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Photosynthesis
About: Photosynthesis is a research topic. Over the lifetime, 19789 publications have been published within this topic receiving 895197 citations.
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TL;DR: It is shown quantitatively that leaves acclimate their photosystem composition to their growth light spectrum and how this changes the wavelength dependence of the photosystem excitation balance and quantum yield for CO2 fixation, and it is proved that combining different wavelengths can enhance quantum yields substantially.
Abstract: The mechanisms underlying the wavelength dependence of the quantum yield for CO 2 fixation (a) and its acclimation to the growth-light spectrum are quantitatively addressed, combining in vivo physiological and in vitro molecular methods. Cucumber (Cucumis sativus) was grown under an artificial sunlight spectrum, shade light spectrum, and blue light, and the quantum yield for photosystem I (PSI) and photosystem II (PSII) electron transport and a were simultaneously measured in vivo at 20 different wavelengths. The wavelength dependence of the photosystem excitation balance was calculated from both these in vivo data and in vitro from the photosystem composition and spectroscopic properties. Measuring wavelengths overexciting PSI produced a higher a for leaves grown under the shade light spectrum (i.e., PSI light), whereas wavelengths overexciting PSII produced a higher a for the sun and blue leaves. The shade spectrum produced the lowest PSI:PSII ratio. The photosystem excitation balance calculated from both in vivo and in vitro data was substantially similar and was shown to determine a at those wavelengths where absorption by carotenoids and nonphotosynthetic pigments is insignificant (i.e., >580 nm). We show quantitatively that leaves acclimate their photosystem composition to their growth light spectrum and how this changes the wavelength dependence of the photosystem excitation balance and quantum yield for CO2 fixation. This also proves that combining different wavelengths can enhance quantum yields substantially.
287 citations
TL;DR: The effects of long-term CO2 enhancement and varying nutrient availability on photosynthesis and ribulose-1,5-bisphosphate carboxylase/oxygenase (rubisco) were studied on loblolly pine seedlings and demonstrated acclimation of photosynthetic processes to elevated CO2 through reallocation of N.
Abstract: The effects of long-term CO2 enhancement and varying nutrient availability on photosynthesis and ribulose-1,5-bisphosphate carboxylase/oxygenase (rubisco) were studied on loblolly pine (Pinus taeda L.) seedlings grown in two atmospheric CO2 partial pressures (35 and 65 Pa) and three nutrient treatments (low N, low P, and high N and P). Measurements taken in late autumn (November) after 2 years of CO2 enrichment and nutrient addition showed that photosynthetic rates were higher for plants grown at elevated CO2 only when they received supplemental N. Total rubisco activity and rubisco content decreased at elevated CO2, but there was an increase in activation state. At elevated CO2, proportionately less N was found in rubisco and more N was found in the light reaction components. These results demonstrate acclimation of photosynthetic processes to elevated CO2 through reallocation of N. Loblolly pine grown in nutrient conditions similar to native soils (low N availability) had lower needle N and chlorophyll content, lower total rubisco activity and content, and lower photosynthetic rates than plants grown at high N and P. This suggests that the magnitude of the photosynthetic response to a future, high-CO2 environment will be dependent on soil fertility in the system.
287 citations
TL;DR: It is suggested that the concentration of 1,3-bisphosphoglyceric acid may exert control over the rate of isoprene emission from oak leaves, which is related to photosynthetic carbon metabolism.
Abstract: We have investigated the signals which affect the rate of isoprene emission from photosynthesizing leaves of red oak (Quercus rubra L.) using analytical gas-exchange techniques, chlorophyll-fluorescence measurements, and inhibitor feeding. Isoprene emission increased with increasing photon flux density at low CO2 but much less so at high CO2 partial pressure. Photosynthetic CO2 assimilation exhibited the opposite behavior. In CO2-free air, isoprene emission was reduced; above 500 μbar CO2 partial pressure, isoprene emission was also reduced. The high-CO2 effect appeared to be related to low ATP levels which can occur during feedback-limited photosynthesis. At high temperature, which can prevent feedback limitations, isoprene emission remained high as CO2 partial pressure was increased. After exposing the leaves to darkness, isoprene emission declined over 15 min, while photosynthesis stopped within 2 min. Adding far-red light to stimulate cyclic photo-phosphorylation during the post-illumination period stimulated isoprene emission. These analyses lead us to propose that the rate of isoprene emission is regulated by ATP. Analysis of transients indicated that isoprene emission is also related to photosynthetic carbon metabolism. Inhibitor feeding indicated that 3-phosphoglyceric acid and 1,3-bisphosphoglyceric acid are possible candidates for the link between photosynthetic carbon metabolism and the regulation of isoprene emission. Given the ATP dependence, we suggest that the concentration of 1,3-bisphosphoglyceric acid may exert control over the rate of isoprene emission from oak leaves.
287 citations
TL;DR: The earliest CCMs may have evolved in oxygenic cyanobacteria before the atmosphere became oxygenated in stromatolites with diffusion barriers around the cells related to UV screening, and increase the O2 concentration within them, inhibiting rubisco and generating reactive oxygen species, including O3.
Abstract: Inorganic carbon concentrating mechanisms (CCMs) catalyse the accumulation of CO2 around rubisco in all cyanobacteria, most algae and aquatic plants and in C4 and crassulacean acid metabolism (CAM) vascular plants. CCMs are polyphyletic (more than one evolutionary origin) and involve active transport of HCO3−, CO2 and/or H+, or an energized biochemical mechanism as in C4 and CAM plants. While the CCM in almost all C4 plants and many CAM plants is constitutive, many CCMs show acclimatory responses to variations in the supply of not only CO2 but also photosynthetically active radiation, nitrogen, phosphorus and iron. The evolution of CCMs is generally considered in the context of decreased CO2 availability, with only a secondary role for increasing O2. However, the earliest CCMs may have evolved in oxygenic cyanobacteria before the atmosphere became oxygenated in stromatolites with diffusion barriers around the cells related to UV screening. This would decrease CO2 availability to cells and increase the O2 concentration within them, inhibiting rubisco and generating reactive oxygen species, including O3.
286 citations
TL;DR: The diversity of pigment-protein complexes that fuel the conversion of radiant energy to chemical bond energy in land plants and the diverse groups of the algae are highlighted and the ways in which environmental parameters modulate the synthesis of these complexes are detailed.
Abstract: This article focuses on light-harvesting complexes (LHCs) in oxygen evolving photosynthetic organisms. These organisms include cyanobacteria, red algae, plants, green algae, brown algae, diatoms, chrysophytes, and dinoflagellates. We highlight the diversity of pigment-protein complexes that fuel the conversion of radiant energy to chemical bond energy in land plants and the diverse groups of the algae, detail the ways in which environmental parameters (i.e. light quantity and quality, nutrients) modulate the synthesis of these complexes, and discuss the evolutionary relationships among the LHC structural polypeptides.
286 citations