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REYNALDO LUIZ VICTORIA FERNANDO FERNANDES† LUIZ ANTONIO MARTINELLI MARISA DE CÁSSIA PICCOLO PLINIO BARBOSA DE CAMARGO SUSAN TRUMBORE‡ 《Global Change Biology》1995,1(3):165-171
Measurements of the organic carbon inventory, its stable isotopic composition and radiocarbon content were used to deduce vegetation history from two soil profiles in arboreal and grassy savanna ecotones in the Brazilian Pantanal. The Pantanal is a large floodplain area with grass-dominated lowlands subject to seasonal flooding, and arboreal savanna uplands which are only rarely flooded. Organic carbon inventories were lower in the grassy savanna site than in the upland arboreal savanna site, with carbon decreasing exponentially with depth from the surface in both profiles. Changes in 13C of soil organic matter (SOM) with depth differed markedly between the two sites. Differences in surface SOM 13C values reflect the change from C3 to C4 plants between the sites, as confirmed by measurements of 13C of vegetation and the soil surface along a transect between the upland closed-canopy forest and lowland grassy savanna. Changes of 13C in SOM with depth at both sites are larger than the 3–4 per mil increases expected from fractionation associated with organic matter decomposition. We interpret these as recording past changes in the relative abundance of C3 and C4 plants at these sites. Mass balances with 14C and 13C suggest that past vegetational changes from C3 to C4 plants in the grassy savanna, and in the deeper part of the arboreal savanna, occurred between 4600 and 11 400 BP, when major climatic changes were also observed in several places of the South American Continent. The change from C4 to C3, observed only in the upper part of the arboreal savanna, was much more recent (1400 BP), and was probably caused by a local change in the flooding regime. 相似文献
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Water Deficit in Pea Root Tips: Effects on the Cell Cycle and on the Production of Dehydrin-like Proteins 总被引:3,自引:0,他引:3
BRACALE MARCELLA; LEVI MARISA; SAVINI CHRISTIAN; DICORATO WALTER; GALLI MARIA GRAZIA 《Annals of botany》1997,79(6):593-600
Dehydrin-like proteins have been detected in nuclei and cytoplasmof meristematic root tip cells from pea seedlings subjectedto slow dehydration at 90% relative humidity for 48 h or more.Evidence was gained from Western blotting and immunocytochemicalexperiments using an antibody raised against the conserved domainof dehydrin proteins. Flow cytometer analysis has shown thatcycling cells of root tip meristems from dehydrated seedlingsare mostly arrested in G2 phase. Other stress treatments thoughtto involve water depletion (osmotic stress, cold treatment)or to modulate cell response to water deficit (abscisic acid)gave less clear-cut results with all treatments lowering theproportion of cells entering the S phase, but without a definiteand persistent arrest in any preferential phase of the cycle.Possible interrelationships between G2 arrest and dehydrin productionare discussed. Cell cycle; dehydrins; flow cytometry; nuclei; pea; Pisum sativum L.; water stress 相似文献
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MARISA TONIOLO POZZOBON MARIA TERESA SCHIFINO-WITTMANN LUCIANO DE BEM BIANCHETTI 《Botanical journal of the Linnean Society. Linnean Society of London》2006,151(2):259-269
Chromosome numbers were determined in 29 accessions of wild and semidomesticated Capsicum species from the EMBRAPA Hortaliças (Brazil) germplasm collection. 2 n = 24 was found in C. baccatum var. praetermissum , C. chinense , C. flexuosum and C. parvifolium , while C. buforum , C. campylopodium , C. cornutum , C. schottianum , C. villosum var. villosum and five other native south-eastern Brazilian species not yet taxonomically named all had 2 n = 26 chromosomes. These are the first chromosome number determinations for C. cornutum , C. schottianum , C. villosum var. villosum and the five other Brazilian taxa. Our data confirm published data for C. baccatum var. praetermissum , C. campylopodium , C. chinense , C. flexuosum and C. parvifolium , but not for C. buforum . The prevalence of 2 n = 26 chromosomes among Brazilian species, along with the morphological and ecological characteristics presented by the wild and semidomesticated species occurring in Brazil, form a pattern different from that found in Andean wild and semidomesticated species. This supports the hypothesis that there are two different evolutionary lines in the genus and that the native south-eastern Brazilian species belong to the ancestral Capsicum gene pool. © 2006 The Linnean Society of London, Botanical Journal of the Linnean Society , 2006, 151 , 259–269. 相似文献
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Abstract A rapid and simple method has been developed for the simultaneous measurement of juvenile hormone (JH) and JH acid synthesized in vitro by larval corpora allata (CA) of the tobacco hornworm, Manduca sexta. An organic solvent partition of incubation medium efficiently separates JH acid from JH, and a radioimmunoassay which recognizes the two moieties equivalently is then employed to quantify each. The change in the biosynthetic product of the CA from JH to JH acid appears to begin slowly at the time of ecdysis to the last (fifth) larval stadium and is not complete until just prior to wandering (day 4). The inclusion of the JH esterase inhibitor S-benzoyl-O-ethyl phosphoramidothiolate in incubations of corpora allata revealed that the activity of JH esterases from the gland parallels gland activity and that significant hydrolysis of newly synthesized JH by these esterases occurs in incubations of glands taken at the beginnings of the fourth and fifth larval stadia. An allatostatin, which is proposed to inhibit the corpus allatum during the time of the change in its product, inhibits both JH I and JH I acid synthesis. 相似文献
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Photosynthetic and anatomical responses of Eucalyptus grandis leaves to potassium and sodium supply in a field experiment 总被引:4,自引:0,他引:4
PATRICIA BATTIE‐LACLAU JEAN‐PAUL LACLAU CONSTANCE BERI LAURIANE MIETTON MARTA R.ALMEIDA MUNIZ BRUNA CERSÓZIMO ARENQUE MARISA DE CASSIA PICCOLO LIONEL JORDAN‐MEILLE JEAN‐PIERRE BOUILLET YANN NOUVELLON 《Plant, cell & environment》2014,37(1):70-81
Although vast areas in tropical regions have weathered soils with low potassium (K) levels, little is known about the effects of K supply on the photosynthetic physiology of trees. This study assessed the effects of K and sodium (Na) supply on the diffusional and biochemical limitations to photosynthesis in Eucalyptus grandis leaves. A field experiment comparing treatments receiving K (+K) or Na (+Na) with a control treatment (C) was set up in a K‐deficient soil. The net CO2 assimilation rates were twice as high in +K and 1.6 times higher in +Na than in the C as a result of lower stomatal and mesophyll resistance to CO2 diffusion and higher photosynthetic capacity. The starch content was higher and soluble sugar was lower in +K than in C and +Na, suggesting that K starvation disturbed carbon storage and transport. The specific leaf area, leaf thickness, parenchyma thickness, stomatal size and intercellular air spaces increased in +K and +Na compared to C. Nitrogen and chlorophyll concentrations were also higher in +K and +Na than in C. These results suggest a strong relationship between the K and Na supply to E. grandis trees and the functional and structural limitations to CO2 assimilation rates. 相似文献
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MARISA WYCKMANS SAM VAN WASSENBERGH DOMINIQUE ADRIAENS RAOUL VAN DAMME ANTHONY HERREL 《Biological journal of the Linnean Society. Linnean Society of London》2007,92(2):323-334
Within the catfish family Clariidae, species exist with different degrees of jaw adductor hypertrophy. This jaw adductor hypertrophy has been related to bite performance, in turn suggesting a link to dietary specialization. Thus, an increase in the degree of hypertrophy will likely be reflected in an increase in the amount of hard prey in the diet. In the present study, we examine the ontogenetic scaling of cranial structure and diet in a species of catfish with a moderate degree of jaw adductor hypertrophy, Clariallabes longicauda . Additionally, we investigate whether the observed changes in the morphology of the feeding system during growth are linked to changes in diet. The fish examined demonstrate a strong positively allometric growth of the jaw adductors, of head height and of maximal head width, suggesting that larger fish can feed on larger and harder prey. Dietary data confirm these hypotheses and reveal an increase in maximal prey size consumed, the proportion of large prey in the diet, and average prey hardness during ontogeny. Moreover, the observed changes in the proportion of large prey consumed and prey hardness are correlated with an increase in lower jaw width and maximal head width, respectively. An increase in the amount of evasive prey in the diet with fish size is correlated with an increase in hyoid length. In summary, not only size dependent, but also size-independent variation of the feeding system was associated with ontogenetic changes in diet in C. longicauda . © 2007 The Linnean Society of London, Biological Journal of the Linnean Society , 2007, 92 , 323–334. 相似文献