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1.
Int J Biometeorol ; 64(1): 1-13, 2020 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-31385091

RESUMO

Timber production has been prominent in the Brazil scenario to minimize deforestation. Thus, technical information is necessary to define the productive process of the African mahogany in the Midwest region of Brazil, especially with regard to its hydric parameters. Recent studies, reported in the literature, have shown that irrigation improves the performance of young African mahogany plants in the field. Sap flow measurement can be used to estimate transpiration of perennial plants and to determine their water demand. This study evaluated the influence of two water regimes on the transpiration and growth of an African mahogany forest after irrigation has ceased. Moreover, this study also characterizes the seasonal patterns of transpiration and growth of African mahogany under these conditions. African mahogany plants with 2.5 years of age were cultivated in Bonfinopolis-GO and evaluated for 2 years. Treatments were IT-irrigated until 2 years of age-and NIT-non-irrigated. Plant height (PH), breast height diameter (DBH), trunk volume (TRV), leaf area (LA), leaf dry matter (LDM), and transpiration (T) were monitored by heat dissipation probe (HDP) between Oct/2014 and Oct/2015. Higher growth in LA, DBH, and LDM were observed in IT. However, increase in PH and TRV was similar in both treatments. The mean annual T was similar between treatments (15.0 L m-2 month-1). The highest T was recorded in October/2014 (IT = 33.0 L m-2 month-1) and July/2015 (NIT = 20.5 L m-2 month-1). The greater LA and water deficit blades DEF > 30 mm promoted lower transpiration in the irrigated plants. Irrigation maintained plant growth in PH, DBH, and LA in the third year, even after irrigation has ceased. However, non-irrigated plants were similar in TRV (0.065 m3) and transpiration rates (≈ 15 L m-2 month-1). Winter transpiration (11.3 L m-2 month-1) was lower than in summer (18.8 L m-2 month-1) for irrigated plants and similar for non-irrigated plants (≈ 14 L m-2 month-1). Based on that, in order to maintain the homogeneity of the plants, the irrigation in the first 2 years of cultivation is recommended, and also, the sap flow measures presented satisfactory results regarding the determinations of the water needs of African mahogany.


Assuntos
Transpiração Vegetal , Água , Brasil , Folhas de Planta , Estações do Ano
2.
Ying Yong Sheng Tai Xue Bao ; 30(12): 4333-4343, 2019 Dec.
Artigo em Chinês | MEDLINE | ID: mdl-31840480

RESUMO

The regulation on carbon acquisition and water loss plays a critical role in plant growth and survival. Stomata are important portals for plants to control the exchanges of carbon and water between leaves and the atmosphere. Therefore, understanding stomatal control mechanisms and modelling stomatal conductivity are indispensable to accurately simulate carbon and water cycling in terrestrial ecosystems. As global climate change is accelerating in recent years, drought events have become more and more frequent and thus profoundly affect the survival, growth and distribution of plants. In order to deeply understand the underlying mechanism of carbon-water coupling of plants and predict the dynamics of plants and communities under global changes, it is crucial to explore responses of stomatal regulation of plants to drought stress. In this review, we synthesized recent research progress on mechanisms and modeling of plant stomatal regulation under drought stress. First, this review described the active and passive regulation of plant stomatal control in response to drought stress, and discussed the evolution of plant stomatal regulation, including the passive hydraulic regulation of ferns and lycophytes, the active regulation of angiosperms, and the dual-control mechanism of gymnosperms that was proposed as an important transitional type during evolution from ferns to angiosperms. Then, we analyzed the relationship between stomatal and hydraulic regulations, and discussed the debates on the decoupling of plant water potential from stomatal conductivity. The application of stomatal-conductivity optimization models was introduced based on the water use efficiency hypothesis and the maximum carbon gain hypothesis. The model based on the latter had a greater potential of prediction and practical application. Finally, we proposed two issues that should be urgently addressed: 1) to scale up the research of plant stomatal regulation from leaf or individual to ecosystem or even larger scales so as to improve the mechanistic models of carbon and water cycling in terrestrial ecosystems; and 2) to quantify the hydroactive feedback processes of plant stomatal regulation so as to modify current hydraulics models of plant stomatal function.


Assuntos
Secas , Gleiquênias , Ecossistema , Folhas de Planta , Estômatos de Plantas , Transpiração Vegetal , Água
3.
Sci Total Environ ; 694: 133551, 2019 Dec 01.
Artigo em Inglês | MEDLINE | ID: mdl-31756787

RESUMO

Topography exerts control on eco-hydrologic processes via alteration of energy inputs due to slope angle and orientation. Further, water availability varies with drainage position in response to topographic water redistribution and the catena effect on soil depth and thus soil water storage capacity. Our understanding of the spatio-temporal dynamics and drivers of transpiration patterns in complex terrain is still limited by lacking knowledge of how systematic interactions of energy and moisture patterns shape ecosystem state and water fluxes and adaptation of the vegetation to these patterns. To untangle the effects of slope orientation and hillslope position on forest structure and transpiration patterns, we measured forest structure, sap flux, soil moisture, throughfall and incoming shortwave radiation along two downslope transects in a forested head water catchment in south-east Australia. Our plot locations controlled for three systematically varying drainage position levels (topographic wetness index: 5.0, 6.5 and 8.0) and two levels of energy input (aridity index: 1.2 and 1.8). Vegetation patterns were generally stronger related to drainage position than slope orientation, whereas sap velocity variations were less pronounced. However, in combination with stand sapwood area, consistent spatio-temporal transpiration patterns emerged in relation to landscape position, where slope orientation was the primary and drainage position the secondary controlling factor. On short temporal scales, radiation and vapor pressure deficit were most important in regulating transpiration rates, whereas soil water limitation only occurred on shallow soils during summer. The importance of stand structural parameters increased on longer time scales, indicating optimization of vegetation in response to the long-term hydro-climatic conditions at a given landscape position. Thus, vegetation patterns can be conceptualized as a 'time-integrated' predictor variable that captures large fractions of other factors contributing to transpiration patterns.


Assuntos
Ecossistema , Monitoramento Ambiental , Transpiração Vegetal
4.
Oecologia ; 191(3): 519-530, 2019 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-31541317

RESUMO

Transpiration in humid tropical forests modulates the global water cycle and is a key driver of climate regulation. Yet, our understanding of how tropical trees regulate sap flux in response to climate variability remains elusive. With a progressively warming climate, atmospheric evaporative demand [i.e., vapor pressure deficit (VPD)] will be increasingly important for plant functioning, becoming the major control of plant water use in the twenty-first century. Using measurements in 34 tree species at seven sites across a precipitation gradient in the neotropics, we determined how the maximum sap flux velocity (vmax) and the VPD threshold at which vmax is reached (VPDmax) vary with precipitation regime [mean annual precipitation (MAP); seasonal drought intensity (PDRY)] and two functional traits related to foliar and wood economics spectra [leaf mass per area (LMA); wood specific gravity (WSG)]. We show that, even though vmax is highly variable within sites, it follows a negative trend in response to increasing MAP and PDRY across sites. LMA and WSG exerted little effect on vmax and VPDmax, suggesting that these widely used functional traits provide limited explanatory power of dynamic plant responses to environmental variation within hyper-diverse forests. This study demonstrates that long-term precipitation plays an important role in the sap flux response of humid tropical forests to VPD. Our findings suggest that under higher evaporative demand, trees growing in wetter environments in humid tropical regions may be subjected to reduced water exchange with the atmosphere relative to trees growing in drier climates.


Assuntos
Transpiração Vegetal , Árvores , Secas , Florestas , Pressão de Vapor , Água
5.
Plant Sci ; 287: 110199, 2019 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-31481201

RESUMO

Eutrema salsugineum is considered as extremophile model species. To gain insights into the root hydraulic conductivity and the role played by aquaporins in E. salsugineum, we investigated the aquaporin family profiles, plant water status and root hydraulic conductivity under standard (salt-free) and salt stress conditions. We found that there was no variation in the relative electric conductivity of the leaves when the salt concentration was less than 200 mM NaCl, and the transpiration rate dropped to 60.6% at 100 mM NaCl for 14 days compared to that at standard conditions. The pressure chamber techniques indicated that the root hydraulic conductivity of E. salsugineum was repressed by salt stress. However, propionic acid, usually used as an aquaporin inhibitor, unexpectedly enhanced the root hydraulic conductivity of E. salsugineum. The aquaporin family in E. salsugineum was profiled and the PIP aquaporin expression was investigated at the transcriptional and translational levels. Finally, two EsPIPs were identified to play a role in salt stress. The overall study provides evidence on how halophytes maintain their water status and aquaporin regulation pattern under salt stress conditions.


Assuntos
Aquaporinas/metabolismo , Brassicaceae/fisiologia , Regulação da Expressão Gênica de Plantas , Aquaporinas/genética , Transporte Biológico , Brassicaceae/genética , Filogenia , Folhas de Planta/genética , Folhas de Planta/fisiologia , Proteínas de Plantas/genética , Proteínas de Plantas/metabolismo , Raízes de Plantas/genética , Raízes de Plantas/fisiologia , Transpiração Vegetal , Estresse Salino , Tolerância ao Sal , Plantas Tolerantes a Sal , Estresse Fisiológico , Água/metabolismo
6.
Ying Yong Sheng Tai Xue Bao ; 30(8): 2607-2613, 2019 Aug.
Artigo em Chinês | MEDLINE | ID: mdl-31418184

RESUMO

Using Granier-type thermal dissipation probes (TDP), we measured stem xylem sap flow of the natural dominant species Quercus liaotungensis and a reforestation species Robinia pseudoacacia from July to September in 2016 in the semiarid loess hilly region. Meteorological factors and soil water content were simultaneously monitored during the study period. Using cross-correlation analysis, time lag between diurnal patterns of sap flux density and vapor pressure deficit (VPD) was quantitatively estimated. Differences in the time lag between the two species and possible influence by different diameter classes and soil water contents were analyzed. The results showed that the diurnal courses of sap flux density were similar to those of meteorological factors, with daily peaks ear-lier than VPD. The peak of VPD lagged behind the sap flux densities of Q. liaotungensis and R. pseudoacacia 118.2 min and 39.5 min, respectively. The peak of PAR lagged behind the sap flux density of Q. liaotungensis 12.4 min, but was 68.5 min ahead of that for R. pseudoacacia. Time lag between sap flux density and VPD significantly varied between tree species and was affected by soil water content. Those during higher soil water content period were about 32.2 min and 68.2 min longer than those during the period with lower soil water content for the two species, respectively. There was no correlation between time lag and tree diameter classes. The time lag between VPD and sap flux density for R. pseudoacacia was about 21.4 min longer in smaller diameter trees than in larger trees, which was significantly different under the lower soil water content. Our results suggested that the time lag effect between VPD and sap flux densities in the two species reflected their sensitivities to driving factors of transpiration, and that higher soil water content was favorable to sap flux density reaching its peak early. The lower soil water content might lead to lower sensitivity of the trees to meteorological factors. R. pseudoacacia was more sensitive to changes of soil water content.


Assuntos
Transpiração Vegetal/fisiologia , Quercus/fisiologia , Robinia/fisiologia , China , Solo/química , Árvores , Água/análise
7.
Ying Yong Sheng Tai Xue Bao ; 30(7): 2145-2155, 2019 Jul.
Artigo em Chinês | MEDLINE | ID: mdl-31418216

RESUMO

Kilometer-scale evapotranspiration is usually estimated by remote sensing images, combined with empirical or semi-empirical models, with results being verified with empirical data. However, it is usually difficult to obtain real-time measurements which can match the pixel scale of remote sensing. We analyzed kilometer-scale evapotranspiration by the combination of near-infrared and microwave technique in the Ecosystem Research Station of the Yellow River in Xiaolangdi, during period of plantation growth (1st July to 19th October 2016). Results showed that the combination of near-infrared and microwave technique could obtain well diurnal cycles in different weather conditions, with the overall energy balance reaching 0.87. The technique was sensitive to the variation of relative humidity of air, but not sensitive to that of soil moisture. The error of estimation was resulted from Bowen ratios and atmospheric stability. Compared with the eddy covariance method, the error was within a reasonable range. As estimated by the two-wavelength method, the maximum daily and total evapotranspiration of the study area was 3.5 mm and 162.4 mm, respectively.


Assuntos
Transpiração Vegetal , Água , Ecossistema , Rios , Solo
8.
Plant Physiol Biochem ; 142: 246-253, 2019 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-31374377

RESUMO

Transcription factors such as MYB have previously been associated with the plant response to drought. In this work, studies on the function of the barley (Hordeum vulgare L.) transcription factor HvMYB1 show that gene expression is upregulated in wildtype barley roots and leaves under drought and osmotic stress. Transgenic barley plants that overexpress HvMYB1 were found to be more resistant to drought, showing enhanced relative water content and reduced water loss rate and stomatal conductance as compared to control plants. Levels of the osmolyte proline were enhanced as was expression of dehydrin HvDNH6 in the transgenic lines under drought conditions. The levels of the reactive oxygen species H2O2 were enhanced in wildtype roots and leaves by drought, but less so in the HvMYB1 overexpressing lines. Enzyme activity of the low affinity H2O2 degrading enzyme catalase (EC 1.11.1.6) was also lower in droughted HvMYB1 overexpressing lines. Gene expression of the high affinity ROS scavengers ASCORBATE PEROXIDASE and GLUTATHIONE PEROXIDASE was found to be constitutively high in the overexpressing lines, whereas CATALASE gene expression was similar to the control plants. These results suggest a role for HvMYB1 in protecting plants against drought in the vegetative plant by acting as a mediator of abscisic acid action.


Assuntos
Hordeum/metabolismo , Proteínas de Plantas/metabolismo , Fatores de Transcrição/metabolismo , Ácido Abscísico/metabolismo , Desidratação , Regulação da Expressão Gênica de Plantas , Reguladores de Crescimento de Planta/metabolismo , Transpiração Vegetal , Plantas Geneticamente Modificadas
9.
Plant Physiol Biochem ; 142: 283-291, 2019 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-31336356

RESUMO

A greenhouse pot experiment was conducted at the faculty of sciences of Gafsa to evaluate the effect of phosphorus treatment on two pistachio species. The seedlings of Pistacia vera and Pistacia atlantica were subjected to six levels of phosphoric acid (P2O5) (0, 5, 15, 30, 60 and 120 ppm). Stomatal conductance, net photosynthesis, chlorophyll fluorescence (OJIP) and total chlorophyll content were measured after 1, 2, 3, 6, 8, 9 and 12 weeks of treatment. During the experiment, phosphorus application at 5 ppm increased photosynthesis and stomatal conductance, relative to the treatment 0 ppm only in P. atlantica. However, phosphorus supply at 60 and 120 ppm induced toxicity leading to an inhibition of CO2 photo-assimilation rate, an alteration of photosystem II (PSII) structure and function and reduction in leaf chlorophyll content in both species. The (OJIP) transient showed complex changes in O-J, J-I and I-P phases of fluorescence. Due to phosphorus toxicity, both donor and acceptor sides of PSII were damaged, electron transport perturbed and chlorophyll pigment reduced which resulted in the fall of CO2 photo-assimilation rate, followed by mortality in both species.


Assuntos
Dióxido de Carbono/metabolismo , Fósforo/farmacologia , Complexo de Proteína do Fotossistema II/efeitos dos fármacos , Pistacia/efeitos dos fármacos , Clorofila/metabolismo , Relação Dose-Resposta a Droga , Fósforo/metabolismo , Fotossíntese/efeitos dos fármacos , Complexo de Proteína do Fotossistema II/metabolismo , Pistacia/metabolismo , Transpiração Vegetal/efeitos dos fármacos , Plântula/efeitos dos fármacos , Plântula/metabolismo
10.
Sci Total Environ ; 689: 534-545, 2019 Nov 01.
Artigo em Inglês | MEDLINE | ID: mdl-31279200

RESUMO

The spatial distribution of water resources largely influences Earth ecosystems and human civilization. Being a major component of the global water cycle, evapotranspiration (ET) serves as an indicator of the availability of water resources. Understanding the actual ET (ETa) variation mechanism at different spatial and temporal scales can improve management of water use within the sustainable development limits. In this study, remote sensing derived ETa data were used to study water resource fluctuations in the Loess Plateau, China. This region covers diverse climate types from humid to arid and experienced large changes in vegetation cover during a revegetation project between 2000 and 2015. The relations between spatiotemporal variation of ETa, climate factors and vegetation change were explored using statistical methods. The results show that cropland, forestland and grassland take the largest percentage of total ETa. Total ETa exhibited a marginally increasing trend (p < 0.1) during 2000-2010 and no trend during 2011-2015. Windspeed and vegetation cover index highly influenced ETa, followed by atmospheric pressure, air humidity, precipitation, bright sunshine duration and temperature. Temperature has little effect on ETa throughout the Loess Plateau. The monitoring of water resources based upon water balance between precipitation, ETa and river flow changes shows that water consumption deficit is consistent with vegetation changes: it was large during 2000-2010 when vegetation increased rapidly and decreased after 2010. These results could help to develop different water saving strategies across the Loess Plateau and build a better monitoring system of water resources.


Assuntos
Mudança Climática , Conservação dos Recursos Naturais , Ecossistema , Transpiração Vegetal , China
11.
Planta ; 250(5): 1423-1432, 2019 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-31290031

RESUMO

MAIN CONCLUSION: Nitrogen and CO2 supply interactively regulate whole plant nitrogen partitioning and root anatomical and morphological development in tomato plants. Nitrogen (N) and carbon (C) are the key elements in plant growth and constitute the majority of plant dry matter. Growing at CO2 enrichment has the potential to stimulate the growth of C3 plants, however, growth is often limited by N availability. Thus, the interactive effects of CO2 under different N fertilization rates can affect growth, acclimation to elevated CO2, and yield. However, the majority of research in this field has focused on shoot traits, while neglecting plants' hidden half-the roots. We hypothesize that elevated CO2 and low N effects on transpiration will interactively affect root vascular development and plant N partitioning. Here we studied the effects of elevated CO2 and N concentrations on greenhouse-grown tomato plants, a C3 crop. Our main objective was to determine in what manner the N fertilization rate and elevated CO2 affected root development and nitrogen partitioning among plant organs. Our results indicate that N interacting with the CO2 level affects the development of the root system in terms of the length, anatomy, and partitioning of the N concentration between the roots and shoot. Both CO2 and N concentrations were found to affect xylem size in an opposite manner, elevated CO2 found to repressed, whereas ample N stimulated xylem development. We found that under limiting N and eCO2, the N% increase in the root, while it decreased in the shoot. Under eCO2, the root system size increased with a coordinated decrease in root xylem area. We suggest that tomato root response to elevated CO2 depends on N fertilization rates, and that a decrease in xylem size is a possible underlying response that limits nitrogen allocation from the root into the shoot. Additionally, the greater abundance of root amino acids suggests increased root nitrogen metabolism at eCO2 conditions with ample N.


Assuntos
Aclimatação , Dióxido de Carbono/metabolismo , Lycopersicon esculentum/fisiologia , Nitrogênio/metabolismo , Transporte Biológico , Carbono/metabolismo , Lycopersicon esculentum/anatomia & histologia , Lycopersicon esculentum/crescimento & desenvolvimento , Fotossíntese , Raízes de Plantas/anatomia & histologia , Raízes de Plantas/crescimento & desenvolvimento , Raízes de Plantas/fisiologia , Transpiração Vegetal , Xilema/anatomia & histologia , Xilema/crescimento & desenvolvimento , Xilema/fisiologia
12.
Molecules ; 24(13)2019 Jul 04.
Artigo em Inglês | MEDLINE | ID: mdl-31277450

RESUMO

Lemon balm (Melissa officinalis) is a popular herb widely used in medicine. It is often cultivated in soils with substantial heavy metal content. Here we investigate the associated effects of cadmium and copper on the plant growth parameters augmented by the manganese, zinc, and lead uptake indicators. The concentration of all elements in soil and plants was determined by the HR-CS FAAS with the ContrAA 300 Analytik Jena spectrometer. Bioavailable and total forms calculated for all examined metals were augmented by the soil analyses. The index of chlorophyll content in leaves, the activity of net photosynthesis, stomatal conductance, transpiration rate, and intercellular concentration of CO2 were also investigated. Either Cd or Cu acting alone at high concentrations in soil are toxic to plants as indicated by chlorophyll indices and gas exchange parameters. Surprisingly, this effect was not observed when both metals were administered together. The sole cadmium or copper supplementations hampered the plant's growth, lowered the leaf area, and altered the plant's stem elongation. Analysis of variance showed that cadmium and copper treatments of lemon balm significantly influenced manganese, lead, and zinc concentration in roots and above ground parts.


Assuntos
Cádmio/toxicidade , Cobre/toxicidade , Melissa/metabolismo , Dióxido de Carbono/metabolismo , Clorofila/metabolismo , Melissa/efeitos dos fármacos , Fotossíntese/efeitos dos fármacos , Raízes de Plantas/efeitos dos fármacos , Raízes de Plantas/metabolismo , Estômatos de Plantas/efeitos dos fármacos , Transpiração Vegetal/efeitos dos fármacos
13.
Food Chem ; 295: 300-310, 2019 Oct 15.
Artigo em Inglês | MEDLINE | ID: mdl-31174762

RESUMO

While fleshy fruit softening has long been mechanistically linked to cell wall disassembly, the importance of the fruit cuticle in water relations and firmness has been suggested through studies of the long-shelf life delayed fruit deterioration (dfd) tomato genotype. We tested the hypothesis that dynamic cuticle properties and composition affect tomato fruit transpiration and firmness and are influenced by environmental water availability, using dfd and two normally softening fruit cultivars, Ailsa Craig (AC) and M82, grown under control and water stress (WS) conditions. The effect of WS was also assessed following fruit detachment. WS increased fruit firmness, cuticle load, and the expression of cuticle biosynthetic genes, while reducing cuticle permeability and fruit transpiration rate in AC and M82, but not in dfd fruit. This study supports a direct relationship between fruit cuticle properties, transpiration and firmness, and provides insights into the adaptation of tomato genotypes to environments where water can be scarce.


Assuntos
Desidratação , Frutas/fisiologia , Lycopersicon esculentum/fisiologia , Armazenamento de Alimentos , Frutas/química , Frutas/metabolismo , Genótipo , Lycopersicon esculentum/química , Lycopersicon esculentum/metabolismo , Transpiração Vegetal , Água/metabolismo
14.
J Plant Physiol ; 240: 153002, 2019 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-31254740

RESUMO

Suppression of photorespiration by low O2 concentrations (Method 1) and simultaneous measurements of gas exchange and chlorophyll fluorescence (Method 2) are often used to estimate leaf photorespiration rate (Rp) of C3 plants. However, it is largely unknown whether Method 1 and Method 2 can be used equivalently in estimating Rp. Using a field experiment on two wheat cultivars (T. aestivum JM22 and T. aestivum Z39-118) whose leaf gas exchange and chlorophyll fluorescence at low and normal O2 concentrations (2% versus 21% O2) were simultaneously measured across a wide range of light intensities (I), this study assessed the impacts of the two measures on Rp and its response under changing irradiance conditions. All the above quantities increased with the increasing I until reaching the cultivar-specific maximum values and the corresponding saturation light intensities. However, there were significant differences between Rp estimated by Method 1 and Method 2 at the I range from 150 to 2000 µmol m-2 s-1 for T. aestivum JM22 and from 150 to 1000 µmol m-2 s-1 for T. aestivum Z39-118. These findings demonstrated that the two methods cannot be used equivalently under changing irradiance conditions.


Assuntos
Luz , Fotossíntese/efeitos da radiação , Transpiração Vegetal/efeitos da radiação , Triticum/fisiologia , Clorofila/fisiologia , Fluorescência , Oxigênio/análise , Folhas de Planta/fisiologia , Folhas de Planta/efeitos da radiação , Triticum/efeitos da radiação
15.
Artigo em Inglês | MEDLINE | ID: mdl-31248206

RESUMO

Frequent flash droughts can rapidly lead to water shortage, which affects the stability of ecosystems. This study determines the water-use characteristics and physiological mechanisms underlying Moso bamboo response to flash-drought events, and estimates changes to water budgets caused by extreme drought. We analyzed the variability in forest canopy transpiration versus precipitation from 2011-2013. Evapotranspiration reached 730 mm during flash drought years. When the vapor pressure deficit > 2 kPa and evapotranspiration > 4.27 mm·day-1, evapotranspiration was mainly controlled through stomatal opening and closing to reduce water loss. However, water exchange mainly occurred in the upper 0-50 cm of the soil. When soil volumetric water content of 50 cm was lower than 0.17 m3·m-3, physiological dehydration occurred in Moso bamboo to reduce transpiration by defoliation, which leads to water-use efficiency decrease. When mean stand density was <3500 trees·ha-1, the bamboo forest can safely survive the flash drought. Therefore, we recommend thinning Moso bamboo as a management strategy to reduce transpiration in response to future extreme drought events. Additionally, the response function of soil volumetric water content should be used to better simulate evapotranspiration, especially when soil water is limited.


Assuntos
Adaptação Fisiológica , Secas , Transpiração Vegetal/fisiologia , Poaceae/fisiologia , Abastecimento de Água , Água/metabolismo , China
16.
J Plant Physiol ; 237: 104-110, 2019 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-31055228

RESUMO

Biophysical fruit growth depends on a balance among the vascular and transpiration flows entering/exiting the fruit via phloem, xylem and through the epidermis. There is no information on vascular flows of Japanese plums, a species characterized by high-sugar content of its fruit at harvest. Vascular flows of Angeleno plums were monitored by fruit gauges during late fruit development, under the dry environment of the Goulburn Valley, Victoria, Australia. Phloem, xylem flows and skin transpiratory losses were determined, as well as diurnal leaf, stem and fruit pressure potentials. Fruit seasonal development, skin conductance and dry matter accumulation were also monitored. Fruit grew following a double-sigmoid pattern, but fruit size increased only 3.1 g over the last 3 weeks of development. Fruit grew very little in the morning, primarily due to phloem inflows (0.05 g fruit-1hr-1), while water left the fruit via the xylem. Negligible skin transpiration was recorded for vapour pressure deficit (VPD) values below 3 kPa. This growth pattern, in the absence of skin transpiration, suggests apoplastic phloem unloading. However, at VPD values over 3 kPa (e.g. from early afternoon to a peak around 18:00 h), transpiratory losses through the skin (up to 0.25 g fruit-1hr-1) caused fruit to shrink, leading to enhanced phloem and xylem inflows (ca. 0.15 g fruit-1hr-1), a scenario that would correspond to symplastic phloem unloading. Over 24 h the fruit showed a slightly negative total growth, consistent with fruit growth measured in situ during the season at weekly intervals. A few fruit species are known to alter their phloem unloading mechanism, switching from symplastic to apoplastic during the season. Our data support the coexistence in Japanese plum of different phloem unloading strategies within the same day.


Assuntos
Floema/fisiologia , Transpiração Vegetal/fisiologia , Prunus domestica/fisiologia , Crescimento Celular , Meio Ambiente , Frutas/crescimento & desenvolvimento , Frutas/fisiologia , Vitória
17.
Gigascience ; 8(5)2019 05 01.
Artigo em Inglês | MEDLINE | ID: mdl-31081890

RESUMO

BACKGROUND: Rice is susceptible to both drought and heat stress, in particular during flowering and grain filling, when both grain yield and quality may be severely compromised. However, under field conditions, these 2 stresses rarely occur separately. Under well-watered conditions, plants avoid heat stress by transpirational cooling, while this is not possible under drought conditions. Although investigating combined drought and heat stress is clearly more agronomically relevant than analyzing the effects of the single stresses, only a few studies of this stress combination, in particular under field conditions, have been published. RESULTS: Three rice cultivars differing in drought and heat tolerance were grown in the field under control and drought conditions in 3 consecutive years. Drought was applied either during flowering or during early grain filling and resulted in simultaneous heat stress, leading to reduced grain yield and quality. Analysis by gas chromatography-mass spectrometry showed distinct metabolic profiles for the 3 investigated organs (flag leaves, flowering spikelets, developing seeds). The metabolic stress responses of the plants also strongly differed between cultivars and organs. Correlation analysis identified potential metabolic markers for grain yield and quality under combined drought and heat stress from both stress-regulated metabolites and from metabolites with constitutive differences between the cultivars. CONCLUSIONS: Gas chromatography-mass spectrometry resolved metabolic responses to combined drought and heat stress in different organs of field-grown rice. The metabolite profiles can be used to identify potential marker metabolites for yield stability and grain quality that are expected to improve breeding efforts towards developing rice cultivars that are resilient to climate change.


Assuntos
Secas , Metaboloma , Oryza/genética , Termotolerância , Produção Agrícola/métodos , Oryza/fisiologia , Transpiração Vegetal
18.
Sci Total Environ ; 682: 19-30, 2019 Sep 10.
Artigo em Inglês | MEDLINE | ID: mdl-31108267

RESUMO

The Lake Naivasha Basin in Kenya has experienced significant land use cover changes (LUCC) that has been hypothesized to have altered the hydrological regime in recent decades. While it is generally recognized that LUCC will impact evapotranspiration (ET), the precise nature of such impact is not very well understood. This paper describes how land use conversions among grassland and croplands have influenced ET in the Lake Naivasha Basin for the period 2003 to 2012. MODIS data products were used in combination with the European Centre for Medium-Range Weather Forecasts (ECMWF) data sets to model ET using the Surface Energy Balance System (SEBS). The results indicate that conversions from grassland to cropland accounted for increases in ET of up to 12% while conversion from cropland back to grasslands (abandonment) reduced ET by ~4%. This suggests that recently cultivated agricultural lands could increase local water demands, while abandonment of the farms could decrease the water loss and eventually increase the water availability. Also, recovery of ET following re-conversion from cropland to grassland might be impeded due to delayed recovery of soil properties since parts of the catchment are continuously being transformed with no ample time given for soil recovery. The annual ET over the 10 years shows an estimated decline from 724 mm to 650 mm (~10%). This decline is largely explained by a reduction in net radiation, an increase in actual vapour pressure whose net effect also led to decrease in the surface-air temperature difference. These findings suggest that in order to better understand LUCC effects on water resources of Lake Naivasha, it is important to take into account the effect of LUCC and climate because large scale changes of vegetation type from grassland to cropland substantially will increase evapotranspiration with implications on the water balance.


Assuntos
Agricultura , Clima , Transpiração Vegetal , Quênia , Lagos , Solo/química
19.
Planta ; 250(2): 495-505, 2019 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-31089803

RESUMO

MAIN CONCLUSIONS: This study demonstrated that freeze-induced hydraulic failure varies between two Vitis species that have different xylem vessel frequency and grouping. However, seasonal recovery of young grapevines was similar between the species. Sub-freezing temperatures after budburst represent a major threat for the cultivation of fruit crops in temperate regions. Freeze stress might disrupt xylem hydraulic functionality and plant growth; however, it is unclear if hydraulic traits influence the ability of woody plants to cope with freeze stress. We investigated if a grapevine species (Vitis hybrid) with earlier budburst had anatomical traits that cause higher freeze-induced hydraulic failure but also confer a greater ability for seasonal recovery compared to a Vitis vinifera species. Two-year-old Vitis hybrid and vinifera grapevines were container-grown outdoors, assigned to either a control (n = 40) or a freeze-stressed (n = 40) treatment and exposed to a controlled-temperature (- 4 °C) freeze stress shortly after budburst. We found that the Vitis hybrid had greater stem-specific hydraulic conductivity (Ks) and was more vulnerable to freeze-induced embolism compared to the V. vinifera species, which exhibited a less efficient but safer water transport strategy. Seventy-two hours after the freeze stress, Ks of freeze-stressed V. vinifera was 77.8% higher than that of the control, indicating hydraulic recovery. While the two species did not differ in xylem vessel diameter, Vitis hybrid exhibited higher vessel frequency and percentage of vessel grouping, which could explain its higher Ks and greater freeze-induced Ks loss compared to the V. vinifera vines. While the two species varied in the short-term hydraulic response, they exhibited similar and full hydraulic and vegetative recovery by midseason, including bud freeze tolerance during the following fall and mid-winter.


Assuntos
Vitis/fisiologia , Transporte Biológico , Congelamento , Transpiração Vegetal/fisiologia , Estações do Ano , Especificidade da Espécie , Estresse Fisiológico , Vitis/anatomia & histologia , Vitis/crescimento & desenvolvimento , Água/fisiologia , Xilema/anatomia & histologia , Xilema/crescimento & desenvolvimento , Xilema/fisiologia
20.
Sci Total Environ ; 683: 166-174, 2019 Sep 15.
Artigo em Inglês | MEDLINE | ID: mdl-31132697

RESUMO

Tropical rainforests control the exchange of water and energy between the land surface and the atmosphere near the equator and thus play an important role in the global climate system. Measurements of latent (LE) and sensible heat exchange (H) have not been synthesized across global tropical rainforests to date, which can help place observations from individual tropical forests in a global context. We measured LE and H for four years in a tropical peat forest ecosystem in Sarawak, Malaysian Borneo using eddy covariance, and hypothesize that the study ecosystem will exhibit less seasonal variability in turbulent fluxes than other tropical ecosystems as soil water is not expected to be limiting in a tropical forested wetland. LE and H show little variability across seasons in the study ecosystem, with LE values on the order of 11 MJ m-2 day and H on the order of 3 MJ m-2 day-1. Annual evapotranspiration (ET) did not differ among years and averaged 1579 ±â€¯47 mm year-1. LE exceeded characteristic values from other tropical rainforest ecosystems in the FLUXNET2015 database with the exception of GF-Guy near coastal French Guyana, which averaged 8-11 MJ m-2 day-1. The Bowen ratio (Bo) in tropical rainforests in the FLUXNET2015 database either exhibited little seasonal trend, one seasonal peak, or two peaks. Volumetric water content (VWC) and VPD explained a trivial amount of the variability of LE and Bo in some of the tropical rainforests including the study ecosystem, but were strong controls in others, suggesting differences in stomatal regulation and/or the partitioning between evaporation and transpiration. Results demonstrate important differences in the seasonal patterns in water and energy exchange across different tropical rainforest ecosystems that need to be understood to quantify how ongoing changes in tropical rainforest extent will impact the global climate system.


Assuntos
Atmosfera , Metabolismo Energético , Transpiração Vegetal/fisiologia , Floresta Úmida , Bornéu , Malásia , Estações do Ano , Áreas Alagadas
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