..

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Coral Reef Bleaching - Marine Biology Organization

The environmental controls on the seasonal variations of ecosystem apparent quantum yield ( α ), maximum photosynthesis rate ( P max ) and ecosystem respiration ( R e ) were investigated in the three forest ecosystems.

Ecophysiology of coffee growth and production - SciELO

We thank Jonathan Cheng, Heather Rhee, and Trung Nguyen for their assistance in the field, Greg Cane, Alexis Reed, Lisa Tiemann, Dachun Zhang, and Guihong Zhang for their assistance in the laboratory, and the Los Angeles Department of Water and Power for access to their property. This research was funded by the UC Center for Water Resources grant WR-986 and the University of Kansas General Research Fund allocation 2301447.

Ecophysiology of coffee growth and production

In this study, soil inorganic N availability declined during the growing season. Measurements of N availability and leaf N were correlated with photosynthesis in the grass D. spicata, but not in the shrub species A. torreyi or E. nauseosa. Seasonal declines in photosynthesis were observed in D. spicata and E. nauseosa, but only in the sites with greater soil inorganic N. Leaf N in all species declined throughout the season in conjunction with decreasing soil inorganic N. This relationship was significant for D. spicata across all three sites. The distribution of D. spicata is consistent with this trend, as the grass-dominated site was associated with the greatest soil N availability. Further studies are needed to better understand the controls and limitations of photosynthesis in A. torreyi, which was fairly constant both in space and in time, despite large differences in N availability across sites. However, our results suggest that in this shallow groundwater ecosystem, N availability may be an important control on photosynthesis of D. spicata.

Ecofisiologia do crescimento e da produção do cafeeiro

Photosynthesis of E. nauseosa declined in the intermediate site in 2005, but remained constant in the intermediate site in 2006 and in the shrubland site in both 2005 and 2006 (Fig. ). There was no correlation between photosynthesis and N availability, suggesting that leaf N concentrations were greater than the requirements for photosynthesis, perhaps because other nutrients were limiting. In previous studies in Owens Valley, E. nauseousa has been shown to be phosphorus limited when water is available (Drenovsky and Richards , ).

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