Factors influencing fatigue in UK nurses working in respiratory clinical areas during the second wave of the Covid-19 pandemic: An online survey.

AIMS AND OBJECTIVES: This study explores UK nurses' experiences of working in a respiratory clinical area during the COVID-19 pandemic over winter 2020. BACKGROUND: During the first wave of the pandemic, nurses working in respiratory clinical areas experienced significant levels of anxiety and depression. As the pandemic has progressed, levels of fatigue in nurses have not been assessed. METHODS: A cross-sectional e-survey was distributed via professional respiratory societies and social media. The survey included Generalised Anxiety Disorder Assessment (GAD7), Patient Health Questionnaire (PHQ9, depression), a resilience scale (RS-14) and Chalder mental and physical fatigue tools. The STROBE checklist was followed as guidance to write the manuscript. RESULTS: Despite reporting anxiety and depression, few nurses reported having time off work with stress, most were maintaining training and felt prepared for COVID challenges in their current role. Nurses reported concerns over safety and patient feedback was both positive and negative. A quarter of respondents reported wanting to leave nursing. Nurses experiencing greater physical fatigue reported higher levels of anxiety and depression. CONCLUSIONS: Nurses working in respiratory clinical areas were closely involved in caring for COVID-19 patients. Nurses continued to experience similar levels of anxiety and depression to those found in the first wave and reported symptoms of fatigue (physical and mental). A significant proportion of respondents reported considering leaving nursing. Retention of nurses is vital to ensure the safe functioning of already overstretched health services. Nurses would benefit from regular mental health check-ups to ensure they are fit to practice and receive the support they need to work effectively. RELEVANCE TO CLINICAL PRACTICE: A high proportion of nurses working in respiratory clinical areas have been identified as experiencing fatigue in addition to continued levels of anxiety, depression over winter 2020. Interventions need to be implemented to help provide mental health support and improve workplace conditions to minimise PTSD and burnout.

Experimental evidence for recovery of mercury-contaminated fish populations.

Anthropogenic releases of mercury (Hg)1-3 are a human health issue4 because the potent toxicant methylmercury (MeHg), formed primarily by microbial methylation of inorganic Hg in aquatic ecosystems, bioaccumulates to high concentrations in fish consumed by humans5,6. Predicting the efficacy of Hg pollution controls on fish MeHg concentrations is complex because many factors influence the production and bioaccumulation of MeHg7-9. Here we conducted a 15-year whole-ecosystem, single-factor experiment to determine the magnitude and timing of reductions in fish MeHg concentrations following reductions in Hg additions to a boreal lake and its watershed. During the seven-year addition phase, we applied enriched Hg isotopes to increase local Hg wet deposition rates fivefold. The Hg isotopes became increasingly incorporated into the food web as MeHg, predominantly from additions to the lake because most of those in the watershed remained there. Thereafter, isotopic additions were stopped, resulting in an approximately 100% reduction in Hg loading to the lake. The concentration of labelled MeHg quickly decreased by up to 91% in lower trophic level organisms, initiating rapid decreases of 38-76% of MeHg concentration in large-bodied fish populations in eight years. Although Hg loading from watersheds may not decline in step with lowering deposition rates, this experiment clearly demonstrates that any reduction in Hg loadings to lakes, whether from direct deposition or runoff, will have immediate benefits to fish consumers.

Experiences of nurses caring for respiratory patients during the first wave of the COVID-19 pandemic: an online survey study.

BACKGROUND: Nurses have been at the forefront of the pandemic response, involved in extensive coordination of services, screening, vaccination and front-line work in respiratory, emergency and intensive care environments. The nature of this work is often intense and stress-provoking with an inevitable psychological impact on nurses and all healthcare workers. This study focused on nurses working in respiratory areas with the aim of identifying and characterising the self-reported issues that exacerbated or alleviated their concerns during the first wave of the COVID-19 pandemic. METHODS: An online survey was developed consisting of 90 questions using a mixture of open-ended and closed questions. Participant demographic data were also collected (age, gender, ethnicity, number of years qualified, details of long-term health conditions, geographical location, nursing background/role and home life). The online survey was disseminated via social media and professional respiratory societies (British Thoracic Society, Primary Care Respiratory Society, Association of Respiratory Nurse Specialists) over a 3-week period in May 2020 and the survey closed on 1 June 2020. RESULTS: The study highlights the experiences of nurses caring for respiratory patients during the first wave of the pandemic in early 2020. Concerns were expressed over the working environment, the supply and availability of adequate protective personal equipment, the quality of care individuals were able to deliver, and the impact on mental health to nurses and their families. A high number provided free-text comments around their worries and concerns about the impact on their household; these included bringing the virus home, the effect on family members worrying about them, mental health and the impact of changing working patterns, and managing with children. Although both formal and informal support were available, there were inconsistencies in provision, highlighting the importance of nursing leadership and management in ensuring equity of access to services. CONCLUSIONS: Support for staff is essential both throughout the pandemic and afterwards, and it is important that preparation of individuals regarding building resilience is recognised. It is also clear that psychological support and services for nurses and the wider healthcare team need to be available and quickly convened in the event of similar major incidents, either global or local.

Transport of mercury on the finest particles results in high sediment concentrations in the absence of significant ongoing sources.

The mercury contaminated upper Penobscot Estuary in Maine provided a unique opportunity to rigorously examine the effect of sediment type and particle size on mercury concentrations in sediments, and to explain why sediments at different locations in the estuary had different mercury concentrations. This is because the Penobscot Estuary contains a large, well-mixed pool of mobile sediments of many different types (muds, sand, gravel, wood chips), which are the source of material for the permanently deposited surface sediments. Despite this mixing, average surface sediment mercury concentrations were very different in different locations, ranging from 238 ng/gdw to 1032 ng/gdw in the 11 subareas studied. Average total mercury concentrations were highly related to the type of sediment (wood chips > muds > sands) regardless of location in the estuary. The characteristics in both mobile and surface sediments that were positively related to total mercury concentrations were % organic matter (measured as loss on ignition) and %fines (measured usually as <62.5 µ). Also, in a subset of samples it was shown that mercury was positively associated only with the very finest (<44 µ) particles. Thus, side embayments of the estuary such as the Orland River and Mendall Marsh, which experience lower velocity currents and so accumulate more fine particles, tended to be much higher in mercury concentrations. This knowledge will be important in managing remediation of this system, as fine particles can be the most difficult to trap or to retain if dredging is employed. Methyl mercury was well correlated with total mercury and so its distribution would also be affected by transport characteristics. This was the case even in the mobile sediments, which were more oxic and not expected to provide a good habitat for methylation.

A wolf in sheep's clothing? Patients' and healthcare professionals' perceptions of oxygen therapy: An interpretative phenomenological analysis.

BACKGROUND: Despite emerging evidence and guidelines, poor prescribing and administration of oxygen therapy persists. This study aimed to explore healthcare professionals' (HCPs) and patients' perceptions of oxygen. DESIGN: Semi-structured interviews with 28 patients and 34 HCPs. FINDINGS: Three master themes uncovered: oxygen as a panacea, the burden of oxygen and antecedents to beliefs. Patients used oxygen for breathlessness and as an enabler; they were grateful to oxygen and accepted it as part of the disease. HCPs used oxygen because it helps patients; it works; and it makes HCPs feel better. But oxygen is not benign and a burden is evident with potential antecedents to beliefs revealed. SUMMARY: The findings suggest that a set of fixed beliefs regarding oxygen exist, influenced by several impacting factors. The perception that oxygen is a universal remedy presides, but is, at times, contradictory. These findings will raise awareness of entrenched cultures, influence future educational and research strategies, and inform policy.

An evaluation of National Health Service England's Care Maker Programme: A mixed-methods analysis.

AIMS AND OBJECTIVES: To investigate the impact and sustainability of the Care Maker programme across England from the perspective of those involved in its delivery. BACKGROUND: The Care Maker programme was launched in England in 2013. It aims to support the "Compassion in Practice" strategy, with particular emphasis on the 6Cs of care, compassion, competence, communication, courage and commitment. Care Makers were recruited in an ambassadorial role. The intention was to inspire individuals throughout the National Health Service in England to bridge national policy with those delivering care. DESIGN: A mixed methods design was chosen, but this article focuses on two of the four distinct empirical data collection phases undertaken as part of this evaluation: a questionnaire with Care Makers; and two case studies of separate National Health Service trust sites. METHOD: Data were collected for this evaluation in 2015. An online questionnaire was distributed to the total population of Care Makers across the National Health Service in England. It included a combination of open and closed questions. The case studies involved semistructured telephone interviews with a range of professionals engaged with the Care Maker programme across the trust sites. RESULTS: Care Makers reported that participation in the programme had offered opportunities in terms of improving the quality-of-care provision in the workplace as well as contributing towards their own professional development. CONCLUSION: The Care Maker programme has supported and helped underpin the nursing, midwifery and care strategy "Compassion in Practice". RELEVANCE TO CLINICAL PRACTICE: This model of using volunteers to embed strategy and policy could potentially be used in other areas of clinical practice and indeed in other countries.

Investigation of uptake and retention of atmospheric Hg(II) by boreal forest plants using stable Hg isotopes.

Although there is now a general consensus among mercury (Hg) biogeochemists that increased atmospheric inputs of inorganic Hg(II) to lakes and watersheds can result in increased methylmercury (MeHg) concentrations in fish, researchers still lack kinetic data describing the movement of Hg from the atmosphere, through watershed and lake ecosystems, and into fish. The use of isotopically enriched Hg species in environmental studies now allows experimentally applied new Hg to be distinguished from ambient Hg naturally present in the system. Four different enriched stable Hg(II) isotope "spikes" were applied sequentially over four years to the ground vegetation of a microcatchment at the Experimental Lakes Area (ELA) in the remote boreal forest of Canada to examine retention of Hg(II) following deposition. Areal masses of the spikes and ambient THg (all forms of Hg in a sample) were monitored for eight years, and the pattern of spike retention was used to estimate retention of newly deposited ambient Hg within the ground vegetation pool. Fifty to eighty percent of applied spike Hg was initially retained by ground vegetation. The areal mass of spike Hg declined exponentially over time and was best described by a first-order process with constants(k) ranging between 9.7 x 10(-40 day(-1) and 11.6 x 10(-4) day(-1). Average halflife (t1/2) of spike Hg within the ground vegetation pool (+/-S.D.) was 704 +/- 52 days. This retention of new atmospheric Hg(II) by vegetation delays movement of new Hg(II) into soil, runoff, and finally into adjacent lakes. Ground-applied Hg(II) spikes were not detected in tree foliage and litterfall, indicating that stomatal and/or root uptake of previously deposited Hg (i.e., "recycled" from ground vegetation or soil Hg pools) were likely not large sources of foliar Hg under these experimental conditions.

Long-term wet and dry deposition of total and methyl mercury in the remote boreal ecoregion of Canada.

Although a positive relationship between atmospheric loadings of inorganic mercury (Hg(II)) to watersheds and concentrations of methyl mercury (MeHg) in fish has now been established, net wet and dry deposition of Hg(II) and MeHg to watersheds remains challenging to quantify. In this study, concentrations and loadings of total mercury (THg; all forms of Hg in a sample) and MeHg in open area wet deposition, throughfall, and litterfall were quantified atthe remote Experimental Lakes Area in the boreal ecoregion, NW Ontario, Canada. Between 1992 and 2006, mean annual THg and MeHg loadings in the open were 36 +/- 17 and 0.5 +/- 0.2 mg ha(-1), respectively. Throughfall THg and MeHg loadings were generally 2-4 times and 0.8-2 times higher, respectively, than loadings in the open. Loadings of both THg and MeHg were highest under an old growth spruce/fir canopy and lowest under a deciduous maple canopy, whereas loadings under young jack pine and wetland spruce/pine/alder canopies were intermediate. Litterfall generally represented the largest input of THg (86-105 mg ha(-1)) and MeHg (0.7-0.8 mg ha(-1)) to the landscape on an annual basis. Using the "direct" method of estimating dry deposition (thoughfall + litterfall - open loadings), we calculated that annual dry deposition of THg and MeHg under forest canopies ranged from 105 to 201 mg ha(-1), whereas dry deposition of MeHg ranged from 0.7 to 1.2 mg ha(-1). Photoreduction and emission of wet-deposited Hg(ll) from canopy foliage were accounted for, resulting in 3-5% (5-6 mg ha(-1)) higher annual estimates of dry deposition than via the direct method alone. NetTHg and MeHg loadings to this remote landscape were lower than at any other previously studied forested site globally. This study shows that THg and MeHg loading can be extremely variable within a heterogeneous boreal landscape and that processes such as Hg photoreduction and emission from foliage should be considered when estimating dry deposition of Hg.

Effect of pH on intracellular accumulation of trace concentrations of Hg(II) in Escherichia coli under anaerobic conditions, as measured using a mer-lux bioreporter.

The effects of pH on the uptake and accumulation of Hg(II) by Escherichia coli were determined at trace, environmentally relevant, concentrations of Hg and under anaerobic conditions. Hg(II) accumulation was measured using inducible light production from E. coli HMS174 harboring a mer-lux bioreporter plasmid (pRB28). The effect of pH on the toxicity of higher concentrations of Hg(II) was measured using a constitutive lux plasmid (pRB27) in the same bacterial host. In this study, intracellular accumulation and toxicity of Hg(II) under anaerobic conditions were both significantly enhanced with decreasing pH over the pH range of 8 to 5. The pH effect on Hg(II) accumulation was most pronounced at pHs of <6, which substantially enhanced the Hg(II)-dependent light response. This enhanced response did not appear to be due to pH stress, as similar results were obtained whether cells were grown at the same pH as the assay or at a different pH. The enhanced accumulation of Hg(II) was also not related to differences in the chemical speciation of Hg(II) in the external medium resulting from the changes in pH. Experiments with Cd(II), also detectable by the mer-lux bioreporter system, showed that Cd(II) accumulation responded differently to pH changes than the net accumulation of Hg(II). Potential implications of these findings for our understanding of bacterial accumulation of Hg(II) under anaerobic conditions and for bacteria-mediated cycling of Hg(II) in aquatic ecosystems are discussed. Arguments are provided suggesting that this differential accumulation is due to changes in uptake of mercury.

Whole-ecosystem study shows rapid fish-mercury response to changes in mercury deposition.

Methylmercury contamination of fisheries from centuries of industrial atmospheric emissions negatively impacts humans and wildlife worldwide. The response of fish methylmercury concentrations to changes in mercury deposition has been difficult to establish because sediments/soils contain large pools of historical contamination, and many factors in addition to deposition affect fish mercury. To test directly the response of fish contamination to changing mercury deposition, we conducted a whole-ecosystem experiment, increasing the mercury load to a lake and its watershed by the addition of enriched stable mercury isotopes. The isotopes allowed us to distinguish between experimentally applied mercury and mercury already present in the ecosystem and to examine bioaccumulation of mercury deposited to different parts of the watershed. Fish methylmercury concentrations responded rapidly to changes in mercury deposition over the first 3 years of study. Essentially all of the increase in fish methylmercury concentrations came from mercury deposited directly to the lake surface. In contrast, <1% of the mercury isotope deposited to the watershed was exported to the lake. Steady state was not reached within 3 years. Lake mercury isotope concentrations were still rising in lake biota, and watershed mercury isotope exports to the lake were increasing slowly. Therefore, we predict that mercury emissions reductions will yield rapid (years) reductions in fish methylmercury concentrations and will yield concomitant reductions in risk. However, a full response will be delayed by the gradual export of mercury stored in watersheds. The rate of response will vary among lakes depending on the relative surface areas of water and watershed.

Evaluation of mercury toxicity as a predictor of mercury bioavailability.

Many studies on bioavailability of toxic metals have made the assumption that observation of toxicity is evidence thatthe metal was taken into the cells (i.e., was "bioavailable"). A second assumption is that results at the high concentrations necessary for toxic effect are applicable to the lower concentrations more commonly found in the environment. These assumptions were specifically tested for mercury (Hg(II)) toxicity (at concentrations of 0.25-50 nM Hg) and uptake (at lower concentrations of 0.005-0.015 nM Hg) in the aquatic bacterium, V. anguillarum. Toxicity was measured as reduction in levels of constitutively expressed bioluminescence in V. anguillarum pRB27. Hg(II) uptake was measured using the Hg(II)-inducible mer-lux operon in V. anguillarum pRB28. In experiments where the predominant Hg species was changed from HgCl2 to Hg(OH)2 or Hg(NH3)2(2+), toxicity results accurately predicted that there would be no effect of the dominant species on Hg(II) uptake at lower HgT concentrations. However, toxicity tests with these same ligands failed to predict that there would be an effect on Hg(II) uptake when conditions were changed from aerobic to anaerobic. Toxicity tests also failed to predict the effect of 5 mM histidine additions on Hg(II) uptake, as histidine addition protected cells completely from Hg toxicity under both aerobic and anaerobic conditions, at concentrations up to 50 nM Hg, but did not prevent Hg(II) uptake. Uptake occurred at low HgT concentrations (0.01 nM) at the same rate when histidine was added under aerobic conditions and was substantially increased under anaerobic conditions. Thus, toxicity assays for Hg under a variety of conditions were not always a reliable predictor of the effects of those conditions on Hg(II) uptake into the cell.

The rise and fall of mercury methylation in an experimental reservoir.

For the past 9 years, we experimentally flooded a wetland complex (peatland surrounding an open water pond) at the Experimental Lakes Area (ELA), northwestern Ontario, Canada, to examine the biogeochemical cycling of methyl mercury (MeHg) in reservoirs. Using input-output budgets, we found that prior to flooding, the wetland complex was a net source of approximately 1.7 mg MeHg ha(-1) yr(-1) to downstream ecosystems. In the first year of flooding, net yields of MeHg from the reservoir increased 40-fold to approximately 70 mg MeHg ha(-1) yr(-1). Subsequently, annual net yields of MeHg from the reservoir declined (10-50 mg MeHg ha(-1) yr(-1)) but have remained well above natural levels. The magnitude and timing of Hg methylation in the flooded peat portion of the wetland reservoir were very different than in the open water region of the reservoir. In terms of magnitude, net Hg methylation rates in the peat in the first 2 years of flooding were 2700 mg ha(-1) yr(-1), constituting over 97% of the MeHg produced at the whole-ecosystem level. But in the following 3 years, there was a large decrease in the mass of MeHg in the flooded peat due to microbial demethylation. In contrast, concentrations of MeHg in the open water region and in zooplankton, and body burdens of Hg in cyprinid fish, remained high for the full 9 years of this study. Microbial activity in the open water region also remained high, as evidenced by continued high concentrations of dissolved CO2 and CH4. Thus, the large short-term accumulation of MeHg mass in the peat appeared to have only a small influence on concentrations of MeHg in the biota; rather MeHg accumulation in biota was sustained by the comparatively small ongoing net methylation of Hg in the flooded pond where microbial activity remained high. In large reservoirs, where the effects of wind and fetch are greater than in the small experimental reservoir we constructed, differences can occur in the timing and extent of peat and soil erosion, effecting either transport of MeHg to the food chain or the fueling of microbial activity in open water sediments, both of which could have important long-term implications for MeHg concentrations in predatory fish.

Reactivity and mobility of new and old mercury deposition in a boreal forest ecosystem during the first year of the METAALICUS study. Mercury Experiment To Assess Atmospheric Loading In Canada and the US.

The METAALICUS (Mercury Experiment To Assess Atmospheric Loading In Canada and the US) project is a whole ecosystem experiment designed to study the activity, mobility, and availability of atmospherically deposited mercury. To investigate the dynamics of mercury newly deposited onto a terrestrial ecosystem, an enriched stable isotope of mercury (202Hg) was sprayed onto a Boreal forest subcatchment in an experiment that allowed us, for the first time, to monitor the fate of 'new' mercury in deposition and to distinguish it from native mercury historically stored in the ecosystem. Newly deposited mercury was more reactive than the native mercury with respect to volatilization and methylation pathways. Mobility through runoff was very low and strongly decreased with time because of a rapid equilibration with the large native pool of "bound" mercury. Over one season, only approximately 8% of the added 212Hg volatilized to the atmosphere and less than 1% appeared in runoff. Within a few months, approximately 66% of the applied 202Hg remained associated with above ground vegetation, with the rest being incorporated into soils. The fraction of 202Hg bound to vegetation was much higher than seen for native Hg (<5% vegetation), suggesting that atmospherically derived mercury enters the soil pool with a time delay, after plants senesce and decompose. The initial mobility of mercury received through small rain events or dry deposition decreased markedly in a relatively short time period, suggesting that mercury levels in terrestrial runoff may respond slowly to changes in mercury deposition rates.

Demographic consequences of inflorescence-feeding insects for Liatris cylindracea, an iteroparous perennial.

While floral herbivores and predispersal seed predators often reduce plant reproductive output, their role in limiting plant fitness and population growth is less clear, especially for iteroparous perennial plant species. In this study we experimentally excluded floral herbivores and predispersal seed predators (insecticide spray versus water control) over a 2-year period to examine the effect of inflorescence-feeding insects on levels of seed production, seedling emergence, and juvenile establishment for Liatris cylindracea, an iteroparous perennial plant. In addition, we collected detailed demographic data on all life stage transitions for an additional set of individuals in the same population over 4 years. We used the experimental and demographic data to construct stochastic individual-based simulations to evaluate the overall effect of inflorescence-feeding insects on adult recruitment per maternal plant (a fitness component) and population growth rate. The insect exclusion experiments showed that damage due to insects decreased seed production, seedling emergence, and juvenile establishment for both years' experiments. These results indicate that recruitment was seed-limited through juvenile establishment, and that inflorescence-feeding insects influenced the degree of seed limitation. Results of the individual-based simulation models, which included individual demographic and temporal stochasticity, showed that inflorescence-feeding insects negatively affected the number of adult offspring per maternal plant recruited into the population and population growth rate for both years' experiments. Taken together, the results of the experimental exclusions and the individual-based models indicate that inflorescence-feeding insects can influence population growth rate, and have the potential to act as a selective force for the evolution of traits in this plant species.

QUANTITATIVE GENETICS OF SIZE AND PHENOLOGY OF LIFE-HISTORY TRAITS IN CHAMAECRISTA FASCICULATA.

Despite numerous adaptive scenarios concerning the evolution of plant life-history phenologies few studies have examined the heritable basis for and genetic correlations among these phenologies. Documentation of genetic variation for and covariation among reproductive phenologies is important because it is this variation/covariation that will determine the potential for response to evolutionary forces. To address this problem, I conducted a breeding experiment to determine narrow-sense heritabilities for and genetic correlations among the phenologies of life-history events and plant size in Chamaecristafasciculata, a temperate summer annual plant species. Paternal families showed no evidence of heritable variation for two estimates of plant size, six measures of reproductive phenology or two fitness components. Similarly, paternal estimates of genetic correlations among these traits were low or zero. In contrast, maternal estimates of heritability suggested the influence of maternal parent on one estimate of plant size and four phenological traits. Likewise, maternal effects influenced maternal estimates of genetic correlations. These maternal effects can arise from three sources: endosperm nuclear, cytoplasmic genetic and/or maternal phenotypic. The degree to which the phenology of one life-history trait acts as a constraint on the evolution of other phenological traits depends on the source of the maternal influence in this species.

SPATIAL AND TEMPORAL VARIATION IN SELECTION ON CORRELATED LIFE-HISTORY TRAITS AND PLANT SIZE IN CHAMAECRISTA FASCICULATA.

Intraspecific studies of selection on multiple traits of a plant's life history provide insight as to how the composite life history of an organism evolves. Current understanding of selection on plant life-history traits is deficient in three important areas: 1) the effects of selection through correlated traits, 2) the effects of selection on a trait throughout the plant's lifetime, and 3) spatial and temporal variation in selection on plant life-history traits among populations and years. This study documents spatial and temporal variation in selection on three life-history and two morphological traits for two natural populations of Chamaecrista fasciculata, a native summer annual. Life-history and morphological traits (date of seedling emergence, size at establishment, size prior to reproduction, date of initial flowering, and date of initial fruit maturation) varied significantly between sites and/or years. Selection on traits varied either spatially, between sites and among transects within one site, or temporally, between years. In addition, life-history traits were phenotypically correlated among themselves and with morphological traits; correlations were generally constant over time and space. Indirect selection caused changes in means and variances in traits not under direct selection, but which were correlated with traits under selection. Selection on date of emergence varied in direction and magnitude among different life-cycle stages, while selection on other traits varied only in magnitude among life stages of the plant. This study documents the complexity of the selective process and the importance of considering multiple life stages and traits when studying the evolution of life-history traits.

REPRODUCTIVE PHENOLOGIES IN LOBELIA INFLATA (LOBELIACEAE) AND THEIR ENVIRONMENTAL CONTROL.

Flowering and fruiting phenologies of individual plants and flowers of Lobelia inflata, a North American summer annual, were studied in the field and greenhouse to determine whether onset of flowering and fruit maturation were correlated, and the degree to which these reproductive phenologies were influenced by the environment. Within each of two field populations, larger plants flowered earlier and produced more flowers than smaller plants. Onset of flowering was positively correlated with onset of fruit maturation but not perfectly so. Two factors decreased the intensity of this correlation. First, at the flower level, the earlier a flower bloomed, the longer the resulting fruit took to develop. Second, fruit development times varied significantly among individual plants. In the greenhouse, individuals watered more frequently attained greater size and flowered earlier than individuals watered less frequently. Nutrient additions did not affect plant size or onset of flowering. These results indicate that for the summer annual Lobelia inflata, reproductive phenologies are phenotypically correlated, and that timing of reproduction is resource and size dependent, as it is for other monocarpic plant species.

Extrafloral nectaries: ants, herbivores and fecundity in Cassia fasciculata.

Extrafloral nectaries of Cassia fasciculata attract nectar feeding ants which protect the plant against leaf herbivores. High ant visitation in late July coincided with high herbivore densities at two sites in east central Iowa. The highest level of leaf herbivory occurred during the time of flowering and early fruit filling, just after the peak of herbivore and ant activity. Results of ant exclusion experiments at the two sites showed that ant visitation resulted in decreased herbivore numbers, decreased leaf area loss, increased growth, and at one site decreased plant mortality. However, this reduction in leaf area loss and increase in growth did not translate into seed set differences between plants with and without ants at either site. Initial plant size was more important than the presence or absence of ants in determining fecundity for this temperate annual during a year of summer drought.