ABSTRACT
Forest disturbances increase the proportion of fast-growing tree species compared to slow-growing ones. To understand their relative capacity for carbon uptake and their vulnerability to climate change, and to represent those differences in Earth system models, it is necessary to characterise the physiological differences in their leaf-level control of water use efficiency and carbon assimilation. We used wood density as a proxy for the fast-slow growth spectrum and tested the assumption that trees with a low wood density (LWD) have a lower water-use efficiency than trees with a high wood density (HWD). We selected 5 LWD tree species and 5 HWD tree species growing in the same location in an Amazonian tropical forest and measured in situ steady-state gas exchange on top-of-canopy leaves with parallel sampling and measurement of leaf mass area and leaf nitrogen content. We found that LWD species invested more nitrogen in photosynthetic capacity than HWD species, had higher photosynthetic rates and higher stomatal conductance. However, contrary to expectations, we showed that the stomatal control of the balance between transpiration and carbon assimilation was similar in LWD and HWD species and that they had the same dark respiration rates.
Subject(s)
Water , Wood , Forests , Trees/physiology , Photosynthesis/physiology , Carbon , Nitrogen , Plant LeavesABSTRACT
Although apparent light inhibition of leaf day respiration is a widespread reported phenomenon, the mechanisms involved, including utilization of alternate respiratory pathways and substrates and light inhibition of TCA cycle enzymes are under active investigation. Recently, acetate fermentation was highlighted as a key drought survival strategy mediated through protein acetylation and jasmonate signaling. Here, we evaluate the light-dependence of acetate transport and assimilation in Populus trichocarpa trees using the dynamic xylem solution injection (DXSI) method developed here for continuous studies of C1 and C2 organic acid transport and light-dependent metabolism. Over 7 days, 1.0 L of [13C]formate and [13C2]acetate solutions were delivered to the stem base of 2-year old potted poplar trees, while continuous diurnal observations were made in the canopy of CO2, H2O, and isoprene gas exchange together with δ13CO2. Stem base injection of 10 mM [13C2]acetate induced an overall pattern of canopy branch headspace 13CO2 enrichment (δ13CO2 +27‱) with a diurnal structure in δ13CO2 reaching a mid-day minimum followed by a maximum shortly after darkening where δ13CO2 values rapidly increased up to +12‱. In contrast, 50 mM injections of [13C]formate were required to reach similar δ13CO2 enrichment levels in the canopy with δ13CO2 following diurnal patterns of transpiration. Illuminated leaves of detached poplar branches pretreated with 10 mM [13C2]acetate showed lower δ13CO2 (+20‱) compared to leaves treated with 10 mM [13C]formate (+320‱), the opposite pattern observed at the whole plant scale. Following dark/light cycles at the leaf-scale, rapid, strong, and reversible enhancements in headspace δ13CO2 by up to +60‱ were observed in [13C2]acetate-treated leaves which showed enhanced dihydrojasmonic acid and TCA cycle intermediate concentrations. The results are consistent with acetate in the transpiration stream as an effective activator of the jasmonate signaling pathway and respiratory substrate. The shorter lifetime of formate relative to acetate in the transpiration stream suggests rapid formate oxidation to CO2 during transport to the canopy. In contrast, acetate is efficiently transported to the canopy where an increased allocation towards mitochondrial dark respiration occurs at night. The results highlight the potential for an effective integration of acetate into glyoxylate and TCA cycles and the light-inhibition of citrate synthase as a potential regulatory mechanism controlling the diurnal allocation of acetate between anabolic and catabolic processes.
ABSTRACT
Increasing severity and frequency of drought is predicted for large portions of the terrestrial biosphere, with major impacts already documented in wet tropical forests. Using a 4-year rainfall exclusion experiment in the Daintree Rainforest in northeast Australia, we examined canopy tree responses to reduced precipitation and soil water availability by quantifying seasonal changes in plant hydraulic and carbon traits for 11 tree species between control and drought treatments. Even with reduced soil volumetric water content in the upper 1 m of soil in the drought treatment, we found no significant difference between treatments for predawn and midday leaf water potential, photosynthesis, stomatal conductance, foliar stable carbon isotope composition, leaf mass per area, turgor loss point, xylem vessel anatomy, or leaf and stem nonstructural carbohydrates. While empirical measurements of aboveground traits revealed homeostatic maintenance of plant water status and traits in response to reduced soil moisture, modeled belowground dynamics revealed that trees in the drought treatment shifted the depth from which water was acquired to deeper soil layers. These findings reveal that belowground acclimation of tree water uptake depth may buffer tropical rainforests from more severe droughts that may arise in future with climate change.
Subject(s)
Trees , Water , Carbon , Droughts , Forests , Plant Leaves , RainforestABSTRACT
Devido ao padrão de beleza imposto atualmente, tem aumentado a procura por tratamentos estéticos como a massagem clássica, porém sua suposta ação lipolítica ainda é uma questão controversa na literatura. O objetivo deste estudo foi verificar o efeito da massagem clássica estética nas adiposidades localizadas, por meio de perimetria do abdome, quadril e coxas e pela estimativa da espessura da tela subcutânea da parede abdominal (ETS) por ultrassonografia. Oito voluntárias (idade 33,9±8,9 anos, peso 65,1±8,4 kg) foram avaliadas quanto a MC, IMC e ETS 30 dias antes, logo antes do início da intervenção e após esta. Foram efetuadas 12 sessões de massagem clássica estética em coxas, glúteos e abdome por 30 minutos, três vezes por semana. Foi encontrada redução significativa apenas da perimetria na região do quadril (p=0,012), mas não da ETS (p=0,301). A massagem clássica estética contribuiu apenas para a redução da perimetria do quadril, e não modificou outras medidas nem a espessura da tela subcutânea da região abdominal.
Due to current beauty standards, the search for aesthetic treatments, including classical massage, has increased; however, its presumed lipolytic action is still controversial in literature. The purpose of this study was to assess the effect of classical massage on localized adiposity, by means of abdomen, hip and thigh perimeter measuring, nd by estimating thickness of abdominal wall fat by ultrasonography. Eight volunteers (33.9±8.9 years old, 65.1±8.4 kg) were assessed as to weight, body mass index, body perimeter measures and by abdomen ultrasonography at three moments: control (30 days before treatment), just before, and after treatment. The latter consisted of 12 thrice-weekly, 30-minute massage sessions on thighs, buttocks, and abdomen. Results showed a significant reduction at hip perimeter (p=0.012), but none of subcutaneous fat tissue thickness (p=0.301). Classical aesthetic massage hence did not modify abdominal wall fat, but did reduce hip perimeter.
Subject(s)
Humans , Female , Adult , Adiposity , Anthropometry , Body Mass Index , Subcutaneous Fat , MassageABSTRACT
O estudo sensitométrico de filmes radiológicos permite extrair informaçöes importantes sobre suas características intrínsecas responsáveis pelo seu desempenho. Sabe-se que a resposta sensitométrica desejada pode ser obtida ajustando-se as condiçöes de processamento. Este estudo pretende identificar as condiçöes de processamento nas quais pode-se obter respostas semelhantes de três tipos de filmes radiológicos dos fabricantes DuPont, IBF, Kodak e Fuji, utilizados em exames de mamografia, radiologia convencional e tomografia computadorizada, medicina nuclear e ultra-som. Os filmes foram sensibilizados e relevados na processadora M7A-Kodak, variando-se a temperatura a cada 0, 5ºC para o intervalo entre 30, 0ºC e 38, 5ºC.Foram utilizados os químicos IBF e Kodak. Os parâmetros extraídos das curvas sensitométricas foram: gradiente médio, velocidade relativa, base + véu e densidade máxima. A análise estatística foi aplicada, para comparar a influência da temperatura, químicos e filmes, para cada um dos parâmetros. A análise de variância mostrou interaçöes significantes entre filmes , temperaturas e químicos.
