Physiological Drought Stress Research Articles

Acclimation of mature spruce and beech to five years of repeated summer drought – The role of stomatal conductance and leaf area adjustment for water use

Forests globally are experiencing severe droughts, leading to significant reductions in growth, crown dieback and even tree mortality. The ability of forest ecosystems to acclimate to prolonged and repeated droughts is critical for their survival with ongoing climate change. In a five-year throughfall exclusion experiment, we investigated the long-term physiological and morphological acclimation of mature Norway spruce (Picea abies [L.] KARST.) and European beech (Fagus sylvatica L.) to repeated summer drought at the leaf, shoot and whole tree level. Throughout the drought period, spruce reduced their total water use by 70 % to only 4–9 L per day and tree, while beech was less affected with about 30 % reduction of water use. During the first two summers, spruce achieved this by closing their stomata by up to 80 %. Additionally, from the second drought summer onwards, spruce produced shorter shoots and needles, resulting in a stepwise reduction of total leaf area of over 50 % by the end of the experiment. Surprisingly, no premature leaf loss was observed. This reduction in leaf area allowed a gradual increase in stomatal conductance. After the five-year drought experiment, water consumption per leaf area was the same as in the controls, while the total water consumption of spruce was still reduced. In contrast, beech showed no significant reduction in whole-tree leaf area, but nevertheless reduced water use by up to 50 % by stomatal closure. If the restriction of transpiration by stomatal closure is sufficient to ensure survival of Norway spruce during the first drought summers, then the slow but steady reduction in leaf area will ensure successful acclimation of water use, leading to reduced physiological drought stress and long-term survival. Neighboring beech appeared to benefit from the water-saving strategy of spruce by using the excess water.

Drought accentuates the role of mycorrhiza in phosphorus uptake, part II – The intraradical enzymatic response

Edaphic drought reduces phosphorus (P) diffusivity in soils and arbuscular mycorrhizal fungi (AMF) can compensate for this. We recently showed, along a high-resolution substrate moisture gradient, that AMF effectively deliver P to plants under drought from areas beyond the reach of roots. Here, we investigated how edaphic drought affected the active sites of P exchange between AMF and plants inside the roots using different histochemical stains.Inoculation of dwarf tomato plants (cv. MicroTom) with AMF (Rhizophagus irregularis) slightly increased water retention (decreased the water potential) in substrates, decreased root length, and increased shoot P concentrations compared to non-mycorrhizal plants. Despite their reduced root length, mycorrhizal tomato plants showed a surprisingly congruent physiological drought stress response with their non-mycorrhizal counterparts. However, the activity of alkaline phosphatase (ALP) detected in intraradical fungal structures decreased significantly as soil and xylem water potentials decreased. The decline of ALP activity with increasing drought intensity was accompanied by a reduction of elevated P concentration benefits in shoots of mycorrhizal plants compared to non-mycorrhizal plants.Therefore, we conclude that edaphic drought can restrict the nutritional advantages that plants receive from AMF at the root-fungal interface. This is one of the direct consequences of drought.

Characterization of wheat genotypes for PEG-induced physiological drought stress at seedling stage

Abiotic stresses like drought frequently reduce the productivity of wheat, an important global cereal crop farmed for food, feed and raw materials. Therefore, attempt should be made to search for drought tolerance in wheat cultivars. The purpose of the study was to look into how morphological features thirty wheat genotypes were affected by PEG-induced physiological drought stress at germination and seedling stages. Seven morphological traits viz germination percentage, root number, shoot length, shoot fresh weight, root fresh weight, shoot dry weight, root dry weight was measured at 14 days of stress condition and significant variation was observed in most of the traits due to genotypes, treatments, and genotype × treatment interaction. Drought stress causes a significant decrease in almost all morphological traits during the germination and early seedling stages, and among the genotypes SA-2 and SA-3 were performed best. A positive significant correlation was found among the morphological traits, except for fresh and dry weight of shoot. Principle Component Analysis (PCA) showed that only first two PCs were significant and had eigenvalues > 1. The first two PCs cover the 72.78% of total variation. Multi Trait Stability Index (MTSI) showed that SA-3, SA-2, BL-1020 and PV-79 performed well in drought stress condition and these genotypes can be further used for breeding program to develop drought tolerant high yielding wheat variety.

Satellite solar-induced chlorophyll fluorescence tracks physiological drought stress development during 2020 southwest US drought.

Monitoring and estimating drought impact on plant physiological processes over large regions remains a major challenge for remote sensing and land surface modeling, with important implications for understanding plant mortality mechanisms and predicting the climate change impact on terrestrial carbon and water cycles. The Orbiting Carbon Observatory 3 (OCO-3), with its unique diurnal observing capability, offers a new opportunity to track drought stress on plant physiology. Using radiative transfer and machine learning modeling, we derive a metric of afternoon photosynthetic depression from OCO-3 solar-induced chlorophyll fluorescence (SIF) as an indicator of plant physiological drought stress. This unique diurnal signal enables a spatially explicit mapping of plants' physiological response to drought. Using OCO-3 observations, we detect a widespread increasing drought stress during the 2020 southwest US drought. Although the physiological drought stress is largely related to the vapor pressure deficit (VPD), our results suggest that plants' sensitivity to VPD increases as the drought intensifies and VPD sensitivity develops differently for shrublands and grasslands. Our findings highlight the potential of using diurnal satellite SIF observations to advance the mechanistic understanding of drought impact on terrestrial ecosystems and to improve land surface modeling.

Improvement of Salinity Tolerance in Water-Saving and Drought-Resistance Rice (WDR)

Rice is one of the most economically important staple food crops in the world. Soil salinization and drought seriously restrict sustainable rice production. Drought aggravates the degree of soil salinization, and, at the same time, increased soil salinity also inhibits water absorption, resulting in physiological drought stress. Salt tolerance in rice is a complex quantitative trait controlled by multiple genes. This review presents and discusses the recent research developments on salt stress impact on rice growth, rice salt tolerance mechanisms, the identification and selection of salt-tolerant rice resources, and strategies to improve rice salt tolerance. In recent years, the increased cultivation of water-saving and drought-resistance rice (WDR) has shown great application potential in alleviating the water resource crisis and ensuring food and ecological security. Here, we present an innovative germplasm selection strategy of salt-tolerant WDR, using a population that is developed by recurrent selection based on dominant genic male sterility. We aim to provide a reference for efficient genetic improvement and germplasm innovation of complex traits (drought and salt tolerance) that can be translated into breeding all economically important cereal crops.

Variety-Specific Transcriptional and Alternative Splicing Regulations Modulate Salt Tolerance in Rice from Early Stage of Stress

Salt stress poses physiological drought, ionic toxicity and oxidative stress to plants, which causes premature senescence and death of the leaves if the stress sustained. Salt tolerance varied between different rice varieties, but how different rice varieties respond at the early stage of salt stress has been seldom studied comprehensively. By employing third generation sequencing technology, we compared gene expressional changes in leaves of three rice varieties that varied in their level of tolerance after salt stress treatment for 6 h. Commonly up-regulated genes in all rice varieties were related to water shortage response and carbon and amino acids metabolism at the early stage of salt stress, while reactive oxygen species cleavage genes were induced more in salt-tolerant rice. Unexpectedly, genes involved in chloroplast development and photosynthesis were more significantly down-regulated in the two salt tolerant rice varieties ‘C34’ and ‘Nona Bokra’. At the same time, genes coding ribosomal protein were suppressed to a more severe extent in the salt-sensitive rice variety ‘IR29’. Interestingly, not only variety-specific gene transcriptional regulation, but also variety-specific mRNA alternative splicing, on both coding and long-noncoding genes, were found at the early stage of salt stress. In summary, differential regulation in gene expression at both transcriptional and post-transcriptional levels, determine and fine-tune the observed response in level of damage in leaves of specific rice genotypes at early stage of salt stress.

Soil-plant interactions modulated water availability of Swiss forests during the 2015 and 2018 droughts.

Central Europe has been experiencing unprecedented droughts during the last decades, stressing the decrease in tree water availability. However, the assessment of physiological drought stress is challenging, and feedback between soil and vegetation is often omitted because of scarce belowground data. Here we aimed to model Swiss forests' water availability during the 2015 and 2018 droughts by implementing the mechanistic soil‐vegetation‐atmosphere‐transport (SVAT) model LWF‐Brook90 taking advantage of regionalized depth‐resolved soil information. We calibrated the model against soil matric potential data measured from 2014 to 2018 at 44 sites along a Swiss climatic and edaphic drought gradient. Swiss forest soils' storage capacity of plant‐available water ranged from 53 mm to 341 mm, with a median of 137 ± 42 mm down to the mean potential rooting depth of 1.2 m. Topsoil was the primary water source. However, trees switched to deeper soil water sources during drought. This effect was less pronounced for coniferous trees with a shallower rooting system than for deciduous trees, which resulted in a higher reduction of actual transpiration (transpiration deficit) in coniferous trees. Across Switzerland, forest trees reduced the transpiration by 23% (compared to potential transpiration) in 2015 and 2018, maintaining annual actual transpiration comparable to other years. Together with lower evaporative fluxes, the Swiss forests did not amplify the blue water deficit. The 2018 drought, characterized by a higher and more persistent transpiration deficit than in 2015, triggered widespread early wilting across Swiss forests that was better predicted by the SVAT‐derived mean soil matric potential in the rooting zone than by climatic predictors. Such feedback‐driven quantification of ecosystem water fluxes in the soil–plant‐atmosphere continuum will be crucial to predicting physiological drought stress under future climate extremes.

The potential of stable carbon isotope ratios and leaf temperature as proxies for drought stress in banana under field conditions

Drought stress is a major limiting factor for banana production and the incidence of drought spells is expected to increase with climate change. Climate smart practices and varieties are needed, but evaluation in the field is hampered by a lack of reliable physiological drought stress indicators. We investigated the potential of using stable carbon isotope ratios (δ13C) and leaf temperature and its derived DANS (Degrees above Non-Stressed Canopy) index as proxies for drought stress in banana. Leaf samples were taken for δ13C analysis and leaf temperature was monitored throughout the day in a field trial with different banana plant stages (mother and daughter plants) under two irrigation treatments (rainfed and irrigated) during the dry season in Arusha, Tanzania. We found that δ13C, leaf temperature and DANS were highly sensitive proxies for drought stress in banana. Soil volumetric water content had a significant effect on both δ13C values and DANS. There was a significant difference in δ13C (1.5 ± 0.1‰, p < 0.01) and afternoon leaf temperature (7 ± 1 °C, p < 0.01) between the rainfed and irrigated treatment. To deal with variability in δ13C within the leaf, we developed a banana tailored sampling method. This study also revealed the complexity of carbon isotope dynamics in the intertwined system of mother and daughter plants. Daughter plants had more negative δ13C values (−1.9 ± 0.1‰, p < 0.01) and lower temperatures (4 ± 1 °C) than mother plants. This indicates less stress, but interpretation of the δ13C ratio is complicated by the potential carbon flux from mother to daughter plant. Once we have a full understanding of these complexities within the plant, the δ13C and leaf temperature based methods we developed, can be directly implemented for both mother and daughter plants under various field conditions.

Functional Traits of Terrestrial Plants in the Intertidal: A Review on Mangrove Trees.

AbstractTrue mangroves are vascular plants (Tracheophyta) that evolved into inhabiting the mid and upper intertidal zone of tropical and subtropical soft-sediment coasts around the world. While several dozens of species are known from the Indo-West Pacific region, the Atlantic-East Pacific region is home to only a mere dozen of true mangrove species, most of which are rare. Mangrove trees can form dense monospecific or multispecies stands that provide numerous ecosystem services. Despite their eminent socioecological and socioeconomic relevance and the plethora of studies on mangroves, many details of the ecology of mangrove ecosystems remain unknown; and our knowledge about general ecological principles in mangrove ecosystems is scarce. For instance, the functional trait concept has hardly been applied to mangroves. Here we provide an inventory of 28 quantitative and 8 qualitative functional traits of true mangrove species and stipulate some insight into how these traits may drive ecosystem structure and processes. The differentiation between true mangroves and mangrove associates, which can dwell inside as well as outside mangrove forests, is reflected by a number of leaf traits. Thus, true mangroves exhibit lower specific leaf area, lower leaf N content, and lower K∶Na ratio, and higher leaf succulence, higher Na and Cl content, and higher osmolality than mangrove associates. True mangrove species that form pure stands produce larger leaves and exhibit higher N content per leaf area, higher leaf K and Ca content, greater maximum plant height, longer propagules, and lower root porosity than more sporadic species. The species-specific expression of most traits does not reflect the species' position along intertidal gradients, suggesting that adaptation to tidal inundation does not explain these traits. Rather, many of the traits studied herein exhibit strong phylogenetic signals in true mangroves. Thus, wood density is high in most species of the Rhizophoraceae, irrespective of their habitat or maximum height. On the other hand, species of the genus Sonneratia exhibit low wood density and do not grow taller than 20 m. Some leaf traits of true mangroves are more like those of plants from drier environments, reflecting the perception that a saline environment creates physiological drought stress. Along the same line, most true mangrove species exhibit sclerophyllous leaf traits. The few major mangrove tree species of the Atlantic-East Pacific are as distinct from each other, with regard to some traits, as are the many mangrove species of the Indo-West Pacific. We hypothesize that this phenomenon explains the similarly high biomass of mangrove forests in both the species-rich Indo-West Pacific and the species-poor Atlantic-East Pacific.

Rice aquaporin OsPIP2;2 is a water-transporting facilitator in relevance to drought-tolerant responses.

In rice (Oryza sativa), the PLASMA MEMBRANE INTRINSIC PROTEIN (PIP) family of aquaporin has 11 members, OsPIP1;1 to OsPIP1;3, and OsPIP2;1 to OsPIP2;8, which are hypothesized to facilitate the transport of H2O and other small compounds across cell membranes. To date, however, only OsPIP1;2, OsPIP2;1, and OsPIP2;4 have been demonstrated for substrate selectivity in their source plant (rice). In this study, OsPIP2;2 was characterized as the most efficient facilitator of H2O transport across cell membranes in comparison with the other 10 OsPIPs. In concomitant tests of all OsPIPs, four genes (OsPIP1;3, OsPIP2;1, OsPIP2;2, and OsPIP2;4) were induced to express in leaves of rice plants following a physiological drought stress, while OsPIP2;2 was expressed to the highest level. After de novo expression in frog oocytes and yeast cells, the four OsPIP proteins were localized to the plasma membranes in trimer and tetramer and displayed the activity to increase the membrane permeability to H2O. In comparison, OsPIP2;2 was most supportive to H2O import to oocytes and yeast cells. After de novo expression in tobacco protoplasts, OsPIP2;2 exceeded OsPIP1;3, OsPIP2;1, and OsPIP2;4 to support H2O transport across the plasma membranes. OsPIP2;2‐mediated H2O transport was accompanied by drought‐tolerant responses, including increases in concentrations of proline and polyamines, both of which are physiological markers of drought tolerance. In rice protoplasts, H2O transport and drought‐tolerant responses, which included expression of marker genes of drought tolerance pathway, were considerably enhanced by OsPIP2;2 overexpression but strongly inhibited by the gene silencing. Furthermore, OsPIP2;2 played a role in maintenance of the cell membrane integrity and effectively protected rice cells from electrolyte leakage caused by the physiological drought stress. These results suggest that OsPIP2;2 is a predominant facilitator of H2O transport in relevance to drought tolerance in the plant.

Effects of organic fertilizer application on flag leaf C/N ratio, photosynthetic characteristics and yield of spring wheat with full plastic film mulching

A field experiment was conducted in the rain-fed semi-arid region of central Gansu in 2016 and 2017, with the treatments 1) hill-drop flat planting with full plastic film mulching (PMS), 2) hill-drop flat planting with full plastic film mulching plus organic fertilizers (PMO), and 3) hill-drop flat planting without soil mulching (CK). We investigated the relations among soil moisture, photosynthetic rate (Pn), stomatal conductance (gs) and transpiration rate (Tr), C/N ratio, and total nitrogen of flag leaf from the heading stage to the seed-filling stage in different treatments to probe into their effects on the yield and yield components of spring wheat variety 'Longchun 27'. The results showed that organic fertilizer application could increase soil moisture at the middle and late growth stages of spring wheat. PMO increased soil water storage in 0-300 cm depth from the heading stage to the seed filling stage by 4.6% and 8.5%, decreased population canopy temperature by 0.1-1.3 ℃ and 1.4-4.9 ℃, increased net photosynthetic rate of flag leaf by 9.3% and 29.7%, stomatal conductance by 30.9% and 103.8%, transpiration rate by 5.1% and 55.0%, total nitrogen content by 6.6% and 18.9%, and decreased C/N ratio by 6.4% and 22.8%, respectively. Compared with PMS and CK, PMO significantly improved grain number per spike and 1000-grain weight, and increased grain yield by 9.1% and 53.7%, respectively. From the heading stage to filling stage, the Pn and gs of flag leaf had negative correlation with C/N, while C/N was negatively correlated with grain yield. Consequently, PMO could improve soil water storage and promote photosynthesis of flag leaf, reduce the intensity of physiological drought stress and the limitations of nitrogen absorption and assimilation in flag leaf from the heading stage to the seed-filling stage, and increase grain number and grain weight and consequently the yield of spring wheat in semi-arid region.

Early Growth Response of Hararghe Coffee Selections to Soil Moisture Deficit at Seedling Stage at Mechara, Eastern Ethiopia

Drought is among the major factors that adversely affect coffee production in most parts of Ethiopia. Hararghe coffee is despite its economic importance in the world market and in the national economy of the country; its productivity is very low primarily because of periodic soil moisture deficit stresses and many other factors. Therefore, this experiment was conducted to screen and evaluate Hararghe coffee genotypes for drought tolerant in response to soil moisture stresses. A total of nineteen coffee genotypes; fourteen promising coffee selections and five released varieties were evaluated for morphological and physiological drought stress traits using Completely Randomized Design with three replications. The experiment was conducted at Mechara Agricultural Research Center in a rain shelter. Eight pairs of true leaf coffee seedlings were subjected to two watering regimes (water-stress by withholding irrigation and well-watered control). The analysis of variance results revealed significant variation among coffee genotypes for water deficit stress. Therefore, based on preliminary observations and visual assessments of recovery plants, the genotypes were grouped into three categories of drought tolerance; sensitive, moderately sensitive and relatively tolerant. However, genotypes from each category should also be tested for their morphological, physiological and biochemical responses to drought in order to identify more tolerant types and come up with a recommendation for further selection and breeding works for drier coffee growing areas of the country.

Topographic, edaphic and climate influences on aspen (Populus tremuloides) drought stress on an intermountain bunchgrass prairie

Quaking aspen, Populus tremuloides, has experienced severe declines in recent years in part due to the effects of changing climate and extreme drought. This study set out to investigate these effects by assessing associations of climatic, edaphic and topographic variables with physiological drought stress in aspen. The study took place on the Zumwalt Prairie in northeastern Oregon, a semi-arid bunchgrass prairie where aspen occur in isolated stands associated with riparian areas and late-season persistence of snow drifts. Using a 33-year time series of Landsat imagery to detect associations of aspen stands late-season snow cover and field measurements of soil moisture in aspen stands during 2017, we found while snow dominated stands were associated with greater soil moisture during spring, levels had equilibrated to those of other upland stands by summer. Measurements of predawn and midday stem Ψ in multiple height classes of aspen ramets revealed associations of both shallow soil moisture and vapor pressure deficit with physiological drought stress in aspen. Analysis of soil texture class revealed an important association with midday stem Ψ, with finer textured soils associated with decreased stem Ψ in comparison to coarser textured soils. While neither topographical characteristics nor snow cover were found to be important drivers of drought stress, topographical curvature was found to have a strong influence on summer soil moisture in upland stands. These findings contribute to our understanding of aspen physiology, drought ecology and landscape hydrology toward the xeric margin of aspen’s range. This information can help land managers anticipate and adapt to changing climates and understand their effects on key plant species such as aspen.

Drought adaptation in populations of Inga vera subsp. affinis (DC.) T.D.Penn. that are exposed to extensive seasonal flooding

Inga vera Willd. subsp. affinis (DC.) T.D.Penn. is a main component of riparian forests, widely used in agroforestry in many parts of tropical south America and can thrive in a variety of environments that include sites that are flooded for up to six months. Here, we contribute a wood anatomical study in flooded versus non-flooded environments to discover features that enable the wide environmental plasticity of this species. Population differences in anatomical and structural traits point to a drought adaptation syndrome in the flooded population sample. Four anatomical traits, vessel lumen diameter, intervessel pit diameter, fiber lumen diameter and fiber length showed significant population differences. Further, scanning electron microscopy revealed qualitative differences in vestures on the inside walls of vessel elements. Our results support the view that flood conditions can paradoxically induce physiological drought stress due to anaerobic conditions in the root zone, which leads to physiological and structural features normally observed in drought-adapted tree populations. Our observations also suggest that planting stock obtained from flooded areas may contain adaptive traits that could also be useful for cultivation and land reclamation applications under drier conditions that are anticipated in the future due to climate change.

Linking Forest Flammability and Plant Vulnerability to Drought

Globally, fire regimes are being altered by changing climatic conditions. New fire regimes have the potential to drive species extinctions and cause ecosystem state changes, with a range of consequences for ecosystem services. Despite the co-occurrence of forest fires with drought, current approaches to modelling flammability largely overlook the large body of research into plant vulnerability to drought. Here, we outline the mechanisms through which plant responses to drought may affect forest flammability, specifically fuel moisture and the ratio of dead to live fuels. We present a framework for modelling live fuel moisture content (moisture content of foliage and twigs) from soil water content and plant traits, including rooting patterns and leaf traits such as the turgor loss point, osmotic potential, elasticity and leaf mass per area. We also present evidence that physiological drought stress may contribute to previously observed fuel moisture thresholds in south-eastern Australia. Of particular relevance is leaf cavitation and subsequent shedding, which transforms live fuels into dead fuels, which are drier, and thus easier to ignite. We suggest that capitalising on drought research to inform wildfire research presents a major opportunity to develop new insights into wildfires, and new predictive models of seasonal fuel dynamics.

引黄灌区次生盐碱地速生杨光谱与光合特性对不同秸秆层的响应

PDF HTML阅读 XML下载 导出引用 引用提醒 引黄灌区次生盐碱地速生杨光谱与光合特性对不同秸秆层的响应 DOI: 10.5846/stxb201809051893 作者: 作者单位: 北京林业大学,宁夏大学新技术应用研究开发中心,北京林业大学理学院,宁夏大学新技术应用研究开发中心 作者简介: 通讯作者: 中图分类号: 基金项目: “宁夏（中阿）旱区资源评价与环境调控重点实验室”建设项目与宁夏科技支撑项目“银川国家农业园区盐渍化改良技术的研究与示范” Response of spectral reflectance and photosynthetic characteristics of fast-growing poplar (Populus) to different straw layers in secondary saline-alkali land in the Yellow River irrigation area Author: Affiliation: Beijing Forestry University,Development Center of New Technique Application and Research, Ningxia University,College of Science, Beijing Forestry University,Development Center of New Technique Application and Research, Ningxia University Fund Project: Ningxia(China-Arab) key laboratory of Resource Assessment and Environmental Regulation in Arid Region & Research and Demonstration on the Improvement Technology of Salinization in Yinchuan National Agricultural Park 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:在宁夏引黄灌区次生盐碱地，设置了填埋秸秆层（B）、覆盖秸秆层（M）、填埋配合覆盖秸秆层（B+M）和无任何处理（空白对照，CK）共4种处理，通过随机区组试验，在土壤水盐变化的基础上，通过分析速生杨光谱及光合特性对秸秆层响应，探究不同秸秆层的植物光合速率、色素含量、营养状况以及受胁迫等情况，以期更准确的反应出各处理的改良效果及植被恢复情况。研究结果表明：（1）秸秆层有助于提升灌区次生盐碱地速生杨的光谱与光合等生理状况。B、M和B+M均能显著提升速生杨叶片的最大净光合速率与饱和光强，其中，B和B+M还能够明显降低速生杨叶片的光补偿点和暗呼吸速率，M则不能。B和B+M均显著提高速生杨叶片的净光合速率、蒸腾速率、气孔导度等光合参数。另外，B+M的速生杨叶片光合色素含量最高，营养状况最好，其他光谱参数结果与CK相比都有显著提高。处理B和M也可以显著提高速生杨叶片光合色素含量和营养状况，但效果均不如B+M。（2）B与B+M均能降低不同时期的土壤盐分含量，但B+M在不同时期提高土壤含水量的效果均高于B。M也能降低土壤盐分和提升土壤含水量，但不同时期的效果均不如处理B+M。综合试验结果，在引黄灌区次生盐碱地，不同秸秆层均能不同程度的调节土壤水盐变化，缓解水盐胁迫，提升速生杨光合与光谱特性，其中B+M作为秸秆层效果最佳。 Abstract:Soil secondary salinization an escalating problem worldwide, especially in arid and semi-arid regions. Plants growing in salt-affected soils may suffer from physiological drought stress, ion toxicity, and mineral deficiency that lead to reduced growth and biomass. At present, in the study of secondary salinization soil amelioration, more attention is focused on the influence of soil salt ions, and soil physical and chemical properties than on the evaluation of amelioration and vegetation restoration. However, this assessment does not simultaneously consider the effects on the growth and physiological conditions of vegetation. Utilization of the straw layer in soil is a widely used and effective measure for soil salinity control. To study the response of the spectral reflectance and photosynthetic characteristics of fast-growing poplar (Populus) to different straw interlayers, a field experiment was conducted in the typical secondary salinized land of the northwestern salinized and ecologically fragile area of Ningxia. The experiment was established with four treatments: straw interlayer (B), straw mulching (M), straw interlayer plus straw mulching (B+M), and no addition of straw interlayer (CK). All treatments were arranged in a randomized complete block design with four blocks. Based on the change of soil salt and water in the background, the response of the straw layer was studied by analyzing the spectrum and photosynthetic characteristics of the fast-growing poplar. The photosynthetic rate, pigment content, nutritional status, and stress of the above-ground plants under different straw layer conditions were measured to more accurately reflect the effect of each treatment on saline soil improvement and above-ground vegetation restoration. It is of great significance to further study the physiological indexes, such as reflectance spectra and photosynthetic characteristics of plants. The results showed that: (1) different straw layers had different effects on water and salt regulation, resulting in different soil conditions among different treatments, which caused changes in pigment content, nutritional status, and physiological and biochemical conditions of the plants; (2) by detecting the plant reflection spectrum and photosynthetic characteristics, changes in plant growth and physiological conditions could be reflected. Based on this, we could use the reflectance spectrum and photosynthetic characteristics of fast-growing poplar to respond to different straw layers and more accurately assess improvement measures. The maximum net photosynthetic rate and saturation light intensity of B, M, and B+M treatment were significantly increased, and the B and B+M treatment light compensation points and dark respiration rates were significantly reduced. B and B+M treatment significantly increased the leaf photosynthetic rate (Pn), transpiration rate (Tr), stomata conductance (Gs), and intercellular CO2 concentration (Ci). The spectral reflectance of plant leaves, chlorophyll content of the B+M treatment was highest, and photosynthetic and nutrition performed best. Compared with that of the control group, other spectral reflectance indices significantly improved. The B and M treatments also significantly improved chlorophyll content and photosynthetic characteristics, but were less effective than B+M; (3) the experimental study showed that the reflectance spectrum and photosynthetic characteristics of fast-growing poplar responded differently to different straw layers. The straw layer helped to improve the physiological condition of fast-growing poplar. Based on the results of comprehensive reflection spectrum and photosynthetic characteristics, B+M was the most suitable straw layer model for the improvement of secondary saline-alkaline land in the Northwest Yellow River irrigation area. 参考文献 相似文献 引证文献

The Influence of Substrate Hydraulic Conductivity on Plant Water Status of an Ornamental Container Crop Grown in Suboptimal Substrate Water Potentials

Many soilless substrates are inefficient with regard to water (i.e., high porosity and low water holding capacity), which provides an excellent opportunity to increase water efficiency in containerized production. We suggest that increasing hydraulic conductivity in the dry range of substrate moisture content occurring during production can increase water availability, reduce irrigation volume, and produce high quality, marketable crops. Three substrates were engineered using screened pine bark (PB) and amending with either Sphagnum peatmoss or coir to have higher unsaturated hydraulic conductivity between water potentials of −100 and −300 hPa. There was no correlation between substrate unsaturated hydraulic conductivity and saturated hydraulic conductivity (r = 0.04, P = 0.8985). Established Hydrangea arborescens (L.) ‘Annabelle’ plants were grown in the three engineered and a conventional (control) PB substrates exposed to suboptimal irrigation levels (i.e., held at substrate water potentials between −100 and −300 hPa) for 32 days. The plants in the engineered substrates outperformed the control in every growth and morphological metric measured, as well as exhibiting fewer (or no) physiological drought stress indicators (i.e., vigor, growth, plant development, etc.) compared with the control. We observed increased vigor measures in plants grown in substrates with higher unsaturated hydraulic conductivity, as well as greater plant water uptake. The coir increased unsaturated hydraulic conductivity and provided an increased air space when incorporated into coarse bark vs. if peat was incorporated into bark at the same ratio by volume. Increasing PB hydraulic conductivity, through screening bark or amending bark with fibrous materials, in concert with low irrigations can produce marketable, vigorous crops while reducing water consumed and minimizing water wasted in ornamental container production.

MhYTP1 and MhYTP2 from Apple Confer Tolerance to Multiple Abiotic Stresses in Arabidopsis thaliana

The first YTH domain-containing RNA binding protein (YTP) was found in rat, where it was related to oxidative stress. Unlike characterizations in yeast and animals, functions of plant YTPs are less clear. Malus hupehensis (Pamp.) Rehd. YTP1 and YTP2 (MhYTP1 and MhYTP2) are known to be active in leaf senescence and fruit ripening. However, no research has been published about their roles in stress responses. Here, we investigate the stress-related functions of MhYTP1 and MhYTP2 in Arabidopsis thaliana. Both of the two genes participated in salicylic acid (SA), jasmonic acid (JA), and abscisic acid (ABA) signaling and play roles in plant responses to oxidative stress, chilling, high temperature, high salinity, and mannitol induced physiological drought stress. Moreover, MhYTP1 plays leading roles in SA and ABA signaling, and MhYTP2 plays leading roles in JA signaling and oxidative stress responses. These results will fill a gap in our knowledge about plant YTPs and stress responses and provide a foundation for future attempts to improve stress tolerance in apple.

Evaluating Spatially Resolved Influence of Soil and Tree Water Status on Quality of European Plum Grown in Semi-humid Climate.

In orchards, the variations of fruit quality and its determinants are crucial for resource effective measures. In the present study, a drip-irrigated plum production (Prunus domestica L. “Tophit plus”/Wavit) located in a semi-humid climate was studied. Analysis of the apparent electrical conductivity (ECa) of soil showed spatial patterns of sand lenses in the orchard. Water status of sample trees was measured instantaneously by means of leaf water potential, Ψleaf [MPa], and for all trees by thermal imaging of canopies and calculation of the crop water stress index (CWSI). Methods for determining CWSI were evaluated. A CWSI approach calculating canopy and reference temperatures from the histogram of pixels from each image itself was found to suit the experimental conditions. Soil ECa showed no correlation with specific leaf area ratio and cumulative water use efficiency (WUEc) derived from the crop load. The fruit quality, however, was influenced by physiological drought stress in trees with high crop load and, resulting (too) high WUEc, when fruit driven water demand was not met. As indicated by analysis of variance, neither ECa nor the instantaneous CWSI could be used as predictors of fruit quality, while the interaction of CWSI and WUEc did succeed in indicating significant differences. Consequently, both WUEc and CWSI should be integrated in irrigation scheduling for positive impact on fruit quality.

Differential response to physiological drought stress in tolerant and susceptible cultivars of canola

In this study, two cultivars of Brassica napus L. viz., Okapi (drought sensitive) and Zarfam (drought tolerant) were evaluated for their response to drought stress at physiological and molecular levels. Physiological drought stress was imposed on 10-day-old seedlings grown in half MS medium containing 200 mM mannitol at 0, 3, 12 and 24 h. At physiological level, water deficit changed ascorbate peroxidase, peroxidase and catalase activities in both the cultivars. However, the magnitude of changes differed in roots and shoots and was also genotype specific. Drought stress caused change in lipid peroxidation in terms of malondialdehyde (MDA) accumulation, soluble sugar and total protein contents in two cultivars with Zarfam responding earlier (3 h) compared to Okapi (12 h). At molecular level, there were significant variations between two cultivars in response to drought stress. Drought stress significantly up-regulated Auxin responsive protein (ARP), MPK3, Protein kinase (PK) and MPK4 genes transcript level in Okapi, while down-regulated expression in Zarfam. It can be concluded that drought stress imposed adverse effects on both cultivars by exertion of different responses.