Early Plant Research Articles

Response of crop seed germination and primary root elongation to a binary mixture of diclofenac and naproxen.

Non-steroidal anti-inflammatory drugs, diclofenac (DCF) and naproxen (NPX), represent a group of environmental contaminants often detected in various water and soil samples. This work aimed to assess possible phytotoxic effects of DCF and NPX in concentrations 0.1, 1 and 10 mg/L, both individually and in binary mixtures, on the seed germination and primary root elongation of crops, monocots Allium porrum and Zea mays, and dicots Lactuca sativa and Pisum sativum. Results proved that the seed germination was affected by neither individual drugs nor their mixture. The response of primary root length in monocot and dicot species to the same treatment was different. The Inhibition index (%) comparing the root length of drug-treated plants to controls proved to be approximately 10% inhibition in the case of dicots lettuce and pea, and nearly 20% inhibition in monocot leek, but almost 20% stimulation in monocot maize. Assessment of the binary mixture effect confirmed neither synergistic nor antagonistic interaction of DCF and NPX on early plant development in the applied concentration range.

Integrating mechanical and cultural methods for weed control in organic chickpea

Abstract The Northern Great Plains of the United States is a major production region for organic pulse crops that are prone to yield losses due to weeds. Weed management in organic systems relies on the integration of several tactics to stack additive effects and for redundancy to deal with variable efficacy of individual weed management practices. To address the need for effective, integrated weed management, we conducted a 2-yr trial that evaluated the effects of planting date, seeding rate, and preemergent weed control practices (shallow tillage and flame weeding) on weed biomass, crop density, and yield in organically managed chickpea (Cicer arietinum L.) in Montana. Stacking weed management practices increased yields. Early planting had the largest effects on yields, increasing them by 1.8- to 3.6-fold compared with planting 10 to 14 d later. Increasing the seeding rate from the standard rate (43 viable seeds m−2) by 50% increased yields by 47% from 889 to 1,304 kg ha−1. Both preemergent weed control practices increased yields by 40% to 50 % relative to the non-weeded controls. By integrating all three practices, yields of organic chickpea increased greater than 6-fold from 318 kg ha−1 in the controls to 2,006 kg ha−1. The effects of weed control treatments on midseason weed biomass were complex and variable. Although efficacy of the cultural (seeding rate and planting date) and physical (preemergent) treatments on weed biomass varied between years and when combined with other treatments, their full integration, that is, early planted, at higher seeding rate, and preemergent weed control, produced consistently lower weed biomass (84% reduction on average) compared with the standard grower practice (later planting, standard seeding rate, no preemergent weed control). The results lend support to the concept of integrating multiple weed management practices to achieve weed control and high yields in organically managed crops.

Impacts of black soldier fly, Hermetia illucens, larval frass on the emergence and seedling vigor of three vegetable crop species

Abstract The waste material from rearing black soldier fly, Hermetia illucens (L.), (Diptera: Stratiomyidae), larvae (BSFL), frass, could serve as a partial replacement for fertilizer or growing media, such as peat. Studies have shown that depending on the crop life cycle, long or short, the incorporation of frass can have positive impacts on vegetable growth. Investigating the earlier stages of growth, such as emergence, can provide more information on the acute impacts of insect frass on plant production. Two greenhouse studies were designed to investigate the use of frass in vegetable production at the seedling stage: BSFL frass as a partial replacement for peat in a growth germination medium and BSFL frass as a fertility replacement in a growth germination medium. Tomato, lettuce, and arugula seeds were grown in a standard control growing media, a growing media amended with frass to partially replace peat, and a growing media with frass applications to substitute the fertility source. In all treatments and varieties, the control growing media produced better or comparable results to the treatments. As a peat replacement, the two tomato varieties, lettuce, and arugula seedlings grown in frass had comparable seedling vigour and days to emergence to those grown in the control. As a fertility replacement, seedlings grown in frass had significantly lower percent emergence in all four cultivars when compared to the control. The tomato varieties also had significantly lower seedling vigour in the BSFL fertility treatments than the control. Depending on crop and growing media composition, the impacts of frass on early plant development vary. The adoption of frass into growing practices should include preliminary tests for nutrient composition and microbial contamination.

Integration of fungal transcriptomics and metabolomics provides insights into the early interaction between the ORM fungus Tulasnella sp. and the orchid Serapias vomeracea seeds

In nature, germination of orchid seeds and early plant development rely on a symbiotic association with orchid mycorrhizal (ORM) fungi. These fungi provide the host with the necessary nutrients and facilitate the transition from embryos to protocorms. Despite recent advances in omics technologies, our understanding of this symbiosis remains limited, particularly during the initial stages of the interaction. To address this gap, we employed transcriptomics and metabolomics to investigate the early responses occurring in the mycorrhizal fungus Tulasnella sp. isolate SV6 when co-cultivated with orchid seeds of Serapias vomeracea. The integration of data from gene expression and metabolite profiling revealed the activation of some fungal signalling pathways before the establishment of the symbiosis. Prior to seed contact, an indole-related metabolite was produced by the fungus, and significant changes in the fungal lipid profile occurred throughout the symbiotic process. Additionally, the expression of plant cell wall-degrading enzymes (PCWDEs) was observed during the pre-symbiotic stage, as the fungus approached the seeds, along with changes in amino acid metabolism. Thus, the dual-omics approach employed in this study yielded novel insights into the symbiotic relationship between orchids and ORM fungi and suggest that the ORM fungus responds to the presence of the orchid seeds prior to contact.

Climate-adaptative management strategies for soybean production under ENSO scenarios in Southern Brazil: An in-silico analysis of crop failure risk

CONTEXTSoybeans (Glycine max L.) are a crucial crop for global food security, and the state of Rio Grande do Sul (RS), Brazil, plays a significant role. However, climate instability, particularly water stress (WS), is a major concern in this region, causing large interannual yield variability. OBJECTIVEThis study aims to address this issue using an in-silico approach to: i) characterize WS and spatial patterns and their frequency within ENSO events; and ii) explore climate-adaptative management strategies such as planting dates and maturity groups to mitigate the risk of crop failure and maximize seed yield and profits. METHODSCrop growth simulations were performed testing three soybean maturity groups (MG, 5.0, 5.8, and 6.4) and eight planting dates (from October 5th to January 20th) over 30 years at 187 locations in RS, Brazil, using APSIM Next Generation. Failure risk was calculated as the percentage of simulations that yielded less than the economic break-even soybean yield in a given scenario. RESULTS AND CONCLUSIONSThe simulated yields were clustered into four regions: Northeast, North, Central, and Southwest. Four WS seasonal patterns were then defined (no stress, early stress, late stress, and whole season stress). On average, WS reduced yields up to 2 Mg ha-1 (∼50 % relative to the maximum). WS varied among regions, with the SW experiencing more frequent and severe stress (up to 50 % of whole season stress during La Nina). ENSO events influenced WS frequency, with El Niño events associated with reduced stress and La Niña events to increased stress. The MG 5.0 resulted in a higher probability of failure risk in all regions. Early planting dates resulted in the highest yield variability (up to 5 Mg ha-1). Climate-adaptative management strategies, such as optimizing planting dates and maturity groups, resulted in a 15 % reduction in crop failure. SIGNIFICANCEOur findings provide valuable insights for developing targeted approaches to enhance soybean yield stability, thereby increasing the resilience of agriculture in the face of future climate uncertainties.

More than rapid identification—Free plant identification apps can also be highly accurate

Abstract Hart et al. (2023) conducted a study to evaluate the accuracy of five plant identification apps based on snapshot images as used in practice by field ecologists. Their results revealed varying accuracies per app, ranging from 86.9% to 46.4%. We explore the reasons why apps failed to deliver the expected result. We re‐evaluated the image dataset using another plant identification app (Flora Incognita) in order to understand the discrepancies between ground truth and app predictions. We found that mismatches between the given and returned labels can arise due to incorrect app prediction, incorrect ground truth, multiple species per image or taxonomical inconsistencies. For some images depicting early developmental plant stages, the ground truth could not be verified, resulting in some cases where both the ground truth and the app predictions could neither be confirmed nor refuted. After accounting for these aspects, Flora Incognita reached an accuracy of 98.8% on the same image dataset. Our results highlight the untapped potential of plant ID apps, as they can be highly accurate. As shown here, one area of application could be spotting misidentifications in scientific image collections, especially if multiple apps disagree with the given label. Read the free Plain Language Summary for this article on the Journal blog.

Gene Expression Analysis for Drought Tolerance in Early Stage of Potato Plant Development

Drought has increasingly affected the yield of Solanum tuberosum L. (potato) every year over the last decade, posing serious economic problems for the global agricultural industry. Therefore, it is important to research drought tolerance in plants and obtain more robust varieties of crops. The aim of the present work was to study the expression of drought-upregulated genes in drought-tolerant and drought-sensitive varieties of potato. Bioreactors were used to identify whether each variety was drought-tolerant or drought-sensitive; then, expression analysis was performed according to the morphological characteristics of the plantlets in two different media: Murashige and Skoog (MS) medium and MS medium with 20% PEG-6000 to simulate osmotic stress. Based on the quantitative parameters of six initial varieties, two varieties were selected (Gala and Aksor) for further gene expression analysis. The expression of genes commonly upregulated in drought (ER24, TAS14, DREB147315, PP2C, 102605413 and NF-YC4) was higher in the drought-tolerant variety than in the sensitive one. Therefore, the expression of these genes can be used to determine the drought tolerance of a potato variety in vitro in the early plant development stage. Moreover, comparative analysis showed that some of the targeted genes used to identify drought tolerance in this study are conserved across different plant species.

Context dependence of grassland plant response to arbuscular mycorrhizal fungi: The influence of plant successional status and soil resources

Abstract Many of the disturbance‐sensitive, late successional plant species in grasslands respond to arbuscular mycorrhizal (AM) fungi more positively via growth and establishment than plants that readily establish in disturbed areas (i.e. early successional species). Inoculation with AM fungi can therefore aid the establishment of late successional species in disturbed areas. If the differential benefit of AM fungi to late versus early successional plants is context‐dependent, however, this advantage could be diminished in high phosphorus (P) post‐agricultural soils or in future climates with altered precipitation. In this greenhouse experiment, we tested if late successional plant species are less plastic in their reliance on AM fungi than early successional plants by growing 17 plant species of different successional status (9 early and 8 late successional) in full factorial combinations of inoculated or uninoculated with AM fungi, with ambient or high P levels, and with low or high levels of water. AM fungi positively affected the biomass of the 17 grassland plant species, but across all environments, late successional plant species generally responded more positively to AM fungi than early successional plants species. AM fungal growth promotion and change in below‐ground biomass allocation was generally diminished with P fertilizer across all plant species, and while there was significant variation among plant species in the sensitivity of AM fungal responsiveness to P fertilization, this differential sensitivity was not predicted by plant successional status. The role of AM fungi in plant growth promotion was not generally altered by variation in watering, however late successional plant species allocated a greater proportion of their biomass below‐ground in response to AM fungi in low versus high water conditions. Synthesis. Overall greater responsiveness to arbuscular mycorrhizal (AM) fungi by late successional species is consistent with an important role of AM fungi in plant succession, even while AM fungi are less impactful overall in high P soils. However, the increase in responsiveness of below‐ground allocation of late successional species to AM fungi in low water conditions suggests that successional dynamics may be more dependent on AM fungi in future climates that feature greater propensity for drought.

Application of coupled MIKE SHE/MIKE HYDRO on streamflow dynamics under climate change in Lake Tana sub basin, Abay Basin, Ethiopia

AbstractWater availability and quality are fluctuating due to climate change, which has disastrous effects on life. Modeling climate change impact on streamflow in the Lake Tana sub‐basin (LTSB) in selected watersheds was the main goal of the research. This research is unique in that it applies the coupled MIKE SHE/MIKE HYDRO model technique, which has not been applied before to investigate changes in streamflow due to climate change in LTSB. Streamflow in the LTSB was forecasted using the MIKE SHE/MIKE HYDRO model from seven ensembles of GCMs under two emission scenarios (SSP2–4.5 and SSP5–8.5) between 2041 and 2,100. According to the calibration and validation results in the period of 1985–2007, MIKE SHE performs well while simulating streamflow in LTSB. During calibration and validation, the Nash‐Sutcliffe efficiency (NSE) values in all watersheds were greater than 0.8, except for the Ribb watershed calibration, where it was 0.75. The mean monthly changes in temperatures indicate an incremental tendency in the next decades. According to the simulation result, the monthly mean rainfall for SSP2–4.5 and SSP5–8.5 will increase from 0.05 to 61.9% and 2.02 to 46.26% in the 2050s and 8.7 to 44.38% to 6.44 to 66.24% in the 2080s, respectively. Gilgle Abay, Gumara, and Ribb watersheds will lose 56.2, 56.65, 57.01% of their mean monthly streamflow in the 2050s, according to SSP2–4.5. For the Gilgle Abay, Gumara, and Ribb watersheds, streamflow will increase by 6.7% to 21.94%, 6.08% to 23.26%, and 6.51% to 22.88%, accordingly, in the 2050s under SSP5–8.5. Increased rainfall in the watershed could result in floods in the already‐flooded Gumara and Ribb flood plains. The government and community should implement coping mechanisms to lessen the impact of climate change like early warring and planting more trees. Overall, the study showed that it is expected that conditions related to streamflow may change in the future due to climate alteration. By offering a better understanding of current and future climates, the integrated modeling system developed can assist environmentalists, hydrologists, and policymakers in water management and policy intervention.

Use of silver nanoparticles to suppress Cucumber mosaic virus (CMV) in ginger (Zingiber officinale Roscoe) and turmeric (Curcuma longa L.)

Plant viruses have remained a nuisance to profitable and sustainable crop cultivation; and concerted efforts have been exercised to salvage this menace. In this study, the efficacy of silver nanoparticles (AgNPs) against Cucumber mosaic virus (CMV) in ginger and turmeric plants was investigated using the technique of quantitative real-time PCR (qRT-PCR) using SYBR Green. The plants comprising three groups; treated, untreated and healthy controls were mechanically inoculated with a purified CMV suspension at early plant growth. The virus concentration was then measured after the inoculation before silver nanoparticles were applied at 20 ppm per treated plant. The virus concentration significantly declined after the suppressive effect by AgNPs (p < 0.01) in the treated plants from one-month post-inoculation (MPI) and sustained through 5 MPI. Thus, AgNPs have provided an avenue for the management of CMV infection in ginger and turmeric.

Plant community responses to the individual and interactive effects of warming and herbivory across multiple years.

Anthropogenic climate warming affects plant communities by changing community structure and function. Studies on climate warming have primarily focused on individual effects of warming, but the interactive effects of warming with biotic factors could be at least as important in community responses to climate change. In addition, climate change experiments spanning multiple years are necessary to capture interannual variability and detect the influence of these effects within ecological communities. Our study explores the individual and interactive effects of warming and insect herbivory on plant traits and community responses within a 7-year warming and herbivory manipulation experiment in two early successional plant communities in Michigan, USA. We find stronger support for the individual effects of both warming and herbivory on multiple plant morphological and phenological traits; only the timing of plant green-up and seed set demonstrated an interactive effect between warming and herbivory. With herbivory, warming advanced green-up, but with reduced herbivory, there was no significant effect of warming. In contrast, warming increased plant biomass, but the effect of warming on biomass did not depend upon the level of insect herbivores. We found that these treatments had stronger effects in some years than others, highlighting the need for multiyear experiments. This study demonstrates that warming and herbivory can have strong direct effects on plant communities, but that their interactive effects are limited in these early successional systems. Because the strength and direction of these effects can vary by ecological context, it is still advisable to include levels of biotic interactions, multiple traits and years, and community type when studying climate change effects on plants and their communities.

Effects of different cold-resistant agents and application methods on yield and cold-resistance of machine-transplanted early rice.

Cold stress is a critical factor affecting rice production worldwide. The application of cold-resistant agents may improve the cold resistance and yield of crops. To screen for suitable cold-resistant agents for machine-transplanted early rice, the effects of uniconazole, abscisic acid, and zinc-amino acids chelate and their spraying times (seed soaking stage, one leaf and one heart stage, two leaves and one heart stage, 7 days before the transplanting stage, and regreening stage) on the yield and cold resistance of machine-transplanted early rice were investigated. Moreover, the application method (spraying amount: 750 and 1125g ha-1; spraying time: 7 days before the transplanting stage, transplanting stage, regreening stage, and transplanting stage and regreening stage) for the most suitable cold-resistant agent was optimized. The zinc-amino acids chelate was better than the other two cold-resistant agents for promoting rice tillering and increasing the leaf area index, dry matter weight, antioxidant enzyme activities (CAT, SOD, POD) and yield (i.e., 9.22% and 7.14% higher than uniconazole and abscisic acid, respectively), especially when it was applied in the regreening stage. The examination of spraying amounts and times indicated that the zinc-amino acids chelate dosage had no significant effect on the yield and cold resistance of early rice. However, the rice yield and antioxidant enzyme activities were highest when samples were sprayed once in the transplanting stage and the regreening stage. On the basis of the study results, 750g ha-1 zinc-amino acids chelate applications in the transplanting and regreening stages of machine-transplanted early rice plants may be ideal for increasing cold stress resistance and yield.

Closing the gap: examining the impact of source habitat proximity on plant and soil microbial communities in post-mining spoil heap succession.

Revegetation of barren substrates is often determined by the composition and distance of the nearest plant community, serving as a source of colonizing propagules. Whether such dispersal effect can be observed during the development of soil microbial communities, is not clear. In this study, we aimed to elucidate which factors structure plant and soil bacterial and fungal communities during primary succession on a limestone quarry spoil heap, focusing on the effect of distance to the adjoining xerophilous grassland. We established a grid of 35 plots covering three successional stages - initial barren substrate, early successional community and late successional grassland ecosystem, the latter serving as the primary source of soil colonization. On these plots, we performed vegetation surveys of plant community composition and collected soil cores to analyze soil chemical properties and bacterial and fungal community composition. The composition of early successional plant community was significantly affected by the proximity of the source late successional community, however, the effect weakened when the distance exceeded 20 m. Early successional microbial communities were structured mainly by the local plant community composition and soil chemical properties, with minimal contribution of the source community proximity. These results show that on small spatial scales, species migration is an important determinant of plant community composition during primary succession while the establishment of soil microbial communities is not limited by dispersal and is primarily driven by local biotic and abiotic conditions.

Life cycle greenhouse gas emissions assessment: converting an early retirement coal-fired power plant to a biomass power plant

Decommissioning aging coal-fired power plants (CFPPs) represents an effective strategy for reducing greenhouse gas (GHG) emissions, accelerating energy mix diversification, and achieving nationally determined contributions and net-zero emissions targets. However, dismantling the CFPP and building a renewable energy-based power plant with a capacity equal to a dismantled CFPP could burden state finances. Therefore, converting coal to 100% biomass fuel in the aging CFPP is one of the proposals that needs to be studied. This study conducted an environmental assessment concerning the Life Cycle Greenhouse Gas (LC GHG) emissions, encompassing raw material extraction and power plant operation. Five scenarios were analyzed. Two scenarios related to using sawdust and agroforestry residue for biomass fuel in the aging CFPP. The other three scenarios used biomass fuel from Calliandra wood harvested from tropical forests, production forests, and marginal land, which produced GHG emissions from Land Use Change (LUC). This study demonstrates that sawdust and agroforestry residue can reduce global warming impacts compared to coal. The LUC in higher carbon stock land will increase global warming impacts, while the LUC in lower carbon stock land will reduce global warming impacts. A decrease in the aging CFPP efficiency, when coal is converted to 100% biomass, will cause an increase in global warming impacts.

Climate-smart agriculture and food security in climate-vulnerable coastal areas of Bangladesh

The issue of global climate change is increasingly worrisome, particularly for countries heavily reliant on agriculture. To reduce the negative impact of climate change on agriculture, farmers of Bangladesh started adopting different climate smart agriculture (CSA) practices. The CSA sustainably increases productivity, resilience, and food security, which can contribute to the achievement of a number of sustainable development goals (SDGs). However, the adoption of CSA is low especially in the climate-vulnerable coastal areas of Bangladesh. Therefore, this study was conducted to identify the factors affecting the adoption of CSA and its influence on coastal household’s food security. A total of 327 sample farmers from three coastal districts of Bangladesh were interviewed. The collected data were then analyzed by using the binary probit and ordered probit model. The findings indicated that highest 65% of farmers adopted early planting of rice as one of CSA practices. The adoption of CSA practices positively affected by the household annual income, extension services and awareness regarding CSA practices. Moreover, the adopters of CSA were more food secure than non-adopters. For instance, adoption of one additional CSA practice leads to an increase in the likelihood of being food secure by 4.3%. In terms of policy perspective, the adoption of CSA in the coastal areas can be increased through creation of employment opportunities, increasing access to extension services, and broadcasting of CSA-related programs on mass media.

Digital mapping of dates of transplanting and accumulated thermal requirement of rice (Oryza sativa L.) in the subtropics of North Eastern Hill Region, India

ABSTRACT Accurate and timely mapping of rice areas is crucial for effective agricultural planning and food security management in the North Eastern Hill Region of India, especially amid changing climate conditions. This study developed a method to estimate rice transplanting dates by utilizing VH polarized backscattering-coefficients rom Sentinel-1A SAR data and also assessed thermal requirements for rice productivity in Ri-Bhoi district, Meghalaya during kharif 2021. The methodology involved 3 steps- (i) preprocessing data to construct time-series SAR images (ii) rule-based classification of SAR data integrating phenological and topographical information to identify transplanting windows (iii) assessing mapping accuracy. The results when compared with field data, revealed five distinct transplanting windows from early June to early August across 9031 ha of rice area. Overall accuracy was 85%, with a kappa coefficient of 0.74. User and producer accuracies ranged from 0.74 to 0.93 and 0.75 to 0.92, respectively for various transplanting windows. GDD varied between 1432.8°C day and 3290.4°C day, with higher values corresponding to earlier planting dates. This study formulates a robust methodology for rice mapping in hilly, small-field landscapes with multiple transplanting dates by integrating Sentinel-1A SAR data with ancillary and crop phenology information, contributing to improved crop management and climate change adaptations.

Presence of vitamin B12 metabolism in the last common ancestor of land plants.

Vitamin B12, also known as cobalamin, is an essential organic cofactor for methionine synthase (METH), and is only synthesized by a subset of bacteria. Plants and fungi have an alternative methionine synthase (METE) that does not need B12 and are typically considered not to utilize it. Some algae facultatively utilize B12 because they encode both METE and METH, while other algae are dependent on B12 as they encode METH only. We performed phylogenomic analyses of METE, METH and 11 further proteins involved in B12 metabolism across more than 1600 plant and algal genomes and transcriptomes (e.g. from OneKp), demonstrating the presence of B12-associated metabolism deep into the streptophytes. METH and five further accessory proteins (MTRR, CblB, CblC, CblD and CblJ) were detected in the hornworts (Anthocerotophyta), and two (CblB and CblJ) were identified in liverworts (Marchantiophyta) in the bryophytes, suggesting a retention of B12-metabolism in the last common land plant ancestor. Our data further show more limited distributions for other B12-related proteins (MCM and RNR-II) and B12 dependency in several algal orders. Finally, considering the collection sites of algae that have lost B12 metabolism, we propose freshwater-to-land transitions and symbiotic associations to have been constraining factors for B12 availability in early plant evolution. This article is part of the theme issue 'The evolution of plant metabolism'.

The southwesternmost record of late Silurian (Pridolian) early land plants of Gondwana.

The Silurian-Devonian transition played a crucial role in the development of early terrestrial ecosystems due to the rapid diversification of early vascular plants. However, records of Pridolian plants in western Gondwana are scarce, limited to outcrops located in southern Bolivia. In this contribution, an association of fossil plants housed in the Rinconada Formation is presented. This association corresponds to primitive fossil flora with reproductive structures and sterile axes linked to basal tracheophytes. The fossil assemblage is composed of Aberlemnia caledonica, Caia langii Cooksonia cf. cambrensis, C. paranensis, C. cf. pertoni, Hostinella sp, Cf. Isidrophyton sp, Salopella marcensis, Steganoteca striata, two morphotypes of doubtful taxonomy, and graptolites colonies. The association between flora remains and graptolites, represents a parautochthonous assemblage in an inner marine platform, dominated by gravity flows. This record has paleophytogeographic importance indicating the extension of the northwest Gondwana-southern Laurusia unit to more southern areas of Gondwana. This expansion would have been favored by the post-glacial climatic improvement of the Late Silurian, together with a great radiation capacity and environmental flexibility of the flora. Furthermore, the biochron is extended of three taxa (A. caledonica, C. paranensis and Cf. Isidrophyton sp) first known from the Lochkovian, to the Pridoli.

The impact of elevated temperatures and CO2 on seed germination and early plant morphology: The case of native Fabaceae plants in the UAE

The impact of elevated temperatures and CO2 on seed germination and early plant morphology: The case of native Fabaceae plants in the UAE

Terrigenous or not? δ13C reveals the origin of the retene and dehydroabietic acid methyl ester

Retene and dehydroabietic acid methyl ester (DAME) are biomarkers linked mostly to terrigenous organic matter. However, their aquatic origin from algae and/or cyanobacteria has been discussed in the past few years. The complex origin of retene and DAME can lead to misinterpretation during biomarker interpretation, which can be minimalised with the support of isotopic analyses. This study contains the results of thirty-two compound-specific isotope analyses (CSIA) of δ13C performed on retene and forty-six CSIA analyses of δ13C performed on DAME. Obtained δ13C results were compared with simple biomarker results to tie isotopic data with the origin of organic matter. Pure aquatic retene and DAME were present within the Middle Cambrian and Early Ordovician samples, as the first appearance of plants was noted in the Middle Ordovician.CSIA was performed on a wide spectrum of the Cambrian-Silurian, Late Triassic-Middle Jurassic, and Neogene samples. Cambrian-Silurian strata include aquatic-origin retene and DAME, as evidenced by their comparatively low carbon isotopic signature. The average δ13C for retene and DAME within Cambrian-Silurian strata was equal to −31.7 ‰ and − 30.8 ‰, respectively. The Late Triassic-Middle Jurassic strata were dominated by terrigenous organic matter, resulting in higher δ13C values in comparison with the Cambrian-Silurian strata. The average δ13C for retene and DAME within the Late Triassic–Middle Jurassic strata was equal to −25.2 ‰ and − 26.3 ‰, respectively. The average δ13C for retene and DAME within the Neogene strata was equal to −27.3 ‰ in both cases, as these strata also contain a significant input of terrigenous organic matter. Some Neogene samples containing strong aquatic organic matter admixture are characterised by a lower δ13C for retene and/or DAME, oscillating around −28.0 ‰ to −30.0 ‰ for both compounds. Despite possible terrigenous input within some Silurian samples, the δ13C for retene and DAME still shows values typical for aquatic origin. These results suggest that retene and DAME within the Silurian strata should not be linked with non-vascular plants or that, due to their affinity with algae and cyanobacteria, the early plants were characterised by a relatively low δ13C composition, characteristic for phytoplankton organic matter. δ13C of retene and DAME were compared with δ13C of C16-C30n-alkanes and stigmastane, which supported the thesis about isotopic differences in aquatic and terrigenous retene and DAME.