Background and aims The survival and coexistence of plants in water-limited environments are related to their ability to coordinate water acquisition and regulation of water loss. To assess the ...coordination among below and aboveground hydraulic traits and the diversity of water-use strategies, we evaluated rooting depth and several leaf hydraulic traits of 15 species in campos rupestres, a seasonally-dry biodiversity hotspot in central Brazil. Methods We assessed the depth of plant water acquisition by excavating roots and analyzing the stable isotope composition of hydrogen (δD) and oxygen (δ18O) in the xylem and soil water. We also measured mid-morning stomatal conductance, leaf-water potential at turgor loss point (ΨTLP) and pre-dawn leaf water potentials (ΨPD) during wet and dry seasons. Results We demonstrated that rooting depth is a good predictor of seasonal variations in stomatal conductance and ΨPD. Shallow-rooted plants had greater variation in stomatal conductance and ΨPD than deep-rooted plants. Woody plants with shallower roots also had lower ΨTLP than deep-rooted plants, revealing higher drought resistance. Conclusion We demonstrate that shallow-rooted species, more exposed to variation in water availability, have mechanisms to confer drought resistance through turgor maintenance. Our results support the theory of hydrological niche segregation and its underlying trade-offs related to drought resistance.
Campos rupestres is an extremely phosphorus (P)‐impoverished rocky ecosystem in Brazil. Velloziaceae is an important plant family in this environment, and some species colonize exposed quartzite ...rock. However, we know virtually nothing about their root development and nutrient acquisition within the rock outcrops and their possible role in rock weathering and landscape formation.
We tested the hypothesis that Velloziaceae dissolve P from the rock, enhancing rock weathering. The study was carried out with two Barbacenia species (Velloziaceae) that colonize quartzite rocks. We assessed the root specializations and exudates, and determined the mineralogical composition of the rocks.
The quartzite rocks contained a low concentration of total P in a matrix composed predominantly of silica. Using transmission electron microscopy, we show root growth perpendicular to the rock‐bedding planes. A micro‐XRF set‐up at the XRF beamline of a synchrotron evidenced root‐associated rock dissolution.
The investigated roots show novel morphological and physiological specializations, coined vellozioid roots, which are highly effective at P acquisition. These carboxylate‐releasing roots function like other specialized roots in nutrient‐depleted soils. The rocks represent a barrier for most species, but due to their chemical and physical actions inside the rocks, vellozioid roots play a pivotal role in rock weathering, contributing to shaping the campos rupestres landscapes.
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Soil salinization is a common problem impacting plant physiology and agricultural productivities. In order to monitor soil salinization in plant physiological experiments, a salinity monitoring ...system - SProb - was produced to improve our understanding of plant responses to salinity, using open hardware Arduino platform. An experiment was performed and designed to calibrate and check the viability and accuracy of SProb to be used in scientific researches. Salt concentrations were manipulated to identify sensor ability in determining salt accumulation or leaching in soils. Also, two mangrove plant species were grown to identify if root presence would affect soil salt measurements. The soil osmotic potential (Ψ
s
) was estimated from SProb results and correlated with predawn and midday leaf water potential (Ψ
l
) of the mangrove plants, to identify if Ψ
s
would affect plants water regulations. It was also shown that SProb described well the soil salt accumulation or leaching along the time, and the measurements were not affected by the presence of roots. The ranges of Ψ
s
matched with the range of mangrove Ψ
l
, and the Ψ
l
decreased with the decrease in Ψ
s
(increase in salinity). It was confirmed that the SProb sensor is efficient, cheap and has enough accuracy to monitor soil salt concentration. Thus, SProb can be used in plant physiological experiments increasing our ability to make accurate science when such technology is not available in research centers.
Trees' responses to mistletoes occur at multiple organization levels (e.g., leaf, individual, population), yet integrating these multi‐scale responses is still challenging. Here, we compared the ...traits of infected versus uninfected trees over multiple scales, from leaf anatomy and physiology to canopy allometries and individual growth rate and survivorship. We tested the hypotheses that mistletoes lead in the host (1) the production of leaves with a conservative resource‐use strategy, (2) more mechanically stable canopies and (3) reductions in growth and survival probability in the trees they infect. We addressed these hypotheses in the widespread savanna tree Vochysia thyrsoidea and xylem‐tapping mistletoe Psittacanthus robustus in the Brazilian Cerrado, a global biodiversity hotspot. We found that (1) mistletoe infection did not affect key traits associated with resource conservativeness, such as leaf mass per area (LMA) and carbon assimilation rates (A). Likewise, (2) hosts did not increase the mechanical safety of their trunks in response to mistletoe infection since infected and uninfected trees had a similar allometric scaling between height and crown volume against stem diameter. (3) At the population level, both the relative growth rate and survival probability decreased as the number of parasites increased. However, zero growth and a 50% chance of mortality were estimated to occur in a minority of heavily infected trees (>7 and 14 parasites, respectively). Our results challenge the idea that mistletoes have a ubiquitous negative impact on their hosts. We highlight, therefore, the need for clarifying the mechanisms that allow trees to maintain their functioning even in the face of mistletoe parasitism.
Mistletoes are aerial hemiparasitic plants which occupy patches of favorable habitat (host trees) surrounded by unfavorable habitat and may be possibly modeled as a metapopulation. A metapopulation ...is defined as a subdivided population that persists due to the balance between colonization and extinction in discrete habitat patches. Our aim was to evaluate the dynamics of the mistletoe Psittacanthus robustus and its host Vochysia thyrsoidea in three Brazilian savanna areas using a metapopulation approach. We also evaluated how the differences in terms of fire occurrence affected the dynamic of those populations (two areas burned during the study and one was fire protected). We monitored the populations at six-month intervals. P. robustus population structure and dynamics met the expected criteria for a metapopulation: i) the suitable habitats for the mistletoe occur in discrete patches; (ii) local populations went extinct during the study and (iii) colonization of previously non-occupied patches occurred. The ratio of occupied patches decreased in all areas with time. Local mistletoe populations went extinct due to two different causes: patch extinction in area with no fire and fire killing in the burned areas. In a burned area, the largest decrease of occupied patch ratios occurred due to a fire event that killed the parasites without, however, killing the host trees. The greatest mortality of V. thyrsoidea occurred in the area without fire. In this area, all the dead trees supported mistletoe individuals and no mortality was observed for parasite-free trees. Because P. robustus is a fire sensitive species and V. thyrsoidea is fire tolerant, P. robustus seems to increase host mortality, but its effect is lessened by periodic burning that reduces the parasite loads.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
To comprehend how mistletoes affect their host functioning is a key matter in plant ecology. As yet, it is not clear whether the impact of mistletoes is confined to infected branches or the entire ...host is compromised as well. Here, we compared leaf functional traits between branches infected by mistletoes (infected), uninfected branches yet close to mistletoe attachment (neighbour), and branches of trees without any mistletoe (control). Our model species pairs were
Phoradendron crassifolium
infecting
Eremanthus erythropappus
tree and
Psittacanthus robustus
infecting
Vochysia thyrsoidea
tree. The study was carried out in the Brazilian savannah,
Cerrado
. We found that neighbour branches of
E. erythropappus
suffered a greater reduction in specific leaf area compared to infected branches. Control branches occupied an intermediary position between infected and neighbour branches. On the other hand, both infected and neighbouring branches of
V. thyrsoidea
suffered a reduction in carbon assimilation rate compared to control trees. As far as we know, our study is the first to describe the presence of mistletoe affecting the healthy branches neighbouring the mistletoe attachment. This finding sheds light on the need to consider both infected and neighbouring branches when evaluating the effects of parasitism on tropical trees.
Introduction: The study of herbivory is fundamental in ecology and includes how plants invest in strategies and mechanisms to reduce herbivore damage. However, there is still a lack of information ...about how the environment, plant density, and functional traits influence herbivory in aquatic ecosystems. Objective: To assess if there is a relationship between herbivory, environmental variables, and plant traits two species of Montrichardia, a neotropical aquatic plant. Methods: In September 2018, we studied 78 specimens of Montrichardia arborescens and 18 of Montrichardia linifera, in 18 sites in Melgaço, Pará, Brazil. On each site, we measured water depth, distance to the margin, and plant density. From plants, we measured plant height and leaf thickness, and photographed the leaves to calculate the specific leaf area and percentage herbivory. To identify anatomical structures, we collected fully expanded leaves from three individuals per quadrat. Results: For M. arborescens, plants with thicker leaves and higher specific leaf area have less herbivore damage. For M. linifera, plants from deeper sites and with thicker leaves had more herbivore damage, while plants that grew farther from the margin had less damage. We found anatomical structures related to defense, such as idioblast cells with phenolic compounds, and cells with solid inclusions that can contribute to avoiding severe damage. Conclusions: Herbivory in these Montrichardia species canbe explained by a combination of plant and environmental traits (patch isolation and water depth). The main plant traits are leaf thickness and area, but chemical compounds and solid inclusions also help Montrichardia to sustain less damage than other macrophytes.
Exploring the density-dependence theory is crucial to understanding how size patterns among individuals are established. This study tested if percent cover affects the morphological and allometric ...relationship variation of individuals of
Eichhornia azurea
(Swart) Kunth, an emergent perennial mat-forming macrophyte commonly found in the lower Amazon region. We predicted that (1)
E. azurea
found in sites with high percent coverage would have larger, thicker, heavier leaves and longer petioles than individuals found in sites with low percent coverage; (2) the percent coverage affects the allometric relationship between branch length and number of leaves. To test our predictions, we sampled sites with low and high
E. azurea
percent cover. Sampling occurred in Caxiuanã Bay located in Caxiuanã National Forest on the lower Amazon. The results supported our predictions, in which individuals of high percent cover sites had longer petioles, more leaves, thicker leaves and higher leaf mass per area. Individuals in low percent cover sites showed a positive relationship between branch length and number of leaves. These results indicate that
E. azurea
exhibits morphological and allometric plasticity in response to plant density which may help explain the success of
E. azurea
in a variety of habitats across South America.
The rocky, seasonally-dry and nutrient-impoverished soils of the Brazilian campos rupestres impose severe growth-limiting conditions on plants. Species of a dominant plant family, Velloziaceae, are ...highly specialized to low-nutrient conditions and seasonal water availability of this environment, where phosphorus (P) is the key limiting nutrient. Despite plant-microbe associations playing critical roles in stressful ecosystems, the contribution of these interactions in the campos rupestres remains poorly studied. Here we present the first microbiome data of Velloziaceae spp. thriving in contrasting substrates of campos rupestres. We assessed the microbiomes of Vellozia epidendroides, which occupies shallow patches of soil, and Barbacenia macrantha, growing on exposed rocks. The prokaryotic and fungal profiles were assessed by rRNA barcode sequencing of epiphytic and endophytic compartments of roots, stems, leaves and surrounding soil/rocks. We also generated root and substrate (rock/soil)-associated metagenomes of each plant species. We foresee that these data will contribute to decipher how the microbiome contributes to plant functioning in the campos rupestres, and to unravel new strategies for improved crop productivity in stressful environments.
ABSTRACT The present study seeks to characterize the composition, structure, and functional traits of the tree stratum of a Semideciduous Forest in Pouso Alegre, MG, Brazil (22º12’43”S and ...45º59’30”W), by comparing Edge and Interior habitats and their relation to human impacts and soil variables. The tree community (diameter at 1.3 m (DBH) higher than 5 cm) was inventoried using the point-centered quarter method by laying out 12 transects of 450 m each (six transects in the Edge and six in the Interior). Functional traits – wood density and seed mass – were obtained by genus. The impact evaluation and soil sample collection were realized per transect. We found significant differences in terms of the basal area (higher in Interior), diversity (higher in Interior) and community seed mass (higher in Edge). The effects of higher values of soil traits such as Calcium, Magnesium, cation sum (CS) and base saturation (V) on species composition were stronger in the Interior, while human induced impacts and soil Potassium had an overwhelming effect on the Edge.
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