RESUMO
PREMISE OF THE STUDY: It is unclear to what extent the co-occurrence of angiosperm and gymnosperm species in some marginal ecosystems is explained by reduced growth in angiosperms due to carbon (C) limitation and by high stress tolerance in gymnosperms associated with lack of vessels and resource conservation. METHODS: We examined growth patterns and traits associated with C balance in four evergreen angiosperm species (including one vesselless species, Drimys winteri) and three gymnosperm tree species of a cold-temperate rainforest in southern Chile. We measured the mean basal area increment for the first 50 (BAI50 ) and the last 10 years (BAI10 ), wood density, leaf lifespan, and nonstructural carbohydrate (NSC) concentrations in different organs. KEY RESULTS: BAI50 was 6-fold higher in angiosperms than in gymnosperms and ca. 4-fold higher in Drimys than in the fastest-growing gymnosperm. BAI10 and aboveground NSC concentrations were significantly higher and leaf lifespan lower in angiosperms than in gymnosperms; these differences, however, were largely driven by the slow growth and low NSC concentrations of the Cupressaceae species (Pilgerodendron uviferum), while the two Podocarpaceae had BAI10 and NSC concentrations similar to angiosperms. In angiosperms, NSC and starch concentrations were generally higher in species with lower BAI10 , indicating no severe C limitation. CONCLUSIONS: The co-occurrence of angiosperms and gymnosperms in cold-temperate rainforests of southern Chile is not explained by growth disadvantages and C limitation in angiosperms. Long leaf longevity, but not lack of vessels, appeared to favor resource conservation and C balance in some gymnosperms (Podocarpaceae).
Assuntos
Cupressaceae/crescimento & desenvolvimento , Drimys/crescimento & desenvolvimento , Floresta Úmida , Metabolismo dos Carboidratos , Cupressaceae/metabolismo , Drimys/metabolismo , Folhas de Planta/fisiologia , Estresse Fisiológico , Madeira/fisiologiaRESUMO
The natural compound dendocarbin A, C15H22O3, is a sesquiterpene lactone isolated for the first time from Drimys winteri for var chilensis. The compound crystallizes in the orthorhombic space group P212121 and its X-ray crystal structure confirmed the S/R character of the chiral centres at C-5/C-10 and C-9/C-11, respectively. The α-OH group at C-11 was found to be involved in intermolecular hydrogen bonding, defining chains along the <100> 21 screw axis.
Assuntos
Drimys/química , Sesquiterpenos/química , Sesquiterpenos/isolamento & purificação , Cristalografia por Raios X , Drimys/metabolismo , Estrutura Molecular , Sesquiterpenos/síntese químicaRESUMO
Foliar water uptake (FWU) is a common water acquisition mechanism for plants inhabiting temperate fog-affected ecosystems, but the prevalence and consequences of this process for the water and carbon balance of tropical cloud forest species are unknown. We performed a series of experiments under field and glasshouse conditions using a combination of methods (sap flow, fluorescent apoplastic tracers and stable isotopes) to trace fog water movement from foliage to belowground components of Drimys brasiliensis. In addition, we measured leaf water potential, leaf gas exchange, leaf water repellency and growth of plants under contrasting soil water availabilities and fog exposure in glasshouse experiments to evaluate FWU effects on the water and carbon balance of D. brasiliensis saplings. Fog water diffused directly through leaf cuticles and contributed up to 42% of total foliar water content. FWU caused reversals in sap flow in stems and roots of up to 26% of daily maximum transpiration. Fog water transported through the xylem reached belowground pools and enhanced leaf water potential, photosynthesis, stomatal conductance and growth relative to plants sheltered from fog. Foliar uptake of fog water is an important water acquisition mechanism that can mitigate the deleterious effects of soil water deficits for D. brasiliensis.
Assuntos
Drimys/fisiologia , Folhas de Planta/metabolismo , Altitude , Transporte Biológico , Brasil , Deutério/análise , Deutério/metabolismo , Drimys/crescimento & desenvolvimento , Drimys/metabolismo , Secas , Estômatos de Plantas/fisiologia , Transpiração Vegetal , Solo , Árvores , Água , Tempo (Meteorologia) , Xilema/metabolismoRESUMO
Ganoderma australe is a basidiomycete responsible for a natural process of selective and extensive lignin degradation. Fatty acids, thiobarbituric acid reactive substances (TBARS), Fe3+-reduction and enzymatic activities were monitored in cultures of G. australe growing on Drimys winteri wood chips. Linoleic acid was de novo synthesized, and steadily increased during 12 weeks of cultivation. Part of the unsaturated fatty acids underwent peroxidation as TBARS accumulated with biodegradation time. TBARS accumulation was proportional to the wood weight and component losses. Manganese-dependent peroxidase and lignin peroxidase were not detected in the culture extracts, whereas laccase-induced oxidation of syringaldazine peaked after 2 weeks (104+/-9 micromol oxidized min(-1) kg(-1) of dry wood), subsequently decreasing. On the other hand, nonenzymatic Fe3+-reducing activity increased as a function of cultivation time and could be involved in the initiation of lipid peroxidation.