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The Brazilian Cerrado is the second largest Brazilian biome. In recent decades, a reduction in rainfall has indicated an extension of the dry season. Among the many native species of the Cerrado of the Annonaceae family and used in folk medicine, Annona crassiflora Mart. has fruits of high nutritional value and its by-products are sources of bioactive compounds, such as alkaloids. The aim of the study was to investigate how water stress impacts the production of alkaloids. The study was carried out in a nursery, and the knowledge was flood, field capacity and drought. Gas exchange, chlorophyll a fluorescence, antioxidant enzymes, total soluble sugars, starch, reducing sugars, sucrose, total alkaloids and liriodenine were analyzed. We observed that plants subjected to drought had an increase in the production of total alkaloids and liriodenine, without a reduction in photosynthetic metabolism. Plants kept under drought and flood conditions dissipated higher peroxidase activity, while catalase was higher in flooded plants. Starch showed the highest concentration in flooding plants without differing from drought plants; the lowest trehalose concentrations were found in both drought and flooding plants. The drought stimulated the synthesis of total alkaloids and liriodenine without reducing the primary metabolism, which suggests adaptation to Cerrado conditions. [ABSTRACT FROM AUTHOR]

Climate change will have large consequences for flooding frequencies in freshwater systems. In interaction with anthropogenic activities (flow regulation, channel restoration and catchment land‐use) this will both increase flooding and drought across the world. Like in many other ecosystems facing changed environmental conditions, it remains difficult to predict the rate and trajectory of vegetation responses to changed conditions. Given that critical ecosystem services (e.g. bank stabilization, carbon subsidies to aquatic communities or water purification) depend on riparian vegetation composition, it is important to understand how and how fast riparian vegetation responds to changing flooding regimes. We studied vegetation changes over 19 growing seasons in turfs that were transplanted in a full‐factorial design between three riparian elevations with different flooding frequencies. We found that (a) some transplanted communities may have developed into an alternative stable state and were still different from the target community, and (b) pathways of vegetation change were highly directional but alternative trajectories did occur, (c) changes were rather linear but faster when flooding frequencies increased than when they decreased, and (d) we observed fastest changes in turfs when proxies for mortality and colonization were highest. These results provide rare examples of alternative transient trajectories and stable states under field conditions, which is an important step towards understanding their drivers and their frequency in a changing world. To explore pathways of vegetation change after various flooding regime changes, we transplanted vegetation turfs full‐factorial between three riparian elevations (upland, middle and low elevation). Vegetation changes were directional and faster when flooding frequencies increased than when they decreased. After 19 growing seasons, we found indications for alternative stable states and alternative trajectories under field conditions, which is an important step towards understanding their drivers and their frequency in a changing world. [ABSTRACT FROM AUTHOR]

Ethnomedicinal plants play a very important role in the life of human beings. Bihar is a state where 80% people depend on plants and plants part for their diseases and their treatment. The studies indicate the value of traditional system of medicines, economically useful plants and possible effects of climate changes on medicinal plants. It is true that climate changes are causing noticeable effect on life cycles and distribution of the plant species in Saran district. Medicinal plants are widely used at present. A large no. of people in Bihar is directly dependent on the healthcare treatment by medicinal plants that is why it is a matter of concern in Bihar. It is very necessary to improve our understanding about the effects on medicinal plants by various researched and stems in present article. To know the present condition of medicinal plants and the effect of climatic changes on them in Saran district, Bihar. [ABSTRACT FROM AUTHOR]

Vegetation response to flooding across large dryland areas such as Australia's Murray Darling Basin (MDB) is not understood synoptically and with locally relevant detail. We filled this knowledge gap by quantifying vegetation dynamics, defined here as greening and browning due to changing chlorophyll content and leaf area index, in response to flooding and rainfall across the floodplains of the entire MDB. We quantified vegetation and flooding dynamics using the same data source, namely 26 years of high resolution, wall-to-wall satellite data, in a top down statistical modeling approach, where we controlled for rainfall. Our time series (1986–2011) covered a period of extreme hydroclimatic variability, including the South East Australian Millennium Drought, thus providing a research opportunity to investigate how the relationship between vegetation and flooding changed during wet and dry periods. Our results showed that besides rainfall, flooding plays a key role in driving floodplain vegetation dynamics, yet the role of flooding varied across the MDB floodplains. We quantified a change in the relationship of how vegetation responds to rainfall and flooding with an unprecedented level of spatial detail. The change in the relationships coincided primarily with the onset of the Millennium Drought, yet local and regional differences in the timing of the change did occur, suggesting that the beginning of the Millennium Drought did not impact all floodplain areas at the same time. Our synoptic while locally relevant quantification of the changing response of vegetation to rainfall and flooding is a first step to help underpin Australia's investment into environmental water allocations. [ABSTRACT FROM AUTHOR]

The input of leaf litter from riparian vegetation could be affected by changes in precipitation and modifications to the hydrological regime. We analyse the pattern of leaf litterfall at the community scale as well as the breakdown rate in a mixed gallery forest that covers the levees of the Paraná River oxbow lake. Litterfall was collected biweekly for 4 years that represents different rainfall and hydrologic regimes of the Paraná River including flood and prolonged drought: 1996-1997 (PA), 1999-2000 (PB), 2005-2006 (PC) and 2007-2008 (PD). To analyse leaf breakdown, litter bags were incubated on the forest floor during flooding conditions (FFo) and dry conditions (DFo) and in the oxbow lake (FOx). The total annual leaf litterfall were 8.97, 11.15, 10.42 and 14.43 tn ha−1 yr−1 for PA, PB, PC and PD, respectively. Our results suggest that with the increasing severity of the dry season and decreasing hydrologic connectivity, the annual leaf litterfall increases, whereas its seasonal pattern does not change. Regardless of the seasonal pattern of rainfall and hydrological regime in each study period, leaf fall occurred throughout the year, and the peak was recorded between August and October. Leaves decomposed fastest in FOx, and the leaf breakdown on the forest floor was slower during flooding conditions than in dry conditions. Regular floods are natural occurrences that do not affect the leaf production of the Paraná mixed forest, and the leaf processing depends on the oxygen concentrations. Prolonged droughts led to high annual leaf production, which is mainly processed within this forest. Copyright © 2015 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Soybean is stress-sensitive crop that exhibits markedly reduced growth under flooding and drought conditions. Three S-adenosylmethionine synthetases (SAMs) proteins were identified as flooding and drought responsive proteins in soybean using a proteomic technique. To better understand the role of these SAMs proteins in soybean under flooding and drought stresses, temporal, organ, and stress specificities were examined at mRNA and enzyme activity levels. The activity of SAMs decreased in response to the flooding, however, it was not significantly changed by NaCl, cold, gibberellic acid, and calcium in soybean roots. The activity of SAMs was induced in roots and hypocotyls under drought. The mRNA expression of the S- adenosylmethionine synthetase ( SAMs) family was down-regulated in root tips and roots under the flooding and the drought, and SAMs 1 and SAMs 2 were down-regulated in roots under both stresses. A gene 1-aminocyclopropane-1-carboxylate synthase was up-regulated in root tips, roots, and hypocotyls under drought, however, it was not changed in root tips and roots under the flooding. In addition, 1-aminocyclopropane-1-carboxylate oxidase was induced in root tips under flooding and drought. These results suggest that SAMs was involved in the response to the flooding and drought and it might affect ethylene biosynthesis in soybean. [ABSTRACT FROM AUTHOR]

One of the most important hydro-climatic hazards is that of hydric deficits, i.e. drought or flood. Droughts can occur in any region on the Globe but the strongest effects are in arid, semi-arid and sub-humid areas where ecosystems are characterised by high fragility. Drought can also occur in areas where annual or periodical precipitations are "normal" or close to multi-annual means, but the water comes from rare precipitations (mm/min) with high intensities that do not allow accumulation of water in the soil. This type of drought is increasingly frequent in southern and eastern Romania and it tends to extend to central and western Romania. World Meteorological Organisation proposed to define drought as an atmospheric sequence characterised by amounts of precipitations 60% lower than those considered normal. The goal of this paper is to study drought hazard in the conditions of Oravita, Romania, during 2-11-2013. The three years were analysed through the prism of several indicators of drought characterisation in literature and compared to multi-annual mean values. We analysed the following hydro-climatic hazard monitoring parameters in the area of Oravita: the sum of monthly and annual precipitations, the monthly and annual mean of evapotranspiration, the monthly and annual hydric deficits and their graphic representation, monthly and annual mean temperatures and their evolution; we also calculated and analysed climate indicators of characterisation (Thornthwaite, Lang, characterisation depending on deficit of precipitations, etc.). From the point of view of the rainfall regime, an important indicator in defining drought and excess of humidity, the sum of monthly precipitations during summer or spring and their annual amount help draw a conclusion regarding the existence of hydro-climatic hazards during the studied period. Depending on the deficit of precipitations, compared to monthly, seasonal and annual multi-annual means, June, August and September are excessively droughty or droughty in all analysed years. The year 2013 was a very droughty year if we take into account the vegetation period; overall, 2013 was a little droughty year. Results show that there were droughty periods in the three years in Oravita, particularly during the hot season (April- September); 2013 proved the droughtiest year and it is labelled as semi-arid depending on all analysed indicators. [ABSTRACT FROM AUTHOR]

Temporary ponds (TPs) are shallow water bodies characterized by alternating phases of drought and flooding. They exhibit a small-scale zonation with a central belt (CB), an intermediate belt, and an outer belt (OB). Starting from the hypothesis that plant assemblage composition is affected by the position within TPs, our aims were to define the small-scale patterns of plant functional types, soil evolution, and soil physicochemical properties and to analyze their relationships and how they were affected by pond characteristics (i.e., elevation, substratum, total size, belt size, maximum water depth, and hydroperiod). Our results pointed out that patterns of plant functional types and soil evolution followed the position within the pond, soil physicochemical properties were weakly affected, and there was a relationship between plant functional types, soil small-scale patterns, and pond characteristics. Principal component analysis showed a positive correlation of Alfisols with CB, aquatic and amphibious species, maximum water depth, and hydroperiod, and of Entisols with OB and terrestrial species. A combined microtopography–hydrology effect was the primary factor controlling soil evolution and plant functional type patterns. As a consequence, modification in topographic shape and/or hydrologic parameters could alter TP environments. The results provide information for management strategies as an answer to the concerns surrounding continued worldwide TP decline. [ABSTRACT FROM AUTHOR]

Northern peatlands represent a long-term net sink for atmospheric CO2, but these ecosystems can shift from net carbon (C) sinks to sources based on changing climate and environmental conditions. In particular, changes in water availability associated with climate control peatland vegetation and carbon uptake processes. We examined the influence of changing hydrology on plant species abundance and ecosystem primary production in an Alaskan fen by manipulating the water table in field treatments to mimic either sustained flooding (raised water table) or drought (lowered water table) conditions for 6 years. We found that water table treatments altered plant species abundance by increasing sedge and grass cover in the raised water table treatment and reducing moss cover while increasing vascular green area in the lowered water table treatment. Gross primary productivity was lower in the lowered treatment than in the other plots, although there were no differences in total biomass or vascular net primary productivity among the treatments. Overall, our results indicate that vegetation abundance was more sensitive to variation in water table than total biomass and vascular biomass accrual. Finally, in our experimental peatland, drought had stronger consequences for change in vegetation abundance and ecosystem function than sustained flooding. [ABSTRACT FROM AUTHOR]

Copyright of Canadian Journal of Forest Research is the property of Canadian Science Publishing and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

In central Cambodia, rapidly growing non-endemic species are often planted for timber production. The introduction of non-endemic species into stands with native species has been found to alter the forest transpiration characteristics in this region with distinct dry and rainy seasons defined by the different rainfall patterns. However, less is understood about the underlying processes, especially the ecophysiological characteristics of native species that are adapted to the highly seasonal environments and the non-endemic species that acclimate to those environments. Leaf ecophysiological traits were measured for two native and two representative non-endemic tree species in central Cambodia to examine whether species-specific seasonal trends in transpiration could be explained by leaf ecophysiological traits. Photosynthetic capacity as represented by the maximum carboxylation rate ( V cmax25 ) of each species remained constant in the rainy and dry seasons. Native species had high stomatal conductance ( g sw ) and the parameter for its response to the environments ( m ) in the rainy season and lower levels in the dry season. Additionally, the seasonal change in g sw for non-endemic species was less clear despite the seasonality in the tree-level transpiration. A multi-layer model that incorporated the measured data related to the leaf ecophysiological traits and their seasonal changes successfully reproduced the daily canopy-scale transpiration rate ( E canopy ). The modeled E canopy successfully reproduced most of the seasonal and day-to-day changes in measured E canopy using sap flux measurements and showed the strong control of leaf ecophysiological traits over E canopy and the species-specific seasonal trends. Two reduction events in measured E canopy were, however, not explained by the simulation, possibly as a result of species-specific factors that were not considered in this study, i.e., the reduction in water uptake by a native species caused by drought and the hypoxic effects of flooding on the roots of a non-endemic species. [ABSTRACT FROM AUTHOR]

Efforts to restore species threatened by introduced pathogens often include breeding resistance into susceptible native species from resistant exotics, but this is a lengthy and expensive process. Naturally occurring hybrids between susceptible and resistant species may accelerate this process if they fulfill the desired species' ecological function. To explore this possibility, we exposed the following seedlings to drought and flood treatments in a controlled environment: Juglans cinerea L. (butternut), which has been devastated by an exotic pathogen; Juglans ailantifolia Carr. var. cordiformis (heartnut); Juglans × bixbyi Rehd. [ailanthifolia × cinerea] (buartnut), multigenerational hybrids between butternut and heartnut; and Juglans nigra L. (black walnut). There was a strong taxa × treatment interaction. Butternut had a negative response toflood treatments, expressed by reduced leaf area (LA), photosynthetic assimilation (A), and chlorophyll fluorescence (Fv/Fm). Heartnut had a negative response to drought, expressed by lower LA and A. Hybrid A and LA were reduced in response to both treatments. Results indicate that hybrid drought and flood tolerance may limit their overall ability to completely occupy the ecological niche formerly filled by butternut. However, the strong dichotomous response of progenitors to moisture stress suggests that hybrids could be efficiently screened for J. cinerea character in conjunction with disease resistance. [ABSTRACT FROM AUTHOR]

Copyright of Brazilian Journal of Biology is the property of Instituto Internacional de Ecologia and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Abstract: Plant communities in dryland riparian ecosystems are influenced by flood disturbance and water availability. As global climate change alters stream flow regimes, there is increasing need to understand which traits allow plant species to persist under increased stress and disturbance. Small seed mass is part of a strategy that adapts for disturbance, but the role of seed mass as an adaptation for drought is less well documented. For dryland riparian plant communities, we asked, does seed mass vary with water availability and flood frequency? We compared community seed mass between sites that vary in flow permanence (longitudinal water gradient) and between hydrogeomorphic surfaces within sites (lateral gradients of moisture and disturbance). Using data from four rivers in Arizona, we contrasted seed mass between plant groups. We found community seed mass to be greater at sites with ephemeral than perennial flow, and to increase laterally from wet, frequently-flooded channel edges to dry, less disturbed terraces. Seed mass varied by moisture group (smallest for hydroriparian species) and by disturbance group (smallest for disturbance species), and showed a trend for being greater in introduced species. We conclude that small seed mass is independently associated with wet and disturbed conditions in dryland riparian ecosystems. [Copyright &y& Elsevier]

Both flooding and drought are important in determining plant distribution in wetlands. However, the roles of plant's physiological response to flooding and drought in accounting for plant distribution are far from clear. To this end, three typical wetland plants with different distribution patterns (high-elevation species Miscanthus sacchariflorus, low-elevation species Carex brevicuspis and Polygonum hydropiper) in Dongting Lake were treated with three water levels (flooding 25 cm, control 0 cm, drought −25 cm), and relative growth rate (RGR), malondialdehyde (MDA) content, electrolyte leakage and proline content were investigated. The RGR of the three species decreased significantly in both flooding and drought treatments. Compared to the control, the RGR of M. sacchariflorus decreased more in the flooding treatment but less in the drought treatment compared to the other two species. The contents of MDA in the three species increased in both flooding and drought treatments, except for P. hydropiper in the flooding treatment. MDA contents increased more in M. sacchariflorus in the flooding treatment but less in the drought treatment compared to the other two species. Only M. sacchariflorus had a higher electrolyte leakage in the flooding treatment, and drought led to a higher electrolyte leakage in P. hydropiper and C. brevicuspis. Proline content increased 69.2, 66.7 and 39.6 % in P. hydropiper, C. brevicuspis and M. sacchariflorus in the flooding treatment, and increased 44.2, 13.0 and 45.3 % in the drought treatment, respectively. These results suggest that M. sacchariflorus has a higher tolerance to drought but a lower tolerance to flooding than do the other two species, which might be the intrinsic mechanisms accounting for their different distribution patterns. [ABSTRACT FROM AUTHOR]

ABSTRACT Vulnerability of wetland vegetation to water table changes is a widely studied topic in the field of ecology. Extreme flood or drought conditions imposed on wetlands cause disappearance of plants or shift in the vegetation regime. The recovery of such plant compositions is of particular importance when the wetland is subjected to frequent water table fluctuations resulting from land use changes and requires knowledge of mechanisms underlying evolution of plant growth to changing hydrologic conditions. We used a spatially varying, coupled groundwater-vegetation growth model to investigate the survival mechanism of wetland herbaceous plants. The plants were subjected to long-term water table drainage because of land use changes that caused the disappearance of one of the species composition. In an effort to revive the disappeared species, hypothetical soil saturation was introduced onto the study domain through elevated water table level. Even though the system had returned to hydrologically favourable environment, the disappeared species was unable to recover, which in turn led to the evaluation of factors that determine the re-emergence of the species through sensitivity analysis. The results of the sensitivity analysis showed that the disappeared species recovered during scenarios of reduced duration of drawdown, increased assimilation rates and increased competitiveness. The analysis also showed that the competitiveness of the plants, which was modelled by the classic Lotka-Volterra algorithm, supersedes any of the unfavourable plant growth characteristics. The results of this study demonstrated the ability of the groundwater-vegetation response model to facilitate an understanding of plant development and a hierarchy of important factors that promote their growth in altered hydrologic conditions. Copyright © 2012 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Bioretention basins are man-made topographic depressions designed to collect and retain surface water runoff. In most cases these basins are used to prevent flooding and/or remove environmentally harmful pollutants and sediments from entering natural aquatic systems. To maximize environmental benefits, these systems are often planted with flood-tolerant wetland hydrophytes that are capable of withstanding extended periods of drought. Unfortunately, little is known about how these plants respond to extreme hydrologies while breaking seasonal dormancy. The purpose of this study was to better understand the morphological and physiological responses of three wetland species ( Pontederia cordata L., Saururus cernuus L., and Schoenoplectus tabernaemontani C.C. Gmel. Palla) often used in bioretention basins while emerging from dormancy in either flooded or drought conditions. Results indicate that only S. tabernaemontani was affected morphologically by drought with lower leaf area and aboveground biomass. While significant reductions in stomatal surface indices were also observed in drought-treated S. tabernaemontani, all three species had reductions in stomatal conductance ( g) when grown in drier soils. Moreover, drought conditions promoted decreases in leaf water potential ( Ψ) for all three species, and reductions in tissue water content ( θ) for P. cordata and S. tabernaemontani. Based on the overall morphological and physiological responses, S. cernuus maintained the lowest productivity, and appeared to be the best suited for tolerating sustained soil water deficits. If high plant productivity is desired, however, S. tabernaemontani was able to maintain high plant growth while making necessary modifications that facilitated greater drought-resistance. [ABSTRACT FROM AUTHOR]

The objective of this study was to evaluate the impact of drought and flooding on the photosynthetic activity of Japanese plum (Prunus salicina Lindh), cultivar 'America'. We analyzed the chlorophyll fluorescence and leaf gas exchange in plants, with approximately 12 months, grown in greenhouse and subjected to water deficit. Analyses were initiated two days after the onset of drought and one day after the flooding, resulting in four evaluations during the maintenance of stress. Net photosynthesis was reduced by stomatal limitation in both stresses. The condition of water restriction did not alter the maximum quantum yield. The photosynthetic performance indexes showed differences between stresses, featuring the plants of plum cv America as the most susceptible to drought than flooding. [ABSTRACT FROM AUTHOR]

Studying tolerance limits in organisms exposed to climatic variations is key to understanding effects on behaviour and physiology. The presence of pollutants may influence these tolerance limits, by altering the toxicity or bioavailability of the chemical. In this work, the plant species Brassica rapa and Triticum aestivum and the earthworm Eisenia andrei were exposed to different levels of soil moisture and carbaryl, as natural and chemical stressors, respectively. Both stress factors were tested individually, as well as in combination. Acute and chronic tests were performed and results were discussed in order to evaluate the responses of organisms to the combination of stressors. When possible, data was fitted to widely employed models for describing chemical mixture responses. Synergistic interactions were observed in earthworms exposed to carbaryl and drought conditions, while antagonistic interactions were more representative for plants, especially in relation to biomass loss under flood-simulation conditions. [Copyright &y& Elsevier]

Abstract  The impact of long-term seasonal soil freezing, drought, and waterlogging on the rhizosphere of young Scots pine trees (Pinus sylvestris L., age class 1) has been simulated in experiments. The results have shown that cold stress exposure leads to reduction of the rates of linear and radial tree growth and of chlorophyll content in needles, a shift in the peak of starch content, and initiation of free amino acid deposition in the aboveground plant parts. Drought activates utilization of carbohydrate reserves and amino acid accumulation in the root bast, whereas soil waterlogging stimulates deposition of carbohydrates but causes a decrease in the levels of chlorophyll and amino acids in all plant tissues. [ABSTRACT FROM AUTHOR]

The article focuses on the effects of droughts, floods and hurricanes on violets. Drought conditions often lead to lowering of water levels causing oxygen level depletion, which results to higher bacteria level in water that can affect plants. Flooding conditions create water flows from farmlands that often contain high nitrogen, which can be mixed into the water supply of plants. It suggests to plant growers to learn about the water supply source and be aware of the possible environmental changes.