Genetic determinants of seed protein plasticity in response to the environment in Medicago truncatula.

As the frequency of extreme environmental events is expected to increase with climate change, identifying candidate genes for stabilizing the protein composition of legume seeds or optimizing this in a given environment is increasingly important. To elucidate the genetic determinants of seed protein plasticity, major seed proteins from 200 ecotypes of Medicago truncatula grown in four contrasting environments were quantified after one-dimensional electrophoresis. The plasticity index of these proteins was recorded for each genotype as the slope of Finlay and Wilkinson's regression and then used for genome-wide association studies (GWASs), enabling the identification of candidate genes for determining this plasticity. This list was enriched in genes related to transcription, DNA repair and signal transduction, with many of them being stress responsive. Other over-represented genes were related to sulfur and aspartate family pathways leading to the synthesis of the nutritionally essential amino acids methionine and lysine. By placing these genes in metabolic pathways, and using a M. truncatula mutant impaired in regenerating methionine from S-methylmethionine, we discovered that methionine recycling pathways are major contributors to globulin composition establishment and plasticity. These data provide a unique resource of genes that can be targeted to mitigate negative impacts of environmental stresses on seed protein composition.

Gene co-expression analysis of tomato seed maturation reveals tissue-specific regulatory networks and hubs associated with the acquisition of desiccation tolerance and seed vigour.

BACKGROUND: During maturation seeds acquire several physiological traits to enable them to survive drying and disseminate the species. Few studies have addressed the regulatory networks controlling acquisition of these traits at the tissue level particularly in endospermic seeds such as tomato, which matures in a fully hydrated environment and does not undergo maturation drying. Using temporal RNA-seq analyses of the different seed tissues during maturation, gene network and trait-based correlations were used to explore the transcriptome signatures associated with desiccation tolerance, longevity, germination under water stress and dormancy. RESULTS: During maturation, 15,173 differentially expressed genes were detected, forming a gene network representing 21 expression modules, with 3 being specific to seed coat and embryo and 5 to the endosperm. A gene-trait significance measure identified a common gene module between endosperm and embryo associated with desiccation tolerance and conserved with non-endospermic seeds. In addition to genes involved in protection such LEA and HSP and ABA response, the module included antioxidant and repair genes. Dormancy was released concomitantly with the increase in longevity throughout fruit ripening until 14 days after the red fruit stage. This was paralleled by an increase in SlDOG1-2 and PROCERA transcripts. The progressive increase in seed vigour was captured by three gene modules, one in common between embryo and endosperm and two tissue-specific. The common module was enriched with genes associated with mRNA processing in chloroplast and mitochondria (including penta- and tetratricopeptide repeat-containing proteins) and post-transcriptional regulation, as well several flowering genes. The embryo-specific module contained homologues of ABI4 and CHOTTO1 as hub genes associated with seed vigour, whereas the endosperm-specific module revealed a diverse set of processes that were related to genome stability, defence against pathogens and ABA/GA response genes. CONCLUSION: The spatio-temporal co-expression atlas of tomato seed maturation will serve as a valuable resource for the in-depth understanding of the dynamics of gene expression associated with the acquisition of seed vigour at the tissue level.

Inference of Longevity-Related Genes from a Robust Coexpression Network of Seed Maturation Identifies Regulators Linking Seed Storability to Biotic Defense-Related Pathways.

Seed longevity, the maintenance of viability during storage, is a crucial factor for preservation of genetic resources and ensuring proper seedling establishment and high crop yield. We used a systems biology approach to identify key genes regulating the acquisition of longevity during seed maturation of Medicago truncatula. Using 104 transcriptomes from seed developmental time courses obtained in five growth environments, we generated a robust, stable coexpression network (MatNet), thereby capturing the conserved backbone of maturation. Using a trait-based gene significance measure, a coexpression module related to the acquisition of longevity was inferred from MatNet. Comparative analysis of the maturation processes in M. truncatula and Arabidopsis thaliana seeds and mining Arabidopsis interaction databases revealed conserved connectivity for 87% of longevity module nodes between both species. Arabidopsis mutant screening for longevity and maturation phenotypes demonstrated high predictive power of the longevity cross-species network. Overrepresentation analysis of the network nodes indicated biological functions related to defense, light, and auxin. Characterization of defense-related wrky3 and nf-x1-like1 (nfxl1) transcription factor mutants demonstrated that these genes regulate some of the network nodes and exhibit impaired acquisition of longevity during maturation. These data suggest that seed longevity evolved by co-opting existing genetic pathways regulating the activation of defense against pathogens.

Adjustments of embryonic photosynthetic activity modulate seed fitness in Arabidopsis thaliana.

In this work, we dissect the physiological role of the transient photosynthetic stage observed in developing seeds of Arabidopsis thaliana. By combining biochemical and biophysical approaches, we demonstrate that despite similar features of the photosynthetic apparatus, light absorption, chloroplast morphology and electron transport are modified in green developing seeds, as a possible response to the peculiar light environment experienced by them as a result of sunlight filtration by the pericarp. In particular, enhanced exposure to far-red light, which mainly excites photosystem I, largely enhances cyclic electron flow around this complex at the expenses of oxygen evolution. Using pharmacological, genetic and metabolic analyses, we show that both linear and cyclic electron flows are important during seed formation for proper germination timing. Linear flow provides specific metabolites related to oxygen and water stress responses. Cyclic electron flow possibly adjusts the ATP to NADPH ratio to cope with the specific energy demand of developing seeds. By providing a comprehensive scenario of the characteristics, function and consequences of embryonic photosynthesis on seed vigour, our data provide a rationale for the transient building up of a photosynthetic machinery in seeds.

Assessing Glycosylated Hemoglobin Thresholds for Development of Cardiovascular Disease by Racial and Ethnic Groups.

BACKGROUND: Diabetes is the strongest risk factor for cardiovascular disease, and although glycosylated hemoglobin (HbA1c) levels are known to vary by race, no racial and ethnic-specific diagnostic thresholds exist for diabetes in prediction of cardiovascular disease events. The purpose of this study is to determine whether HbA1c thresholds for predicting major adverse cardiovascular events (MACEs) differ among racial and ethnic groups. METHODS AND RESULTS: This is a retrospective cohort study of Kaiser Permanente Northern California adult members (n=309 636) with no history of cardiovascular disease who had HbA1c values and race and ethnicity data available between 2014 and 2019. Multivariable logistic regression was used to evaluate the odds of MACEs by the following racial and ethnic groups: Filipino, South Asian, East Asian, Black, White, and Hispanic. A Youden index was used to calculate HbA1c thresholds for MACE prediction by each racial and ethnic group, stratified by sex. Among studied racial and ethnic groups, South Asian race was associated with the greatest odds of MACEs (1.641 [95% CI, 1.456-1.843]; P<0.0001). HbA1c was a positive predictor for MACEs, with an odds ratio of 1.024 (95% CI, 1.022-1.025) for each 0.1% increment increase in HbA1c. HbA1c values varied between 6.0% and 7.6% in MACE prediction by race and ethnicity and sex. White individuals, South Asian individuals, East Asian women, and Black men had HbA1c thresholds for MACE prediction in the prediabetic range, between 6.0% and 6.2%. Black women, Hispanic men, and East Asian men had HbA1c thresholds of 6.2% to 6.6%, less than the typical threshold of 7.0% that is used as a treatment goal. CONCLUSIONS: Findings suggest that the use of race and ethnic- and sex-specific HbA1c thresholds may need to be considered in treatment goals and cardiovascular disease risk estimation.

A method to determine antifungal activity in seed exudates by nephelometry.

BACKGROUND: One of the levers towards alternative solutions to pesticides is to improve seed defenses against pathogens, but a better understanding is needed on the type and regulation of existing pathways during germination. Dormant seeds are able to defend themselves against microorganisms during cycles of rehydration and dehydration in the soil. During imbibition, seeds leak copious amounts of exudates. Here, we developed a nephelometry method to assay antimicrobial activity (AA) in tomato seed exudates as a proxy to assess level of defenses. RESULTS: A protocol is described to determine the level of AA against the nonhost filamentous fungus Alternaria brassicicola in the exudates of tomato seeds and seedlings. The fungal and exudate concentrations can be adjusted to modulate the assay sensitivity, thereby providing a large window of AA detection. We established that AA in dormant seeds depends on the genotype. It ranged from very strong AA to complete absence of AA, even after prolonged imbibition. AA depends also on the stages of germination and seedling emergence. Exudates from germinated seeds and seedlings showed very strong AA, while those from dormant seeds exhibited less activity for the same imbibition time. The exudate AA did not impact the growth of a pathogenic fungus host of tomato, Alternaria alternata, illustrating the adaptation of this fungus to its host. CONCLUSIONS: We demonstrate that our nephelometry method is a simple yet powerful bioassay to quantify AA in seed exudates. Different developmental stages from dormant seed to seedlings show different levels of AA in the exudate that vary between genotypes, highlighting a genetic diversity x developmental stage interaction in defense. These findings will be important to identify molecules in the exudates conferring antifungal properties and obtain a better understanding of the regulatory and biosynthetic pathways through the lifecycle of seeds, from dormant seeds until seedling emergence.

BASIC PENTACYSTEINE1 regulates ABI4 by modification of two histone marks H3K27me3 and H3ac during early seed development of Medicago truncatula.

Introduction: The production of highly vigorous seeds with high longevity is an important lever to increase crop production efficiency, but its acquisition during seed maturation is strongly influenced by the growth environment. Methods: An association rule learning approach discovered MtABI4, a known longevity regulator, as a gene with transcript levels associated with the environmentally-induced change in longevity. To understand the environmental sensitivity of MtABI4 transcription, Yeast One-Hybrid identified a class I BASIC PENTACYSTEINE (MtBPC1) transcription factor as a putative upstream regulator. Its role in the regulation of MtABI4 was further characterized. Results and discussion: Overexpression of MtBPC1 led to a modulation of MtABI4 transcripts and its downstream targets. We show that MtBPC1 represses MtABI4 transcription at the early stage of seed development through binding in the CT-rich motif in its promoter region. To achieve this, MtBPC1 interacts with SWINGER, a sub-unit of the PRC2 complex, and Sin3-associated peptide 18, a sub-unit of the Sin3-like deacetylation complex. Consistent with this, developmental and heat stress-induced changes in MtABI4 transcript levels correlated with H3K27me3 and H3ac enrichment in the MtABI4 promoter. Our finding reveals the importance of the combination of histone methylation and histone de-acetylation to silence MtABI4 at the early stage of seed development and during heat stress.

Making the most of what we have: What does the future hold for Emergency Department data?

Over 10 million ED visits occur each year across Australia and Aotearoa New Zealand. Outside basic administrative data focused on time-based targets, there is minimal information about clinical performance, quality of care, patient outcomes, or equity in emergency care. The lack of a timely, accurate or clinically useful data collection represents a missed opportunity to improve the care we deliver each day. The present paper outlines a proposal for a National Acute Care Secure Health Data Environment, including design, possible applications, and the steps taken to date by the Australasian College for Emergency Medicine ED Epidemiology Network in collaboration with the College of Emergency Nursing Australasia. Optimal use of the existing information collected routinely during clinical care of emergency patients has the potential to enable data-driven quality improvement and research, leading to better care and better outcomes for millions of patients and families each year.

A simple and efficient method to search for selected primary transcripts: non-coding and antisense RNAs in the human pathogen Enterococcus faecalis.

Enterococcus faecalis is a commensal bacterium and a major opportunistic human pathogen. In this study, we combined in silico predictions with a novel 5'RACE-derivative method coined '5'tagRACE', to perform the first search for non-coding RNAs (ncRNAs) encoded on the E. faecalis chromosome. We used the 5'tagRACE to simultaneously probe and characterize primary transcripts, and demonstrate here the simplicity, the reliability and the sensitivity of the method. The 5'tagRACE is complementary to tiling arrays or RNA-sequencing methods, and is also directly applicable to deep RNA sequencing and should significantly improve functional studies of bacterial RNA landscapes. From 45 selected loci of the E. faecalis chromosome, we discovered and mapped 29 novel ncRNAs, 10 putative novel mRNAs and 16 antisense transcriptional organizations. We describe in more detail the oxygen-dependent expression of one ncRNA located in an E. faecalis pathogenicity island, the existence of an ncRNA that is antisense to the ncRNA modulator of the RNA polymerase, SsrS and provide evidences for the functional interplay between two distinct toxin-antitoxin modules.

Negative pressure dressings and the impact on pain management on thoracic incisions in patients undergoing oesophagectomy: a pilot study.

BACKGROUND: Pain control is recognised as a crucial post-operative measure for patients undergoing oesophagectomy with a thoracotomy incision for oesophageal cancer, where ineffective breathing due to pain is directly correlated with increased morbidity. The analgesic benefits of negative pressure wound therapy (NPWT) appear to be a relatively new and emerging finding. This pilot study aims to investigate the effects of NPWT on post-operative pain control and determine the feasibility of a larger trial. METHOD: Ten consecutive patients undergoing oesophagectomy were prospectively enrolled to have a PREVENA Incision Management System placed over a closed thoracotomy wound. This dressing was changed at post-operative day 5 and removed after day 10. Post-operative morbidity was recorded and analgesia was prescribed by the Acute Pain Service who were blinded to the study aims. Analgesia requirements were recorded in oral morphine equivalents (OME) and compared to 30 patients that had previously undergone oesophagectomy via thoracotomy. RESULTS: One patient was withdrawn from the study and there was no significant differences in patient demographics. The study group had less average daily analgesia requirements and reduced overall reported pain. Patients in the study group were less likely to develop pneumonia (44% and 57%) and less likely to require re-operation for complications of their surgery (0% and 10%). CONCLUSION: This pilot study shows reduced post-operative analgesia requirements and reduced morbidity when using NPWT over a closed thoracotomy wound, and affirms the feasibility of a future randomized control trial.

Genetic Variability in Seed Longevity and Germination Traits in a Tomato MAGIC Population in Contrasting Environments.

The stable production of high vigorous seeds is pivotal to crop yield. Also, a high longevity is essential to avoid progressive loss of seed vigour during storage. Both seed traits are strongly influenced by the environment during seed development. Here, we investigated the impact of heat stress (HS) during fruit ripening on tomato seed lifespan during storage at moderate relative humidity, speed (t50) and homogeneity of germination, using a MAGIC population that was produced under optimal and HS conditions. A plasticity index was used to assess the extent of the impact of HS for each trait. HS reduced the average longevity and germination homogeneity by 50% within the parents and MAGIC population. However, there was a high genetic variability in the seed response to heat stress. A total of 39 QTLs were identified, including six longevity QTLs for seeds from control (3) and HS (3) conditions, and six plasticity QTLs for longevity, with only one overlapping with a longevity QTL under HS. Four out of the six longevity QTL co-located with t50 QTL, revealing hotspots for seed quality traits. Twenty-one QTLs with intervals below 3 cM were analyzed using previous transcriptome and gene network data to propose candidate genes for seed vigour and longevity traits.

Dataset for transcriptome and physiological response of mature tomato seed tissues to light and heat during fruit ripening.

Seed vigor is an estimate of how successfully a seed lot will establish seedlings under a wide range of environmental conditions, with both the embryo and the surrounding endosperm playing distinct roles in the germination behaviour. Germination and seedling establishment are essential for crop production to be both sustainable and profitable. Seed vigor traits are sequentially acquired during development via genetic programs that are poorly understood, but known to be under the strong influence of environmental conditions. To investigate how light and temperature have an impact on the molecular mechanisms governing seed vigor at harvest, RNA sequencing was performed on Solanum lycopersicum cv. Moneymaker seed tissues (i.e. embryo and endosperm) that were dissected from fruits that were submitted to standard or high temperature and/or standard or dim light. The dataset encompassed a total of 26.5 Gb raw data from mature embryo and endosperm tissues transcriptomes. The raw and mapped reads data on build SL4.0 and annotation ITAG4.0 are available under accession GSE158641 at NCBI Gene Expression Omnibus (GEO) database. Data on seed vigor characteristics are presented together with the differentially expressed gene transcripts. GO and Mapman annotations were generated on ITAG4.0 to analyse this dataset and are provided for datamining future datasets.

Genome-Wide Association Studies of Seed Performance Traits in Response to Heat Stress in Medicago truncatula Uncover MIEL1 as a Regulator of Seed Germination Plasticity.

Legume seeds are an important source of proteins, minerals, and vitamins for human and animal diets and represent a keystone for food security. With climate change and global warming, the production of grain legumes faces new challenges concerning seed vigor traits that allow the fast and homogenous establishment of the crop in a wide range of environments. These seed performance traits are regulated during seed maturation and are under the strong influence of the maternal environment. In this study, we used 200 natural Medicago truncatula accessions, a model species of legumes grown in optimal conditions and under moderate heat stress (26°C) during seed development and maturation. This moderate stress applied at flowering onwards impacted seed weight and germination capacity. Genome-wide association studies (GWAS) were performed to identify putative loci or genes involved in regulating seed traits and their plasticity in response to heat stress. We identified numerous significant quantitative trait nucleotides and potential candidate genes involved in regulating these traits under heat stress by using post-GWAS analyses combined with transcriptomic data. Out of them, MtMIEL1, a RING-type zinc finger family gene, was shown to be highly associated with germination speed in heat-stressed seeds. In Medicago, we highlighted that MtMIEL1 was transcriptionally regulated in heat-stressed seed production and that its expression profile was associated with germination speed in different Medicago accessions. Finally, a loss-of-function analysis of the Arabidopsis MIEL1 ortholog revealed its role as a regulator of germination plasticity of seeds in response to heat stress.

Medicago ABI3 Splicing Isoforms Regulate the Expression of Different Gene Clusters to Orchestrate Seed Maturation.

Seed maturation comprises important developmental processes, such as seed filling and the acquisition of seed germination capacity, desiccation tolerance, longevity, and dormancy. The molecular regulation of these processes is tightly controlled by the LAFL transcription factors, among which ABSCISIC ACID INSENSITIVE 3 (ABI3) was shown to be involved in most of these seed maturation processes. Here, we studied the ABI3 gene from Medicago truncatula, a model legume plant for seed studies. With the transcriptomes of two loss-of-function Medicago abi3 mutants, we were able to show that many gene classes were impacted by the abi3 mutation at different stages of early, middle, and late seed maturation. We also discovered three MtABI3 expression isoforms, which present contrasting expression patterns during seed development. Moreover, by ectopically expressing these isoforms in Medicago hairy roots generated from the abi3 mutant line background, we showed that each isoform regulated specific gene clusters, suggesting divergent molecular functions. Furthermore, we complemented the Arabidopsis abi3 mutant with each of the three MtABI3 isoforms and concluded that all isoforms were capable of restoring seed viability and desiccation tolerance phenotypes even if not all isoforms complemented the seed color phenotype. Taken together, our results allow a better understanding of the ABI3 network in Medicago during seed development, as well as the discovery of commonly regulated genes from the three MtABI3 isoforms, which can give us new insights into how desiccation tolerance and seed viability are regulated.

Deep learning-based detection of seedling development.

BACKGROUND: Monitoring the timing of seedling emergence and early development via high-throughput phenotyping with computer vision is a challenging topic of high interest in plant science. While most studies focus on the measurements of leaf area index or detection of specific events such as emergence, little attention has been put on the identification of kinetics of events of early seedling development on a seed to seed basis. RESULT: Imaging systems screened the whole seedling growth process from the top view. Precise annotation of emergence out of the soil, cotyledon opening, and appearance of first leaf was conducted. This annotated data set served to train deep neural networks. Various strategies to incorporate in neural networks, the prior knowledge of the order of the developmental stages were investigated. Best results were obtained with a deep neural network followed with a long short term memory cell, which achieves more than 90% accuracy of correct detection. CONCLUSION: This work provides a full pipeline of image processing and machine learning to classify three stages of plant growth plus soil on the different accessions of two species of red clover and alfalfa but which could easily be extended to other crops and other stages of development.

Comparison of surface emissions and subsurface distribution of cis- and trans-1,3-dichloropropene and chloropicrin in sandy field beds covered with four different plastic films.

The purpose of this study was to conduct a field study at a Florida field site on surface emissions and subsurface distribution of cis-and trans-1,3-dichloropropene (1,3-D) and chloropicrin (CP) in raised beds injected with Telone C35 with four replications. A total of 16 beds were applied with Telone C35 by chisel injection and covered with four different plastic films, 4 beds for each film. Each bed was installed with five 20-cm long soil pore air probes and a surface air collection pan at arbitrarily locations along the length of each bed for sampling soil pore air and surface air, respectively, for analysis of the three biologically active compounds, cis- and trans-1,3-D and CP. We found that average concentrations of the three compounds at 20-cm depth among the beds covered with four different plastic films generally were not statistically different. Among the four beds covered with the same plastic film, average concentrations of the three compounds were statistically different only in the four metallic PE covered beds at 5 and 24 hours after injection. Volatilization rates of the three compounds among the beds covered with four different plastic films, with the exception of CP at 48 hours after injection, were not statistically different. It appeared that initial upward diffusion and volatilization flux were influenced by solar radiation. Initial subsurface concentrations of the three compounds and volatilization flux, especially cis-1,3-D, were greater in the beds on the east side of the field than that in the beds on the west side of the field. Whether or not difference in initial subsurface concentrations of the compounds between east side beds and west side beds may influence fumigant efficacy remains to be determined.

Does Delay to Theater Lead to Increased Infection Rates in Hand Trauma? A Retrospective Cohort Study.

BACKGROUND: In an ideal health system, traumatic wounds would be surgically managed within 24 hours; however, resource constraints result in patients with open wounds commonly waiting much longer for surgery. Does this result in increased morbidity? This study compares infection rates over time for patients who received operative management of traumatic hand injuries. METHODS: A retrospective analysis was undertaken of patients admitted between July 2014 and June 2015 who presented within 24 hours of sustaining a hand injury and subsequently underwent operative repair. Patient and injury data were collected from arrival time at emergency departments across 3 Victorian metropolitan hospitals within the same network. Admission and outpatient follow-up of these patients was reviewed for signs of infection and treatment with antibiotics. RESULTS: Six hundred thirty-eight patients met inclusion criteria, 8 of the 429 patients treated within 24 hours of presentation developed an infection (1.86%) compared with 11 of the 209 patients treated after 24 hours of presentation (5.26%). Using Fisher's exact analysis, a statistically significant association was identified (P = 0.024). An odds ratio of 2.924 was calculated, with a number needed to harm of 26. When time was analyzed as a continuous variable using logistic regression, there was no statistical significance. CONCLUSION: This study shows some evidence that a timing may be important to reduce the rates of infection and raises the possibility that there may be a double peak for infection risk at the 6-hour and 24-hour marks. This gives a basis of potential further study.

Four-dimensional computed tomography scan utility in parathyroidectomy for primary hyperparathyroidism with low baseline intact parathyroid hormone.

OBJECTIVES/HYPOTHESIS: The prevalence of multiglandular disease (MGD) of the parathyroid has been reported to be higher in patients with primary hyperparathyroidism and low baseline intact parathyroid hormone (PTH) levels (<100 pg/mL). Low baseline PTH is associated with lower localization rate and positive predictive value with both preoperative sestamibi and ultrasound. This study sought to evaluate our experience with four-dimensional computed tomography (4D-CT) for the localization of abnormal parathyroid glands, including MGD, in patients with low baseline intact PTH (LBiPTH). STUDY DESIGN: A single institution case series. METHODS: A case series of patients with primary hyperparathyroidism with low baseline PTH or an inconclusive sestamibi, who underwent surgery with a single surgeon from April 2012 to June 2015 following 4D-CT to help with abnormal gland localization. RESULTS: We identified 14 patients who underwent a 4D-CT in the setting of primary hyperparathyroidism and LBiPTH. A sestamibi scan had been ordered in 71% and was inconclusive in all cases. No ultrasound was performed. In all patients, 4D-CT was 84.6% sensitive in localizing abnormal glands, yielding a positive predictive value of 91.7%. Overall, 42.9% of patients had evidence of MGD, and 4D-CT detected 83.3% of MGD cases. A focused unilateral exploration was performed in 28.6% of cases, and a four-gland exploration was performed in all remaining patients. CONCLUSIONS: In patients with hypercalcemia and LBiPTH, with higher likelihood of MGD and of inconclusive results on sestamibi, 4D-CT may be a superior modality for localizing smaller adenoma or multiple hypercellular glands. This may allow for improved interpretation of intraoperative PTH results, and in a minority of cases, a focused parathyroid exploration. LEVEL OF EVIDENCE: 4 Laryngoscope, 127:1476-1482, 2017.

Henry's law constants and mass transfer coefficients for methyl bromide and 1,3-dichloropropene applied to Florida sandy field soil.

Methyl bromide, a pre-emergent soil fumigant, is scheduled to be phased out in the US by 2005, with exceptions for critical use. Comparison of some of the physical constants related to distribution and retention for methyl bromide (MBr) to other fumigants yields a useful quantification of possible alternatives. In this study, the atmospheric and subsurface dissipation of methyl bromide as well as (Z)- and (E)-1,3-dichloropropene (1,3-D) isomers in Telone II were examined. The Henry's law constants of the three chemicals at soil temperature and their mass transfer coefficients for movement through an agricultural mulch of UV-resistant, high-density polyethylene (PE) were evaluated using field data. At the soil temperature of 16.4 degrees C, calculated Henry's law constant gave a fumigant ranking of MBr (0.21)>>(Z)-1,3-D (0.041)>(E)-1,3-D (0.027). Since rapid subsurface distribution of a fumigant is highly dependent on the amount in the gas phase, the greater value for Henry's law constant implies faster distribution throughout the soil. After distribution through the soil, retention of the fumigant becomes imperative. Calculation of the fumigant's mass transfer coefficients through PE from field data gave a ranking of the three chemicals: MBr (1.08 cm/h)<(E)-1,3-D (3.25 cm/h)<(Z)-1,3-D (4.13 cm/h). With mass transfer coefficients of this magnitude, it was concluded that PE film was an inadequate barrier for retaining these fumigants in an agricultural setting.

Diffusion and emissions of 1,3-dichloro propene in Florida sandy soil in microplots affected by soil moisture, organic matter, and plastic film.

The main objective of this study was to determine the influence of soil moisture, organic matter amendment and plastic cover (a virtually impermeable film, VIF) on diffusion and emissions of (Z)- and (E)-1,3-dichloropropene (1,3-D) in microplots of Florida sandy soil (Arredondo fine sand). Upward diffusion of the two isomers in the Arredondo soil without a plastic cover was greatly influenced by soil-water content and (Z)-1,3-D diffused faster than (E)-1,3-D. In less than 5 h after 1,3-D injection to 30 cm depth, (Z)- and (E)-1,3-D in air dry soil had diffused to a 10 cm depth, whereas diffusion for the two isomers was negligible in near-water-saturated soil, even 101 h after injection. The diffusion rate of (Z)- and (E)-1,3-D in near-field-capacity soil was between the rates in the two water regimes. Yard waste compost (YWC) amendment greatly reduced diffusion of (Z)- and (E)-1,3-D, even in air-dry soil. Although upward diffusion of (Z)- and (E)-1,3-D in soil with VIF cover was slightly less than in the corresponding bare soil; the cover promoted retention of vapors of the two isomers in soil pore air in the shallow subsurface. More (Z)-1,3-D vapor was found initially in soil pore air than (E)-1,3-D although the difference declined thereafter. As a result of rapid upward movement in air-dry bare soil, (Z)- and (E)-1,3-D were rapidly volatilized into the atmosphere, but emissions from the near-water-saturated soil were minimal. Virtually impermeable film and YWC amendment retarded emissions. This study indicated that adequate soil water in this sandy soil is needed to prevent rapid emissions, but excess soil water slows diffusion of (Z)- and (E)-1,3-D. Thus, management for optimum water in soil is critical for pesticidal efficacy and the environment.