Aspectos fenológicos reprodutivos de Qualea grandiflora Mart. em Cerrado

Qualea grandiflora is a typical species of the ‘Cerradão’ physiognomy, of ecological, floristic and medicinal importance. However, there are few studies regarding to its phenology. In view of the above, the objective was to verify the seasonality and the influence of the climatic variables on the reproductive events of Qualea grandiflora in ‘Cerradão’. Fifteen (15) individuals were visited and visited monthly between July 2016 and June 2018 to record the events: flower buds, anthesis, immature and ripe fruits. Fournier's intensity and synchrony were correlated with precipitation, maximum, average and minimum temperature through the Spearman's correlation, and seasonality using circular statistics. The species itself produced buds and flowers during the rainy season, which resulted in a positive correlation with precipitation. The fruit formation occurred both in the rainy and dry season, whereas the fruit ripening occurred in the dry season. The immature fruit event was the only non-seasonal event due to its duration. The reproductive events of Qualea grandiflora correlated with temperature and precipitation, so the species uses this influence to enhance its chances of reproduction.Qualea grandiflora é uma espécie típica da fisionomia cerradão, de importância ecológica, florística e medicinal. No entanto, são pouco os estudos no que se refere a sua fenologia. Diante do exposto, objetivou-se verificar a sazonalidade e influência das variáveis climáticas nos eventos reprodutivos de Qualea grandiflora em cerradão. Marcaram-se 15 indivíduos que foram visitados mensalmente entre julho de 2016 e junho de 2018 para registrar os eventos: botões florais, antese, frutos imaturos e maduros. A intensidade de Fournier e sincronia foram correlacionadas com a precipitação, temperatura máxima, média e mínima através da correlação de Spearman, e a sazonalidade por meio da estatística circular. A espécie produziu botões e flores durante a estação chuvosa, o que resultou em correlação positiva com a precipitação. A formação de frutos ocorreu tanto na época chuvosa quanto na seca, já a maturação dos frutos ocorreu na estação seca. O evento de frutos imaturos foi o único não sazonal devido a sua duração. Os eventos reprodutivos de Qualea grandiflora se correlacionaram com a temperatura e a precipitação, de modo que a espécie utiliza essa influência para potencializar suas chances de reprodução

Variations in bark structural properties affect both water loss and carbon economics in neotropical savanna trees in the Cerrado region of Brazil

International audienceEven after complete stomatal closure, plants lose water through the leaf cuticles and bark. This residual water conductance of leaves (g(leaf-res)) and stems (g(bark)) can negatively impact plant water balance and affect plant survival in seasonally dry environments. However, little is known about the costs and benefits associated with such water leaks, especially on stem level. Here, we characterized the structural and functional determinants of the variability in g(bark) across tropical savanna species to elucidate how variations in this trait are related to contrasting growth strategies. The high variability in g(bark) across species was associated with morphoantomical properties of the outer bark (thickness, density and lenticel investment), and such characteristics influenced both stem transpiration and respiration, suggesting the existence of a trade-off between water conservation and oxygen permeability, which reflected contrasting growth and dehydration tolerance strategies. For instance, species with higher g(bark) and g(leaf-res) presented a fast resource acquisition strategy but were more prone to drought-induced mortality by hydraulic failure. However, model simulations revealed that the relative contribution of g(leaf-res) and g(bark) to overall water balance depended on whether leaves were less or more resistant to cavitation than the stems. Synthesis. By combining correlative studies, experimental results and a modelling exercise, we provide a new understanding of the costs and benefits associated with the variability in g(bark) across tropical savanna species and a new perspective for studies of water relations and carbon economics in species from a hyperdiverse savanna

Where do leaf water leaks come from? Trade‐offs underlying the variability in minimum conductance across tropical savanna species with contrasting growth strategies

International audiencePlants continue to lose water from their leaves even after complete stomatal closure. Although this minimum conductance (g(leaf-res)) has substantial impacts on strategies of water use and conservation, little is known about the potential drivers underlying the variability of this trait across species. We thus untangled the relative contribution of water leaks from the cuticle and stomata in order to investigate how the variability in leaf morphological and anatomical traits is related to the variation ing(leaf-res)and carbon assimilation capacity across 30 diverse species from the Brazilian Cerrado. In addition to cuticle permeance, water leaks from stomata had a significant impact ong(leaf-res). The differential pattern of stomata distribution in the epidermis was a key factor driving this variation, suggesting the existence of a trade-off between carbon assimilation and water loss throughg(leaf-res). For instance, higherg(leaf-res), observed in fast-growing species, was associated with the investment in small and numerous stomata, which allowed higher carbon assimilation rates but also increased water leaks, with negative impacts on leaf survival under drought. Variation in cuticle structural properties was not linked tog(leaf-res). Our results therefore suggest the existence of a trade-off between carbon assimilation efficiency and dehydration tolerance at foliar level

A Structure Shaped by Fire, but Also Water: Ecological Consequences of the Variability in Bark Properties Across 31 Species From the Brazilian Cerrado

Bark is a structure involved in multiple physiological functions, but which has been traditionally associated with protection against fire. Thus, little is known about how the morpho-anatomical variations of this structure are related to different ecological pressures, especially in tropical savanna species, which are commonly subjected to frequent fire and drought events. Here we evaluated how the structural and functional variations of bark are related to the processes of resilience and resistance to fire, as well as transport and storage of water in 31 native species from the Brazilian Cerrado. Because of their thick bark, none of the trees analyzed were top-killed after a severe fire event. The structural and functional variations of the bark were also associated with water storage and transport, functions related to properties of the inner bark. In fact, species with a thicker and less dense inner bark were the ones that had the highest water contents in the wood, bark, and leaves. Lower bark density was also related to higher stem hydraulic conductivity, carbon assimilation, and growth. Overall, we provide strong evidence that in addition to protection from fire, the relative investment in bark also reflects different strategies of water use and conservation among many Cerrado tree species