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JOHN E. ERICKSON J. PATRICK MEGONIGAL GARY PERESTA BERT G. DRAKE 《Global Change Biology》2007,13(1):202-215
Elevated atmospheric carbon dioxide concentrations ([CO2]) generally increase plant photosynthesis in C3 species, but not in C4 species, and reduce stomatal conductance in both C3 and C4 plants. In addition, tissue nitrogen concentration ([N]) often fails to keep pace with enhanced carbon gain under elevated CO2, particularly in C3 species. While these responses are well documented in many species, implications for plant growth and nutrient cycling in native ecosystems are not clear. Here we present data on 18 years of measurement of above and belowground biomass, tissue [N] and total standing crop of N for a Scirpus olneyi‐dominated (C3 sedge) community, a Spartina patens‐dominated (C4 grass) community and a C3–C4‐mixed species community exposed to ambient and elevated (ambient +340 ppm) atmospheric [CO2] in natural salinity and sea level conditions of a Chesapeake Bay wetland. Increased biomass production (shoots plus roots) under elevated [CO2] in the S. olneyi‐dominated community was sustained throughout the study, averaging approximately 35%, while no significant effect of elevated [CO2] was found for total biomass in the C4‐dominated community. We found a significant decline in C4 biomass (correlated with rising sea level) and a concomitant increase in C3 biomass in the mixed community. This shift from C4 to C3 was accelerated by the elevated [CO2] treatment. The elevated [CO2] stimulation of total biomass accumulation was greatest during rainy, low salinity years: the average increase above the ambient treatment during the three wettest years (1994, 1996, 2003) was 2.9 t ha−1 but in the three driest years (1995, 1999, 2002), it was 1.2 t ha−1. Elevated [CO2] depressed tissue [N] in both species, but especially in the S. olneyi where the relative depression was positively correlated with salinity and negatively related with the relative enhancement of total biomass production. Thus, the greatest amount of carbon was added to the S. olneyi‐dominated community during years when shoot [N] was reduced the most, suggesting that the availability of N was not the most or even the main limitation to elevated [CO2] stimulation of carbon accumulation in this ecosystem. 相似文献
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Diverse methods for the disruption of cell entanglements and pellets of the moss Physcomitrella patens were tested in order to improve the homogeneity of suspension cultures. The morphological characterization of the moss was carried out by means of image analysis. Selected morphological parameters were defined and compared to the reduction of the carbon dioxide fixation, and the released pigments after cell disruption. The size control of the moss entanglements based on the rotor stator principle allowed a focused shear stress, avoiding a severe reduction in the photosynthesis. Batch cultures of P. patens in a 30.0-l pilot tubular photo-bioreactor with cell disruption showed no significant variation in growth rate and a delayed cell differentiation, when compared to undisrupted cultures. A highly controlled photoautotrophic culture of P. patens in a scalable photo-bioreactor was established, contributing to the development required for the future use of mosses as producers of relevant heterologous proteins. 相似文献
115.
Cloning and characterization of micro-RNAs from moss 总被引:16,自引:0,他引:16
Arazi T Talmor-Neiman M Stav R Riese M Huijser P Baulcombe DC 《The Plant journal : for cell and molecular biology》2005,43(6):837-848
Micro-RNAs (miRNAs) are one class of endogenous tiny RNAs that play important regulatory roles in plant development and responses to external stimuli. To date, miRNAs have been cloned from higher plants such as Arabidopsis, rice and pumpkin, and there is limited information on their identity in lower plants including Bryophytes. Bryophytes are among the oldest groups of land plants among the earth's flora, and are important for our understanding of the transition to life on land. To identify miRNAs that might have played a role early in land plant evolution, we constructed a library of small RNAs from the juvenile gametophyte (protonema) of the moss Physcomitrella patens. Sequence analysis revealed five higher plant miRNA homologues, including three members of the miR319 family, previously shown to be involved in the regulation of leaf morphogenesis, and miR156, which has been suggested to regulate several members of the SQUAMOSA PROMOTER BINDING-LIKE (SPL) family in Arabidopsis. We have cloned PpSBP3, a moss SPL homologue that contains an miR156 complementary site, and demonstrated that its mRNA is cleaved within that site suggesting that it is an miR156 target in moss. Six additional candidate moss miRNAs were identified and shown to be expressed in the gametophyte, some of which were developmentally regulated or upregulated by auxin. Our observations suggest that miRNAs play important regulatory roles in mosses. 相似文献
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Antiviral property and mechanisms of a sulphated polysaccharide from the brown alga Sargassum patens against Herpes simplex virus type 1 总被引:3,自引:0,他引:3
A sulphated polysaccharide (SP-2a) from the brown alga Sargassum patens (Kütz.) Agardh (Sargassaceae) was found to significantly inhibit the in vitro replication of both the acyclovir (ACV)-sensitive and -resistant strains of Herpes simplex virus type 1 (HSV-1), in dose-dependent manners, with 50% inhibitions occurring with 1.5–5.3 μg/ml of the polysaccharide. SP-2a exhibited extracellular virucidal activity only against the ACV-sensitive strains, but not the resistant strain, at the concentration of 100 μg/ml. The strongest antiviral activities against the different strains of HSV-1 were observed when this polysaccharide was present during and after adsorption of the virus to host cells. The inhibitory effect of SP-2a on virus adsorption occurred dose-dependently in all the HSV-1 strains tested, and the adsorption of the ACV-resistant DM2.1 strain was reduced by 81.9% (relative to control) with 4 μg/ml of the polysaccharide. This study clearly demonstrated that the antiviral mode of action of SP-2a is mediated mainly by inhibiting virus attachment to host cells, and this sulphated polysaccharide might have different modes of action against the ACV-sensitive and -resistant strains of HSV-1. 相似文献
118.
BACKGROUND AND AIMS: In angiosperms xyloglucan endotransglucosylase (XET)/hydrolase (XTH) is involved in reorganization of the cell wall during growth and development. The location of oligo-xyloglucan transglucosylation activity and the presence of XTH expressed sequence tags (ESTs) in the earliest diverging extant plants, i.e. in bryophytes and algae, down to the Phaeophyta was examined. The results provide information on the presence of an XET growth mechanism in bryophytes and algae and contribute to the understanding of the evolution of cell wall elongation in general. METHODS: Representatives of the different plant lineages were pressed onto an XET test paper and assayed. XET or XET-related activity was visualized as the incorporation of fluorescent signal. The Physcomitrella genome database was screened for the presence of XTHs. In addition, using the 3' RACE technique searches were made for the presence of possible XTH ESTs in the Charophyta. KEY RESULTS: XET activity was found in the three major divisions of bryophytes at sites corresponding to growing regions. In the Physcomitrella genome two putative XTH-encoding cDNA sequences were identified that contain all domains crucial for XET activity. Furthermore, XET activity was located at the sites of growth in Chara (Charophyta) and Ulva (Chlorophyta) and a putative XTH ancestral enzyme in Chara was identified. No XET activity was identified in the Rhodophyta or Phaeophyta. CONCLUSIONS: XET activity was shown to be present in all major groups of green plants. These data suggest that an XET-related growth mechanism originated before the evolutionary divergence of the Chlorobionta and open new insights in the evolution of the mechanisms of primary cell wall expansion. 相似文献
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Seed dormancy characteristics of Spartina alterniflora were delineated previously by Plyler and Carrick (American Journal of Botany, vol. 80, pp. 752–756, 1993). This study was undertaken in order to determine whether or not the dormancy characteristics of S. patens are similar. As in the previous study, the site of a dormancy mechanism was determined by assessing the germinability of surgically altered dormant seeds. Likewise, the effects of three growth-regulating substances (abscisic acid, fusicoccin, and gibberellic acid), prechilling, and light were studied by assessing the germinability of appropriately treated dormant seeds. Surgical injury to the endosperm, and to a lesser extent the scutellum, produced significant germination in S. patens, whereas only injury to the scutellum produced germination in S. alterniflora. Exogenously applied abscisic acid was highly effective in maintaining dormancy in injured seeds of both species. Gibberellic acid and fusicoccin were ineffective in promoting germination in S. patens, but fusicoccin was highly effective in breaking dormancy in 5. alterniflora. Prechilling was effective in breaking dormancy in S. patens but not in S. alterniflora. In S. patens, treatments that broke dormancy were only successful when seeds were exposed to light during the germination period. It is concluded that the dissimilarities in the dormancy mechanisms may be manifestations of the different environmental adaptations these closely related species display. 相似文献