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31.
Long-term effects of elevated CO2 and nutrients on photosynthesis and rubisco in loblolly pine seedlings 总被引:17,自引:13,他引:4
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. 相似文献
32.
THOMAS CAVALIER-SMITH 《The Journal of eukaryotic microbiology》1993,40(5):609-615
ABSTRACT. The recently established protozoan phylum Opalozoa Cavalier-Smith 1991 includes all those zooflagellates with tubular mitochondrial cristae that never have cortical alveoli or rigid tubular ciliary hairs (retronemes), and also the opalinids, proteomyxids sensu stricto, and plasmodiophorids. Opalozoa totally lack plastids but usually (though not invariably) have peroxisomes. They always have well-developed Golgi dictyosomes. The trophic phase is a unicellular ciliated phagotroph except in the only intracellular parasites, the plasmodiophorids, where it is a non-phagotrophic and non-ciliated microplasmodium, and in the proteomyxids where it is an amoeboflagellate (which may sometimes be nonciliated) or a multicellular meroplasmodium. Unlike the phagotrophic Mycetozoa, opalozoans do not form aerial fruiting bodies, but encystation is common. The first detailed classification of the phylum is presented here. It is divided into four subphyla (three new), eight classes (four new, one emended), three subclasses (all new), three superorders (all new) and 22 orders of which 12 are new and one is emended. Diagnoses of these taxa are given, as well as lists of the 31 families (11 new) and 62 genera included within them. Opalozoa, which include Cercomonas and Heterornita , the commonest soil flagellates, are ecologically and evolutionarily important. 相似文献
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MARDER EVE; ABBOTT LAURENCE F.; BUCHHOLTZ FRANK; EPSTEIN IRVING R.; GOLOWASCH JORGE; HOOPER SCOTT L.; KEPLER THOMAS B. 《Integrative and comparative biology》1993,33(1):29-39
SYNOPSIS. The stomatogastric nervous system of decapod crustaceansis an ideal system for the study of the processes underlyingthe generation of rhythmic movements by the nervous system.In this chapter we review recent work that uses mathematicalanalyses and computer simulations to understand: 1) the roleof individual currents in controlling the activity of neurons,and 2) the effects of electrical coupling on the activity ofneuronal oscillators. The aim of this review is to highlight,for the physiologist, what these studies have taught us aboutthe organization and function of single cell and multicellularneuronal oscillators. 相似文献
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- A study has been made of the relationships between the synthesesof carbohydrate, protein, and fat by Penicillium lilacinum Thomin presence of different amounts of sodium nitrate us a definedsucrose salts medium.
- Under the defined experimental conditionsincreases in the concentrationof NO2 in the medium werefollowed by increases in therates at which nitrogen and sugarwere taken up by the fungus,in the quantities assimilated,and in total and protein nitrogenin the felt. These conditionsprevailed so long as unassimilatedsugar was available.
- Mediaof lower NO3 concentration (for example, 0·32or 0·64 per cent. (w/v) NaNO2;) yielded feltsricher in carbohydrate than were those grown in media of higherNO2; content (0·96 or 1·28 per cent. (w/v)NaNO3 The carbohydrate content of the felts increased graduallyuntil the sugar in the medium was exhausted; carbohydrate contentthen decreased.
- Media of lower NO3; concentration weremore conduciveto fat synthesis than those of higher NO3;content.
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