Belowground Tissues Research Articles

Non-target-site resistance mechanism of barnyardgrass [Echinochloa crus-galli (L.) P. Beauv.] to florpyrauxifen-benzyl.

Florpyrauxifen-benzyl (FPB) is an arylpicolinate herbicide (Group IV) for barnyardgrass control in rice. One susceptible (Sus) and three putative FPB-resistant (R1, R2, and R3) barnyardgrass biotypes were selected based on resistant/susceptible (R/S) ratios obtained from dose-response tests and used to investigate the potential resistance mechanisms. Based on visual control results, the R/S ratios of barnyardgrass biotypes R1, R2, and R3 were 60-, 33-, and 16-fold greater than the Sus standard, respectively. Sequencing results of TIR1 and AFB genes in the tested barnyardgrass revealed no difference between Sus and R barnyardgrass biotypes. Absorption of [14 C]-FPB in Sus barnyardgrass increased over time and reached 90%, which was >10 percentage points greater than that in R biotypes. The [14 C]-FPB absorption in all R barnyardgrass equilibrated after 48 h. For both Sus and R barnyardgrass, most [14 C]-FPB absorbed was present in the treated leaf (79.8-88.8%), followed by untreated aboveground (9.5-18.6%) and belowground tissues (1.3-2.2%). No differences in translocation were observed. Differences between Sus and R barnyardgrass biotypes were found for FPB metabolism. Production of the active metabolite, florpyrauxifen-acid, was greater in Sus barnyardgrass (21.5-52.1%) than in R barnyardgrass (5.5-34.9%). In conclusion, reductions in FPB absorption and florpyrauxifen-acid production may contribute to the inability to control barnyardgrass with FPB. © 2021 Society of Chemical Industry.

A newly established virus-induced gene silencing method via seed imbibition for functional genomics at early germination stages in cotton

Virus-induced gene silencing (VIGS) is a promising genetic tool without the need for transformation, and leaf injection is commonly used for inoculation (Li-VIGS), a fact that limits its application at the early plant development stages, which are crucial to seedling survival and crop yield. In this study, an improved VIGS system was developed via simplified seed imbibition (Si-VIGS) of the widely used tobacco rattle virus (TRV) to extend functional gene studies during upland cotton seed germination. Compared with Li-VIGS, GhCLA1 and GhPGF genes were silenced in Si-VIGS procedures mediated directly by either the Agrobacterium culture or the reproduced virus sap, and Si-VIGS exhibited better gene silencing results in belowground tissues. By gene function screening in cDNA libraries from germinated cotton seeds, a key control gene in cotton seed germination, GhGOLS2 (galactitol synthase 2), was discovered. The seed germination process was significantly inhibited after silencing GhGOLS2, which made it an ideal visual marker for Si-VIGS-like canonical leaf bleaching in Li-VIGS. Furthermore, an accelerated root growth phenotype accompanied the silencing of a putative cotton FERONIA receptor kinase gene GhFER. Then, the function of GhHSL1 (HOOKLESS1, an important cotton seedling emergence gene) in the formation of apical hooks was successfully investigated using Si-VIGS. In addition, the validity period of virus sap and the applicability of Si-VIGS in various cotton varieties were successfully evaluated. Collectively, a novel Si-VIGS system focusing on functional gene assessment in cotton seed germination and early seedling stages was established in this study, thus broadening the applicable range of VIGS and facilitating functional genomic studies in cotton.

Phytochelatin and coumarin enrichment in root exudates of arsenic-treated white lupin.

Soil contamination with toxic metalloids, such as arsenic, can represent a substantial human health and environmental risk. Some plants are thought to tolerate soil toxicity using root exudation, however, the nature of this response to arsenic remains largely unknown. Here, white lupin plants were exposed to arsenic in a semi-hydroponic system and their exudates were profiled using untargeted liquid chromatography-tandem mass spectrometry. Arsenic concentrations up to 1ppm were tolerated and led to the accumulation of 12.9μg As g-1 dry weight (DW) and 411 μg As g-1 DW in above-ground and belowground tissues, respectively. From 193 exuded metabolites, 34 were significantly differentially abundant due to 1ppm arsenic, including depletion of glutathione disulphide and enrichment of phytochelatins and coumarins. Significant enrichment of phytochelatins in exudates of arsenic-treated plants was further confirmed using exudate sampling with strict root exclusion. The chemical tolerance toolkit in white lupin included nutrient acquisition metabolites as well as phytochelatins, the major intracellular metal-binding detoxification oligopeptides which have not been previously reported as having an extracellular role. These findings highlight the value of untargeted metabolite profiling approaches to reveal the unexpected and inform strategies to mitigate anthropogenic pollution in soils around the world.

Enhancement of the Cd phytoremediation efficiency of Festuca arundinacea by sonic seed treatment

It has been reported that both naturally occurring and artificially created sounds can alter the physiological parameters of various plants. A series of experiments were designed in the present study to estimate the physiological responses and the variation in the Cd decontamination capacity of Festuca arundinacea under sonic wave treatments. Plant seeds were treated by sound waves of frequency 200, 300, 400, 500, and 1000 Hz, and the germinated seedlings were transplanted to Cd-polluted soil. The results showed that all the sonic treatments increased the whole plant dry weight of F. arundinacea compared with that of the control, and the highest value was observed in the 200 Hz treatment. The Cd content in below-ground and aerial tissues of the species increased with increasing frequency till 400 Hz, after which they became constant. A higher proportion of senescent and dead leaf tissues was observed in the high-frequency treatment (1000 Hz), and more Cd was transferred to these failing tissues. Therefore, in the 1000 Hz treatment, a significantly greater amount of Cd could be eliminated by harvesting the senescent and dead leaf tissues of the species compared with that of the other treatments. The concentrations of dissolved organic matter (DOM) and the proportions of hydrophilic fractions which have a strong Cd affinity, in the rhizosphere soil of F. arundinacea increased with the increase in sound frequency. Cd extraction ability of DOM also increased with increasing frequency. This study indicated that a suitable sonic treatment can improve the phytoextraction efficiency of F. arundinacea, and also explained the mechanism from the perspective of the variations in soil DOM.

Unravelling the interactive effect of soil and atmospheric mercury influencing mercury distribution and accumulation in the soil-rice system

Mercury (Hg) accumulation in rice is an emerging health concern worldwide. However, sources and interactions responsible for Hg species accumulation in different rice tissues are still uncertain. Four experimental plots were carefully designed at an artisanal Hg mining site and a control site to evaluate the effect of atmospheric and soil Hg contents on Hg accumulation in rice. We showed that inorganic Hg (IHg) contents in rice tissues grown either in contaminated or control site soil (non-contaminated soil) were higher at Hg artisanal mining site than those at the control site. Elevated total gaseous mercury (TGM) levels in ambient air were the predominant source of IHg to rice at the Hg mining area. Methylmercury (MeHg) concentrations in rice plant tissues increased in proportionality with MeHg contents in paddy soil. Our results suggest that both atmosphere and soil Hg sources have been impacted the IHg accumulation in rice. Above ground rice tissues, grains, leaves, and stalk accumulated IHg from both atmosphere and soil to varying degrees. Nonetheless, the study also provides the first direct evidence that atmospheric Hg accumulated by above-ground rice tissues could be translocated to below-ground tissues (roots). However, the extent to which atmosphere or soil Hg contributes to IHg in rice tissues may vary with each source's concentration gradient at the given site. No evidence of in planta Hg methylation was found during the current study. Hence, paddy fields are potential MeHg production sites, whereas paddy soil is a unique MeHg accumulation source in rice plants. This study expands and clarifies the contribution of various sources involved in Hg accumulation in the soil rice system. The findings here provide the basis for future research strategies to deal with the global issue of Hg contaminated rice.

Metal(loid) uptake and partitioning within the saltmarsh halophyte, Juncus kraussii

An investigation was conducted over three estuaries in SE Australia with a gradient in metal(loid) contamination to assess metal(loid) (Cu, Zn, As, Se, Cd and Pb) accumulation and transport within the halophytic saltmarsh rush, Juncus kraussii. Sydney Olympic Park exhibited the most elevated metal(loid) contamination, followed by Hunter Wetlands and Lake Macquarie. J. kraussii exhibited a strong ability to restrict metal(loid) movement into the root system, with the exception of cadmium (BCFs < 1.0) and unrestricted flow from root to culm excepting Se, Cd (TFs < 1). Pb and Zn exhibited elevated translocation between roots and culms (TF 4.4 and 7.3, respectively). Despite barriers for uptake into the below-ground tissues, most metal(loid)s were accumulated to the roots with environmental dose (except for Cu and Cd) and linear relationships were present between the root and culm (for As and Se) and the sediment and culm (for As, Se, Cd, and Pb).

Phytoremediation Perspectives of Seven Aquatic Macrophytes for Removal of Heavy Metals from Polluted Drains in the Nile Delta of Egypt.

Simple SummarySome main drains in the Nile Delta of Egypt are subjected to heavy pollution loads and used to irrigate crops and vegetables. Here, we assessed the pollution level and the ability of some wild aquatic macrophytes (Cyperus alopecuroides, Echinochloa stagnina, Eichhornia crassipes, Ludwigia stolonifera, Phragmites australis, Ranunculus sceleratus, and Typha domingensis) to accumulate eight heavy metals (Fe, Cu, Zn, Mn, Co, Cd, Ni, and Pb) in three of the polluted drains (Amar, El-Westany, and Omar-Beck). The sediment in the three drains exceeded the worldwide permissible ranges of Cu, Zn, and Pb, but it ranged within safe limits for Mn, Cd, Ni, and Co. P. australis accumulated the highest levels of Fe, Co, Cd, and Ni, while E. crassipes contained the highest concentrations of Cu, Zn, Mn and Pb. The bioaccumulation factor was > 1 for the investigated heavy metals (except Cu) in all species, except C. alopecuroides. Accordingly, these species could be applied for the accumulation and phytostabilization of these metals.The current study addressed the heavy metals accumulation potentials of seven perennial aquatic macrophytes (Cyperus alopecuroides, Echinochloa stagnina, Eichhornia crassipes, Ludwigia stolonifera, Phragmites australis, Ranunculus sceleratus and Typha domingensis) and the pollution status of three drains (Amar, El-Westany and Omar-Beck) in the Nile Delta of Egypt. Nine sites at each drain were sampled for sediment and plant analyses. Concentrations of eight metals (Fe, Cu, Zn, Mn, Co, Cd, Ni, and Pb) were determined in the sediment and the aboveground and belowground tissues of the selected macrophytes. Bioaccumulation factor (BF) and translocation factor (TF) were computed for each species. The sediment heavy metals concentrations of the three drains occurred in the following order: El-Westany > Amar > Omar-Beck. The concentrations of sediment heavy metals in the three drains were ordered as follows: Fe (438.45–615.17 mg kg−1) > Mn (341.22–481.09 mg kg−1) > Zn (245.08–383.19 mg kg−1) > Cu (205.41–289.56 mg kg−1) > Pb (31.49–97.73 mg kg−1) > Cd (13.97–55.99 mg kg−1) > Ni (14.36–39.34 mg kg−1) > Co (1.25–3.51 mg kg−1). The sediment exceeded the worldwide permissible ranges of Cu, Zn and Pb, but ranged within safe limits for Mn, Cd, Ni and Co. P. australis accumulated the highest concentrations of Fe, Co, Cd and Ni, while E. crassipes contained the highest concentrations of Cu, Zn, Mn, and Pb. Except for C. alopecuroides and Cu metal, the studied species had BF values greater than one for the investigated heavy metals. Nevertheless, the TFs of all species (except Cd in L. stolonifera) were less than one. Hence, the studied species are appropriate for accumulation, biomonitoring, and phytostabilization of the investigated metals.

Nutrient uptake, microstructural changes and antioxidative mechanisms in Phyllostachys vivax transplanted into coastal site

AbstractChinese timber bamboo (Phyllostachys vivax McClure) has been successfully introduced to the coastal belt of eastern China. However, the mechanisms of nutrient uptake and antioxidative protection of P. vivax in response to salinity adaptation in coastal areas remains unclear. P. vivax forests were studied in their native and coastal transplantation sites within the coastal belt of China. In particular, nutrient allocation, anti‐oxidative enzyme activities, biomass accumulation, water contents, water potentials, and root system morphologies vs. microstructures were evaluated in plants from the two sites. Plant morphology adapted to the coastal saline soils by increasing root/shoot ratios and the length of large diameter rhizome, increasing vascular numbers, and lightening epidermal cells within rhizomes. The ratio of Ca2+/Na+ increased, while K+/Na+, Mg2+/Na+ decreased after transplanted to the coastal sites. Nitrogen nutrient contents were significantly positive correlated with plant growth characteristics of P. vivax. The Mg2+, Na+, and Ca2+ concentrations contributed more significantly to differences among organs, while N, Mg2+, Na+, and Ca2+ contents contributed more to root systems. The activities of superoxide dismutase (SOD), peroxidase (POD), and ascorbate peroxidase (APX) decreased, while the levels of glutathione (GSH) and ascorbic acid (AsA) increased in belowground tissues. In contrast, catalase (CAT) activities and protein contents were similar among plants of both sites. The contributions of CAT and proteins were higher for the principal components explaining variation among different organs, while the contributions of APX, CAT, POD, and proteins were higher for root systems.

Disruption of Traditional Grazing and Fire Regimes Shape the Fungal Endophyte Assemblages of the Tall-Grass Brachypodium rupestre.

The plant microbiome is likely to play a key role in the resilience of communities to the global climate change. This research analyses the culturable fungal mycobiota of Brachypodium rupestre across a sharp gradient of disturbance caused by an intense, anthropogenic fire regime. This factor has dramatic consequences for the community composition and diversity of high-altitude grasslands in the Pyrenees. Plants were sampled at six sites, and the fungal assemblages of shoots, rhizomes, and roots were characterized by culture-dependent techniques. Compared to other co-occurring grasses, B. rupestre hosted a poorer mycobiome which consisted of many rare species and a few core species that differed between aerial and belowground tissues. Recurrent burnings did not affect the diversity of the endophyte assemblages, but the percentages of infection of two core species -Omnidemptus graminis and Lachnum sp. -increased significantly. The patterns observed might be explained by (1) the capacity to survive in belowground tissues during winter and rapidly spread to the shoots when the grass starts its spring growth (O. graminis), and (2) the location in belowground tissues and its resistance to stress (Lachnum sp.). Future work should address whether the enhanced taxa have a role in the expansive success of B. rupestre in these anthropized environments.

Low Light Availability Reduces the Subsurface Sediment Carbon Content in Halophila beccarii From the South China Sea.

Eutrophication, dredging, agricultural and urban runoffs, and epiphyte overgrowth could reduce light availability for seagrass. This may affect “blue carbon” stocks in seagrass beds. However, little research is available on the effect of light intensities on carbon sequestration capacity in seagrass beds, especially small-bodied seagrasses. The dominant seagrass Halophila beccarii, a vulnerable species on the IUCN Red List, was cultured in different light intensities to examine the response of vegetation and sediment carbon in seagrass beds. The results showed that low light significantly reduced leaf length and above-ground biomass, while carbon content in both above-ground and below-ground tissues were not affected. Low light reduced both the above-ground biomass carbon and the total biomass carbon. Interestingly, while under saturating light conditions, the subsurface and surface carbon content was similar, under low light conditions, subsurface sediment carbon was significantly lower than the surface content. The reduction of subsurface sediment carbon might be caused by less release flux of dissolved organic carbon from roots in low light. Taken together, these results indicate that reduced light intensities, to which these meadows are exposed to, will reduce carbon sequestration capacity in seagrass beds. Measures should be taken to eliminate the input of nutrients on seagrass meadows and dredging activities to maintain the “blue carbon” storage service by enhancing light penetration into seagrass.

Evaluation of the nutrient status and forage quality of the hippo grass (Vossia cuspidata (Roxb.) Griff.) along Ismailia canal, Egypt

The present study aims at investigating the potential of the hippo grass for sequestering inorganic and organic nutrients in its biomass, in addition to its forage quality along Ismailia Canal, Egypt. Eight sites including 6 polluted and 2 unpolluted were selected for a seasonal plant, water and sediment investigations. The nutrients and nutritional value of the plant tissues were estimated. The highest aboveground biomass was recorded during summer, while the lowest was in winter. The plant had the highest contents of Na, K, N and Mg during winter, while P and Ca during spring and autumn, respectively. Also, Na, K and P had the highest concentrations (176.7 mg kg−1, 206.9 mg kg−1 and 1.1%) in the belowground, while N, Ca and Mg (0.9, 1.6 and 0.5%) in the aboveground organs. The contents of the investigated elements (except Na) were comparable in polluted and unpolluted canals with no significant differences. The aboveground parts had the highest values of ether extract (1.1%) during summer, crude fibres (60.2%) during spring, and total proteins (5.6%) during winter. The belowground tissues had the highest values of metabolized, digestible and net energy (2.4, 2.0 and 1.0 Mcal kg−1) during winter. In contrast, the aboveground shoots had the highest amounts of digestible crude protein (1.7%) during winter and gross energy during spring. The nutritional value of the hippo grass from unpolluted canals were greater than polluted ones for both above- and belowground parts. Hippo grass can sequester large amounts of nutrients. Consequently, this plant can be used in restoring eutrophic water through harvesting the aboveground biomass during the growing season. Besides, the aboveground shoots of the hippo grass could be used as a forage for dairy cattle, goat, beef cattle and sheep.

The symbiotic nitrogen fixation by legumes in a legume‐companion and a legume‐dominant alpine steppe on the central Tibetan Plateau

AbstractSymbiotic N2‐fixing plant species occur in many stressful environments, including the central Tibetan Plateau, where the legume species Oxytropis microphylla, Oxytropis glacialis, Astragalus arnoldii occur in the alpine steppe at elevations as high as 4700 m above sea level, either as companion or as dominant species, accounting for 13.91–60.25% of the total aboveground steppe biomass. However, the degree to which they are nutritionally reliant upon symbiotic N2 fixation is still unclear. We measured the symbiotic nitrogen fixation rate in a legume‐companion (LC) and a legume‐dominant (LD) alpine steppe community using the 15N isotope dilution technique. The N derived from the atmosphere (%Ndfa) in the three legume species ranged from 17% to 61% in aboveground tissues and from 70% to 88% in belowground tissues. The N2 fixation rate was estimated to be 0.25 ± 0.04 and 1.39 ± 0.20 g N m−2 year−1 for LC and LD based on the aboveground biomass. It was 0.86 ± 0.04 and 2.77 ± 0.22 gNm−2 year−1 for LC and LD, respectively, when both above and belowground tissues were considered. The total biological nitrogen fixation (BNF) of the alpine steppe on the Tibetan Plateau (ca. 0.7 million km2) can then be conservatively estimated at approximately 0.6 T g N year−1 using the BNF estimate from the LC community. Our findings indicate that estimates based solely on aboveground biomass and LC communities might drastically underestimate the N inputs arising from BNF by legumes to the alpine ecosystem N budget.

Cadmium subcellular distribution and chemical form in Festuca arundinacea in different intercropping systems during phytoremediation

Intercropping with Cicer arietinum L has been suggested to improve the Cd decontamination capacity of Festuca arundinacea. However, the mechanisms stimulating this effect have not been revealed. The current study was designed to evaluate the changes in the subcellular distribution and chemical forms of Cd in different leaf types of F. arundinacea intercropped with C. arietinum L under different schemes. The results indicated that more than half of the Cd was bound in the cell wall in plant organs under all planting schemes, showing that cell wall deposition is an important detoxication pathway for the metal. Relative to the monoculture scheme, coordinate and malposed intercropping schemes increased the Cd concentration deposited in the cytoplasm of below-ground tissues from 37.6% to 45.2% and 45.1%, respectively. Additionally, the proportion of inorganic and water-soluble Cd in the below-ground parts of F. arundinacea increased from 73.6% in the monoculture scheme to 80.6% and 84.7%, in the coordinate and malposed intercropping schemes, respectively. The results exhibited that intercropping schemes can activate the metal in below-ground tissues and move it to aerial parts. The present study revealed the promoting mechanism of intercropping schemes on the phytoremediation efficiency of F. arundinacea for Cd at a subcellular level.

Fungal symbionts of endangeredCrocanthemum canadense(Cistaceae) in Nova Scotia

Crocanthemum canadense (L.) Britton (Cistaceae) is critically imperiled in Nova Scotia. The decline of Nova Scotian Crocanthemum canadense is largely due to the loss of the Annapolis Valley sand barrens habitat. Fungal symbionts may aid in nutrient and water acquisition as well as plant defenses. The role of fungal associations with Crocanthemum canadense is unknown; our goal was to identify fungal symbionts to inform ongoing conservation research. We isolated fungi from eighteen Crocanthemum canadense plants collected from Greenwood, Nova Scotia. Using internal transcribed spacer (ITS) rDNA barcoding of fungal cultures, we identified 58 fungal taxa. ITS2 meta-amplicon barcoding of roots and rhizosphere soil revealed 241 fungi with basidiomycetes accounting for 53.8% of reads. Chaetothyriales sp., Mycetinis scorodonius, Acidomelania panicicola, and Scleroderma citrinum were the most abundant root associates based on meta-amplicon data. We quantified percent root colonization of arbuscular mycorrhizal fungi (AMF) using root staining and microscopy. The average AMF colonization rate of the roots was 29.6% (n = 18). Our research provides a foundation for understanding the fungal community in this declining habitat and the first account of fungal symbionts in the above- and below-ground tissues and rhizosphere of Crocanthemum canadense. Identifying fungi influencing endangered Nova Scotian Crocanthemum canadense is valuable for developing conservation strategies.

Nutrient sequestration potential of water primrose Ludwigia stolinefera (Guill. & Perr.) P.H. Raven: A strategy for restoring wetland eutrophication.

The current work investigates the capacity of the water primrose (Ludwigia stolinefera) to sequester inorganic and organic nutrients in its biomass to restore eutrophic wetlands, besides its nutritive quality as fodder for animals. The nutrient elements and nutritive value of the water primrose were assessed seasonally in polluted and unpolluted watercourses. The water primrose plants’ highest biomass was attained during summer; then, it was significantly reduced till it reached its lowest value during winter. In the polluted canal, the plant root and shoot accumulated higher contents of all nutrient elements (except Na and Mg) rather than in the unpolluted Nile. They accumulated most investigated nutrients in the growing season during summer. The shoots accumulated higher contents of N, P, Ca, and Mg than the root, which accumulated higher concentrations of Na and K. Therefore, summer season is the ideal time to harvest water primrose for removing the maximum nutrients for restoring eutrophic watercourses. The aboveground tissues had the highest values of ether extract (EE) during spring and the highest crude fibers (CF) and total proteins (TP) during summer. In contrast, the belowground tissues had the lowest EE, CF, and TP during winter. In spring, autumn, and winter seasons, the protein content in the grazeable parts (shoots) of the water primrose was within the range, while in summer, it was higher than the minimum requirement for the maintenance of animals. There was a decrease in crude fibers and total proteins, while an increase in soluble carbohydrates content in the below- and above-ground tissues of water primrose under pollution stress. The total protein, lipids, and crude fibers of the aboveground parts of water primrose support this plant as a rough forage.

Greenhouse Evaluation of Pinewood Biochar Effects on Nutrient Status and Physiological Performance in Muscadine Grape (Vitis rotundifolia L.)

Muscadine grape is a perennial crop that is highly responsive to local environmental factors and viticulture practices. Biochar is a promising soil amendment used to improve soil water and nutrient retention and promote plant growth. The present study aimed to assess the effects of different pinewood biochar rates on nutrient status and vegetative parameters of muscadine grape cv. Alachua grown on a nutrient-poor sandy soil, Ultisols (97.2% sand, 2.4% silt, and 0.4% clay), and mixed with five different rates (0%, 5%, 10%, 15%, and 20%) of biochar based on weight. Variations in soil moisture, temperature, and leaf greenness value [soil plant analysis development (SPAD) reading], net photosynthesis rate, and plant root and shoot dry weights were measured. In addition, the nutrient status of the soil, plant root, and shoot were determined. The results indicated that the higher rate of biochar could significantly (P &lt; 0.05) improve soil moisture. Biochar can also decrease soil temperature, although there were no significant differences among treatments. Regarding the nutrient status, the biochar amendment increased the nutrient content of phosphorus (P), potassium (K), magnesium (Mg), and calcium (Ca), as well as the soil organic matter content and cation exchange capacity. Higher nutrient contents in soil lead to increased P and Mg in both aboveground and belowground muscadine plant tissues and decreased nitrogen (N), iron (Fe), and copper (Cu) in the root part. There were no significant differences observed in SPAD values, net photosynthesis, or dry weights of the root and shoot. This study demonstrates that the addition of biochar may enhance the soil water and nutrient status as well as improve plant P and Mg uptake; however, it showed no significant differences in the physiological performance of muscadine grape plants.

Insights into How Spinosad Seed Treatment Protects Onion From Onion Maggot (Diptera: Anthomyiidae).

Onion maggot, Delia antiqua (Meigen), is a serious pest of onion Allium cepa L. in northern temperate regions. Over the last decade, D. antiqua has been managed principally using a pesticide seed treatment package containing the reduced-risk insecticide spinosad. While spinosad protects onion seedlings from D. antiqua, very little is known regarding how protection occurs. The main objectives of this study were to assess susceptibility of 1- and 2-wk-old larvae to spinosad through two different modes of exposure: ingestion and contact, and to evaluate larval feeding behavior in choice and no-choice tests with onion seedlings grown from treated and untreated seeds. Results showed that spinosad was more than twice as lethal to 1-wk than 2-wk-old larvae when it was ingested, but was equally toxic to both larval ages via contact exposure. In choice assays, larvae preferred feeding on untreated plants; however, without a choice, larvae fed and survived equally well on untreated and treated plants, suggesting that spinosad may have a deterrent effect. In a field study, levels of spinosad within young onion plants and in the soil around roots were monitored in addition to the cumulative number of onion seedlings killed by D. antiqua. Spinosad was detected in the soil and in both aboveground and belowground plant tissue, indicating that spinosad translocates into foliage, but declines in plant tissue and soil as plant mortality from D. antiqua feeding increases. Together, these results provide valuable insight into how spinosad protects onion seedlings and reveal key areas in need of further investigation.

Experimental evidence of microbial inheritance in plants and transmission routes from seed to phyllosphere and root.

While the environment is considered the primary origin of the plant microbiome, the potential role of seeds as a source of transmitting microorganisms has not received much attention. Here we tested the hypothesis that the plant microbiome is partially inherited through vertical transmission. An experimental culturing device was constructed to grow oak seedlings in a microbe-free environment while keeping belowground and aboveground tissues separated. The microbial communities associated with the acorn's embryo and pericarp and the developing seeding's phyllosphere and root systems were analysed using amplicon sequencing of fungal ITS and bacterial 16S rDNA. Results showed that the seed microbiome is diverse and non-randomly distributed within an acorn. The microbial composition of the phyllosphere was diverse and strongly resembled the composition found in the embryo, whereas the roots and pericarp each had a less diverse and distinct microbial community. Our findings demonstrate a high level of microbial diversity and spatial partitioning of the fungal and bacterial community within both seed and seedling, indicating inheritance, niche differentiation and divergent transmission routes for the establishment of root and phyllosphere communities.

Mechanosensing and Plant Growth Regulators Elicited During the Thigmomorphogenetic Response

The influence of mechanical bending or flexing of trees, due primarily to wind, on tree growth and development has been observed and reported for hundreds of years. This response was defined as the thigmomorphogenetic response in 1973. In general, the response of trees and other plants to bending is a reduction in extension/height growth, increase in radial growth, and increased allocation from above-ground to below-ground tissues accompanied by changes in biomechanical properties of the xylem. Within the last 50 years, significant advancements have been reported in characterizing the response of trees to this mechanical perturbation. Current research has advanced the understanding of how plants respond after mechanopreception via molecular signaling and physiological changes in growth regulation. This review provides insight into these subcellular reactions of thigmomorphogenesis and a summary of recent advances.

In situ barium phytoremediation in flooded soil using Typha domingensis under different planting densities

The management of initial planting density can be a strategy to increase barium phytoextraction from soil, reducing the time required for soil decontamination. To delimit the ideal planting density for barium (Ba) phytoremediation using Typha domingensis, we conducted a 300-day experiment in an area accidentally contaminated with barite. Four initial planting densities were tested: 4, 8, 12, and 16 plantsm−2 (D4, D8, D12, and D16 treatments, respectively). Plant development was evaluated periodically, and the phytoextraction efficiency was determined at the end of the trial. The initial planting density affected Ba phytoremediation by T. domingensis monoculture. Phytoextraction potential was better represented by the mass-based translocation factor (mTF) than the concentration-based translocation factor. D16 promoted the highest final number of plants and biomass production, but the mass of Ba in the aerial part did not differ among D8, D12, and D16. D4 resulted in more Ba accumulated belowground than aboveground (6.3 times higher), whereas D12 and D16 achieved the greatest mTFs. Higher absorption of Ba from soil can be achieved using less T. domingensis individuals at the beginning of the treatment (D4 and D8) but with high accumulation in belowground tissues. We conclude that the D8 density is considered the most appropriate if considering the phytoextraction potential and field management facilitated using fewer plants.