RESUMO
Increases in hydrological extremes, including drought, are expected for Amazon forests. A fundamental challenge for predicting forest responses lies in identifying ecological strategies which underlie such responses. Characterization of species-specific hydraulic strategies for regulating water-use, thought to be arrayed along an 'isohydric-anisohydric' spectrum, is a widely used approach. However, recent studies have questioned the usefulness of this classification scheme, because its metrics are strongly influenced by environments, and hence can lead to divergent classifications even within the same species. Here, we propose an alternative approach positing that individual hydraulic regulation strategies emerge from the interaction of environments with traits. Specifically, we hypothesize that the vertical forest profile represents a key gradient in drought-related environments (atmospheric vapor pressure deficit, soil water availability) that drives divergent tree water-use strategies for coordinated regulation of stomatal conductance (gs) and leaf water potentials (ΨL) with tree rooting depth, a proxy for water availability. Testing this hypothesis in a seasonal eastern Amazon forest in Brazil, we found that hydraulic strategies indeed depend on height-associated environments. Upper canopy trees, experiencing high vapor pressure deficit (VPD), but stable soil water access through deep rooting, exhibited isohydric strategies, defined by little seasonal change in the diurnal pattern of gs and steady seasonal minimum ΨL. In contrast, understory trees, exposed to less variable VPD but highly variable soil water availability, exhibited anisohydric strategies, with fluctuations in diurnal gs that increased in the dry season along with increasing variation in ΨL. Our finding that canopy height structures the coordination between drought-related environmental stressors and hydraulic traits provides a basis for preserving the applicability of the isohydric-to-anisohydric spectrum, which we show here may consistently emerge from environmental context. Our work highlights the importance of understanding how environmental heterogeneity structures forest responses to climate change, providing a mechanistic basis for improving models of tropical ecosystems.
Assuntos
Florestas , Árvores , Água , Água/metabolismo , Água/fisiologia , Árvores/fisiologia , Brasil , Secas , Transpiração Vegetal/fisiologia , Solo/química , Folhas de Planta/fisiologiaRESUMO
We tested an approach to estimate daily canopy net photosynthesis, A, based on estimates of transpiration, E, using measurements of sap flow and water-use efficiency, ω, by measuring δ13C in CO2 respired from shoots in the canopies of two conifers (Podocarpaceae) native to New Zealand. The trees were planted in adjacent 20-year-old stands with the same soil and environmental conditions. Leaf area index was lower for Dacrycarpus dacrydioides D.Don in Lamb (1.34 m2 m-2) than for Podocarpus totara G.Benn. ex D.Don var. totara (2.01 m2 m-2), but mean (± standard error) stem diameters were the same at 152 ± 21 mm for D. dacrydioides and 154 ± 25 mm for P. totara. Over a 28-day period, daily A (per unit ground area) ranged almost five-fold but there were no significant differences between species (mean 2.73 ± 1.02 gC m-2 day-1). This was attributable to higher daily values of E (2.63 ± 0.83 mm day-1) and lower ω (1.35 ± 0.53 gC kg H2O-1) for D. dacrydioides compared with lower E (1.82 ± 0.72 mm day-1) and higher ω (1.90 ± 0.77 gC kg H2O-1) for P. totara. We attributed this to higher nitrogen availability and nitrogen concentration per unit foliage area, Na, and greater exposure to irradiance in the D. dacrydioides canopy compared with P. totara. Our findings support earlier observations that D. dacrydioides is more adapted to sites with poor drainage. In contrast, the high retention of leaf area and maintaining low rates of transpiration by P. totara, resulting in higher water-use efficiency, is an adaptive response to survival in dry conditions. Our findings show that physiological adjustments for two species adapted to different environments led to similar canopy photosynthesis rates when the trees were grown in the same conditions. We demonstrated consistency between whole-tree and more intensive shoot-scale measurements, confirming that integrated approaches are appropriate for comparative estimates of carbon uptake in stands with different species.
Assuntos
Fotossíntese , Estômatos de Plantas , Água , Fotossíntese/fisiologia , Água/metabolismo , Água/fisiologia , Estômatos de Plantas/fisiologia , Brotos de Planta/fisiologia , Traqueófitas/fisiologia , Traqueófitas/metabolismo , Transpiração Vegetal/fisiologia , Adaptação Fisiológica , Árvores/fisiologia , Folhas de Planta/fisiologia , Folhas de Planta/metabolismo , Nova ZelândiaRESUMO
Vulnerability curves (VCs) have been measured extensively to describe the differences in plant vulnerability to cavitation. Although the roles of hydraulic conductivity (Ks,max) and hydraulic safety (P50, embolism resistance), both of which are parameters of VCs ('sigmoidal' type), in tree demography have been evaluated across different forests, the direct linkages between VCs and tree demography are rarely explored. In this study, we combined measured VCs and plot data of 16 tree species in Panamanian seasonal tropical forests to investigate the connections between VCs and tree mortality, recruitment and growth. We found that the mortality and recruitment rates of evergreen species were most significantly positively correlated with P50. However, the mortality and recruitment rates of deciduous species only exhibited significant positive correlations with parameter a, which describes the steepness of VCs and indicates the sensitivity of conductivity loss with water potential decline, but is often neglected. These differences among evergreen and deciduous species may contribute to the poor performance of existing quantitative relationships (such as the fitting relationships for all 16 species) in capturing tree mortality and recruitment dynamics. Additionally, evergreen species presented a significant positive relationship between relative growth rate (RGR) and Ks,max, while deciduous species did not display such relationship. The RGR of both evergreen and deciduous species also displayed no significant correlations with P50 and a. Further analysis demonstrated that species with steeper VCs tended to have high mortality and recruitment rates, while species with flatter VCs were usually those with low mortality and recruitment rates. Our results highlight the important role of parameter a in tree demography, especially for deciduous species. Given that VC is a key component of plant hydraulic models, integrating measured VC rather than optimizing its parameters will help improve the ability to simulate and predict forest response to water availability.
Assuntos
Modelos Biológicos , Caules de Planta , Árvores , Árvores/fisiologia , Árvores/crescimento & desenvolvimento , Caules de Planta/fisiologia , Caules de Planta/crescimento & desenvolvimento , Florestas , Água/fisiologia , Água/metabolismo , PanamáRESUMO
Forest ecosystems face increasing drought exposure due to climate change, necessitating accurate measurements of vegetation water content to assess drought stress and tree mortality risks. Although Frequency Domain Reflectometry offers a viable method for monitoring stem water content by measuring dielectric permittivity, challenges arise from uncertainties in sensor calibration linked to wood properties and species variability, impeding its wider usage. We sampled tropical forest trees and palms in eastern Amazônia to evaluate how sensor output differences are controlled by wood density, temperature and taxonomic identity. Three individuals per species were felled and cut into segments within a diverse dataset comprising five dicotyledonous tree and three monocotyledonous palm species on a wide range of wood densities. Water content was estimated gravimetrically for each segment using a temporally explicit wet-up/dry-down approach and the relationship with the dielectric permittivity was examined. Woody tissue density had no significant impact on the calibration, but species identity and temperature significantly affected sensor readings. The temperature artefact was quantitatively important at large temperature differences, which may have led to significant bias of daily and seasonal water content dynamics in previous studies. We established the first tropical tree and palm calibration equation which performed well for estimating water content. Notably, we demonstrated that the sensitivity remained consistent across species, enabling the creation of a simplified one-slope calibration for accurate, species-independent measurements of relative water content. Our one-slope calibration serves as a general, species-independent standard calibration for assessing relative water content in woody tissue, offering a valuable tool for quantifying drought responses and stress in trees and forest ecosystems.
Assuntos
Florestas , Árvores , Clima Tropical , Água , Madeira , Madeira/química , Água/metabolismo , Árvores/fisiologia , Ecossistema , Secas , Arecaceae/fisiologia , Arecaceae/metabolismo , BrasilRESUMO
One strategy to improve olive (Olea europaea ) tree drought tolerance is through the symbiosis of arbuscular mycorrhizal fungi (AMF), which helps alleviate water deficit through a combination of morphophysiological effects. Cuttings of olive varieties Arbequina (A) and Barnea (B) were grown with (+AMF) or without (-AMF) inoculum in the olive grove rhizosphere soil. One year after establishment, pots were exposed to four different water regimes: (1) control (100% of crop evapotranspiration); (2) short-period drought (20days); (3) long-period drought (25days); and (4) rewatering (R). To evaluate the influence of AMF on tolerance to water stress, stem water potential, stomatal conductance and the biomarkers for water deficit malondialdehyde, proline, soluble sugars, phenols, and flavonoids were evaluated at the end of the irrigation regimes. Stem water potential showed higher values in A(+) and B(+) in all water conditions, and the opposite was true for stomatal conductance. For proline and soluble sugars, the stem water potential trend is repeated with some exceptions. AMF inoculum spore communities from A(+ and -) and B(+ and -) were characterised at the morphospecies level in terms of richness and abundance. Certain morphospecies were identified as potential drought indicators. These results highlight that the benefits of symbiotic relationships between olive and native AMF can help to mitigate the effects of abiotic stress in soils affected by drought.
Assuntos
Micorrizas , Olea , Rizosfera , Água , Olea/microbiologia , Micorrizas/fisiologia , Água/metabolismo , Secas , Prolina/metabolismo , Simbiose , Estômatos de Plantas/fisiologia , Caules de Planta/microbiologia , Raízes de Plantas/microbiologia , Malondialdeído/metabolismoRESUMO
Alzheimer's disease (AD) is an age-dependent neurodegenerative disease that is typically sporadic and has a high social and economic cost. We utilized the intracerebroventricular administration of streptozotocin (STZ), an established preclinical model for sporadic AD, to investigate hippocampal astroglial changes during the first 4 weeks post-STZ, a period during which amyloid deposition has yet to occur. Astroglial proteins aquaporin 4 (AQP-4) and connexin-43 (Cx-43) were evaluated, as well as claudins, which are tight junction (TJ) proteins in brain barriers, to try to identify changes in the glymphatic system and brain barrier during the pre-amyloid phase. Glial commitment, glucose hypometabolism and cognitive impairment were characterized during this phase. Astroglial involvement was confirmed by an increase in glial fibrillary acidic protein (GFAP); concurrent proteolysis was also observed, possibly mediated by calpain. Levels of AQP-4 and Cx-43 were elevated in the fourth week post-STZ, possibly accelerating the clearance of extracellular proteins, since these proteins actively participate in the glymphatic system. Moreover, although we did not see a functional disruption of the blood-brain barrier (BBB) at this time, claudin 5 (present in the TJ of the BBB) and claudin 2 (present in the TJ of the blood-cerebrospinal fluid barrier) were reduced. Taken together, data support a role for astrocytes in STZ brain damage, and suggest that astroglial dysfunction accompanies or precedes neuronal damage in AD.
Assuntos
Doença de Alzheimer , Aquaporina 4 , Astrócitos , Estreptozocina , Astrócitos/metabolismo , Animais , Doença de Alzheimer/metabolismo , Doença de Alzheimer/patologia , Masculino , Aquaporina 4/metabolismo , Conexina 43/metabolismo , Barreira Hematoencefálica/metabolismo , Água/metabolismo , Hipocampo/metabolismo , Ratos Wistar , Ratos , Modelos Animais de DoençasRESUMO
Embolism resistance of xylem tissue varies among species and is an important trait related to drought resistance, with anatomical attributes like pit membrane thickness playing an important role in avoiding embolism spread. Grafted Citrus trees are commonly grown in orchards, with the rootstock being able to affect the drought resistance of the whole plant. Here, we evaluated how rootstocks affect the vulnerability to embolism resistance of the scion using several rootstock/scion combinations. Scions of 'Tahiti' acid lime, 'Hamlin', 'Pera' and 'Valencia' oranges grafted on a 'Rangpur' lime rootstock exhibit similar vulnerability to embolism. In field-grown trees, measurements of leaf water potential did not suggest significant embolism formation during the dry season, while stomata of Citrus trees presented an isohydric response to declining water availability. When 'Valencia' orange scions were grafted on 'Rangpur' lime, 'IAC 1710' citrandarin, 'Sunki Tropical' mandarin or 'Swingle' citrumelo rootstocks, variation in intervessel pit membrane thickness of the scion was found. The 'Rangpur' lime rootstock, which is known for its drought resistance, induced thicker pit membranes in the scion, resulting in higher embolism resistance than the other rootstocks. Similarly, the rootstock 'IAC 1710' citrandarin generated increased embolism resistance of the scion, which is highly relevant for citriculture.
Assuntos
Citrus , Raízes de Plantas , Xilema , Citrus/fisiologia , Xilema/fisiologia , Raízes de Plantas/fisiologia , Água/metabolismo , Secas , Folhas de Planta/fisiologia , Folhas de Planta/anatomia & histologia , Estômatos de Plantas/fisiologiaRESUMO
Large trees in plantations generally produce more wood per unit of resource use than small trees. Two processes may account for this pattern: greater photosynthetic resource use efficiency or greater partitioning of carbon to wood production. We estimated gross primary production (GPP) at the individual scale by combining transpiration with photosynthetic water-use efficiency of Eucalyptus trees. Aboveground production fluxes were estimated using allometric equations and modeled respiration; total belowground carbon fluxes (TBCF) were estimated by subtracting aboveground fluxes from GPP. Partitioning was estimated by dividing component fluxes by GPP. Dominant trees produced almost three times as much wood as suppressed trees. They used 25 ± 10% (mean ± SD) of their photosynthates for wood production, whereas suppressed trees only used 12 ± 2%. By contrast, dominant trees used 27 ± 19% of their photosynthate belowground, whereas suppressed trees used 58 ± 5%. Intermediate trees lay between these extremes. Photosynthetic water-use efficiency of dominant trees was c. 13% greater than the efficiency of suppressed trees. Suppressed trees used more than twice as much of their photosynthate belowground and less than half as much aboveground compared with dominant trees. Differences in carbon partitioning were much greater than differences in GPP or photosynthetic water-use efficiency.
Assuntos
Carbono , Eucalyptus , Fotossíntese , Árvores , Água , Madeira , Eucalyptus/fisiologia , Eucalyptus/metabolismo , Carbono/metabolismo , Árvores/fisiologia , Árvores/metabolismo , Água/metabolismo , Madeira/fisiologia , Transpiração Vegetal/fisiologia , Modelos BiológicosRESUMO
The inclusion of protein in the regular human diet is important for the prevention of several chronic diseases. In the search for novel alternative protein sources, plant-based proteins are widely explored from a sustainable and ecological point of view. Duckweed (Lemna minor), also known as water lentil, is an aquatic plant with potential applications for human consumption due to its protein content and carbohydrate contents. Among all the conventional and novel protein extraction methods, the utilization of ultrasound has attracted the attention of scientists because of its effects on improving protein extraction and its functionalities. In this work, a Box-Behnken experimental design was proposed to optimize the alkaline extraction of protein from duckweed. In addition, an exploration of the effects of ultrasound on the morphological, structural, and functional properties of the extracted protein was also addressed. The optimal extraction parameters were a pH of 11.5 and an ultrasound amplitude and processing time of 60% and 20 min, respectively. These process conditions doubled the protein content extracted in comparison to the value from the initial duckweed sample. Furthermore, the application of ultrasound during the extraction of protein generated changes in the FTIR spectra, color, and structure of the duckweed protein, which resulted in improvements in its solubility, emulsifying properties, and foaming capacity.
Assuntos
Araceae , Poluentes Químicos da Água , Humanos , Poluentes Químicos da Água/análise , Água/metabolismoRESUMO
Failure in irrigation management of grapevines grown in the Brazilian semiarid region can affect bud fertility. Adequate irrigation, considering both the development of bunches in the current cycle and the formation of fertile buds for subsequent cycles, can bring significant advances to viticulture. Therefore, the objective of this research was to investigate the effect of different irrigation levels during flowering on the formation of buds and potential bunches of 'Arra 15' grapevine and its relationship with metabolic processes. A field experiment was carried out in a commercial vineyard in Petrolina, Pernambuco, Brazil, during the 2021 and 2022 seasons. The experiment was designed in randomized blocks with four replications and five irrigation levels (70; 85; 100; 115 and 130% of crop evapotranspiration - ETc) during three production cycles. The variables fertile bud, vegetative bud, dead bud, potential fertility of the basal, median, and apical regions of the branches, number of potential bunches, reducing sugar, total soluble sugar, net photosynthesis, stomatal conductance, transpiration, and relative chlorophyll index were evaluated. The 115% ETc irrigation level improved the number of fertile buds and number of potential bunches. Irrigation level above 115% ETc increased gas exchange and relative chlorophyll index, while 70% ETc increased leaf sugar content. The most appropriate irrigation strategy is the application of 115% ETc during the flowering stage, for the increase of fertile buds and potential bunches of the next cycle, without influencing the vine metabolism. Total soluble sugars are a promising indicator of water deficit during flowering and as an indicator of vegetative bud formation for the next cycle.