John Raven

..If these motors are involved, some mechanism is needed to amplify the speeds known for the motors to explain the order of magnitude higher speeds seen for auxin transport...

..How can we determine the distribution of uncultured marine microorganisms? Targeted metagenomics has provided the complete chloroplast genome sequence, and the distribution, for a picoplanktonic pelagophyte alga...

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..The outcome of such work would be important for relating the global distribution of diazotrophy to P availability. There are no known P acquisition mechanisms specific to diazotrophs...

..More investigations, including studies of genetic adaptation, are needed...

..Specimens of a bryozoan collected on Scott's Antarctic expeditions, and subsequently, provide clear evidence of recent increases in growth rate after 80 years of constancy...

..CCMs are currently not part of models as to how global environmental change has altered, and is likely to further alter, algal and aquatic plant primary productivity...

..New work shows that the cyanobacterium Aphanizomenon ovalisporum obtains inorganic phosphate by secreting the cyanotoxin cylindrospermopsin, which induces alkaline phosphatase in other phytoplankton species...

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..g. through predation) is a fine one, and thus subject to a complex selective process, is illustrated by the diversity of mixotrophic strategies in extant phytoplankton...

..Overall, there has been less biological feedback on the availability of substrates for calcification than is the case for silicification...

..Palaeogeochemical evidence suggests that CCMs evolved later than did at least some of the extracellular chemical transformation and/or accumulation mechanisms for other resources...

..This would decrease CO(2) availability to cells and increase the O(2) concentration within them, inhibiting rubisco and generating reactive oxygen species, including O(3)...

..Other examples involve changes in pH, or temperature, of a compartment containing an equilibrium mixture of CO2 and HCO3-...

..Different conclusions have been reached depending on the organism investigated and the techniques used, and several aspects require further study...

..e. the competitive inhibition of the carboxylase activity of ribulose bisphosphate carboxylase-oxygenase by oxygen via the oxygenase activity, and oxygen damage to nitrogenase in diazotrophic organisms...

..The impact of low temperatures on photosynthesis by marine macrophytes is predicted to favour diffusive CO(2) entry rather than a CO(2)-concentrating mechanism. Some evidence favours this suggestion, but more data are needed...

..Finer structures involved in the uptake of nutrients of low diffusivity in soil evolved at least 400 million years ago as arbuscular mycorrhizas or as evaginations of "roots" ("root hairs")...

..But the genomic legacy of cyanobacterial ancestry extends far beyond the chloroplast itself, and persists in organisms that have lost chloroplasts completely...

..Water supply is also important in determining denitrification rates on land and on N (and C) fluxes from terrestrial to aquatic systems...

..This article considers the roles of epidermal fusion and intercalary growth in the phylogeny and ontogeny of fused floral elements, and the importance of fusion for angiosperm evolution...

..These data show that altritol can be synthesized by Notheia, with implications for the number of gains and losses of the capacity to synthesize altritol in the evolution of the Fucales...

..The potential of bulk foliar tissue measurements to act as simple predictors of the NH(3) compensation point is discussed...

..sylvatica is sufficiently buffered to eliminate the need for correction of H(+) concentration for dilution during extraction, but that it is necessary to correct the NH(4)(+) concentration of apoplast extracts for dilution...

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..The photosynthetic apparatus is, consequently, protected from damage under high-incident photon flux densities...

..Genetically and functionally, these insect symbionts show considerable similarity to organelles...

..We therefore propose that the mtCA is involved in supplying HCO(3)(-) for anaplerotic assimilation catalyzed by phosphoenolpyruvate carboxylase, which provides C skeletons for N assimilation under some circumstances...

..Here we examine the geological, geochemical, and biological processes that contributed to the rise of these three, distantly related, phytoplankton groups...

..Finally, observations and palaeorecords across a range of timescales allow assessment of the Earth's climate sensitivity, a metric influencing our ability to decide what constitutes 'dangerous' climate change...

..We discuss the diversity of CCMs, their evolutionary origins, and the role of the environment in CCM modulation...

..Differences in the responses of the photosynthetic apparatus of these two marine microalgae are mechanistic and probably representative of evolutionary divergences associated with strategies for dealing with environmental perturbations...

..We propose the maintenance of balanced cell composition (homeostasis) as an evolutionary strategy related to environmental transitory changes...

..Alternative mechanisms which have not been eliminated include the production of CO(2) from HCO (3) (-) at low pH maintained by a H(+) pump, in a compartment close to that containing Rubisco...

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..Furthermore, it emphasizes the requirement for metabolic and functional genetic and enzymic analyses before accepting the presence of C(4)-metabolic enzymes as evidence for C(4) photosynthesis...

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