Low Water Regimes Research Articles

Fertility islands, keys to the establishment of plant and microbial diversity in a highly alkaline hot desert

The distribution of plant communities in hot desert ecosystems is discontinuous and resembles the pattern of heterogeneous resource patches, known as “fertility islands”. Understanding the key factors that allow plants to establish in these conditions, as well as their associated microbial diversity, is crucial to the comprehension and preservation of these ecosystems. Saudi Arabia in the Arabian Peninsula, is one of the driest regions in the world, with a very low water regime and low soil nutrient contents. The establishment of ecosystems in these arid desert conditions is therefore subject to numerous constraints. Understanding the biotic and abiotic factors linked to the formation of fertility islands, from the perspective of soil composition and its associated microbiome, both in the soil and in the roots of associated plant community, is therefore a fundamental issue for the preservation of these ecosystems. In this study, we analyzed the soil composition between a fertility island and bare soil. The proportions of micro- and macro-elements important for plant nutrition, namely magnesium, phosphorus, potassium and iron were higher in the fertility island. We also observed that soil bacterial and fungal diversity increased in the fertility island. Key taxa such as Rhizobia and Glomeraceae which play important roles in ecosystem functioning were identified in both the fertility island soil and in the roots of the established plant community. These results confirm that plant establishment is linked to soil conditions, in line with the fertility island hypothesis, and that the microbial community in the fertility island differs both in diversity and in composition from that of the bare soil. Fertility islands soils and the roots of established plant community harbor a microbiome potentially crucial to ecosystem functioning, and are of major interest for conservation and agronomy programs.

Small-scale variation in available water capacity of the soil influences height growth of single trees in Southern Germany

Aim of study: Detecting possible small-scale soil effects on height growth of single trees in monospecific stands of three important tree species (Abies alba, Fagus sylvatica, and Picea abies).
 Area of study: 37 mature stands along an ecological gradient in Southern Germany from the cold and wet “optimal niche zone” to warmer and drier niche zones, including gravelly soils with poor water supply.
 Material and methods: Measurement of achieved height and age of 15 to 20 sample trees per stand. Estimation of the available water capacity of the soil (AWC) in close proximity to sample trees based on soil texture following the German soil survey guidelines. Examining height growth depending on niche zone and AWC. 
 Main results: On sites (stand level) with the lowest water regime, height growth increased significantly with AWC of microsites. The estimated effect on height growth over the whole range of AWC values was almost 8 m at those sites. In contrast, the effect was negative on optimal sites. For intermediate and marginal sites, the effect was positive, albeit not significant for marginal sites.
 Research highlights: To our knowledge this is the first study about small-scale effects of AWC on height growth of single trees in temperate European forests. Small-scale soil variability should be considered in future scientific studies and practical evaluation, involving single tree performance at stands with low water regime. This seems particularly important in genetic environmental associations studies and in the process of selecting trees for breeding purposes in such stands.

Transcriptomic landscape of tomato traditional long shelf-life landraces under low water regimes

‘Corbarino’ (COR) and ‘Lucariello’ (LUC) belong to the family of Mediterranean long shelf-life tomato landraces, producing high quality fruits under low water input cultivation regime in their traditional cultivation area. Understanding the morpho-physiological and molecular details of the peculiar drought stress tolerance of these two genotypes may be key to their valorization as breeding material. RNA sequencing of leaf samples of COR and LUC subjected to drought stress by water withholding in a semi-controlled greenhouse identified 3089 and 2135 differentially expressed genes respectively. These included COR- and LUC-specific annotated genes, as well as genes containing single nucleotide polymorphisms as compared to reference genome. Enriched Gene Ontology categories showed that categories such as response to water, oxidoreductase activity, nucleotide salvation and lipid biosynthesis-related processes were enriched among up-regulated DEGs. By contrast, growth and photosynthesis related genes were down-regulated after drought stress, consistent with leaf gas exchange and biomass accumulation measurements. Genes encoding cell wall degrading enzymes of the pectinase family were also down-regulated in drought stress conditions and upregulated in rewatering, indicating that cell wall composition/hardness is important for drought stress responses. Globally our results contribute to understanding the transcriptomic and physiological responses of representative tomato genotypes from Southern Italy, highlighting a promising set of genes to be investigated to improve tomato tolerance to drought.

Physiological and biochemical features of fig cultivars (<I>Ficus carica</I> L.) from the collection of the Nikita Botanical Gardens

Background. Identification of promising fig cultivars (Ficus carica L.) with high content of bioactive compounds in fruits and increased adaptability to moisture deficiency is important for breeding and fruit growing in arid regions.Methods. The chemical analysis of fruits was performed using conventional methods. The content of essential elements was measured on a Kvant 2MT atomic absorption spectrophotometer. Drought resistance was assessed using the method of determining the water-holding capacity and resistance to dehydration in the leaves of fruit crops.Results. Fruits of cv. ‘Muason’ demonstrated the highest dry matter content (26.60 ± 1.30%), total phenolic compounds (169.0±26.0 mg%), sugars (mono: 15.03 ± 1.25%, and total: 17.46 ± 0.56%), water-soluble pectin (1.17%), total pectin substances (1.99%), and K (13565 ± 805 mg/kg); fruits of cv. ‘Pomoriysky’ had the maximum content of Ca (532 ± 65 mg/kg), Mg (982 ± 121 mg/kg), and Mn (1.98 ± 0.182 mg/kg); ‘Sabrutsiya Rozovaya’ excelled in the content of ascorbic acid (17.32 ± 0.78 mg%), Fe (15.413 ± 1.989 mg/kg), Zn (10.688 ± 1.338 mg/kg), and Cu (1.435 ± 0.132 mg/kg). ‘Sabrutsiya Rozovaya’ showed high drought resistance, ‘Pomoriysky’ had a medium degree of resistance, while ‘Muason’ demonstrated low water regime values. The loss of 15–20% of moisture by the leaves is critical: dehydration exceeding this limit leads to the impossibility of restoring satisfactory turgor. Conclusion. Fruits of the studied fig cultivars belong to the group of products with high K and Mg content, and satisfactory content of Fe, Zn and Mn. ‘Sabrutsiya Rozovaya’, a potentially adaptable cultivar with resistance to hydrothermal stress, was identified for its increased water-retaining capacities and high reparative ability of leaf tissues. It is recommended for use in the breeding for drought resistance and for establishment of large-scale plantations in arid regions.

Impact of substrate depth and irrigation regime on growth, flowering and physiological indices of Greek sage (Salvia fruticosa Mill.) grown on urban extensive green roof systems

The broad application of extensive green roofs in the Mediterranean region is hindered by the stressful climatic conditions of the summer period, which is characterized by drought and heat extremes that challenge plant survival and growth. The use of native plants can provide a sustainable solution in overcoming these challenges. The aim of the present study was twofold: Firstly, to investigate the growth and flowering of the native Greek sage (Salvia fruticosa Mill.) when grown as part of an extensive green roof phytocommunity under two different substrate depths (either 8 cm or 15 cm) and two levels of irrigation (either high or low). Secondly, to determine several physiological indices in order to quantify the water stress tolerance response of Greek sage when grown under the above-mentioned green roof conditions with the imposition of three drought periods (20–25 July, 22–31 August, 23 September–10 October 2014). The deeper substrate (15 cm) promoted growth regardless of the level of irrigation and the number of flowers was favored by the deeper substrate with the higher water regime treatment. Although the shallow substrate depth and the low irrigation regime reduced growth and flowering, all plants survived. The imposition of drought stress periods resulted in a gradual decrease of total soluble sugars, proline and electrolyte leakage. Chlorophyll fluorescence (Fv/Fm) fluctuated between the three drought periods and SPAD increased in the drought period that was imposed during fall. During the first drought period, plants subjected to the shallow depth (8 cm) and irrigated with the low water regime, accumulated more sugars and had a higher chlorophyll fluorescence. By contrast, plants growing in the deeper substrate depth of 15 cm provided moderate sugars, but the lowest chlorophyll fluorescence. In the second drought period, the only index that varied between treatments was proline, which was increased for the plants growing in the shallow substrate depth and irrigated with the high-water regime. The lowest proline concentration occurred in plants growing in the deeper substrate depth receiving low irrigation. SPAD increased on the third drought period for plants growing in the deeper substrate. It was concluded that Greek sage can be successfully grown in extensive green roof systems with minimal inputs of water resources even at substrate depths of 8 cm. Out of the tested physiological indices, none could be employed as a standalone indicator of the Greek sage water stress magnitude.

Genomic footprints of selection in early-and late-flowering pearl millet landraces.

Pearl millet is among the top three-cereal production in one of the most climate vulnerable regions, sub-Saharan Africa. Its Sahelian origin makes it adapted to grow in poor sandy soils under low soil water regimes. Pearl millet is thus considered today as one of the most interesting crops to face the global warming. Flowering time, a trait highly correlated with latitude, is one of the key traits that could be modulated to face future global changes. West African pearl millet landraces, can be grouped into early- (EF) and late-flowering (LF) varieties, each flowering group playing a specific role in the functioning and resilience of Sahelian smallholders. The aim of this study was thus to detect genes linked to flowering but also linked to relevant traits within each flowering group. We thus investigated genomic and phenotypic diversity in 109 pearl millet landrace accessions, i.e., 66 early-flowering and 43 late-flowering, grown in the groundnut basin, the first area of rainfed agriculture in Senegal dominated by dry cereals (millet, maize, and sorghum) and legumes (groundnuts, cowpeas). We were able to confirm the role of PhyC gene in pearl millet flowering and identify several other genes that appear to be as much as important, such as FSR12 and HAC1. HAC1 and two other genes appear to be part of QTLs previously identified and deserve further investigation. At the same time, we were able to highlight a several genes and variants that could contribute to the improvement of pearl millet yield, especially since their impact was demonstrated across flowering cycles.

Selected Indices to Identify Water-Stress-Tolerant Tropical Forage Grasses.

Periods of soil water stress have been recurrent in the Cerrado region and have become a growing concern for Brazilian tropical pasture areas. Thus, the search for forage grasses more tolerant to water stress has intensified recently in order to promote more sustainable livestock. In a greenhouse experiment, the degree of water stress tolerance of nine tropical forage grass cultivars was studied under different soil water regimes. The investigation followed a 9 × 3 factorial design in four randomized blocks. Nine cultivars from five species of perennial forage grasses were tested: Urochloa brizantha (‘BRS Piatã’, ‘Marandu’, and ‘Xaraés’), Panicum maximum (‘Aruana’, ‘Mombaça’, and ‘Tanzânia’), Pennisetum glaucum (‘ADR 300’), Urochloa ruziziensis (‘Comum’), and Paspalum atratum (‘Pojuca’). These cultivars were grown in pots under three soil water regimes (high soil water regime—HSW (non-stressful condition), middle soil water regime—MSW (moderate water stress), and low soil water regime—LSW (severe water stress)). Plants were exposed to soil water stress for 25 days during the tillering and stalk elongation phases. Twelve tolerance indices, including tolerance index (TOL), mean production (MP), yield stability index (YSI), drought resistance index (DI), stress tolerance index (STI), geometric mean production (GMP), yield index (YI), modified stress tolerance (k1STI and k2STI), stress susceptibility percentage index (SSPI), abiotic tolerance index (ATI), and harmonic mean (HM), were calculated based on shoot biomass production under non-stressful (YP) and stressful (YS) conditions. Soil water stress decreased leaf area, plant height, tillering capacity, root volume, and shoot and root dry matter production in most cultivars, with varying degrees of reduction among tropical forage grasses. Based on shoot biomass production under controlled greenhouse conditions, the most water-stress-tolerant cultivars were P. maximum cv. Mombaça and cv. Tanzânia under the MSW regime and P. maximum cv. Aruana and cv. Mombaça under the LSW regime. P. maximum cv. Mombaça has greater adaptability and stability of shoot biomass production when grown under greenhouse conditions and subjected to soil water stress. Therefore, this forage grass should be tested under field conditions to confirm its forage production potential for cultivation in tropical regions with the occurrence of water stress. The MP, DI, STI, GMP, YI, k2STI, and HM tolerance indices were the most suitable for identifying forage grass cultivars with greater water stress tolerance and a high potential for shoot biomass production under LSW regime.

Possible widespread occurrence of vermiculite on Mars

On Earth, trioctahedral (Mg-rich) vermiculite occurs as a transient alteration product of Mg/Fe2+-mica and chlorite, pyroxene, olivine, amphibole and even plagioclase where there is a nearby Mg source, indicating mild/short-lived weathering or hydrothermal conditions. On Mars, the abundant mafic rocks and low water availability suggest the likelihood of widespread vermiculite formation from the Noachian to the early Hesperian. Although it can be challenging to identify vermiculite by remote sensing or in situ infrared spectroscopy alone, we show that numerous previous remote sensing results suggest that vermiculite is widespread on the martian surface and perhaps a more common mineral on that planet than on Earth. Investigation of rocks from Riotinto (SW Spain) provides an example of how chlorite alters to vermiculite in an acidic environment. Similar incomplete vermiculite replacements of Mg/Fe2+-mica, chlorite and mafic minerals could have resulted on Mars from acidic to neutral weathering at low water regimes. While possible bias exists towards remote sensing detection of vermiculite on Mars in sites (1) with advanced alteration and (2) where vermiculite is not mixed (at pixel level) with other phyllosilicates, we find that vermiculite occurs in Noachian terrains, in sites (wider than pixel level) where other phyllosilicates are detected, and that vermiculite has more Fe3+ than is typical on Earth.

Bromus tectorum responses to intergenerational drought: Implications for evolvability and selection under climate warming

AbstractBromus tectorum poses a substantial threat to sagebrush steppe in the North American intermountain west. Responses of B. tectorum to increasing aridity across the western USA may influence the species’ ability to invade new habitats and further dominate colonised regions. We investigated the phenotypic plasticity of stomatal density, root and shoot length, and root:shoot length ratio across replicates of 23 genotypes subjected to two generations of high and low watering regimes. Shoot lengths greatly increased, root lengths increased and root:shoot ratios decreased with higher levels of progeny (F1) watering. We did not detect explicit transgenerational parental (P) effects on the reaction norms of any trait. Stomatal density did not vary consistently with F1 watering, suggesting a diversified bet‐hedging strategy. As a consequence, heritability for stomatal density did not differ significantly from zero, indicating that evolvability was extremely low. Highest overall potentials for phenotypic selection (the ratio of among‐to‐within genotype trait variances) occurred for shoot length, followed by root length, stomatal density and root:shoot length ratio. Potentials for phenotypic selection were variable among traits and watering treatments. Highest potentials for stomatal density occurred in well‐watered progeny of water‐starved parent plants (i.e. plants from the combined low P H2O, high F1 H2O regime), whereas the highest potentials for phenotypic selection for shoot length occurred for the combined high P H2O, high F1 H2O treatment. We conclude that B. tectorum expresses complex phenotypic trade‐offs with successive exposure to drought, and that phenotypic responses for some traits may allow the species to expand its fundamental niche in response to climate change.

Two studies of the potential of drought preconditioning to enhance deep root production in seedlings of western larch (Larix occidentalis)

Climate change is increasing the frequency and intensity of drought in the western USA. Evidence suggests that drought preconditioning of plants may improve the survival of planted seedlings under dry conditions through enhanced water uptake by roots, but the mechanisms underlying enhanced survival under drought remain unknown. We tested whether the vertical distribution of roots in root plug cross-sections varied with drought preconditioning and seed source. We subjected western larch (Larix occidentalis Nutt.) seedlings from eight different provenances to Low (50-65% gravimetric water content), Moderate (65-75%), and High (≥75%) watering regimes in a nursery. We then investigated dry root mass across four root-plug sections, including the taproot and three lateral root cross-sections (top 1/3rd, middle 1/3rd, and bottom 1/3rd of root plugs). We also tested for carry-over effect of drought preconditioning on the mass of egressed roots observed among cross-sections of potting soil in a 30-day potted study. Root plug mass varied significantly (P< 0.001) with watering regime, root plug cross-section, and an interaction between watering regime and cross-section. Overall, seedlings that received less water produced lateral root plug cross-sections of greater mass, which coincided with taproots of less mass. In contrast to findings from the root plug study, the distribution of egressed root mass among cross-sections of potting soil did not vary with drought preconditioning. This is the first study to assess seedling root growth in response to drought preconditioning in western larch with a focus on the distribution of root mass in root plugs and egressed root mass among soil cross-sections. We expect this work to facilitate future efforts to improve drought hardiness of western larch seedlings. Future improvement of western larch seedlings will require investigation into whether altered root plug mass distribution translates to improved seedling performance in outplanting trials.

Efficiency of Fez WWTP: multi-parameter evaluation of water and sediment quality.

In order to assess the impact of the proper functioning of wastewater treatment plants (WWTPs) and sanitation networks on the quality of water and surface sediments of the Oued Fez River and its tributaries, and ultimately their outlet in the Sebou River, physico-chemical, geochemical and mineralogical analyses were performed. The components were studied in high- and low-water regimes at eight sites. Seven heavy metals (As, Cd, Cr, Cu, Ni, Pb and Zn) were investigated in the sediments, with a decreasing trend being identified as Zn > Cu > Pb > Cr > As > Ni > Cd, and a mobility sequence as Cu > Pb > Zn > Ni > Cr. A comparison of the total heavy metal concentrations in the Oued Fez and Sebou River sediments with those of previous studies indicated a reduction in the harmful and polluting contribution of the Oued Fez to the Sebou River. The heavy metal assessment was achieved using environmental indices and sediment quality guidelines. The obtained results indicate that the presence of heavy metals in the sediment mainly comes from anthropogenic activities. Based on these results and their comparison with those from previous studies, the contribution of WWTPs and sanitation networks to improving the water quality of the middle Sebou River is clearly noteworthy.

Quinoa for the Brazilian Cerrado: Agronomic Characteristics of Elite Genotypes under Different Water Regimes

Quinoa stands out as an excellent crop in the Cerrado region for cultivation in the off-season or irrigated winter season. Here, we tested the effects of different water regimes on the agronomic characteristics, physiology, and grain quality of different elite quinoa genotypes under field conditions. The experiment was conducted under field conditions at Embrapa Cerrados (Planaltina, DF, Brazil). The experimental design was in randomized blocks, in a split-plot scheme, with four replications. The plots were composed of 18 quinoa genotypes and modified BRS Piabiru (the currently used genotype), and the split-plots were divided into 4 different water regimes. The following variables were evaluated: productivity and productivity per unit of applied water (PUAA), plant height, flavonoids, anthocyanins, gas exchange, chlorophyll, leaf proline, and relative water content. Our results showed that water regimes between 309 and 389 mm can be recommended for quinoa in the Cerrado region. CPAC6 and CPAC13 presented the highest yield and PUAA under high and intermediate WRs, and hence were the most suitable for winter growth under irrigation. CPAC17 is most suitable for off-season growth under rainfed conditions, as it presented the highest PUAA under the low WRs (247 and 150). CPAC9 stood out in terms of accumulation of flavonoids and anthocyanins in all WRs. Physiological analyses revealed different responses of the genotypes to water restriction, together with symptoms of stress under lower water regimes. Our study reinforces the importance of detailed analyses of the relationship between productivity, physiology, and water use when choosing genotypes for planting and harvest in different seasons.

Bromine and iodine species in drinking water supply system along the Changjiang River in China: Occurrence and transformation

Bromine (Br) and iodine (I) in source water can form highly toxic brominated or iodinated disinfection byproducts in treatment plants. For the first time, the occurrence of Br and I speciation and their proportion, transformation in the drinking water supply system along the Changjiang River were investigated. 96 water samples were collected from eight drinking water treatment plants under conditions of low, normal, and flood water regimes. Total Br (TBr) and total I (TI) concentrations were quantified by inductively coupled plasma mass spectrometry (ICPMS) and inorganic Br/I forms (bromide, bromate, iodide, and iodate) were determined by high-performance liquid chromatography coupled with ICPMS. Concentrations of organic Br/I were calculated as the difference between total Br/I and inorganic Br/I. Water regimes had different effect on Br and I species, and there were different rules in untreated and treated water samples. Apparent increase of TBr and TI concentrations after water treatment were observed, which indicated the possibility of Br/I introduction by chlorine-containing disinfectant. The occurrence of TBr, TI, bromide, and total organic I in the river were investigated to increase with the direction of flow. In addition, TBr and TI concentrations correlated with the concentrations of artificial sweeteners (e.g., acesulfame and sucralose, a kind of wastewater indicator), suggesting the influence of domestic sewage on Br and I in the river. In untreated water, bromide was the main Br species, and after treatment more than 50% was transformed into organic Br. Iodoorganics were the majority of I species in raw water and were partly transformed into iodate after treatment. Overall, the Br/I species have accumulation potential in the Changjiang River and organic forms occupy high proportion in treated water samples, which should be paid more attention.

Assessment of Dietary Bioactive Phenolic Compounds and Agricultural Sustainability of an African Leafy Vegetable Corchorus olitorius L.

Corchorus olitorius L. is an African leafy vegetable of high nutritional interest. To assess its agricultural suitability to sustainable cultivation conditions and its potential benefits for human nutrition, its phytochemical content in response to conservation agriculture practices [i.e., no-tillage (NT) and cover crop maintenance] and low water regime were evaluated and compared with response under conventional agriculture management. Hydric stress and NT did not affect the content of antioxidant metabolites, compared to conventional agricultural practices. In both conditions, leaves were found to be a great source of phenolic compounds. The effect of these phenolic fractions was assessed on two colon cell phenotypes to evaluate putative nutraceutical properties. Polyphenol-enriched extracts (PEEs) displayed selective cytotoxic activities against tumor Caco-2 cells but not on the healthy CCD841 line. PEEs were able to trigger oxidative stress and to inhibit the activity of glutathione-independent antioxidant enzymes on Caco-2 cells. C. olitorius showed to be a promising crop for improving both agricultural sustainability and health benefits due to the great amount of antioxidant compounds in leaves, whose occurrence is not altered by stressful farming conditions. Given its high adaptability, the cultivation of this crop is therefore recommendable also in the Mediterranean Basin.

Evaluation of anatomical and physiological traits of Solanum pennellii Cor. associated with plant yield in tomato plants under water-limited conditions

Although intensively studied, few works had looked into S. pennellii’s ability to cope with water-deficit conditions from a breeding point of view. In this study, we assessed potential traits of S. pennellii, that had previously been linked to high yields in other plant species, under long-term water-limited conditions and made a parallel with plant yield. For this purpose, the drought-resistant tomato genotypes IL 3–5 and IL 10–1, and the drought-sensitive IL 2–5 and IL 7–1 at seed level, together with both parents the S. pennellii accession LA 716 and the cultivar M82 were kept at 50 and 100% ASW throughout the growing season. Our findings confirm the superiority of LA 716 under water-limited conditions compared to the other S. lycopersicum genotypes in terms of plant water status maintenance. Percentual reduction on plant yield was higher in IL 3–5 and IL 10–1 than in M82 plants, indicating no correlation between drought resistance on germination and plant productive stages. A strong positive correlation was found between fruit yield and A, gs, and Ψleaf at 50% ASW, suggesting these traits as important selection criteria. LT and gmin, LA 716’s most promising traits, did not show a linear correlation with fruit yield under low water regimes. This study unravels traits behind tomato performance under water-limited conditions and should work as guidance for breeders aiming at developing drought-resistant tomato cultivars.

Improvement of growth performance of Amorpha fruticosa under contrasting regime of water and fertilizer in coal-contaminated spoils using response surface methodology

BackgroundWater availability and nutrient-status of soils play crucial roles in seedling establishment and plant survival in coal-spoiled areas worldwide. Restoration of spoils pertains to the application of proper doses of nutrients and water, and selection of particular plant species for efficient revegetation. This study aimed at examining the potential effects of different combinations of soil-water and fertilizers (nitrogen, N and phosphorus, P) on morpho-physiological and biochemical attributes of Amorpha fruticosa grown in coal-mined spoils. Three factors five-level central-composite-design with optimization technique response surface methodology (rsm) was used to optimize water irrigation and fertilizer application strategies.ResultsOur results revealed a strong correlation between experimental data and predicted values developed from the rsm model. The best responses of A. fruticosa in terms of plant height, stem diameter, root length, and dry biomass were observed under a high-water regime. Low-water regime caused a notable reduction in growth-associated parameters, and fertilization with either N or P did not show positive effects on those parameters, indicating that soil-water was the most influential factor for growth performance. Leaf water potential, gas-exchange parameters, and chlorophyll content significantly increased under high levels of soil-water, N and P, suggesting a synergistic effect of these factors for the improvement of photosynthesis-related parameters. At low soil-water contents and N-P fertilizer application levels, enhanced accumulation of malondialdehyde and proline indicated that A. fruticosa suffered from oxidative and osmotic stresses. Amorpha fruticosa also responded to oxidative stress by accelerating the activities of superoxide dismutase, catalase, and peroxidase. The effects of both fertilizers relied on soil-water, and fertilization was most effective under well-watered conditions. The maximum growth of A. fruticosa was observed under the combination of soil-water, N-dose and P-dose at 76% field capacity, 52.0 mg kg− 1 and 49.0 mg kg− 1, respectively.ConclusionOur results demonstrate that rsm effectively designed appropriate doses of water and N-P fertilizer to restore coal-spoiled soils. Furthermore, A. fruticosa responded to low-water and fertilizer-shortage by upregulating defensive mechanism to avoid damage induced by such deficiencies. Finally, our findings provide effective strategies for revegetation of coal-contaminated spoils with A. fruticosa using appropriate doses of water and N-P fertilizers.

Eco-physiological responses of desert and riverain legume plant species to extreme environmental stress

Abstract Drought and heat events frequency and severity are expected to increase in the near future as responses to global warming, influencing crops productivity and human diet as result in the increasing soil aridity and area affected by drought. It is becoming increasingly important to find new crop plants or genotypes of crops that have adaptation strategies to water loss at extreme arid conditions. It was hypothesized that growth and development of plants are affected differently by drought stress, depending on their nature habitats whether desert or riverain. In this current research, we compared the changes in physiological behavior between desert and riverain legume plants, as response to drought stress at two levels of water regimes. Rates of transpiration were highly correlated to radiation. Transpiration increases with the increase in photosynthetic active radiation (PAR) at both levels of water regimes. Highest photosynthesis (pn) and transpiration (E) were achieved in R. minima at both low water regime and high PAR (1250). The super oxide dismutase (SOD), catalase (CAT), phenyl ammonia lyase (PAL) and peroxidase activities were higher in Rhynchosia minima. Drought stress induced significant accumulation of total sugars, flavonoids, saponins, proteins and phenolics. The higher photosynthesis rate, higher flavonoids and phenolics content and stronger activity of protective enzymes were the important physiological reasons for the drought resistance of Rhynchosia minima.

Arbuscular mycorrhizal fungi colonization and physiological functions toward wetland plants under different water regimes.

Arbuscular mycorrhizal fungi (AMF) have been widely reported to occur in the association with wetland plants. However, the factors that affect AMF colonization in wetland plants and physiological functions in AMF inoculated wetland plants are poorly studied. This study investigated the effects of four water regimes (below the surface of sands: water levels of 5cm, 9cm, 11cm, and fluctuating water depth (9-11cm)) on AMF root colonization in two wetland plants (Phalaris arundinacea and Scirpus sylvaticus) which are commonly used in constructed wetland. Results showed that two lower water regimes were the most suitable for the formation of root colonization by AMF. Plant species did not show any significant difference in AMF colonization. The AMF colonization of 15.6-23.3% in the roots of both wetland plants were determined under the water regimes of 11cm and 9-11cm. In comparison to the non-inoculated plants, root length, shoot height, biomass, shoot total phosphorus and chlorophyll contents of both wetland plants under the fluctuating water regimes (9-11cm) were increased by 35.4-46.2%, 13.1-26.6%, 33.3-114.3%, 25.7-80% and 14.3-24%, respectively. Although malondialdehyde (MDA) contents in both AMF inoculated wetland plants were decreased under the lower water levels, the MDA contents under the water regime of 11cm were still high. Therefore, these results indicated that the physiological functions in wetland plants with high AMF colonization might be improved under a specific water regime condition (e.g. depth of fluctuating water regime).

Morphological and Physiological Responses of Seven Different Soybean (Glycine Max L. Merr.) Cultivars to Drought Stress

Soybean is an economically important crop used as a vital source of oil, vegetable protein, and other commercial products. Cultivation of soybean fetches reasonable income for the marginal farmer. Lack of rainfall and other improper monsoon conditions have generated a deep impact on the cultivation of the soybean crop making it highly essential to select drought resistant varieties that can have a higher outcome even under low water regimes. In our study, we compared the morphological and physiological responses of seven soybean cultivars: PUSA 9712, LSB 1, DSB 20, ADB 22, JS 335, NRC 37, and MAUS 61 which are popularly grown in India. These cultivars were subjected to drought stress by withholding water until the leaf water potentials reached 0, -1, -1.5, and -2 MPa, respectively. Morphological studies were performed by measuring root length, shoot length, plant height, and total biomass whereas physiological studies were performed by measuring relative water content, water uptake capacity, water retention capacity, membrane stability index, water saturation deficiency, and electrolytic leakage. All varieties used for this study showed a positive response during drought stress conditions by making certain morphological adjustments and physiological transformations. However, cultivars PUSA 9712 and LSB 1 showed better performance than, DSB 20, ADB 22, JS 335, NRC 37, and MAUS 61 under drought stress conditions. Such studies are useful in breeding programs and agronomic practices for the selection of superior soybean varieties with the capability of withstanding drought.

Geochemical modelling of experimental O2–SO2–CO2 reactions of reservoir, cap-rock, and overlying cores

Carbon dioxide streams stored geologically from industrial sources e.g. coal oxy-fuel firing sources, steel or cement processing, may contain gas impurities including O2, NOx and SOX which may have higher reactivity to rock than pure CO2. Supercritical CO2 with O2 and SO2 impurities (0.16 and 2% respectively) was reacted with core from the Precipice Sandstone, Evergreen Formation, and Hutton Sandstone of the Surat Basin, Australia. The Precipice Sandstone is a low salinity target reservoir for CO2 storage, where the Evergreen Formation would be the overlying cap-rock, and the Hutton Sandstone is an overlying aquifer. High and low water regimes were investigated with core sections either submerged in bulk gas saturated water, or suspended in the water saturated supercritical gas head at reservoir in situ conditions of 60 °C and 12 MPa. During O2–SO2–CO2 water rock reactions in bulk solution, a low solution pH (~1–2) was measured owing to the relatively high gas impurity concentrations used. Dissolution of reactive minerals from the core including Fe-chlorite, ankerite, siderite, and plagioclase was directly observed. The Evergreen Formation cap-rock and Hutton Sandstone cores reacted here contained ~ 5–10 times higher total concentrations of elements such as Fe, Al, Ti, Ba than the Precipice Sandstone core. Several cations were mobilised to solution including Mn, Co, Zn, Sr, Si, and Mg. Increasing dissolved concentrations of Mn, and Co were strongly correlated with Fe (R2 = 0.99) during reaction of the Precipice Sandstone core. Dissolved Co and Sr were strongly correlated with Fe during reaction of the Evergreen Formation core. Dissolved Mn was somewhat correlated with Fe (R2 = 0.99) from reaction of the Hutton Sandstone core, from both carbonate and chlorite dissolution. During gas-water reaction with the Hutton Sandstone core, dissolved element concentrations subsequently decreased, by incorporation into newly formed Fe oxide precipitates observed with Cr and Ni signatures. Geochemical models were built and validated with good agreement attained with experiments, predicting Fe-chlorite and minor carbonate minerals were the main minerals dissolving. Reactive surface areas initially estimated by a modified geometric method needed substantial increases for example in the case of chlorite (up to 2000x), and decreases for carbonates (2–10x) to match experimental data. A 30 year simulation of reservoir rock reactivity showed that the lowered pH was buffered by mineral dissolution. Compared to previously published pure CO2-water-rock reactions, the concentrations of ions such as Si generally were initially higher through reaction of more silicate minerals at the lower generated pH, and the oxidation of sulphides. Compared to SO2–CO2-water reactions, the concentrations of cations were similar, but with O2 present dissolved Fe subsequently decreased as Fe-oxide, sulphate and clay minerals precipitated. Cap-rock showed reactivity to wet supercritical O2–SO2–CO2 fluid in the supercritical gas headspace. Corrosion of minerals including ankerite and Fe-chlorite were observed, along with precipitation of oxide, sulphate and silicate minerals on rock surfaces. These results have implications for impacts in CO2 storage sites where gas impurities may be co-injected with CO2 and accumulate in the near wellbore region.