Hydric Condition Research Articles

A water adsorption study on wheat pericarp macrofibrils using atomic force microscopy

Wheat pericarp, which is the most external layer of the wheat kernel, is composed of a polysaccharide matrix, where cellulose macrofibrils, hemicellulose, and lignin are their main components. These polysaccharides modified their structure due to the hydric condition to which they are subjected. This effect is considered as an advantage in the wheat milling process. However, no information about micro and nanostructural changes on wheat pericarp macrofibrils due to their hydric condition, studied by the AFM technique and image analysis, has been reported. On the other hand, cellulose macrofibrils have been extensively studied by AFM but performing the study at constant relative humidity (RH) level. Hence, this study aimed to investigate the water adsorption process on wheat pericarp macrofibrils using AFM and control the RH to which samples were subjected during examinations with a lab equipment specially developed for the AFM experiment. The RH was modified from 10 to 90 %, and peak force error images were acquired, from which macrofibrils' diameter, swelling behavior, and water adsorption isotherms were calculated, using image analysis tools. Also, as an application from the water adsorption isotherms, the specific surface area and the hygroscopic swelling coefficients were determined. Results showed that wheat pericarp macrofibrils presented an unusual swelling behavior, with the most notorious changes after reaching a moisture content in equilibrium to 40 % of RH. The average diameter of the macro-fibrils varied from 45 to 48 nm. The water vapor adsorption isotherm obtained from AFM micrographs image analysis did not resemble the sigmoidal IUPAC Type II, generally obtained by applying gravimetric methods. Results suggest that the macrofibrils swelling controls water accessibility to the internal macrofibrils structures. It was proved with this study the feasibility of using AFM and image analysis to build water vapor isotherms and other mass transport parameters based on the macrofibrils swelling.

Toward Smart Soil Sensing in v4.0 Agriculture: A New Single-Shape Sensor for Capacitive Moisture and Salinity Measurements.

Modern agriculture imposes the need for better knowledge of the soil moisture content to rationalize the amount of water needed to irrigate farmlands. In this context, since current technological solutions do not correspond to the cost or use criteria, this paper presents a design for a new original capacitive bi-functional sensor to measure soil moisture and salinity. In this paper, we outline the design stages from simulation to finished elements of the optimal design to deployment in the fields, considering the mechanical integration constraints necessary for industrialization. The measurement electronics were developed based on the sensor’s electric model to obtain a double measurement. An on-site (field lot) measurement program was then carried out to validate the system’s good performance in real-time. Finally, this performance was matched with that of leading commercially available sensors on the market. This work demonstrates that, after deployment of the sensors, the overall system makes it possible to obtain a precise image of cultivated soil’s hydric condition, with the best response time.

Cambio climático y distribución potencial de frijol lima en Mesoamérica y Aridoamérica

Los objetivos de esta investigación fueron caracterizar los descriptores ecológicos y evaluar los impactos del cambio climático en la distribución potencial del frijol lima Phaseolus lunatus L. en las regiones de Mesoamérica y Aridoamérica. Se integró una base de datos de sitios de ocurrencia tomando seis fuentes. A partir, de las coordenadas geográficas de dichos sitios de ocurrencia y mediante el uso de sistemas de información geográfica, se extrajeron valores de variables agroclimáticas derivados de rasters de los sistemas Worldclim, USGS/NASA SRTM y CGIAR. Así se integró una matriz de datos agroclimáticos mediante la cual se determinaron los descriptores ecológicos de Phaseolus lunatus. Se modeló la distribución de P. lunatus con el modelo Maxent. Los resultados mostraron que P. lunatus se adapta a una amplia gama de condiciones ambientales que incluye una condición hídrica que va de semiárida a húmeda, una condición térmica que oscila de templada a muy cálida, y tiene presencia en los rangos altitudinal, térmico y pluvial de 0-2 386 msnm, 13.2-29.9 °C y 400-4 250 mm, respectivamente. Estos descriptores señalan la existencia de poblaciones portadoras de genes resistentes a condiciones de estrés climático. El modelo Maxent modeló satisfactoriamente la distribución de Phaseolus lunatus en los diferentes escenarios climáticos evaluados (AUC= 0.94). El cambio climático proyectado por el modelo HADGEM-ES para 2050 y 2070 y RCPs 4.5 y 8.5 es desfavorable para la distribución de P. lunatus, mientras que según el modelo CCMS4 el clima 2050 y 2070 es favorable en la ruta RCP4.5 y desfavorable en la ruta RCP8.5.

Effects of hydric stress on vibrational frequency patterns of Capsicum annuum plants

ABSTRACT Plants that experience a lack of sufficient irrigation undergo hydric stress, which causes the modification of their mechanical properties. These changes include a complex network of chemical and physical signals that interact between plant-plant and plant-environment systems in a mechanism that is still not well understood, and that differs among species. This mechanical response implies different levels of vibration when the plant experiences structural modifications from self-hydraulic adjustments of flux exchange at specific frequencies, with these carrying behavioral information. To measure these signals, highly sensitive instrumentation that allows the decoding of displacement velocity and displacement of plants, which is possible through calibrated equipment such as 3D scanning laser vibrometers, is necessary. Laser vibrometry technology allows for noninvasive measurements in real-time. Physiological changes could reasonably affect the biomechanical condition of plants in terms of the frequency (hertz) and intensity of the plant’s vibration. In this research, it is proposed that the frequency changes of a plant’s vibration are related to the plant’s hydric condition and that these frequency vibrations have the ecological potential to communicate water changes and levels of hydric stress. The peak of the velocity of plant displacements was found to vary from 0.079 to 1.74 mm/s, and natural frequencies (hertz) range is between 1.8 and 2.6 Hz for plants with low hydric stress (LHS), between 1.3 and 1.6 Hz for plants with medium hydric stress (MHS), and between 6.7 and 7.8 Hz for plants with high hydric stress. These values could act as preliminary references for water management using noninvasive techniques and, knowledge of the range of natural frequencies of hydric stress risk in chili pepper crops can be applied in precision agriculture practices.

Water-stressed or not, the mechanical acclimation is a priority requirement for trees

Periodic bending of young poplars increase the wood production whatever their hydric status; especially in the most highly stressed zones; improving the mechanical behaviour of the stem. The ability of trees to acclimate the building of their structures to windy conditions under various hydric conditions is essential in the context of the predicted climate changes. In this study, we investigated the biomechanical responses of young poplar trees to periodic controlled bending stimulations that mimic the mechanical effect of trees growing under windy conditions. This treatment was conducted for 5 months in well-watered conditions or under hydric stress. Results demonstrate the high impact of thigmomorphogenesis on growth processes, even under the water shortage. While axial growth was reduced by mechanical stimulations and hydric stress, radial growth was strongly increased by the periodic stem bending. The secondary growth was preferentially increased in the direction of highest longitudinal strains leading to the ovalisation of the cross-section. This ovalisation yielded 16%, regardless the hydric condition and generated a huge increase of the bending rigidity of the trees (+ 212%). Further, we observed a differential growth between the side growing under tension and the side growing under compression. A Finite Element model was built to investigate the mechanical benefits of the anisotropic cross-section shapes. This FE model enlightened the modulation of the spatial stress distribution that lead to a reduction of the stress in the weakest zones of the trunk; suggesting an improvement of the mechanical safety margin of wood. Thigmomorphogenesis acclimation appears as a complex and costly, but necessary process for the long-term mechanical support of the trees, even under hydric stress conditions.

Tolerance of apple rootstocks to short-term waterlogging

ABSTRACT: Until few years ago there were limited options of apple rootstocks commercially available for Brazilian growers; although, new series of Geneva® rootstocks introduced recently present desirable features such as vigor control and wider lateral branch angle. On the main apple producing regions of Brazil, intermittent rainfall eventually occurs and waterlogged condition is frequent especially in high clay oxisols; in addition, little is known about the tolerance of rootstocks M.9, Marubakaido/M.9 interstock, G.202, G.213 and G.814 to waterlogging. Thus, the objective of this experiment was to evaluate the tolerance of these rootstocks to short-term waterlogging on root and aerial parameters. Potted ‘Maxi Gala’ apple plants were kept under 48 hours of waterlogging weekly throughout 19 weeks to be compared with a normal hydric condition control. The evaluated variables were: leaf, stem and root dry matter, number and length of new root emission, and number of leaves, mean leaf size and chlorophyll content. Rootstocks G.202, G.814 and Marubakaido/M.9 interstock presented more tolerance to waterlogging, and the main defense mechanism was the emission of new adventitious roots.

NDVI and meteorological data as indicators of the Pampa biome natural grasslands growth

ABSTRACT The present study aimed to characterize the dynamics of NDVI and meteorological conditions, relating both to the annual dynamics of biomass accumulation in natural pastures of the Pampa biome as a way of subsidizing growth modeling. Forage accumulation rate data from a long-term experiment, NDVI data from the MODIS images, and meteorological data measured at the surface were used. We verify that the agrometeorological element associated to the accumulation of forage in the natural grasslands is different according to the season, which is typical of the subtropical climate. Winter is the critical season for livestock production due to the lower forage accumulation rate and lower values of NDVI, conditioned by the decrease of solar radiation and air temperature. In the summer, the limiting factor to forage accumulation is the hydric condition. It was also verified that the variability in the growth of grasslands can be associated with the ENSO phenomenon, being the El Nino favorable and the La Nina unfavorable, especially in the spring-summer period. Considering the verified associations, spectral indices combined with agrometeorological elements are recommended to the adjustment of models of forage accumulation in the Pampa biome natural grasslands.

Soil response to long-term projections of extreme temperature and precipitation in the southern La Plata Basin

Projected changes were estimated considering the main variables which take part in soil-atmosphere interaction. The analysis was focused on the potential impact of these changes on soil hydric condition under extreme precipitation and evapotranspiration, using the combination of Global Climate Models (GCMs) and observational data. The region of study is the southern La Plata Basin that covers part of Argentine territory, where rainfed agriculture production is one of the most important economic activities. Monthly precipitation and maximum and minimum temperatures were used from high quality-controlled observed data from 46 meteorological stations and the ensemble of seven CMIP5 GCMs in two periods: 1970–2005 and 2065–2100. Projected changes in monthly effective temperature and precipitation were analysed. These changes were combined with observed series for each probabilistic interval. The result was used as input variables for the water balance model in order to obtain consequent soil hydric condition (deficit or excess). Effective temperature and precipitation are expected to increase according to the projections of GCMs, with few exceptions. The analysis revealed increase (decrease) in the prevalence of evapotranspiration over precipitation, during spring (winter). Projections for autumn months show precipitation higher than potential evapotranspiration more frequently. Under dry extremes, the analysis revealed higher projected deficit conditions, impacting on crop development. On the other hand, under wet extremes, excess would reach higher values only in particular months. During December, projected increase in temperatures reduces the impact of extreme high precipitation but favours deficit conditions, affecting flower-fructification stage of summer crops.

Displacement of Watershed between Two Karstic Rivers

Groundwater flow circulating in a karstic hydrosystem is very difficult to grasp in space and time. In cases where the karstic aquifer is located between two rivers, the watershed is not easy to identify using a single analysis of a geological map. In this study, the understanding regarding the karstic hydrosystem between the Ardèche and Cèze Rivers, in the South of France, is advanced. This study especially highlights that the watershed of a karstic hydrosystem evolves depending on the hydric condition of the karstic aquifer. The results are obtained by artificial tracing analysis through the karstic network.

Assessing Wheat Traits by Spectral Reflectance: Do We Really Need to Focus on Predicted Trait-Values or Directly Identify the Elite Genotypes Group?

Phenotyping, via remote and proximal sensing techniques, of the agronomic and physiological traits associated with yield potential and drought adaptation could contribute to improvements in breeding programs. In the present study, 384 genotypes of wheat (Triticum aestivum L.) were tested under fully irrigated (FI) and water stress (WS) conditions. The following traits were evaluated and assessed via spectral reflectance: Grain yield (GY), spikes per square meter (SM2), kernels per spike (KPS), thousand-kernel weight (TKW), chlorophyll content (SPAD), stem water soluble carbohydrate concentration and content (WSC and WSCC, respectively), carbon isotope discrimination (Δ13C), and leaf area index (LAI). The performances of spectral reflectance indices (SRIs), four regression algorithms (PCR, PLSR, ridge regression RR, and SVR), and three classification methods (PCA-LDA, PLS-DA, and kNN) were evaluated for the prediction of each trait. For the classification approaches, two classes were established for each trait: The lower 80% of the trait variability range (Class 1) and the remaining 20% (Class 2 or elite genotypes). Both the SRIs and regression methods performed better when data from FI and WS were combined. The traits that were best estimated by SRIs and regression methods were GY and Δ13C. For most traits and conditions, the estimations provided by RR and SVR were the same, or better than, those provided by the SRIs. PLS-DA showed the best performance among the categorical methods and, unlike the SRI and regression models, most traits were relatively well-classified within a specific hydric condition (FI or WS), proving that classification approach is an effective tool to be explored in future studies related to genotype selection.

Toads in the backyard: why do invasive cane toads (Rhinella marina) prefer buildings to bushland?

AbstractLike many invasive species, cane toads (Rhinella marina) in Australia concentrate in the disturbed habitats created by human activity, rather than in pristine areas. We surveyed cane toads in the wet–dry tropics of the Northern Territory to assess the abundances, body sizes, sexes, behaviour, hydration state and feeding rates of toads around buildings compared to those in areas remote from buildings, and conducted experimental trials to assess the effects of building‐related variables (lights and increased toad densities) on the foraging success of toads. Toads around buildings were smaller than bushland conspecifics, and adult sex‐ratios were female‐biased. Toads were more sedentary around buildings than in the bush, but their feeding rates (based on direct observations and faeces production post‐capture) were similar. That similarity, despite twofold‐higher densities of competing toads around building, reflected the strong enhancement of feeding rates due to artificial lights attracting insects (in our experimental trials, a threefold increase regardless of the number of competing toads). Toads collected from around buildings were apparently in better hydric condition. Thus, access to water also may attract toads to buildings. The relative scarcity of adult male toads around buildings likely reflects waterbody‐centred reproductive activities, whereas the concentration of females and juveniles around buildings is driven largely by access to the insects attracted by artificial light. We conclude that buildings enhance the persistence of cane toad populations and may facilitate their spread.

In situ study of the shrinkage-swelling of a clay soil over several cycles of drought-rewetting

This article presents results describing the in situ behavior of clay soils (Pleistocene Brach formation) regarding shrinkage and swelling; an experimental site was established. Different types of sensors were used to continuously measure the movements of the clay bed-rock and variations in the temperature and water content of the soil. These parameters were correlated with annual climatic variations as measured at an on-site meteorological station. The results obtained thus far represent five cycles of drought-rewetting, thus enabling a medium-term study of the shrinkage-swelling of a clay soil over time. A cumulative effect of shrinkage over several cycles was observed with non-negligible variations of water content to a depth of 3m. Almost 1cm of cumulative shrinkage occurred over the first three cycles of a 2-meter-thick clay layer. The last two cycles were marked by a stabilization of the swelling. By determining the accumulated soil hydric condition over time, we discovered a correlation between this parameter and the periods of shrinkage-swelling. The accumulated hydric condition, as defined in this article, is a good indicator of the behavior of soil under shrinkage and swelling.

Alternative overwintering strategies in an Antarctic midge: freezing vs. cryoprotective dehydration

Summary Cryoprotective dehydration is a relatively new addition to our understanding of freeze avoidance strategies employed by polar invertebrates. Although the underlying cellular processes associated with this strategy are similar to those of freeze tolerance, little is known about potential trade‐offs of overwintering in these physiological states. This study compares the potential of larvae of the terrestrial midge Belgica antarctica (Diptera, Chironomidae) to overwinter in these two states. As the only insect with the capacity to tolerate freezing and to cryoprotectively dehydrate, it is an ideal model to compare the benefits and costs of these strategies. Compared to summer‐acclimated larvae, supercooling points of winter‐acclimatized larvae were significantly depressed and were lower than observed minima for their microhabitat temperatures. Thus, if larvae avoid inoculative freezing from environmental ice, they could remain unfrozen via cryoprotective dehydration. Both frozen and cryoprotectively dehydrated larvae readily survived a 32‐day exposure to simulated overwintering temperatures. Freezing had little effect on larval body water content and haemolymph osmolality. In contrast, cryoprotective dehydration at −5 °C resulted in a progressive loss of body water, ultimately reducing larval water content by 62%. This level of dehydration corresponded to an increase in haemolymph osmolality to c. 2750 mOsm kg−1, depressing the haemolymph melting point to −4·9 °C. Freezing and cryoprotective dehydration resulted in distinctly different patterns of glycogen breakdown. Whereas the glycogen content decreased only during the first 14 days in cryoprotectively dehydrated larvae, frozen larvae continued to break down glycogen throughout the 32‐day subzero exposure. However, after recovery at 0 °C for 5 days, glycogen levels were similar in these two groups, as were the levels of total lipids. Our results indicate that freezing and cryoprotective dehydration are both effective in promoting winter survival of larvae, with surprisingly few differences in energetic costs. Whether larvae freeze or become cryoprotectively dehydrated ultimately depends on the hydric condition of their microhabitat. The physiological flexibility of B. antarctica to overwinter in these alternative states likely contributed to its range distribution that extends further south than any other free‐living insect.

Satellite et surveillance du climat : le programme veille climatique / Satellites and climatic surveillance : the Climatic Watch Programme

The Climatic Watch Programme aims to create climatological data files to allow climatic surveillance and to assist in agrometeorology. This is to be achieved by the combined utilisation of satellite meteorologie imagery and ground data. Parameters currently available, are the plotting of the Intertropical convergence zone (ITCZ), ocean surface and land temperatures and the frequency of convective clouds (clouds with a cold top). Other important parameters related to radioactive flows and the climatology of clouds are being studied. Major research has already been conducted into estimating rainfall by satellite, enabling an evaluation of the hydric condition of the soil surface.

Sensitive Periods for the Influence of the Hydric Environment on Eggs and Hatchlings of Painted Turtles (Chrysemys picta)

Eggs of painted turtles (Chrysemys picta) were incubated in wet and dry environments. Half of the eggs in each treatment were transferred to the other treatment at the end of the first trimester, and a similar shift was performed at the end of the second trimester. Thus, eight experimental groups were recognized on the basis of hydric condition to which eggs were exposed in each trimester. The influence of the hydric environment on hatching success, on duration of incubation, and on size ofhatchlings is confined to the last two-thirds of incubation. The lack of effects associated with hydric conditions encountered by eggs during the first one-third of incubation can be explained by "compensatory water exchanges" that occur during the middle trimester. During the middle one-third of incubation, water uptake is greater and more rapid in a moist environment if an egg previously was in dry conditions than if an egg was in wet conditions. Likewise, water loss is more pronounced on a dry substrate during the middle trimester if an egg previously was in wet conditions than if an egg was in dry conditions. No compensatory water exchange occurs during the final trimester, but proximate hydric conditions during this period affect development. Because conditions in natural nests tend to fluctuate during the course of incubation, findings presented here tend to raise doubts regarding the significance of nest-searching behavior reported for females of many oviparous reptiles.