Improved Plant Biomass Research Articles

\u201cIntegrative genomic analysis of the bioprospection of regulators and accessory enzymes associated with cellulose degradation in a filamentous fungus (Trichoderma harzianum)\u201d

BackgroundUnveiling fungal genome structure and function reveals the potential biotechnological use of fungi. Trichoderma harzianum is a powerful CAZyme-producing fungus. We studied the genomic regions in T. harzianum IOC3844 containing CAZyme genes, transcription factors and transporters.ResultsWe used bioinformatics tools to mine the T. harzianum genome for potential genomics, transcriptomics, and exoproteomics data and coexpression networks. The DNA was sequenced by PacBio SMRT technology for multiomics data analysis and integration. In total, 1676 genes were annotated in the genomic regions analyzed; 222 were identified as CAZymes in T. harzianum IOC3844. When comparing transcriptome data under cellulose or glucose conditions, 114 genes were differentially expressed in cellulose, with 51 being CAZymes. CLR2, a transcription factor physically and phylogenetically conserved in Trichoderma spp., was differentially expressed under cellulose conditions. The genes induced/repressed under cellulose conditions included those important for plant biomass degradation, including CIP2 of the CE15 family and a copper-dependent LPMO of the AA9 family.ConclusionsOur results provide new insights into the relationship between genomic organization and hydrolytic enzyme expression and regulation in T. harzianum IOC3844. Our results can improve plant biomass degradation, which is fundamental for developing more efficient strains and/or enzymatic cocktails to produce hydrolytic enzymes.

Tibetan Sheep Adapt to Plant Phenology in Alpine Meadows by Changing Rumen Microbial Community Structure and Function.

The rumen microbiota is strongly associated with host health, nutrient absorption, and adaptability. However, the composition, functioning and adaptability of rumen microbiota in Tibetan sheep (TS) across different phenological periods are unclear. In this study we used sequencing of the V4-V5 region of 16S rRNA, qPCR technology and metagenomics to investigate the adaption of rumen microbiota to forage in different stages of phenology. In a grassy period, due to the high nutritional quality of the forage, TS can produce high concentrations of NH3-N and short fatty acids by increasing the content of key bacteria in the rumen, such as Bacteroidetes, Prevotella, Succiniclasticum, Treponema, Butyrivibrio fibrisolvens, Fibrobacter succinogenes, Prevotella ruminicola, Ruminococcus albus, and Ruminococcus flavefaciens to aid in growth. In the withering period, there was a positive correlation between microorganisms which indicated the closely cooperation between microorganisms, and metagenomic analysis showed that the high genes (GHs and CBMs) and subtribe (GH8, GH12, GH45, GH6, GH9, GH5, GH10, GH3, GH52, GH11, GH57, CBM1, CBM4, CBM6, CBM16, CBM37, CBM13, CBM35, CBM42, CBM32, and CBM62) that encode cellulolytic enzymes were significantly increased when the host faced low quantity and quality of forage. Genes involved in metabolic pathways, fatty acid biosynthesis and biosynthesis of antibiotics were significantly enriched, which indicated that rumen microbiota could improve plant biomass deconstruction and energy maintenance in the face of nutritional deficiencies. In the regreen period, both the composition and function of rumen microbiota had obvious disadvantages, therefore, to improve the competitiveness of microorganisms, we suggest TS should be supplemented with high-protein feed. This study is of great significance for exploring the high altitude adaptability of TS.

Improved Physiological Performances of Sugarcane During Maturation and Ripening Phase by Inoculation of Arbuscular Mycorrhizal Fungi

The objective of this study was to determine the effects of Arbuscular mycorrhizal fungi (AMF), Funneliformis mosseae KKU-BRP-KK6-2, inoculation on sugarcane physiology during the maturation and ripening phases under field conditions. The experiment was conducted using a randomized complete block design with four replications and four treatments, including (1) a control, (2) inoculation with AMF alone: AMF, (3) inoculation with AMF and application of a half dose of chemical fertilizer: AMF + 50%F and (4) application of a full dose of chemical fertilizer: 100%F. After 9 to 12 months of planting, the leaf area index (LAI), height, and diameter in plants treated with AMF + 50%F were recorded highest among all the treatments and were significantly higher than control. The leaf colour intensity (SCMR) values in AMF + 50%F treatments were the highest of all treatments and were significantly higher than the control after 11–12 months, while the relative water content (RWC) in AMF + 50%F treated plants was significantly higher than control after 12 months. After 10–12 months, the percentage Brix value and total fresh weight in sugarcane treated with AMF + 50%F was recorded highest. These results indicate that the application of an effective AMF strain may play an important role in sugarcane physiology in terms of nutrient acquisition, which leads to support plant growth and photosynthetic components that help to improve plant biomass and sugar accumulation.

Relative roles of Arbuscular Mycorrhizae in establishing a correlation between soil properties, carbohydrate utilization and yield in Cicer arietinum L. under As stress

Accumulation of As (metalloid) degrades soil by negatively affecting the activities of soil enzymes, which in turn reduce growth and yield of the inhabiting plant. Arbuscular mycorrhizal (AM) symbiosis can impart metalloid tolerance in plants by secreting glomalin-related soil protein (GRSP) which binds with As or inertly adsorb in the extraradical mycelial surface. However, profitable use of AM requires selection of the most efficient combination of host plant and fungal species. The current study, therefore designed to study the efficacy of 3 a.m. fungal species: Rhizoglomus intraradices (Ri), Funneliformis mosseae (Fm) and Claroideoglomus claroideum (Cc) in imparting arsenate As(V) and arsenite As(III) stress tolerance in Cicer arietinum (chickpea) genotypes (G) – relatively metalloid tolerant- HC 3 and sensitive- C 235. Roots were found to be more severly affected as compared to shoots which resulted into a major decline in uptake of nutrients, chlorophyll concentrations and yield with As(III) inducing more toxic effects than As(V). HC 3 established more effective mycorrhizal symbiosis and was able to extract higher nutrients from the soil than C 235. Ri was most beneficial in improving plant biomass, carbohydrate utilization and productivity followed by Fm and Cc which could be due to its capability to initiate highest percent colonization and least metalloid uptake in roots through higher glomalin production in the soil. Moreover, Ri was highly efficient in improving soil enzymes activities-phosphatases (PHAs), β-glucosidase (BGA) and invertase (INV), thereby, imparting metalloid tolerance in chickpea genotypes. The results suggested use of Ri-chickpea symbiosis as a promising strategy for ameliorating As stress in chickpea.

Rhizobacteria Isolated from Saline Soil Induce Systemic Tolerance in Wheat (Triticum aestivum L.) against Salinity Stress

Halo-tolerant plant growth-promoting rhizobacteria (PGPR) have the inherent potential to cope up with salinity. Thus, they can be used as an effective strategy in enhancing the productivity of saline agro-systems. In this study, a total of 50 isolates were screened from the rhizospheric soil of plants growing in the salt range of Pakistan. Out of these, four isolates were selected based on their salinity tolerance and plant growth promotion characters. These isolates (SR1. SR2, SR3, and SR4) were identified as Bacillus sp. (KF719179), Azospirillum brasilense (KJ194586), Azospirillum lipoferum (KJ434039), and Pseudomonas stutzeri (KJ685889) by 16S rDNA gene sequence analysis. In vitro, these strains, in alone and in a consortium, showed better production of compatible solute and phytohormones, including indole acetic acid (IAA), gibberellic acid (GA), cytokinin (CK), and abscisic acid (ABA), in culture conditions under salt stress. When tested for inoculation, the consortium of all four strains showed the best results in terms of improved plant biomass and relative water content. Consortium-inoculated wheat plants showed tolerance by reduced electrolyte leakage and increased production of chlorophyll a, b, and total chlorophyll, and osmolytes, including soluble sugar, proline, amino acids, and antioxidant enzymes (superoxide dismutase, catalase, peroxidase), upon exposure to salinity stress (150 mM NaCl). In conclusion, plant growth-promoting bacteria, isolated from salt-affected regions, have strong potential to mitigate the deleterious effects of salt stress in wheat crop, when inoculated. Therefore, this consortium can be used as potent inoculants for wheat crop under prevailing stress conditions.

Sustainable land management interventions lead to carbon sequestration in plant biomass and soil in a mixed crop-livestock system: the case of Geda watershed, central highlands of Ethiopia

BackgroundSustainable land management interventions were introduced in Geda watershed in 2012 to reduce soil erosion, improve water infiltration, and increase plant-carbon inputs into the soil. This study explored the impact of the interventions on biomass production, carbon stock, and carbon sequestration. Stratified sampling was employed in the main and the dry seasons in the treated and untreated sub-watersheds that are found adjacent to each other. Above- and below-ground plant biomass, soil bulk density and organic carbon in 0–15- and 15–30-cm depths, and soil moisture content in 0–20- and 20–40-cm depths were collected from the crop, grazing, and tree lucerne plots. All analyses were performed based on standard procedures.ResultsPlant biomass production, carbon stock, and carbon sequestration varied highly significantly (P ≤ 0.001) among sub-watersheds, landscape positions, and land uses. Higher mean values were observed for treated sub-watershed, lower landscape position, and tree lucerne plot. The higher mean values in the lower landscape position of the treated sub-watershed were due to tree lucerne plantation. Similarly, topsoil (0–15 cm) carbon stock was statistically higher (P ≤ 0.001) in the treated sub-watershed and at tree lucerne plot (P ≤ 0.05). In addition, carbon stock by sub-surface soil (15–30 cm) was significantly higher (P ≤ 0.001) in the treated sub-watershed under crop and grazing lands but the higher value was in cropland and in the upper position. This could be due to the decomposition of organic materials from biomasses of crops and biological supporting measures (tree lucerne and Phalaris) facilitated by tillage. Six years of sustainable land management interventions led to the sequestration of 12.25, 7.77, and 13.5 Mg C ha−1 under cropland, tree lucerne, and grazing plots, respectively.ConclusionSustainable land management interventions revealed auspicious ecological impacts in Geda watershed in terms of improving plant biomass production, carbon stock, and correspondingly capturing higher carbon dioxide equivalent taking untreated sub-watershed as a baseline. Prohibition of free grazing was the key element of the intervention to reduce biomass export and increase carbon sequestration in the treated sub-watershed. Thus, sustaining tree lucerne plants as a conservation measure and the prohibition of free grazing practices are principally essential.

Overexpression of a novel cytochrome P450 monooxygenase gene, CYP704B1, from Panax ginseng increase biomass of reproductive tissues in transgenic Arabidopsis.

Cytochrome P450 monooxygenase 704B (CYP704B), a member of the CYP86 clan, was found to be needed in Arabidopsis and rice to biosynthesize precursors of sporopollenin through oxidizing fatty acids. In the present study, we cloned and characterized a CYP704B gene in Panax ginseng, named PgCYP704B1. It shared high sequence identity (98-99%) with CYP704 of Arabidopsis, Theobroma cacao, and Morus notabilis. The phylogenetic comparison of ginseng and higher plants between the members of CYP86 clan revealed that ginseng CYP704 was categorized as a group of CYP704B with dicot plants. The expression of PgCYP704B1 is low in the stem, leaf, and fruit, and high in flower buds, particularly detected in the young gametic cell and tapetum layer of the developing anther. Arabidopsis plants overexpressing PgCYP704B1 improved plant biomass such as plant height, siliques and seed number and size. A cytological observation by transverse and longitudinal semi-thin sections of the siliques cuticles revealed that the cell length increased. Furthermore a chemical analysis showed that PgCYP704B1ox lines increased their cutin monomers contents in the siliques. Our results suggest that PgCYP704B1 has a conserved role during male reproduction for fatty acid biosynthesis and its overexpression increases cutin monomers in siliques that eventually could be used for seed production.

Effects of putrescine application in culture medium in improving chamomile (Chamomilla recutita (L.) Rauschert.) tolerance to osmotic stress under in vitro conditions

In order to assess the effect of osmotic stress induced by mannitol and putrescine under in vitro conditions on some growth parameters of chamomile (Chamomilla recutita (L.) Rauschert.), treatments were arranged and compared for the main effect of osmotic stress induced by mannitol in four levels (0, 2, 4, and 6 g/l), and the interaction effect of osmotic stress*putrescine (0, 0.5, and 1 mM). Osmotic stress, especially induced by 4 and 6 g/l of mannitol, were found to significantly reduce shoot height, root length, the number of shoot and root per plant, the fresh weight of shoot, and the fresh weight of root. At 0.5 mM of putrescine added fresh weight to root, carotenoid, chlorophyll a, and chlorophyll b was increased, compared to plants grown on medium with 0 and 1 mM of putrescine. Plants grown on medium with 0.5 and 1 mM of putrescine had an increased level of flavonoid, phenolic acid, and proline under four levels of mannitol. 0.5 mM of putrescine significantly improved plant biomass and essential oil content in plants grown on medium containing 0 and 2 g/l of mannitol. The results showed that the use of putrescine could improve chamomile tolerance to osmotic stress.

Evaluation of altered biomass mutant contributing increased grain yield in Rice (Oryza sativa L.)

Yield improvement through crop breeding is a constant process to meet increasing yield demand in context of decreasing cultivable land and erratic climatic conditions. Breeding for yield improvement can be achieved through altering plant type. Improving plant biomass can pave way for improving grain yield as grain yield is product of biomass and harvest index. EMS induced mutants serve as a source for creating novel variations for altering plant type. In this view, EMS mutant of Nagina 22 was identified with altered biomass and grain yield. A mapping population of N22 x N22-CC-M4-HT-1333 was studied in F2 and F3 for traits contributing for altered biomass and grain yield. The correlation analysis in F2 and F3 showed that dry matter produced was significantly correlated with grain yield showing the increase in grain yield of the mutant was contributed by dry biomass. This mutant is potential for unraveling the novel ways to improve grain yield and further functional genomics studies.

Arbuscular Mycorrhizal Symbiosis Mitigates Iron (Fe)-Deficiency Retardation in Alfalfa (Medicago sativa L.) Through the Enhancement of Fe Accumulation and Sulfur-Assisted Antioxidant Defense.

Iron (Fe)-deficiency is one of the major constraints affecting growth, yield and nutritional quality in plants. This study was performed to elucidate how arbuscular mycorrhizal fungi (AMF) alleviate Fe-deficiency retardation in alfalfa (Medicago sativa L.). AMF supplementation improved plant biomass, chlorophyll score, Fv/Fm (quantum efficiency of photosystem II), and Pi_ABS (photosynthesis performance index), and reduced cell death, electrolyte leakage, and hydrogen peroxide accumulation in alfalfa. Moreover, AMF enhanced ferric chelate reductase activity as well as Fe, Zn, S and P in alfalfa under Fe-deficiency. Although Fe-transporters (MsIRT1 and MsNramp1) did not induce in root but MsFRO1 significantly induced by AMF under Fe deficiency in roots, suggesting that AMF-mediated Fe enhancement is related to the bioavailability of Fe at rhizosphere/root apoplast rather than the upregulation of Fe transporters under Fe deficiency in alfalfa. Several S-transporters (MsSULTR1;1, MsSULTR1;2, MsSULTR1;3, and MsSULTR3;1) markedly increased following AMF supplementation with or without Fe-deficiency alfalfa. Our study further suggests that Fe uptake system is independently influenced by AMF regardless of the S status in alfalfa. However, the increase of S in alfalfa is correlated with the elevation of GR and S-metabolites (glutathione and cysteine) associated with antioxidant defense under Fe deficiency.

NADH-GOGAT Overexpression Does Not Improve Maize (Zea mays L.) Performance Even When Pyramiding with NAD-IDH, GDH and GS.

Maize plants overexpressing NADH-GOGAT were produced in order to determine if boosting 2-Oxoglurate production used as a carbon skeleton for the biosynthesis of amino acids will improve plant biomass and kernel production. The NADH-GOGAT enzyme recycles glutamate and incorporates carbon skeletons into the ammonium assimilation pathway using the organic acid 2-Oxoglutarate as a substrate. Gene pyramiding was then conducted with NAD-IDH and NADH-GDH, two enzymes also involved in the synthesis of 2-Oxoglurate. NADH-GOGAT overexpression was detrimental for shoot biomass production but did not markedly affect kernel yield. Additional NAD-IDH and NADH-GDH activity did not improve plant performance. A decrease in kernel production was observed when NADH-GDH was pyramided to NADH-GOGAT and NAD-IDH. This decrease could not be restored even when additional cytosolic GS activity was present in the plants overexpressing the three enzymes producing 2-Oxoglutarate. Detailed leaf metabolic profiling of the different transgenic plants revealed that the NADH-GOGAT over-expressors were characterized by an accumulation of amino acids derived from glutamate and a decrease in the amount of carbohydrates further used to provide carbon skeletons for its synthesis. The study suggests that 2-Oxoglutarate synthesis is a key element acting at the interface of carbohydrate and amino acid metabolism and that its accumulation induces an imbalance of primary carbon and nitrogen metabolism that is detrimental for maize productivity.

The Impact of Soil-Applied Biochars From Different Vegetal Feedstocks on Durum Wheat Plant Performance and Rhizospheric Bacterial Microbiota in Low Metal-Contaminated Soil.

Biochar shapes the soil environment and plant growth. Nevertheless, the mechanisms associated with an improved plant biomass and soil microbiome in low metal-contaminated soils are still unclear. In this study, the influence of biochar on soil physico-chemical properties, plant performance, and rhizosphere microbiota in durum wheat was investigated at the above- and belowground levels. Two kinds of biochar from different feedstocks (wood chips and wheat straw pellets) and two Italian durum wheat varieties, Duilio and Marco Aurelio, were analyzed in a greenhouse using a low-nutrient gleyic fluvisol containing a very small amount of Pb and Zn. Four different treatments were performed: soil-only control (C), soil amended with woody biochar equilibrated with nutrient solution (B1+) and non-activated (B1−), and soil amended with non-activated (B2−) wheat straw biochar. Seven weeks after seed germination, (1) the physico-chemical properties of soil, biochars, and mixtures were assessed; (2) the fresh and dry weight of aboveground plant tissues and roots and other morphometric traits were measured; and (3) metabarcoding of the 16S rRNA bacterial gene was performed on rhizosphere soil samples. The results showed that the biochar from wheat straw had stronger impact on both durum varieties, with higher electrical conductivity, higher levels of available K and Na, and a substantial increase of dissolved Na+, K+, and Cl− ions in pore water. Generally, biochar amendment decreased Zn availability for the plants. In addition, biochar improved plant growth in the early growth stage, and the more positive effect was achieved by combining wheat straw biochar with Marco Aurelio. Rhizosphere bacterial microbiota showed variation in alpha diversity only due to treatment; on the other hand, the differential analysis showed consistent variation among samples with significant effects on amplicon sequence variant (ASV) abundance due to the specific biochar treatment as well as the genotype. The pure B1−, due to its scarce nutrient content with respect to the richer types (B1+ and B2−), had a negative impact on microbiota richness. Our study highlights that an appropriate combination of biochar feedstock and crop species may lead to superior yield.

Nickel phytomining from industrial wastes: Growing nickel hyperaccumulator plants on galvanic sludges

Nickel (Ni) is used in numerous industrial processes, with large amounts of Ni-rich industrial wastes produced, which are largely sent to landfill. Nickel recovery from waste materials that would otherwise be disposed is of particular interest. Nickel phytomining represents a new technology in which hyperaccumulator plants are cultivated on Ni-rich substrates for commercial metal recovery. The aim of this study was to investigate the possibility of Ni transfer from industrial waste into plant biomass, to support recovery processes from bio-ores. Different industrial galvanic sludges (containing 85–150 g kg−1 Ni) were converted into artificial substrates (i.e. technosols) and the Ni hyperaccumulator Odontarrhena chalcidica (formerly Alyssum murale) was cultivated on these Ni-rich matrices. A greenhouse pot experiment was conducted for three months including an ultramafic soil control and testing fertilized (NPK) and unfertilized replicates. The results showed that fertilization was effective in improving plant biomass for all the substrates and that O. chalcidica was capable of viably growing on technosols, producing a comparable biomass to O. chalcidica on the control (ultramafic soil). On all technosols, O. chalcidica achieved Ni shoot concentrations of more than >1000 mg Ni kg −1 and maximum Ni uptake was obtained from one of the technosols (26.8 g kg −1 Ni, unfertilized; 20.2 g kg −1 Ni, fertilized). Nickel accumulation from three of the technosols resulted to be comparable with the control ultramafic soil. This study demonstrated the feasibility of transferring Ni from toxic waste into the biomass of Odontarrhena chalcidica and that phytomining from galvanic sludge-derived technosols can provide similar Ni yields as from natural ultramafic soils.

Protective effect of potassium and chitosan supply on growth, physiological processes and antioxidative machinery in sunflower (Helianthus annuus L.) under drought stress

Drought stress is one of the extreme effects of climate change causing large losses in production of crop plants. The risk of recurrent droughts has increased in next decades hence, the development of shot-gun, inexpensive and effective approaches is essential to ensure high yield of crops in drought-prone areas of the world. Exogenous application of nutrients such as potassium (K) has been reported to increase abiotic resistance and improve yield in crops however, knowledge regarding interaction of K with osmoprotectants like chitosan (Ct) still remains elusive. Here, we report the effects of individual or combined K (using K2SO4 as a source) or Ct application on growth, physiological processes and antioxidative defense system of sunflower under drought stress. At first, various doses of K (0, 5, 10, 15, 20, 25 g/l) and Ct (0, 0.1, 0.2, 0.3, 0.4, 0.5 g/l) were foliar applied to evaluate their role in improving plant biomass, water status and total chlorophyll in drought-induced seedlings of sunflower. The optimized K (11.48 g/l) and Ct (0.28 g/l) doses were further tested in second experiment to understand the underlying mechanisms of drought tolerance. Foliar K + Ct spray markedly enhanced the leaf gas exchange characteristics, increased proline, soluble proteins, and free amino acids, upregulated antioxidant defense system and helped to maintain plant water status in sunflower exposed to drought stress. The impact of drought stress was more pronounced at vegetative than reproductive stage and positive effects of combined K and Ct application were related to improved physiological and metabolic processes to improve yield and quality of sunflower under drought stress.

Effects of P fertilization level on phosphorus uptake and agronomic traits under deficit irrigation in winter wheat (T. aestivum L.)

Enhancing the phosphorus (P) use efficiency is critical for the sustainable cultivation of winter wheat. In this study, we investigated the effects of P fertilization level on plant P-uptake and agronomic traits under deficit irrigation, by using two wheat cultivars sharing contrasting water responses (i.e., Jimai 585 and Shimai 22). The high P level treatment (P120) improved plant biomass and P accumulation at each growth stage, grain yields, P remobilization amount to grain (PRA), P remobilization rate (PRR), and P contribution rate (PRR) of the cultivars with respect to the low P treatments (i.e., P90 and P60). Compared with Jimai 585, a cultivar acclimated to affluent water, the drought tolerant cultivar Shimai 22 exhibited similar behaviors on plant biomass, P-associated traits at each stage, and agronomic traits at maturity under P120. However, Shimai 22 was more improvement on P-associated and agronomic traits than Jimai 585 under P60 and P90. P contents were increased whereas moisture contents decreased in soil profile treated by P120 with respect to those by P60. Meanwhile, the soil profile cultivated by Shimai 22 displayed reduced moisture and P contents under P deprivation (i.e., P90 and P60) respect to that by Jimai 585, suggesting the contribution of more consumption of soil P and water storage to improved agronomic traits of Shimai 22. Together, our investigation suggested that suitable P input management positively mediates plant P-associated traits and grain formation capacity under deficit irrigation by improving supply and internal translocation of P across tissues in winter wheat plants.

Effects of grassland management on plant nitrogen use efficiency (NUE): Evidence from a long-term experiment

Grassland management intensification can greatly influence nitrogen (N) dynamics between aboveground and belowground compartments mainly because of the large amount of available N forms, which are repeatedly added to soils. A better understanding of how chronic fertilisation might affect N use efficiency (NUE) in plants can contribute to reducing N losses from soils and improve the sustainability of managed grasslands. Here we address how NUE might be affected by (1) the addition of key nutrients (e.g. N, P, K, Mg) in different combinations, (2) grazing by rabbits, and (3) liming (i.e. CaCO3 applications) in a 22-year-old permanent grassland experiment established in Berkshire, UK, in 1991. We first calculate seven different NUE indexes, which are known to respond either to changes in soil N availability (i.e. endogenous N inputs from soil N mineralization processes) or to exogenous N inputs (i.e. synthetic N fertiliser). We found that plant NUE calculated as plant biomass produced per unit of N acquired significantly decreased under the chronic addition of multiple nutrients (NPKMg) and was even lower under N-only applications. Most NUE indexes significantly decreased under grazing but greatly increased under liming applications. We found evidence that NUE indexes, which accounted for endogenous N sources decreased at increased rates of soil N mineralization. Finally, we found no significant relationships between any of the NUE indexes and estimates of soil N losses (Mg N ha−1) or N retention in soils (i.e. units of soil N retained per unit of N added) calculated from changes in net soil N budget over 22 years. Our study carried out on relatively acidic sandy soils suggests how liming applications in combination with low levels of multi-nutrient additions (NPKMg) can significantly improve plant biomass production per unit of N added thus contributing to enhance the sustainability of managed grassland ecosystems.

Response of arbuscular mycorrhizal fungi and phosphorus solubilizing bacteria to remediation abandoned solid waste of coal mine

Coal is the vital resource of energy in China, but abandoned coal ash and gangue lead to the degradation of vegetation cover and reduce soil quality. Both arbuscular mycorrhizal fungi (AMF) and phosphate solubilizing bacteria (PSB) play a key role in biogeochemical cycle such as soil organic matter decomposition, nutrition release, and energy flow. To improve and reclamation the soil quality and ecological efficiency of the coal mining waste, we investigated the effects of an AMF strain (Glomus mosseae) and a PSB strain (Pantoesstewarti) on phytate mineralization and subsequent transfer to the host plant (Medicago sativa L.) using a two-compartment microcosm with a central 30 mm nylon mesh barrier. The results showed that significantly higher available P (AP), above ground biomass (AGB) and underground biomass (UGB) were in combined inoculation of AMF-PSB than other treatments in root and hyphae compartment. The microbial inoculum of the AMF or PSB had a significant influence on soil acid phosphatase activities (ACP). AMF-PSB enhanced phytate mineralization, improved plant biomass. AP and ACP positively influenced the AGB and UGB. AMF-PSB could be used as bioinoculant to enhance sustainable production of the plant in abandoned solid waste of coal mine.

Arbuscular Mycorrhiza Enhances Biomass Production and Salt Tolerance of Sweet Sorghum.

Arbuscular mycorrhizal (AM) fungi (AMF) are widely known to form a symbiosis with most higher plants and enhance plant adaptation to a series of environmental stresses. Sweet sorghum (Sorghum bicolor (L.) Moench) is considered a promising alternative feedstock for bioalcohol production because of its sugar-rich stalk and high biomass. However, little is known of AMF benefit for biomass production and salt tolerance of sweet sorghum. Here, we investigated the effects of Acaulospora mellea ZZ on growth and salt tolerance in two sweet sorghum cultivars (Liaotian5 and Yajin2) under different NaCl addition levels (0, 0.5, 1, 2, and 3 g NaCl/kg soil). Results showed AMF colonized the two cultivars well under all NaCl addition levels. NaCl addition increased mycorrhizal colonization rates in Yajin2, but the effects on Liaotian5 ranged from stimulatory at 0.5 and 1 g/kg to insignificant at 2 g/kg, and even inhibitory at 3 g/kg. High NaCl addition levels produced negative effects on both AM and non-AM plants, leading to lower biomass production, poorer mineral nutrition (N, P, K), higher Na+ uptake, and lower soluble sugar content in leaves. Compared with non-AM plants, AM plants of both cultivars had improved plant biomass and mineral uptake, as well as higher K+/Na+ ratio, but only Yajin2 plants had a low shoot/root Na ratio. AM inoculation increased the activities of superoxide dismutase (SOD), peroxidase (POD), and catalase (CAT), and soluble sugar content in leaves. Overall, both cultivars benefited from mycorrhization, and Yajin2 with less salt tolerance showed higher mycorrhizal response. In conclusion, AMF could help to alleviate the negative effects caused by salinity, and thus showed potential in biomass production of sweet sorghum in saline soil.

Fungi-assisted phytoextraction of lead: tolerance, plant growth-promoting activities and phytoavailability.

Lead (Pb) is known for its low mobility and persistence in soils. The main aim of the present study was to explore potential of different fungal strains to promote phytoextraction of Pb-contaminated soils. Five non-pathogenic fungal strains (Trichoderma harzianum, Penicillium simplicissimum, Aspergillus flavus, Aspergillus niger, and Mucor spp.) were tested for their ability to modify soil properties (pH and organic matter) and to increase Pb phytoavailability at varying concentrations. Lead tolerance of fungal strains followed the decreasing order as A. niger > T. harzianum > A. flavus > Mucor sp. > P. simplicissimum. Lead solubility induced by A. flavus and Mucor spp. was increased by 1.6- and 1.8-fold, respectively, as compared to the control soil (Pb added, without fungi). A. flavus and Mucor spp. lowered the soil pH by - 0.14 and - 0.13 units, in soils spiked with 2000 mg Pb kg-1. The maximum increase in the percentage of organic matter (OM) recorded was 1.7-fold for A. flavus at 500 mg Pb kg-1 soil. Plant growth-promoting assays confirmed the beneficial role of these fungal strains. Significantly high production of IAA (249 μg mL-1) and siderophores (61%) was observed with A. niger, and phosphate solubilization with P. simplicissimum (58 μg mL-1). Based on the results in Pb-contaminated soils, Pelargonium hortorum L. inoculated with Mucor spp. showed the potential to enhance phytoextraction of Pb by promoting Pb phytoavailability in soil and improving plant biomass production through plant growth-promoting activities.

Ameliorative role of boron to toxicity of aluminum in trifoliate orange roots

Aluminum (Al) toxicity is a major limiting factor for plant productivity. Boron (B) could mitigate Al toxicity in many plant species. However, information about the mechanisms of B alleviating Al toxicity in citrus is lacking. Trifoliate orange rootstock (Poncirus trifoliate L. Raf.) seedlings were irrigated with a nutrient solution containing two B and two Al levels. Results showed that exposure to Al severely impeded plant growth-related parameters. However, B supply improved plant biomass, root activity and relative root elongation under Al stress. Furthermore, B reduced the Al-induced H2O2 accumulation in roots as evidenced by lower fluorescence intensity of H2O2 staining. Boron decreased the Al-stimulated ascorbate (AsA) synthesis by down-regulated AsA synthesis-related metabolites in the L-galactose pathway. Boron alleviated some of the toxic effects of Al by decreasing redox states of AsA and enzyme activities involved in ascorbate-glutathione (AsA-GSH) cycle, ascorbate peroxidase, dehydroascorbate reductase, glutathione reductase and glutathione peroxidase while increased glutathione (GSH) content and γ-glutamylcysteine synthetase (γ-GCS) activity. Overall, our results suggest that B protects roots against Al-induced oxidative stress possibly by reducing metabolites accumulation in the L-galactose pathway of AsA synthesis and regulating AsA-GSH cycle.