Effects Of Short-term Drought Research Articles

Effects of short-term drought, nitrogen application and their interactions on the composition and functional genes of soil microbial communities in alfalfa grassland on the Loess Plateau

Drought and nitrogen addition are important factors influencing soil microorganisms and changes in the soil environment. In the future, droughts will become more frequent, shorter, and more severe. However, little is known about the soil organic carbon components, enzyme activity, and composition, structure, and functional genes of soil microbial communities under short-term drought and nitrogen application conditions. In this study, we used metagenomics sequencing technology to explore the changes in the composition and functional genes of soil microbial communities under short-term drought, nitrogen application, and their interactions in the artificial grasslands of the Loess Plateau. The results indicated that (I) short-term drought, nitrogen application, and their interactions all increased the particulate organic carbon (POC) content. (II) Short-term drought increased the contents of soil microbial biomass carbon (MBC) and microbial biomass nitrogen (MBN), as well as soil enzyme activity. (III) Short-term drought significantly increased the bacterial alpha diversity, whereas the interactions of short-term drought and nitrogen application enhanced the fungal alpha diversity. (IV) The interactions of short-term drought and nitrogen application inhibited Fusarium to prevent plant diseases. (V) Short-term drought enriched the relative abundance of genes related to carbon cycling and amino acid metabolism, while nitrogen application reduced genes related to carbon cycling but enriched genes related to glycan biosynthesis and metabolism. These results clearly showed that, short-term drought altered the composition and functional genes of soil microbial communities. Our research suggests that in the event of frequent short-term droughts in the future, nitrogen addition can be considered to maintain the diversity of soil microbial communities and sustain soil carbon and nitrogen cycling.

Expression patterns of maize PIP aquaporins in middle or upper leaves correlate with their different physiological responses to drought and mycorrhiza.

Here we report the effect of Rhizophagus irregularis on maize leaf expression of six plasma membrane aquaporin isoforms from PIP1 and PIP2 subfamilies under severe drought development and recovery. The novelty of our study is the finding that leaf-specific mycorrhizal regulation of aquaporins is dependent on the position of the leaf on the shoot and changes in parallel with the rate of photosynthesis and the stomatal response to drought. The transcripts were isolated from the upper third (L3) or ear (L5) leaf, which differed greatly in physiological response to stress within each symbiotic variant. Aquaporins expression in upper L3 leaves appeared to be largely not sensitive to drought, regardless of symbiotic status. In contrast, L5 leaf of non-mycorrhizal plants, showed strong down-regulation of all PIPs. Mycorrhiza, however, protected L5 leaf from such limitation, which under maximal stress was manifested by 6-fold and circa 4-fold higher transcripts level for PIP1s and PIP2s, respectively. Distinct expression patterns of L3 and L5 leaves corresponded to differences in key parameters of leaf homeostasis - stomatal conductance, photosynthetic rates, and accumulation of ABA and SA as phytohormonal indicators of drought stress. In result symbiotic plants showed faster restoration of photosynthetic capability, regardless of leaf position, which we recognize as the hallmark of better stress tolerance. In summary, arbuscular mycorrhiza alleviates short-term drought effects on maize by preventing the down-regulation of plasma membrane aquaporins within middle leaves, thereby affecting stomatal conductance.

Enhancing Common Bean Tolerance to Short-term Droughts at the Reproductive Stage using a Soil Fertility Management Approach

Aims: This study was conducted to enhance the tolerance of common beans to drought events occurring at the reproductive stage, from a soil improvement perspective.
 Study Design: Split plot completely randomized design was used.
 Place and Duration of Study: Study was conducted in a screen-house at the Legumes and Oil Seeds Division of CSIR-Crops Research Institute, Ghana, from September 2021 to January 2022.
 Methodology: Municipal Solid Waste Compost and inorganic fertilizer combinations were applied to common beans in a pot experiment. They included control, full rate compost (FRAC), full rate fertilizer (NPK 5:30:30 kg/ha) (FRG), FRG + half rate compost (HRAC) and FRG + FRAC. All soils were maintained at 80% field capacity (FC) from the start of the experiment. At flowering, two groups of plants were water stressed till 40 and 16% FC and returned to 80% FC till physiological maturity, while one group maintained 80% FC throughout study. Forty-five soil samples each and plant data were collected at 3, 7 and 10 weeks after planting. Samples were analyzed for soil organic matter (SOM) and water retention, soil nutrients, crop growth, yield and nutrient uptake. Water and nitrogen use efficiencies (W/NUE) were calculated after harvest.
 Results: During the growing period, highest soil moisture (6-9 cm3/cm3) was retained by FRG and FRG+HRAC, FRG+FRAC; 20-38% more than FRAC and control but was not influenced by SOM. While FRG influenced the highest yield and WUE, combining it with compost rates reduced yield by 56-84% and WUE by 55-64%. WUE correlated positively with NUE.
 Conclusion: Antagonistic effect observed with integrating compost with FRG is likely because compost was not properly cured and immobilized soil nitrogen. Farmers can mitigate short-term drought effects on common beans with adequate nutrient supply through fertilizer application; however, fertilizer should only be integrated with compost after compost quality analysis.

Meeting the Drought Information Needs of Midwest Perennial Specialty Crop Producers

Abstract Agricultural production in the U.S. Midwest is vulnerable to drought, and specialty crop producers are an underserved audience for monitoring information and decision-support tools. We investigate the decision-making needs of apple, grape, and cranberry growers using a participatory process to develop crop-specific decision calendars. The process highlights growers’ decisions and information needs during the winter dormant, growing, harvest, and postharvest seasons. Apple, grape, and cranberry growers tend to be concerned with the effects of short-term drought on current crop quality and quantity, while also considering the long-term drought effect on the health of perennial plants and future years’ production. We find gaps in drought information particularly for tactical and strategic decision-making. We describe the use of decision calendars to identify points of entry for existing drought monitoring resources and tools, and to highlight where additional research and tool development is needed. Significance Statement While drought causes agricultural losses in the U.S. Midwest, more is known about the impacts and decision-support needs of commodity row crop growers in the region than those of perennial specialty crop growers. We find opportunities for climate information providers to tailor drought information delivery to perennial fruit growers according to the season, the parameters that are relevant to their decisions, and the timeframe of information needed for operational, tactical, and strategic decision-making.

Microbial functional genes influenced by short-term experimental drought across European agricultural fields

Agricultural intensification and extreme weather events can represent considerable stress to soil microorganisms and their functions by influencing the key players behind the degradation of soil organic matter. A better understanding of the diversity and abundance of microbial functional genes that predict the functional potential of soils, can link the microbial communities to their key ecosystem functions. As there are still gaps in understanding how the functional genetic diversity behind microbial extracellular enzymes is influenced by events like drought and soil carbon management, an agricultural experiment over a range of different climatic conditions and soil properties was set-up across Europe. In Sweden, Germany and Spain, fields with varying levels of soil organic carbon were subjected to a short-term experimental drought. The diversity and composition of genes encoding for carbohydrate-related extracellular enzymes were determined using a ‘captured metagenomics' technique. Functional gene diversity differed among the European regions and to a range of soil factors such as organic carbon and water content. The functional and taxonomic gene composition significantly differed between the climatic regions, while an effect of short-term drought was only observed in Germany. The results indicate that some soil microbial communities and their functional genes displayed a certain degree of resistance. The results suggest that soil microbial communities respond differently to short-term drought mainly due to regional adaptations to already dry environments and differences in their soil physicochemical properties.

Rapid stomatal response in lemon saves trees and their fruit yields under summer desiccation, but fails under recurring droughts

Lemon (Citrus limon) is a fruit tree with major agricultural importance around the Mediterranean basin and is considered to be highly drought resistant. In this study, we tested the effect of two months summer-desiccation on physiological and yield parameters of mature lemon trees growing under Mediterranean climate during three consecutive years. We also examined the efficiency of current irrigation regime, which is based on reference evapo-transpiration. We measured leaf gas exchange and water potential (Ѱl), monitored sap flow and soil moisture and followed flowering, fruit set and fruit size. Lemon trees showed an isohydric stomatal regulation, as stomata maintained leaf water potential >-2 MPa. Summer desiccation caused a gradual decrease in diurnal tree water use, starting immediately after cessation of irrigation, with leaf gas exchange practically halted at the end of the drought period. Tree function recovered following re-irrigation, and fruit yields were not reduced, but even mildly increased during the first year. In contrast, summer desiccation during two consecutive years caused long-term effects of tree activity decrease, significantly lower yield, main branch collapse and even tree mortality. Irrigation amounts matched closely tree water-use amounts; soil moisture was maintained around 26% (v/v); and irrigation responded dynamically to meteorological changes, indicating that current irrigation regime represents highly efficient water management. The lemon desiccation protocol relied on the physiological capacity of this species to avoid short-term drought effects through stomatal closure. Still, this protocol must be managed carefully, to reduce risk to trees and save yields.

Short-term effects of drought on daily mortality in Spain from 2000 to 2009

Spain is a country of southern Europe that is prone to drought, and it is likely that this type of hydrological extreme will become substantially more frequent and intense in the 21st century, which could lead to greater health risks if adequate adaptive measures are not taken. For the first time, we calculated the relative risks (RRs) of daily natural (ICD10: A00–R99), circulatory (ICD10: I00–I99), and respiratory (ICD: J00–J99) mortality associated with drought events in each province of Spain from 2000 to 2009. For this purpose, we compared the performance of the Standardized Precipitation Index (SPI) and Standardized Precipitation- Evapotranspiration Index (SPEI) obtained at 1 month of accumulation (denoted as SPI-1/SPEI-1) to estimate the short-term risks of droughts on daily mortality using generalised linear models. Attributable risks were calculated from the RR data. The main findings of this study revealed statistically significant associations between the different causes of daily mortality and drought events for the different provinces of Spain, and clear spatial heterogeneity was observed across the country. Western Spain (northwest to southwest) was the region most affected, in contrast to northern and eastern Spain, and daily respiratory mortality was the group most strongly linked to the incidence of drought conditions. Moreover, for a considerable number of provinces, the effect of SPI-1 and SPEI-1 largely reflected the impact of atmospheric pollution and/or heatwaves; however, for other regions, the effect of drought conditions on daily mortality remained when these different climatic events were controlled in Poisson models. When the performances of the SPEI and SPI were compared to identify and estimate the risks of drought on daily mortality, the results were very similar, although there were slight differences in the specific causes of daily mortality.

Does Protein Glycation Impact on the Drought-Related Changes in Metabolism and Nutritional Properties of Mature Pea (Pisum sativum L.) Seeds?

Protein glycation is usually referred to as an array of non-enzymatic post-translational modifications formed by reducing sugars and carbonyl products of their degradation. The resulting advanced glycation end products (AGEs) represent a heterogeneous group of covalent adducts, known for their pro-inflammatory effects in mammals, and impacting on pathogenesis of metabolic diseases and ageing. In plants, AGEs are the markers of tissue ageing and response to environmental stressors, the most prominent of which is drought. Although water deficit enhances protein glycation in leaves, its effect on seed glycation profiles is still unknown. Moreover, the effect of drought on biological activities of seed protein in mammalian systems is still unstudied with respect to glycation. Therefore, here we address the effects of a short-term drought on the patterns of seed protein-bound AGEs and accompanying alterations in pro-inflammatory properties of seed protein in the context of seed metabolome dynamics. A short-term drought, simulated as polyethylene glycol-induced osmotic stress and applied at the stage of seed filling, resulted in the dramatic suppression of primary seed metabolism, although the secondary metabolome was minimally affected. This was accompanied with significant suppression of NF-kB activation in human SH-SY5Y neuroblastoma cells after a treatment with protein hydrolyzates, isolated from the mature seeds of drought-treated plants. This effect could not be attributed to formation of known AGEs. Most likely, the prospective anti-inflammatory effect of short-term drought is related to antioxidant effect of unknown secondary metabolite protein adducts, or down-regulation of unknown plant-specific AGEs due to suppression of energy metabolism during seed filling.

Arbuscular Mycorrhiza in Highly Fertilized Maize Cultures Alleviates Short-Term Drought Effects but Does Not Improve Fodder Yield and Quality.

Under fertilization levels specific to intensive farming, the impact of compensation of soil nutritional value by arbuscular mycorrhiza (AM) might be limited. Therefore, the question arises whether modern crop varieties, selected for high NPK assimilation rate, are able to gain symbiotic benefits under other challenging field conditions, such as drought. Accordingly, in this study we aimed to evaluate the contribution of Rhizophagus irregularis to the drought response of a stay-green corn hybrid in pot cultures equally fertilized until silking, compared to non-mycorrhizal (NM) counterparts. The highest tested fertilization regime not detrimental to the long-term vitality of intraradical hyphae reached the levels recommended for field cultivation of silage corn, except phosphorus application restricted to 60%. Under normal watering, mycorrhiza increased leaf nitrogen and phosphorus acquisition but only in cultures supplied with low NPK levels. At high fertilization levels, only the older leaves retained AM dependency, whereas for other leaf positions the AM-NM differences were leveled out. The similar size and nutritional status of highly fertilized AM and NM cultures, used in this study, eliminated fungal benefits before and during the 2-week drought progression. Nevertheless, mycorrhizal contribution became evident at the time of renewed watering, when AM plants showed much faster reversal of drought-induced leaf senescence symptoms: impaired photosynthesis and nitrogen management. Our results suggest that mycorrhiza can alter drought-induced senescence even in stay-green mutants. Moreover, this effect was apparently not mediated by AM-improved growth but triggered by activation of fungal transport at the time of recovery. Interestingly, the fungal protective potential was shown to be preserved at the expense of lowering AM vesicle number. It can be interpreted as engagement of hyphal nutritional resources targeted to maintain the symbiotic relationship despite the reduced vitality of the host. Finally, we compared the productivity of AM and NM cultures subjected to short-term drought at silking time and further fertilized with moderate or high NPK doses until the grain-filling stage. The yield and nutritive value of green forage showed that alleviation of drought-induced senescence by AM was not sufficient to have a significant positive effect on the final productivity compared to NM plants.

Short-term effects of drought on tropical forest do not fully predict impacts of repeated or long-term drought: gas exchange versus growth.

Are short-term responses by tropical rainforest to drought (e.g. during El Niño) sufficient to predict changes over the long-term, or from repeated drought? Using the world's only long-term (16-year) drought experiment in tropical forest we examine predictability from short-term measurements (1–2 years). Transpiration was maximized in droughted forest: it consumed all available throughfall throughout the 16 years of study. Leaf photosynthetic capacity was maintained, but only when averaged across tree size groups. Annual transpiration in droughted forest was less than in control, with initial reductions (at high biomass) imposed by foliar stomatal control. Tree mortality increased after year three, leading to an overall biomass loss of 40%; over the long-term, the main constraint on transpiration was thus imposed by the associated reduction in sapwood area. Altered tree mortality risk may prove predictable from soil and plant hydraulics, but additional monitoring is needed to test whether future biomass will stabilize or collapse. Allocation of assimilate differed over time: stem growth and reproductive output declined in the short-term, but following mortality-related changes in resource availability, both showed long-term resilience, with partial or full recovery. Understanding and simulation of these phenomena and related trade-offs in allocation will advance more effectively through greater use of optimization and probabilistic modelling approaches.This article is part of a discussion meeting issue ‘The impact of the 2015/2016 El Niño on the terrestrial tropical carbon cycle: patterns, mechanisms and implications’.

Drought consistently alters the composition of soil fungal and bacterial communities in grasslands from two continents.

The effects of short-term drought on soil microbial communities remain largely unexplored, particularly at large scales and under field conditions. We used seven experimental sites from two continents (North America and Australia) to evaluate the impacts of imposed extreme drought on the abundance, community composition, richness, and function of soil bacterial and fungal communities. The sites encompassed different grassland ecosystems spanning a wide range of climatic and soil properties. Drought significantly altered the community composition of soil bacteria and, to a lesser extent, fungi in grasslands from two continents. The magnitude of the fungal community change was directly proportional to the precipitation gradient. This greater fungal sensitivity to drought at more mesic sites contrasts with the generally observed pattern of greater drought sensitivity of plant communities in more arid grasslands, suggesting that plant and microbial communities may respond differently along precipitation gradients. Actinobateria, and Chloroflexi, bacterial phyla typically dominant in dry environments, increased their relative abundance in response to drought, whereas Glomeromycetes, a fungal class regarded as widely symbiotic, decreased in relative abundance. The response of Chlamydiae and Tenericutes, two phyla of mostly pathogenic species, decreased and increased along the precipitation gradient, respectively. Soil enzyme activity consistently increased under drought, a response that was attributed to drought-induced changes in microbial community structure rather than to changes in abundance and diversity. Our results provide evidence that drought has a widespread effect on the assembly of microbial communities, one of the major drivers of soil function in terrestrial ecosystems. Such responses may have important implications for the provision of key ecosystem services, including nutrient cycling, and may result in the weakening of plant-microbial interactions and a greater incidence of certain soil-borne diseases.

Short Term Effects of Drought on Communal Conflict in Nigeria

Despite the surge in quantitative research examining the link between climate variability and conflict, a lot of uncertainty exists concerning whether there is a link. One shortcoming of the current literature is that it focuses mainly on statistical inference in order to establish causation with little attention for the predictive performance of the model. In contrast, this study extends the current literature by focusing on the predictive accuracy of a model linking droughts to communal conflict using data for Nigeria for the period 2006-2014. Using a number of different model specifications and estimation methods to test the robustness of the results, the analysis shows that although the regression results show a positive link between the occurrence of droughts and communal conflict, the predictive accuracy of the model is relatively low. In contrast, accounting for the temporal and spatial dynamics of conflict leads to better forecasts compared to the climate variable.

DYNAMIC EFFECTS OF DROUGHT ON U.S. CROP AND LIVESTOCK SECTORS

AbstractThis study investigates the long-term adjustments to drought by crop and livestock sectors using a dynamic partial equilibrium quarterly model of the U.S. agricultural economy. Results show that short-term drought effects including increases in crop and forage prices are in tandem with decreased live cattle prices resulting from drought-induced beef cattle herd liquidation. Crop price increases in the long run cause livestock inventory reductions, leading to fewer animals moving through the U.S. meat supply chain and increased livestock prices. Longer-term market adjustments cause a significant decrease in consumer surplus, and prolonged drought amplifies and extends the model-predicted results.

Effects of Short-term Drought Stress and Mechanical Harvesting on Sweet Orange Tree Health, Water Uptake, and Yield

One of the primary reasons for the slow adoption of mechanical harvesting by Florida citrus growers is the physical injuries associated with it, including loss of leaves, twigs, flowers, and young fruits, limb breakage, and injuries to the bark and root. However, it has been shown that well-managed trees are capable of tolerating defoliation, limb loss, and root and bark injury caused by mechanical harvesting. Irrigation management is one of the most crucial factors that influence citrus tree health. A multiple-year field study was conducted on ‘Valencia’ sweet orange trees in a commercial citrus grove near Immokalee, FL, to determine the effect of initial tree canopy density and short-term drought stress on tree health, water uptake, and productivity of mechanically harvested trees. Three blocks were based on canopy density and overall appearance and indicated as low, moderate, and high canopy density. The experiment was laid in a split-plot design with four replications of six-tree plots of hand-harvested or mechanically harvested trees, taking drought stress or full irrigation as main treatments. The experimental design was repeated with trees in each plot of one of the three canopy density categories. After harvest, each six-tree plot was split into two three-tree subplots, where one subplot was drought-stressed and the other was fully irrigated. Harvesting was conducted in the Spring of 2010, 2011, and 2012 with the same experimental design and data collection procedures. The effects of short-term drought on water use and stem water potential were masked by heavy rains in Spring 2010 and thus no differences in the irrigation treatments were observed. In 2011 and 2012, stem water potential was unaffected by harvesting method. Water use was unaffected by harvesting method across the 3 years. Drought stress significantly increased pull force required to remove fruit and stem water potential after harvest. Although mechanically harvested trees lost leaf mass, with no rain before harvest, results from Spring 2011 and 2012 indicated that short-term drought stress had no effect on citrus leaf area irrespective of harvest method. Drought stress significantly increased fruit detachment force in low and moderate density but not in high-density trees resulting in increased force required to remove fruit from trees with moderate- to low-density canopies. Yield increased from 2010 to 2011 for mechanically harvested trees compared with hand-harvested for low-canopy density trees by 17% and moderate-canopy density trees by 8%, whereas high-density plots indicated similar yield after mechanical harvesting. Comparatively, yield in 2012 decreased in the low and moderate densities compared with yield in 2011 but increased in the high density by 14% and 53% in hand- and machine-harvested trees, respectively. Despite finding 2- to 3-fold more debris in the mechanically harvested trees than the hand-harvested trees, yields and other measured parameters were unaffected suggesting that mechanical harvesting of citrus trees did not have an adverse effect on growth and production of well-watered citrus trees.

弱光下水分胁迫对不同产地披针叶茴香幼苗生理特性的影响

PDF HTML阅读 XML下载 导出引用 引用提醒 弱光下水分胁迫对不同产地披针叶茴香幼苗生理特性的影响 DOI: 10.5846/stxb201209241351 作者: 作者单位: 中国林业科学研究院亚热带林业研究所,中国林业科学研究院亚热带林业研究所,中国林业科学研究院亚热带林业研究所 作者简介: 通讯作者: 中图分类号: 基金项目: 浙江省科技计划资助项目（2009C32097） Effects of water stress on physiological characteristics of different Illicium lanceolatum ecotypes under low light intensity Author: Affiliation: Research Institute of Subtropical of Forestry,Chinese Academy of Forestry,, Fund Project: 摘要 | 图/表 | 访问统计 | 参考文献 | 相似文献 | 引证文献 | 资源附件 | 文章评论 摘要:选用4个不同产地披针叶茴香（Illicium lanceolatum）（浙江临安（LA）、浙江开化（KH）、江西武宁（WN）和福建南平（NP））1年生盆栽幼苗为试验材料，设置3个光照处理（Ⅰ：25 μmol·m-2·s-1；Ⅱ：50 μmol·m-2·s-1；Ⅲ：75 μmol·m-2·s-1）和2个水分处理（正常供水（CK）和自然干旱2d），探讨弱光环境下短期干旱对披针叶茴香幼苗生理特性及适应性的影响。结果表明：两种水分处理下，披针叶茴香幼苗抗氧化酶活性和渗透调节物质含量对弱光的敏感性存在明显差异。在光处理Ⅱ和Ⅲ条件下，WN产地幼苗经2d水分胁迫后，过氧化氢酶（CAT）活性比正常水分条件明显增加，过氧化物酶（POD）活性在光处理Ⅲ下比正常水分条件的显著增加，各光处理下超氧化物歧化酶（SOD）活性比正常水分的显著下降，丙二醛（MDA）含量相反。水分胁迫后，各光处理下LA产地幼苗的SOD和POD酶活性低于正常水分条件的，可溶性蛋白和MDA含量均较正常水分处理的增加。与正常水分条件相比，水分胁迫后的KH产地幼苗SOD、POD和CAT酶活性在光处理Ⅰ下均显著增加，可溶性蛋白和MDA含量有所下降。NP产地幼苗各光处理的酶活性均表现出水分胁迫后的比正常水分下的有所提高。可知，短期水分胁迫对提高KH、WN和NP产地幼苗对弱光环境的适应性具有显著促进作用。研究揭示短期水分胁迫可通过增加抗氧化酶活性和渗透调节物质含量来提高幼苗对弱光的适应性。 Abstract:Low availability of soil moisture is considered a major limiting factor for plant growth and crop yield worldwide, and it turns to be a more serious problem under the context of global change. A weak light stress, resulting from significantly lower light intensity than light saturation point of plant in long time, will affect the morphogenesis and physiological and biochemical processes of plant. The Chinese anise (Illicium lanceolatum), a traditional medicinal plant in China, has high content of shikimic acids which have effects of antiphlogosis and analgesis, and can reduce platelet aggregation and suppress vascular and cerebral thrombosis. Shikimic acid can also be an intermediate for antivirus and anticancer drugs. Scattering in its natural habitats, I.lanceolatum resources have experienced a rapid decline due to overexploitation. Therefore, it is necessary to study the protection and development strategies of I.lanceolatum resources. Soil moisture and light intensity are important restrictive impact factors for growth and biomass accumulation of I.lanceolatum seedlings. Until now, there is no reports about the mechanism of this species' response to water and light conditions. In order to explore the effect of short-term drought on the plant physiological characteristics and its adaptive capacity under low light intensity, a pot experiment was conducted with one year old I.lanceolatum seedlings for four ecotypes, respectively ecotypes from Linan Zhejiang (LA), Kaihua Zhejiang (KH), Wuning Jiangxi (WN) and Nanping Fujian (NP), treated under three low light intensity (Ⅰ:25μmol·m-2·s-1;Ⅱ:50 μmol·m-2·s-1;Ⅲ:75 μmol·m-2·s-1) and two water supply levels (normal water supply and watering after 2 days drought). The results showed that the sensitivity of antioxidant enzymes activity and osmotic substances contents of I.lanceolatum seedlings to low light intensity was significantly different between two water supply conditions. After 2 days' dought, catalase (CAT) activity of WN ecotype seedlings in the light treatments of Ⅱ and Ⅲ significantly increased compared with that under normal water condition, the peroxidase (POD) activity in the light treatments of Ⅲ also significantly increased, and the malondialdehyde (MDA) contents in all three light treatments increased while the superoxide dismutase (SOD) activity decreased. Under the water stress, the SOD and POD activity of LA ecotype seedlings in all light conditions were lower than those under normal water supply, and the soluble protein and MDA contents were higher. Compared with normal water supply, the SOD, POD and CAT activity of KH ecotype seedlings in the light treatment of Ⅰ increased significantly under water stress, while soluble protein and MDA content decreased. The enzymes activity of NP ecotype seedlings in all light treatments increased after short-term water stress. We concluded that the water stress can significantly promote the adaptability to weak light for KH, WN and NP ecotypes seedlings by increasing antioxidant enzymes activity and osmotic substances contents. This result will provide the theoretical foundation for ex-situ conservation, efficient cultivation, soil moisture and light condition management of I.lanceolatum. 参考文献 相似文献 引证文献

Inhibitory effects of drought induced acidification on phenol oxidase activities in Sphagnum-dominated peatland

Extracellular phenol oxidases play an important role in the soil carbon cycle. How phenol oxidase activity in peatlands will respond to increased aeration induced by water-table drawdown or droughts if global warming continues remains unclear. We investigated the short-term effects of drought induced acidification on phenol oxidase activities of a Sphagnum-dominated peatland in central China. The results indicated a significant acidification induced by drought, with a decline in the average pH value from 5.67 ± 0.08 under waterlogging to 4.84 ± 0.08 in droughted peat. In addition, drought-treated peat had a lower average value of phenol oxidase activities compared to the waterlogging-treated peat (mean values of 0.1404 ± 0.0305 and 0.2623 ± 0.0324 μmol diqc min−1 g−1, respectively). The decreased phenol oxidase activities were mainly attributed to the acidification induced by drought. However, the declines in phenol oxidase activity did not lead to the reduction of the degradation in the deeper peat. Under drought conditions, a considerable part of the adsorbed phenolics, consisting primarily of high molecular-weight organic substances with phenolic groups, were further degraded into smaller-sized or lower molecular weight hydrophilic fractions in the vicinity of the water table. Our results highlight the important role of the water table position in peat decomposition processes. Even with lower activities of phenol oxidase, the decomposition processes were able to effectively keep on going as long as there was sufficient supply of water, oxygen and nutrients.

Leaf physiology and sugar concentrations of transplanted Quercus rubra seedlings in relation to nutrient and water availability

Newly planted seedlings incur transplant stress resulting from poor root-soil contact, which limits access to soil moisture and nutrients and reduces growth for one or more growing seasons. Controlled release fertilizer (CRF) applied at planting may reduce transplant stress by augmenting rhizosphere nutrient availability yet with potential risk of root system damage due to elevated fertilizer salt concentrations, which may be further exacerbated by drought. Under controlled conditions, we examined northern red oak (Quercus rubra L.) leaf physiological parameters and soluble sugar concentrations in response to varying nutrient levels (via CRF application) and moisture availability gradients ranging from drought to flooding. Net photosynthetic rates, transpiration rates, and chlorophyll fluorescence parameters responded positively to CRF application, and no interactions were observed between CRF and moisture availability; however, CRF did not increase soluble sugar concentrations. No effects of short-term drought were observed, but flooding exerted a rapid negative influence on net photosynthetic rates, transpiration rates, and chlorophyll fluorescence parameters; flooding also elevated soluble sugar concentrations, indicative of disrupted carbon partitioning and a much greater sensitivity to root-zone hypoxia than to drought in this species. Lack of interactions between CRF application and soil moisture availability indicates relatively similar responses of fertilized seedlings across moisture gradients.

Exogenous 4-hydroxybenzoic acid and salicylic acid modulate the effect of short-term drought and freezing stress on wheat plants

Exogenous salicylic acid has been shown to confer tolerance against biotic and abiotic stresses. In the present work the ability of its analogue, 4-hydroxybenzoic acid to increase abiotic stress tolerance was demonstrated: it improved the drought tolerance of the winter wheat (Triticum aestivum L.) cv. Cheyenne and the freezing tolerance of the spring wheat cv. Chinese Spring. Salicylic acid, however, reduced the freezing tolerance of Cheyenne and the drought tolerance of Chinese Spring, in spite of an increase in the guaiacol peroxidase and ascorbate peroxidase activity. The induction of cross tolerance between drought and freezing stress was observed: drought acclimation increased the freezing tolerance of Cheyenne plants and cold acclimation enhanced the drought tolerance. The induction of drought tolerance in Cheyenne was correlated with an increase in catalase activity.

Mortality and growth of trees in peat-swamp and heath forests in Central Kalimantan after severe drought

Lowland forests in Central Kalimantan, Indonesian Borneo, are endangered by land conversion and the increasing frequency of severe drought. Knowledge of the tolerance of tropical trees to drought is urgent for the management of these lowland habitats. The short-term effects of drought on tree demography (mortality and growth) were investigated in an ever-wet riparian peat-swamp forest and a heath forest on coarse sandy soil after the 1997 El Nino Southern Oscillation (ENSO) event. This drought was unusually severe because little rain fell during the following rainy season. However, forest-wide mortality following the drought (1997–1999) was not critically high in the peat-swamp (6.13% yr−1) or heath (4.26% yr−1) forest. In both forests, standing trees frequently died during the dry season following the drought. The riparian peat-swamp forest was not flooded until 1998, after the prolonged drought in 1997. The hummock–hollow microtopography resulted in differential mortality of peat-swamp trees. On tall hummocks, standing death increased two-fold (4.99% yr−1) during the dry season, whereas uprooting decreased by one-third (0.85% yr−1) during the following rainy season. In contrast, tree growth was not affected by hummock height. Common canopy species were concentrated on tall hummocks and died standing more often than did understory species found in hollows, indicating species-specific mortality after the drought. The large stand basal area relative to the forest-wide growth rate in diameter suggested less resilience to drought by peat-swamp (45.6 m2 ha−1 and 0.0186 ln[cm] yr−1) than heath (27.9 m2 ha−1 and 0.0232 ln[cm] yr−1) forest. A single severe drought did not cause dramatic changes in the peat-swamp and heath forests; however, an increasing frequency of droughts similar in severity to that of the 1997 ENSO event may have the potential to alter the community structure and dynamics, leading to a consistent decline in Bornean lowland forests.

Short-term effects of drought and salinity on mineral nutrient distribution along growing leaves of maize seedlings

The objectives were to study the effect of drought and salinity on the spatial distribution of mineral nutrients along the growing leaves of maize. Maize plants were grown in a greenhouse in soil under drought and saline conditions for 23 days after sowing. At harvest, the spatial distribution of fresh weight and dry weight contents and mineral nutrient concentrations along growing leaves 4 and 5 of maize was determined. Drought and salinity reduced the fresh weight content regardless of leaf number and caused a similar reduction. However, they affected the dry weight content differently, resulting from the reduction in the relative water content by drought. The results showed that the change in ion concentration along the growing leaf axis for most ions is independent of treatments. Although both drought and salinity cause a low nutrient availability in soil and low nutrient transport in plants, this study showed that except for Na +, there was no difference in the concentrations of most ions at any given location between plants in the control and either of the drought or saline treatments. Thus, reduction in leaf growth under drought and saline conditions may be due to other causes rather than the limitation of nutrients in a short-term period of drought and salt stresses.