Effects of leaf age and tree size on stomatal and mesophyll limitations to photosynthesis in mountain beech (Nothofagus solandrii var. cliffortiodes)     

Whitehead D  Barbour MM  Griffin KL  Turnbull MH  Tissue DT 《Tree physiology》2011,31(9):985-996

Mesophyll conductance, g(m), was estimated from measurements of stomatal conductance to carbon dioxide transfer, g(s), photosynthesis, A, and chlorophyll fluorescence for Year 0 (current-year) and Year 1 (1-year-old) fully sunlit leaves from short (2 m tall, 10-year-old) and tall (15 m tall, 120-year-old) Nothofagus solandrii var. cliffortiodes trees growing in adjacent stands. Rates of photosynthesis at saturating irradiance and ambient CO(2) partial pressure, A(satQ), were 25% lower and maximum rates of carboxylation, V(cmax), were 44% lower in Year 1 leaves compared with Year 0 leaves across both tree sizes. Although g(s) and g(m) were not significantly different between Year 0 and Year 1 leaves and g(s) was not significantly different between tree heights, g(m) was significantly (19%) lower for leaves on tall trees compared with leaves on short trees. Overall, V(cmax) was 60% higher when expressed on the basis of CO(2) partial pressure at the chloroplasts, C(c), compared with V(cmax) on the basis of intercellular CO(2) partial pressure, C(i), but this varied with leaf age and tree size. To interpret the relative stomatal and mesophyll limitations to photosynthesis, we used a model of carbon isotopic composition for whole leaves incorporating g(m) effects to generate a surface of 'operating values' of A over the growing season for all leaf classes. Our analysis showed that A was slightly higher for leaves on short compared with tall trees, but lower g(m) apparently reduced actual A substantially compared with A(satQ). Our findings showed that lower rates of photosynthesis in Year 1 leaves compared with Year 0 leaves were attributable more to increased biochemical limitation to photosynthesis in Year 1 leaves than differences in g(m). However, lower A in leaves on tall trees compared with those on short trees could be attributed in part to lower g(m) and higher stomatal, L(s), and mesophyll, L(m), limitations to photosynthesis, consistent with steeper hydraulic gradients in tall trees.  相似文献   

A MODIFICATION OF THE BUCHNER METHOD OF CULTIVATING ANAEROBIC BACTERIA     

Griffin AM 《Science (New York, N.Y.)》1932,75(1946):416-417

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Experiences and perspectives of farmers from Upstate New York farmers' markets     

Matthew R. Griffin  Edward A. Frongillo 《Agriculture and Human Values》2003,20(2):189-203

Despite the growing popularityof farmers' markets (FMs) across the UnitedStates, the experiences and perspectives offarmers who sell at markets have received verylittle research attention. This study describesthe views of 18 farmers from Upstate New Yorkon the importance of FMs as part of theirlifestyle and livelihood, the challenges theyface selling at markets, and their conceptionsof ideal FMs. Through in-depth, semi-structuredinterviews, farmers expressed economic andsocial motivations for selling at FMs; socialbenefits from interacting with customers; andthe challenges they faced as small-scalefarmers and sellers, including extra-marketcompetition, uncooperative and problematicmarket vendors, rising farm input costs, andchanging consumer trends. Farmers alsodiscussed personal values associated withselling at FMs, such as pride in raising andmarketing one's own products, working togetherwith other farmer-vendors, and providingcustomers with honest information. Visions ofideal FMs were varied among farmers, but therewas general agreement that FMs should provide adiversity of products to attract customers andeducational opportunities for the public tolearn more about FMs and local produce. Theinterdependence of FM farmers was a majoremergent theme across interviews. Findingssuggested that market experiences of FMfarmers, including economic success, are notonly contingent on personal effort, but canalso be affected by the work of fellow vendors.Future research may look to further explore howFM farmers and other vendors interact ascooperative and competitive social and economicunits. At the community level, FM leadershipshould continue to focus on the experiences andperspectives of farmers and other marketvendors, in addition to identifying ways forenhancing cooperative FM enterprises.  相似文献   

cdc2 gene expression at the G1 to S transition in human T lymphocytes   总被引：39，自引：0，他引：39  

Y Furukawa  H Piwnica-Worms  T J Ernst  Y Kanakura  J D Griffin 《Science (New York, N.Y.)》1990,250(4982):805-808

The product of the cdc2 gene, designated p34cdc2, is a serine-threonine protein kinase that controls entry of eukaryotic cells into mitosis. Freshly isolated human T lymphocytes (G0 phase) were found to have very low amounts of p34cdc2 and cdc2 messenger RNA. Expression of cdc2 increased 18 to 24 hours after exposure of T cells to phytohemagglutinin, coincident with the G1 to S transition. Antisense oligodeoxynucleotides could reduce the increase in cdc2 expression and inhibited DNA synthesis, but had no effect on several early and mid-G1 events, including blastogenesis and expression of interleukin-2 receptors, transferrin receptors, c-myb, and c-myc. Induction of cdc2 required prior induction of c-myb and c-myc. These results suggest that cdc2 induction is part of an orderly sequence of events that occurs at the G1 to S transition in T cells.  相似文献   

Nitrite, an electron donor for anoxygenic photosynthesis     

Griffin BM  Schott J  Schink B 《Science (New York, N.Y.)》2007,316(5833):1870

We report a previously unknown process in which anoxygenic phototrophic bacteria use nitrite as an electron donor for photosynthesis. We isolated a purple sulfur bacterium 98% identical to Thiocapsa species that stoichiometrically oxidizes nitrite to nitrate in the light. Growth and nitrate production strictly depended on both light and nitrite. This is the first known microbial mechanism for the stoichiometric oxidation of nitrite to nitrate in the absence of oxygen and the only known photosynthetic oxidation in the nitrogen cycle. This work demonstrates nitrite as the highest-potential electron donor for anoxygenic photosynthesis known so far.  相似文献   

Reactions of singlet oxygen with pine pollen     

B Dowty  J L Laseter  G W Griffin  I R Politzer  C H Walkinshaw 《Science (New York, N.Y.)》1973,181(100):669-670

Exposure of pine pollen to single oxygen, generated in an aqueous environment, resulted in a decrease in the relative quantities of unsaturated fatty acids that could be recovered by solvent extraction of surface and near surface pollen lipids. The involvement of excited oxygen was confirmed by substitution of deuterium oxide for water, which led to a twofold greater decrease in the unsaturated acids. The potential environmental and biomedical implications of these observations are discussed in terms of this model system.  相似文献   

Cooperation, control, and concession in meerkat groups     

Clutton-Brock TH  Brotherton PN  Russell AF  O'Riain MJ  Gaynor D  Kansky R  Griffin A  Manser M  Sharpe L  McIlrath GM  Small T  Moss A  Monfort S 《Science (New York, N.Y.)》2001,291(5503):478-481

"Limited control" models of reproductive skew in cooperative societies suggest that the frequency of breeding by subordinates is determined by the outcome of power struggles with dominants. In contrast, "optimal skew" models suggest that dominants have full control of subordinate reproduction and allow subordinates to breed only when this serves to retain subordinates' assistance with rearing dominants' own litters. The results of our 7-year field study of cooperative meerkats, Suricata suricatta, support the predictions of limited control models and provide no indication that dominant females grant reproductive concessions to subordinates to retain their assistance with future breeding attempts.  相似文献   

Visual orientation in homing bats     

Williams TC  Williams JM  Griffin DR 《Science (New York, N.Y.)》1966,152(3722):677

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Morphologies and origin of elemental carbon in the environment     

Griffin JJ  Goldberg ED 《Science (New York, N.Y.)》1979,206(4418):563-565

Carbon particles extracted from sediments collected by box coring from southeastern Lake Michigan were compared with carbon particles extracted from oil, coal, and wood fly ash. Sediments deposited after 1900 contained coal, oil, and wood carbons; older sediments contained only wood carbon.  相似文献   

Microbial dehalorespiration with 1,1,1-trichloroethane     

Sun B  Griffin BM  Ayala-del-Río HL  Hashsham SA  Tiedje JM 《Science (New York, N.Y.)》2002,298(5595):1023-1025

1,1,1-Trichloroethane (TCA) is a ubiquitous environmental pollutant because of its widespread use as an industrial solvent, its improper disposal, and its substantial emission to the atmosphere. We report the isolation of an anaerobic bacterium, strain TCA1, that reductively dechlorinates TCA to 1,1-dichloroethane and chloroethane. Strain TCA1 required H2 as an electron donor and TCA as an electron acceptor for growth, indicating that dechlorination is a respiratory process. Phylogenetic analysis indicated that strain TCA1 is related to gram-positive bacteria with low DNA G+C content and that its closest relative is Dehalobacter restrictus, an obligate H2-oxidizing, chloroethene-respiring bacterium.  相似文献