Increased Root Biomass Research Articles

Climate and vegetation controlling accumulation and translocation of heavy metals in water tower regions of Qinghai-Tibet Plateau

Understanding how climate and vegetation influencing accumulation and translocation of heavy metals (HMs) in soils and vegetation in the Qinghai-Tibet Plateau (QTP) is critical to assess the ecological risk induced by HMs under the global warming. To accompany this goal, we comprehensively determined the accumulation and translocation of HMs within the interface of soil-vegetation in water tower regions of the QTP. The PMF model results show that 54 %−86 % of cobalt (Co), nickel (Ni), arsenic (As), zinc (Zn) and lead (Pb) in the surface soil are mainly from rock weathering and 54 % of cadmium (Cd) comes from effect of litter return. The increase of vegetation biomass significantly promotes the accumulation of HMs in the surface soil. The increase of root biomass significantly enhances the uptake of Co, Ni, As, Cd and Pb by roots, due to the increasing availability of these HMs in surface soil, but reduces the translocation from roots to shoots. The precipitation and temperature influence HMs translocation by controlling the root biomass. Hence, we speculate that the further global warming in the QTP would enhance HMs accumulation in surface soil, but would not significantly increase HMs accumulation in ground vegetation biomass.

Humidity controls soil organic carbon accrual in grassland on the Qinghai–Tibet Plateau

The huge soil organic C (SOC) storage (around 34 Pg in the top 0.7 m) in Qinghai–Tibet Plateau (QTP) grasslands is commonly explained by slow decomposition of litter under cold climate therein, but this view may not be reliable as humidity also affects microbial activity. We sampled the 20 cm topsoil of grasslands along an altitudinal gradient from 1286 m on the western Loess Plateau (LP) to 4200 m above sea level on the northeastern QTP. The light-fraction SOC (LFOC), composition of non-cellulosic neutral carbohydrates, and amino sugars were used as biomarkers to investigate the intensity of microbial action on SOC as a function of climate along this altitudinal gradient. From the lowest-to the highest-humidity site with rising altitude, the root biomass tripled and the SOC content increased approximately sevenfold (from 13.5 g kg−1 to 93.3 g kg−1). The non-cellulosic neutral carbohydrate, microbial biomass C (MBC), and microbial necromass C (MNC) contents increased, but the LFOC content decreased. The contribution of MNC to the SOC and ratios between microbially- and plant-derived sugars in the non-cellulosic carbohydrate pool increased, but the proportion of LFOC in the SOC dropped. Consequently, besides the increased root biomass, the selective preservation of microbial compounds at colder and more humid sites contributed to SOC accruals in grasslands. The higher MBC in cold and humid grasslands perfectly explained the increased selective preservation of microbial derived C at the expense of plant C in higher-relative to lower-altitude areas. Importantly, the above humidity-controlled accumulations of microbial substances and SOC in grasslands were confirmed by results synthesized from published data across the LP and QTP. The higher SOC contents in cold and humid QTP grasslands relative to warm and dry regions were ascribed to the increased accumulation of microbial residues because of the increased humidity in QTP grasslands.

Microbial necromass in soil profiles increases less efficiently than root biomass in long-term fenced grassland: Effects of microbial nitrogen limitation and soil depth

Grassland fencing is acknowledged as a crucial initiative to enhance biodiversity and to increase soil organic carbon (SOC) content in ecologically fragile regions or barren systems. Theoretical perspectives propose that fencing induced an increase in root biomass, and its penetration into the soil profile introduced organic matter that facilitated SOC formation through microbial necromass and root residues. It is hypothesized that long-term grassland fencing increases root biomass, thereby enhancing SOC formation within the soil profile through microbial residues in badland ecosystems. To test this hypothesis, we selected grasslands subjected to varying durations of fencing post-grazing (i.e., 10, 15, 20, 30, and 40 y). Our investigation aimed to clarify microbial necromass dynamics in 0–100 cm soil profiles after fencing and to identify the influencing factors. Long-term grassland fencing (i.e., >30 y) increased root biomass by 160 %, SOC by 69 %, and necromass by 41 % compared to grazed grassland within the 0–40 cm horizon; in contrast, increased root biomass by 870 %, SOC by 111 %, and necromass by 46 % in the 40–100 cm horizon. Necromass in deep soil (40–100 cm) accounted for about 50 % of total residues in the 0–100 cm profile. Increased root and living microbial biomass stimulated the necromass accumulation, with a more pronounced increase in fungal residues compared with bacterial residues. Nonetheless, microbial nutrient limitation increases C or N-acquisition enzyme coefficients, which subsequently reduced fungal and bacterial residues and stimulated their recycling. Despite substantial increases in root biomass within the soil profile after fencing, limitation of microbial N and depth reduced the effectiveness of enhancing SOC and necromass. In conclusion, although microbial residues were the important source of SOC in grasslands of the Loess Plateau, microbial N limitation impeded necromass accumulation, and the interplay of root biomass, soil depth, and nutrient limitation regulated the dynamics of necromass following grassland fencing.

Deepening Root Inputs: Potential Soil Carbon Accrual From Breeding for Deeper Rooted Maize.

Breeding annual crops for enhanced root depth and biomass is considered a promising intervention to accrue soil organic carbon (SOC) in croplands, with benefits for climate change mitigation and soil health. In annual crops, genetic technology (seed) is replaced every year as part of a farmer's fixed costs, making breeding solutions to climate change more scalable and affordable than management approaches. However, mechanistic understanding and quantitative estimates of SOC accrual potentials from crops with enhanced root phenotypes are lacking. Maize is the highest acreage and yielding crop in the US, characterized by relatively low root biomass confined to the topsoil, making it a suitable candidate for improvement that could be rapidly scaled. We ran a 2-year field experiment to quantify the formation and composition (i.e., particulate (POM), coarse and fine mineral-associated organic matter (chaOM and MAOM, respectively) of new SOC to a depth of 90 cm from the decomposition of isotopically labeled maize roots and exudates. Additionally, we used the process-based MEMS 2 model to simulate the SOC accrual potential of maize root ideotypes enhanced to either shift root production to deeper depths or increase root biomass allocation, assuming no change in overall productivity. In our field experiment, maize root decomposition preferentially formed POM, with doubled efficiency below 50 cm, while root exudates preferentially formed MAOM. Modeling showed that shifting root inputs to deeper layer or increasing allocation to roots resulted in a deterministic increase in SOC, ranging from 0.05 to 0.15 Mg C ha-1 per year, which are at the low end of the range of published SOC per hectare annual accrual estimates from adoption of a variety of crop management practices. Our analysis indicates that for maize, breeding for increasing root inputs as a strategy for SOC accrual has limited impact on a per-hectare basis, although given that globally maize is produced on hundreds of millions of hectares each year, there is potential for this technology and its effect to scale. For maize-soy system that dominates US acres, changes in the overall cropping system are needed for sizable greenhouse gas reductions and SOC accrual. This study demonstrated a modeling and experimental framework to quantify and forecast SOC changes created by changing crop root inputs.

Accumulation of podophyllotoxin in the root culture of Hyptis suaveolens (L.) Poit: A potential natural lignan for clinically useful anticancer drugs

Podophyllotoxin (PTOX) is a natural antiviral, antirheumatic and anticancer molecule, but it is expensive to chemically synthesize. The present study aimed to evaluate growth and PTOX accumulation in root cultures of Hyptis suaveolens treated with different concentrations of auxins, vitamins and myo-inositol. Root cultures grown in liquid medium supplemented with different concentrations of indole-3-butyric acid (IBA), 1-naphthaleneacetic acid (NAA), vitamins and myo-inositol were used to measure biomass production and PTOX content. PTOX quantitation was performed via high-performance liquid chromatography with diode-array detection (HPLC-DAD) using a newly developed analytical method after successful validation. Root culture in MS medium supplemented with 1 mg L−1 IBA +0.5 mg L−1 NAA resulted in the highest root dry weight (248.76 mg) and the highest PTOX concentration in the roots (179.97 μg g−1 root). The roots cultured in liquid MS medium supplemented with 1 mg L−1 IBA +0.5 mg L−1 NAA presented the greatest increase in root biomass and PTOX content. This adequate balance of vitamin and myo-inositol supplementation in liquid MS culture medium increased the root dry weight and PTOX content.

La (NO3)3 substantially fortified Glycyrrhiza uralensis’s resilience against salt stress by interconnected pathways

The taproot of Glycyrrhiza uralensis is globally appreciated for its medicinal and commercial value and is one of the most popular medicinal plants. With the decline of wild G. uralensis resources, cultivated G. uralensis has become a key method to ensure supply. However, soil salinization poses challenges to G. uralensis cultivation and affects the yield and quality of it. In this study, the inhibitory effects of NaCl and Na2SO4 on yield and quality of G. uralensis were comprehensively evaluated in a three-year large-scale pot experiment, and the alleviating effects of supplementation with lanthanum nitrate (La (NO3)3) on G. uralensis were further evaluated under salt stress. The findings indicate that La (NO3)3 significantly strengthened the plant's salt tolerance by enhancing photosynthetic capacity, osmolyte accumulation, antioxidant defenses, and cellular balance of ions, which led to a substantial increase in root biomass and accumulation of major medicinal components. In comparison to the NaCl-stress treatment, the 0.75 M La (NO3)3 + NaCl treatment resulted in a 20% and 34% increase in taproot length and biomass, respectively, alongside a 52% and 43% rise in glycyrrhizic acid and glycyrrhizin content, respectively. Similar improvements were observed with 0.75 M La (NO3)3 + Na2SO4 treatment, which increased root length and biomass by 14% and 26%, respectively, and glycyrrhizic acid and glycyrrhizin content by 40% and 38%, respectively. The combined showed that application of La (NO3)3 not only significantly improved the salt resilience of G. uralensis, but also had a more pronounced alleviation of growth inhibition induced by NaCl compared to Na2SO4 stress except in the gas exchange parameters and root growth. This study provides a scientific basis for high-yield and high-quality cultivation of G. uralensis in saline soils and a new approach for other medicinal plants to improve their salt tolerance.Graphical

Enhancement of Forskolin Production Using Aeroponic Cultivation of Coleus forskohlii and the Impact on the Plant Phytochemistry.

Accessing plant resources to extract compounds of interest can sometimes be challenging. To facilitate access and limit the environmental impact, innovative cultivation strategies can be developed. Forskolin is a molecule of high interest, mainly found in the roots of Coleus forskohlii. The aim of this study was to develop aeroponic cultivation methods to provide a local source of Coleus forskohlii and to study the impact of abiotic stress on forskolin and bioactive metabolite production. Three cultivation itineraries (LED lighting, biostimulant, and hydric stress) along with a control itinerary were established. The forskolin content in the plant roots was quantified using HPLC-ELSD, and the results showed that LED treatment proved to be the most promising, increasing root biomass and the total forskolin content recovered at the end of the cultivation period threefold (710.1 ± 21.3 mg vs. 229.9 ± 17.7 mg). Statistical analysis comparing the LED itinerary to the control itinerary identified stress-affected metabolites, showing that LEDs positively influence mainly the concentration of phenolic compounds in the roots and diterpenes in the aerial parts of Coleus forskohlii. Moreover, to better define the phytochemical composition of Coleus forskohlii cultivated in France using aeroponic cultivation, an untargeted metabolomic analysis was conducted using UHPLC-HRMS/MS analysis and molecular networks on both the root and aerial parts. This study demonstrates that aeroponic cultivation, especially with the application of an LED treatment, could be a very promising alternative for a local source of Coleus forskohlii leading to easy access to the roots and aerial parts rich in forskolin and other bioactive compounds.

Temperature sensitivity of soil respiration to elevated temperature and nitrogen availability

Plastic film mulching (PFM) and nitrogen (N) fertilization are two important agricultural management methods that are used to enhance crop yields in semi-arid dryland agriculture. However, the impacts of PFM and N fertilization on the temperature sensitivity (Q10) of soil respiration (Rt), particularly its heterotrophic (Rh) and autotrophic (Ra) components, remain unclear. To investigate this, a trenching experiment was carried out between 2019 and 2021 in a rainfed maize-cultivated cropland that had been under cultivation for 7 years. There were four treatments: no PFM and N fertilization (control), full PFM without N fertilization (PFM), 150 kg N ha–1 fertilization without PFM (Nfer), and full PFM with 150 kg N ha–1 fertilization (PFM+Nfer). PFM and N fertilization not only enhanced crop yield and root biomass but also increased soil total respiration (Rt) and its components, due to improved soil hydrothermal conditions with PFM and increased N availability with N fertilization. Soil hydrothermal conditions and root biomass were identified as the most important factors influencing Rh and Ra, respectively. The greater increase in Ra (84 %–212 %) compared to Rh (9 %–29 %) resulted in a decrease in the proportion of Rh in Rt decreasing from 81.2 % in the control to 58 % under the PFM+Nfer treatment. The Rh/Rt ratio decreased in all three treatments compared to the control (p < 0.05). The increase in Rh under PFM led to a decrease in soil organic carbon (SOC) by 17 %. Specifically, the soil labile C content (i.e. LFOC 44 %) decreased more under PFM and PFM+Nfer (p < 0.05) compared to control, but not under the Nfer treatment (p > 0.05). Plastic film mulching increased the Q10 of Rh (p < 0.05) through decrease the content of soil labile C, whereas N fertilization had no effect (p > 0.05). Both PFM and N fertilization increased the Q10 of Ra (p < 0.05) by increasing root biomass. The impact of Ra’s Q10 (0.66) on Rt’s Q10 is greater compared to Rh’s Q10 (0.31). To our knowledge, this is the first long-term field study to examine the response of Rt components and their Q10 to PFM and N fertilization. Our results highlight that soil labile C and root biomass are the determining factors for the Q10 of Rh and Ra, respectively. We emphasize the importance of accurately modeling the temperature responses of Rh and Ra when predicting Rt under climate change scenarios.

The Value of Manure and Phosphorus Application to Unlock Immobilized Microbial Phosphorus for Sustainable Intensification of Maize in Zimbabwe

Microbial phosphorus (P) immobilization is a hidden challenge in most parts of sub-Saharan Africa. It affects crop establishment, growth, and response to mineral nitrogen (N) fertilizer application that ultimately reduces crop yields. This research highlighted that split application of N in combination with a medium rate (7 t ha-1) cattle manure and P fertilizer (&gt;36 kg P ha-1) (an intensification pathway) reduced microbial immobilization and increased P uptake subsequently increasing root biomass productivity.

Soil carbon stocks in temperate grasslands reach equilibrium with grazing duration

Lost soil organic carbon (SOC) in degraded grasslands can be restored via the ‘grazing exclusion’ practice, but it was unknown how long (# of years) the restoration process can take. A synthesis of four decades of studies revealed that grazing exclusion increased SOC stocks in the topsoil (0–0.30 m) by 14.8 % (±0.8 Std Err), on average, compared to moderate-to-heavy grazing (MtH); During which SOC stock increased steadily, peaked in Year 18.5, and then declined. At peak, SOC stock was 42.5 % greater under grazing exclusion than under MtH due to 100.4 ± 4.2 % increase in aboveground biomass and 80.3 ± 33.5 % increase in root biomass. Grazing exclusion also increased soil C:N ratio by 7.6 % while decreasing bulk density by 9.4 %. Grazing exclusion could be ceased 18.5 years after initiation of grazing exclusion as plant biomass input balances carbon decomposition and SOC equilibrium occurs then additional benefits start diminishing.

Assessing the role of field isolated Pseudomonas and Bacillus as growth‐promoting rizobacteria on avocado (Persea americana) seedlings

AbstractIntroductionThis research aims to assess the efficacy of two genera of rhizobacteria from avocado field isolated: Pseudomonas and Bacillus, as plant growth‐promoting microorganisms in Hass avocado trees grafted onto Zutano rootstock.Materials and MethodsThe siderophore‐producing and phosphate‐solubilizing capacity of each isolated strain was determined and plant growth‐promoting activity, nutrient accumulation, and nutrient use efficiency in Zutano variety avocado seedlings were evaluated. Molecular identification was carried out by amplification of the 16S rDNA gene of the isolated strains.ResultsPseudomonas putida, Lysinibacillus macroides, Lysinibacillus xylanilyticus, Lysinibacillus fusiformis, Bacillus subtilis and Pseudomonas plecoglossicida, were identified as the PGPR of the Bacillus and Pseudomonas genera, predominant in the avocado rhizosphere. There was found 11 phosphate solubilizing strains and 2 siderophore‐producing strains. The phosphate‐solubilizing strains, B. subtilis and P. plecoglossicida, stimulated the growth of Zutano seedlings, increasing their root dry weight (g), stem dry weight (g), leaf dry weight (g) and leaf area (cm2). Significant differences were found in nutrient uptake efficiency between inoculated plants and noninoculated plants. The increase in root biomass responded to greater phosphorus and potassium absorption in plants inoculated with P. plecoglossicida, due to this strain's high phosphate solubilization efficiency (266%).ConclusionsThe highest plant growth promotion strains were Bac F (B. subtilis), Bac M (P. plecoglossicida) and P1 (P. putida), which achieved the highest increase in root and leaf dry weight, as well as the highest nutrient extractions and nutrient uptake efficiency.

The functional identification and evaluation of endophytic bacteria sourced from the roots of tolerant Achyranthes bidentata to overcome monoculture problems of Rehmannia glutinosa.

The isolation and identification of plant growth-promoting endophytic bacteria (PGPEB) from Achyranthes bidentata roots have profound theoretical and practical implications in ecological agriculture, particularly as bio-inoculants to address challenges associated with continuous monoculture. Our research revealed a significant increase in the abundance of these beneficial bacteria in A. bidentata rhizosphere soil under prolonged monoculture conditions, as shown by bioinformatics analysis. Subsequently, we isolated 563 strains of endophytic bacteria from A. bidentata roots. Functional characterization highlighted diverse plant growth-promoting traits among these bacteria, including the secretion of indole-3-acetic acid (IAA) ranging from 68.01 to 73.25 mg/L, phosphorus and potassium solubilization capacities, and antagonistic activity against pathogenic fungi (21.54%-50.81%). Through 16S rDNA sequencing, we identified nine strains exhibiting biocontrol and growth-promoting potential. Introduction of a synthetic microbial consortium (SMC) in pot experiments significantly increased root biomass by 48.19% in A. bidentata and 27.01% in replanted Rehmannia glutinosa. These findings provide innovative insights and strategies for addressing continuous cropping challenges, highlighting the practical promise of PGPEB from A. bidentata in ecological agriculture to overcome replanting obstacles for non-host plants like R. glutinosa, thereby promoting robust growth in medicinal plants.

Tropical root responses to global changes: A synthesis.

Tropical ecosystems face escalating global change. These shifts can disrupt tropical forests' carbon (C) balance and impact root dynamics. Since roots perform essential functions such as resource acquisition and tissue protection, root responses can inform about the strategies and vulnerabilities of ecosystems facing present and future global changes. However, root trait dynamics are poorly understood, especially in tropical ecosystems. We analyzed existing research on tropical root responses to key global change drivers: warming, drought, flooding, cyclones, nitrogen (N) deposition, elevated (e) CO2, and fires. Based on tree species- and community-level literature, we obtained 266 root trait observations from 93 studies across 24 tropical countries. We found differences in the proportion of root responsiveness to global change among different global change drivers but not among root categories. In particular, we observed that tropical root systems responded to warming and eCO2 by increasing root biomass in species-scale studies. Drought increased the root: shoot ratio with no change in root biomass, indicating a decline in aboveground biomass. Despite N deposition being the most studied global change driver, it had some of the most variable effects on root characteristics, with few predictable responses. Episodic disturbances such as cyclones, fires, and flooding consistently resulted in a change in root trait expressions, with cyclones and fires increasing root production, potentially due to shifts in plant community and nutrient inputs, while flooding changed plant regulatory metabolisms due to low oxygen conditions. The data available to date clearly show that tropical forest root characteristics and dynamics are responding to global change, although in ways that are not always predictable. This synthesis indicates the need for replicated studies across root characteristics at species and community scales under different global change factors.

Dark septate endophytes enhance the drought tolerance of Haloxylon ammodendron in sterilized and nonsterilized soil

Dark septate endophytes (DSEs) are a type of endophytic fungus that commonly colonize plant root systems in extreme environments, and play a role in enhancing resistance to drought stress. To investigate the potential applications of DSEs in improving drought tolerance of desert plants, three DSE strains isolated from Haloxylon ammodendron for strong drought tolerance - Alternaria tellustris (AT), Cladosporium sp. (CL), and Paraphoma radicina (PR) - were screened through pure culture in vitro. Pot experiments of H. ammodendron were then conducted with different DSE, water, and soil treatments. In both sterilized and nonsterilized soil, DSEs showed growth-promoting and drought-resistant properties, with a stronger effect observed under sterilized soil treatment. The results showed that in sterilized soil, AT and CL increased root biomass, total biomass and root shoot ratio under high drought treatment, while PR effectively enhanced branch number and root biomass under normal water treatment. Physiologically, DSEs improved plant drought tolerance by increasing soluble sugar content and superoxide dismutase activity. Notably, DSE inoculation facilitated the uptake and utilization of soil nutrients such as available phosphorus, nitrate nitrogen, and free amino acids by plants in both sterilized and nonsterilized soil. Overall, our study highlights the potential of DSEs in improving drought resistance and promoting the growth of desert plants.

Dark septate endophyte Anteaglonium sp. T010 promotes biomass accumulation in poplar by regulating sucrose metabolism and hormones.

Plant biomass is a highly promising renewable feedstock for the production of biofuels, chemicals and materials. Enhancing the content of plant biomass through endophyte symbiosis can effectively reduce economic and technological barriers in industrial production. In this study, we found that symbiosis with the dark septate endophyte (DSE) Anteaglonium sp. T010 significantly promoted the growth of poplar trees and increased plant biomass, including cellulose, lignin and starch. To further investigate whether plant biomass was related to sucrose metabolism, we analyzed the levels of relevant sugars and enzyme activities. During the symbiosis of Anteaglonium sp. T010, sucrose, fructose and glucose levels in the stem of poplar decreased, while the content of intermediates such as glucose-6-phosphate (G6P), fructose-6-phosphate (F6P) and UDP-glucose (UDPG), and the activity of enzymes related to sucrose metabolism, including sucrose synthase (SUSY), cell wall invertase (CWINV), fructokinase (FRK) and hexokinase, increased. In addition, the contents of glucose, fructose, starch, and their intermediates G6P, F6P and UDPG, as well as the enzyme activities of SUSY, CWINV, neutral invertase and FRK in roots were increased, which ultimately led to the increase of root biomass. Besides that, during the symbiotic process of Anteaglonium sp. T010, there were significant changes in the expression levels of root-related hormones, which may promote changes in sucrose metabolism and consequently increase the plant biomass. Therefore, this study suggested that DSE fungi can increase the plant biomass synthesis capacity by regulating the carbohydrate allocation and sink strength in poplar.

Effects of water extract from Nasturtium officinale R. Br. straw on growth and selenium uptake of peach seedlings

AbstractThe content of selenium (Se) in most horticultural crops is low. To improve Se uptake in fruit trees, we investigated the impact of water extract derived from Nasturtium officinale R. Br. straw on the growth and Se uptake of peach seedlings under Se‐enriched soil by a pot experiment. The water extract of N. officinale straw exhibited notable effects on various growth parameters and Se accumulation in peach seedlings, with the most significant outcomes observed at a 200‐fold dilution. Specifically, the extract led to substantial enhancements in biomass, photosynthetic pigment content, antioxidant enzyme activity, and soluble protein content in peach seedlings. Remarkably, the 200‐fold dilution of N. officinale straw extract resulted in a 60.78% increase in root biomass and a 31.26% increase in shoot biomass when compared to the control. Moreover, the water extract augmented the levels of total Se, inorganic Se, and organic Se, along with the activities of Se metabolism‐related enzymes in peach seedlings. Among various tested dilutions, the 300‐fold and 400‐fold dilutions of N. officinale straw extract exhibited the highest total Se contents in roots and shoots, respectively, indicating increments of 97.26% and 44.08% over their respective controls. Additionally, correlation and gray relational analyses unveiled significant associations between peroxidase activity, soluble protein content, chlorophyll a content, chlorophyll a/b ratio, and the total shoot Se content. In conclusion, the water extract of N. officinale straw holds substantial potential for promoting the growth and Se uptake in peach seedlings, with the best concentration of 300‐fold dilution.

Increasing the planting density of Cryptolepis sanguinolenta (Lindl.) Schlt increased root biomass and cryptolepine yield

Cryptolepis sanguinolenta (Lindl.) Schlt. is an important multipurpose medicinal plant used for the treatment of ailments such as malaria. Despite the ongoing efforts in domesticating the herb, the ideal planting density and its benefits are unknown. A study was conducted to determine the influence of six C. sanguinolenta accessions and three planting densities (15, 30 and 45 plants/1.8 m2) on root biomass, cryptolepine concentration and cryptolepine yield. Also, benefit-cost ratios were determined for each plant density across the four cultivation periods (9, 12, 15 and 18 months). The cultivation of C. sanguinolenta at the highest planting density (45 plants/1.8 m2) increased root biomass (value), cryptolepine content (2.08 mg/100 mg dry root) and cryptolepine yield (23.31 mg mg/1.8 m2) compared to those cultivated at lower planting densities (15 and 30 plants/1.8 m2). The duration for growing C. sanguinolenta had a more significant influence on cryptolepine yield but not the cryptolepine content. Plants cultivated for 15 months gave the maximum cryptolepine yield (10.33 g/bed), indicating 15 months as the optimum time to harvest the roots. The benefit-cost analysis revealed that growing the plant at a density of 45 plants/1.8 m2 (25,920 plants/acre) for 18 months was a more profitable venture with a benefit-cost ratio of 3.45. Commercial cultivation of C. sanguinolenta at 45 plants per bed area of 1.8 m2 (25,920 plants/acre) for 15–18 months is recommended as the most profitable and promising cropping practice to ensure the sustainable supply of planting material.

Response of deep soil water deficit to afforestation, soil depth, and precipitation gradient

In semi-arid and semi-humid regions, deep soil water resources are crucial for vegetation restoration to mediate the ecosystem sustainability. Yet it is still limited on understanding soil water deficit (SWD) caused by vegetation restoration and its response to soil depth and precipitation. To obtain a more accurate measurement of regional SWD, we conducted a two-year soil water monitoring to a depth of 1800 cm under typical vegetation restoration with a precipitation gradient ranging from 300 mm/y to more than 600 mm/y across the Loess Plateau of China. With increasing precipitation gradient, soil water storages in 0–1800 cm depth under both arable cropland and artificial vegetation significantly increased (p < 0.05). Compared to arable cropland, artificial vegetations (forest and shrub) had a significantly greater SWD regardless of either precipitation gradient or soil depth. In particular, the deep-rooted vegetations (R. pseudoacacia and C. korshinskii) on the Loess Plateau demonstrated the greatest SWD in the 0–1800 cm layer due to their great water consumption. Indeed, a positive relationship between the accumulated SWD and the accumulated root biomass was detected, suggesting that the increased root biomass in soil depth may promote soil water consumption. In addition, the relative SWD in artificial vegetation at a depth of 1800 cm decreased significantly (p < 0.05). These findings reveal that there is a mechanism of precipitation self-regulation on the deep SWD, of which is more sensitive in the sub-shallow soil layers. We conclude that the SWD depends on vegetation restoration, soil depth, and precipitation self-regulation, offering a reference for how afforestation affects deep soil water in the Loess Plateau region. This finding also benefits to mediate water balance processes and develop sustainable land management in water-limited regions around the world.

Effect of Co-Inoculation with Growth-Promoting Bacteria and Arbuscular Mycorrhizae on Growth of Persea americana Seedlings Infected with Phytophthora cinnamomi.

Avocado is one of the most in-demand fruits worldwide and the trend towards its sustainable production, regulated by international standards, is increasing. One of the most economically important diseases is root rot, caused by Phythopthora cinnamomi. Regarding this problem, antagonistic microorganism use is an interesting alternative due to their phytopathogen control efficiency. Therefore, the interaction of arbuscular mycorrhizal fungi of the phylum Glomeromycota, native to the Peruvian coast (GWI) and jungle (GFI), and avocado rhizospheric bacteria, Bacillus subtilis and Pseudomonas putida, was evaluated in terms of their biocontrol capacity against P. cinnamomi in the "Zutano" variety of avocado plants. The results showed that the GWI and Bacillus subtilis combination increased the root exploration surface by 466.36%. P. putida increased aerial biomass by 360.44% and B. subtilis increased root biomass by 433.85%. Likewise, P. putida rhizobacteria showed the highest nitrogen (24.60 mg ∙ g-1 DM) and sulfur (2.60 mg ∙ g-1 DM) concentrations at a foliar level. The combination of GWI and Bacillus subtilis was the treatment that presented the highest calcium (16.00 mg ∙ g-1 DM) and magnesium (8.80 mg ∙ g-1 DM) concentrations. The microorganisms' multifunctionality reduced disease severity by 85 to 90% due to the interaction between mycorrhizae and rhizobacteria. In conclusion, the use of growth promoting microorganisms that are antagonistic to P. cinnamomi represents a potential strategy for sustainable management of avocado cultivation.

Synergistic effects of coal waste derived humic substances and inorganic fertilizer as soil amendments for barley in sandy soil

Increasing pressures on land resources requires increased land use efficiency. Over 900 million ha of sandy soils throughout the world are extensively used for agricultural crop production, most requiring nutrient inputs. Although use of humic substances together with inorganic fertilizer as soil amendments has been introduced, their synergistic effects on plant growth in sandy soils are not well addressed. We assessed the efficacy of a lignite waste derived humic substance on barley (Hordeum vulgare L.) growth, with and without inorganic fertilizer. Ten treatments were applied to sandy soils, comprising sole application of the humic product at four rates (NH1, NH2, NH3, NH4), sole application of fertilizer (F), and their combinations (F + NH1, F + NH2, F + NH3, F + NH4). Synergistic effects of nano humus and fertilizer were more notable than the corresponding sole application, particularly on plant biomass and seed production. Combined application with inorganic fertilizer increased root biomass by 92 % (0.1 g per plant), shoot biomass by 80 % (0.5 g per plant), root length by 24 % (3.6 cm), and seed production by 38 % (5 seeds per head) averagely relative to the untreated control, suggesting a strong synergistic effect. The increased seed production was particularly important from an agricultural perspective. Four application rates of nano humus all showed beneficial effects on barley growth with no significant differences. The most distinct positive effect of the humic product as a sole application was on root growth. Our study confirmed that a lignite waste derived humic product, nano humus, together with fertilizer may be an effective soil amendment to enhance agricultural plant growth in sandy soil regions.