The genomic basis of nitrogen utilization efficiency and trait plasticity to improve nutrient stress tolerance in cultivated sunflower.

Maintaining crop productivity is challenging as population growth, climate change, and increasing fertilizer costs necessitate expanding crop production to poorer lands whilst reducing inputs. Enhancing crops' nutrient use efficiency is thus an important goal, but requires a better understanding of related traits and their genetic basis. We investigated variation in low nutrient stress tolerance in a diverse panel of cultivated sunflower genotypes grown under high and low nutrient conditions, assessing relative growth rate (RGR) as performance. We assessed variation in traits related to nitrogen utilization efficiency (NUtE), mass allocation, and leaf elemental content. Across genotypes, nutrient limitation generally reduced RGR. Moreover, there was a negative correlation between vigor (RGR in control) and decline in RGR in response to stress. Given this trade-off, we focused on nutrient stress tolerance independent of vigor. This tolerance metric correlated with the change in NUtE, plasticity for a suite of morphological traits, and leaf element content. Genome-wide associations revealed regions associated with variation and plasticity in multiple traits, including two regions with seemingly additive effects on NUtE change. Our results demonstrate potential avenues for improving sunflower nutrient stress tolerance independent of vigor, and highlight specific traits and genomic regions that could play a role in enhancing tolerance.

Decoupling of functional traits from intraspecific patterns of growth and drought stress resistance.

Intraspecific variation in functional traits may mediate tree species' drought resistance, yet whether trait variation is due to genotype (G), environment (E), or G×E interactions remains unknown. Understanding the drivers of intraspecific trait variation and whether variation mediates drought response can improve predictions of species' response to future drought. Using populations of quaking aspen spanning a climate gradient, we investigated intraspecific variation in functional traits in the field as well as the influence of G and E among propagules in a common garden. We also tested for trait-mediated trade-offs in growth and drought stress tolerance. We observed intraspecific trait variation among the populations, yet this variation did not necessarily translate to higher drought stress tolerance in hotter/drier populations. Additionally, plasticity in the common garden was low, especially in propagules derived from the hottest/driest population. We found no growth-drought stress tolerance trade-offs and few traits exhibited significant relationships with mortality in the natural populations, suggesting that intraspecific trait variation among the traits measured did not strongly mediate responses to drought stress. Our results highlight the limits of trait-mediated responses to drought stress and the complex G×E interactions that may underlie drought stress tolerance variation in forests in dry environments.

Family child care home providers' self-reported nutrition and physical activity practices, self-efficacy, barriers and knowledge: baseline findings from happy healthy homes.

OBJECTIVE: Describe nutrition and physical activity practices, nutrition self-efficacy and barriers and food programme knowledge within Family Child Care Homes (FCCH) and differences by staffing. DESIGN: Baseline, cross-sectional analyses of the Happy Healthy Homes randomised trial (NCT03560050). SETTING: FCCH in Oklahoma, USA. PARTICIPANTS: FCCH providers (n 49, 100 % women, 30·6 % Non-Hispanic Black, 2·0 % Hispanic, 4·1 % American Indian/Alaska Native, 51·0 % Non-Hispanic white, 44·2 ± 14·2 years of age. 53·1 % had additional staff) self-reported nutrition and physical activity practices and policies, nutrition self-efficacy and barriers and food programme knowledge. Differences between providers with and without additional staff were adjusted for multiple comparisons (P < 0·01). RESULTS: The prevalence of meeting all nutrition and physical activity best practices ranged from 0·0-43·8 % to 4·1-16·7 %, respectively. Average nutrition and physical activity scores were 3·2 ± 0·3 and 3·0 ± 0·5 (max 4·0), respectively. Sum nutrition and physical activity scores were 137·5 ± 12·6 (max 172·0) and 48·4 ± 7·5 (max 64·0), respectively. Providers reported high nutrition self-efficacy and few barriers. The majority of providers (73·9-84·7 %) felt that they could meet food programme best practices; however, knowledge of food programme best practices was lower than anticipated (median 63-67 % accuracy). More providers with additional staff had higher self-efficacy in family-style meal service than did those who did not (P = 0·006). CONCLUSIONS: Providers had high self-efficacy in meeting nutrition best practices and reported few barriers. While providers were successfully meeting some individual best practices, few met all. Few differences were observed between FCCH providers with and without additional staff. FCCH providers need additional nutrition training on implementation of best practices.

Testing the effects of species interactions and water limitation on tree seedling biomass allocation and physiology.

Species interactions mediate tree responses to water limitation because competition and/or facilitation alter plant physiology and growth. However, because it is difficult to isolate the effects of plant-plant interactions and water limitation from other environmental factors, the mechanisms underlying tree physiology and growth in coexisting plants under drought are poorly understood. We investigated how species interactions and water limitation impact the physiology and growth of trembling aspen (Populus tremuloides), narrowleaf cottonwood (Populus angustifolia) and ponderosa pine (Pinus ponderosa) seedlings in a controlled environment growth chamber, using aspen as a focal species. Seedlings were grown in pots alone or with a con- or hetero-specific seedling, and were subjected to a water limitation treatment. Growth, water status and physiological traits were measured before, during and after the treatment. Under well-watered conditions, the presence of another seedling affected growth or biomass allocation in all species, but did not impact the physiological traits we measured. Under water limitation, the presence of a competing seedling had a marginal impact on seedling growth and physiological traits in all species. Throughout the study, the magnitude and direction of seedling responses were complex and often species-specific. Our study serves as an important step toward testing how species' interactions modify physiological responses and growth in well-watered and water-limited periods.

Key Traits and Genes Associate with Salinity Tolerance Independent from Vigor in Cultivated Sunflower.

With rising food demands, crop production on salinized lands is increasingly necessary. Sunflower (Helianthus annuus), a moderately salt-tolerant crop, exhibits a tradeoff where more vigorous, high-performing genotypes have a greater proportional decline in biomass under salinity stress. Prior research has found deviations from this relationship across genotypes. Here, we identified the traits and genomic regions underlying variation in this expectation-deviation tolerance (the magnitude and direction of deviations from the expected effect of salinity). We grew a sunflower diversity panel under control and salt-stressed conditions and measured a suite of morphological (growth, mass allocation, plant and leaf morphology) and leaf ionomic traits. The genetic basis of variation and plasticity in these traits was investigated via genome-wide association, which also enabled the identification of genomic regions (i.e. haplotypic blocks) influencing multiple traits. We found that the magnitude and direction of plasticity in whole-root mass fraction, fine root mass fraction, and chlorophyll content, as well as leaf sodium and potassium content under saline conditions, were most strongly correlated with expectation-deviation tolerance. We identified multiple genomic regions underlying these traits as well as a single alpha-mannosidase gene directly associated with this tolerance metric. Our results show that, by taking the vigor-salinity effect tradeoff into account, we can identify unique traits and genes associated with salinity tolerance. Since these traits and genomic regions are distinct from those associated with high vigor (i.e. growth in benign conditions), they provide an avenue for increasing salinity tolerance in high-performing sunflower genotypes without compromising vigor.

Competition and Drought Alter Optimal Stomatal Strategy in Tree Seedlings.

A better understanding of plant stomatal strategies holds strong promise for improving predictions of vegetation responses to drought because stomata are the primary mechanism through which plants mitigate water stress. It has been assumed that plants regulate stomata to maintain a constant marginal water use efficiency and forego carbon gain when water is scarce. However, recent hypotheses pose that plants maximize carbon assimilation while also accounting for the risk of hydraulic damage via cavitation and hydraulic failure. This "gain-risk" framework incorporates competition in stomatal regulation because it takes into account that neighboring plants can "steal" unused water. This study utilizes stomatal models representing both the water use efficiency and carbon-maximization frameworks, and empirical data from three species in a potted growth chamber experiment, to investigate the effects of drought and competition on seedling stomatal strategy. We found that drought and competition responses in the empirical data were best explained by the carbon-maximization hypothesis and that both drought and competition affected stomatal strategy. Interestingly, stomatal responses differed substantially by species, with seedlings employing a riskier strategy when planted with a high water use competitor, and seedlings employing a more conservative strategy when planted with a low water use competitor. Lower water users in general had less stomatal sensitivity to decreasing Ψ L compared to moderate to high water users. Repeated water stress also resulted in legacy effects on plant stomatal behavior, increasing stomatal sensitivity (i.e., conservative behavior) even when the seedling was returned to well-watered conditions. These results indicate that stomatal strategies are dynamic and change with climate and competition stressors. Therefore, incorporating mechanisms that allow for stomatal behavioral changes in response to water limitation may be an important step to improving carbon cycle projections in coupled climate-Earth system models.

Widespread drought-induced tree mortality at dry range edges indicates that climate stress exceeds species' compensating mechanisms.

Drought-induced tree mortality is projected to increase due to climate change, which will have manifold ecological and societal impacts including the potential to weaken or reverse the terrestrial carbon sink. Predictions of tree mortality remain limited, in large part because within-species variations in ecophysiology due to plasticity or adaptation and ecosystem adjustments could buffer mortality in dry locations. Here, we conduct a meta-analysis of 50 studies spanning >100 woody plant species globally to quantify how populations within species vary in vulnerability to drought mortality and whether functional traits or climate mediate mortality patterns. We find that mortality predominantly occurs in drier populations and this pattern is more pronounced in species with xylem that can tolerate highly negative water potentials, typically considered to be an adaptive trait for dry regions, and species that experience higher variability in water stress. Our results indicate that climate stress has exceeded physiological and ecosystem-level tolerance or compensating mechanisms by triggering extensive mortality at dry range edges and provides a foundation for future mortality projections in empirical distribution and mechanistic vegetation models.

Early Care and Education Teacher's Role in Obesity Prevention and Healthy Development of Young American Indian Children.

INTRODUCTION: The purpose of this study was to develop an understanding of how stakeholders, specifically early care and education (ECE) teachers, perceive their role in the development of young American Indian children, and envision working with health care providers and parents in order to enhance children's health. METHODOLOGY: Twenty tribally affiliated ECE teachers from Oklahoma participated in interviews. Thematic analysis was conducted, and three main themes, each with two to three subthemes, emerged. RESULTS: Teachers felt that nutrition and physical activity were important to children's health. Teachers had little professional interaction with health care providers but desired more. Parental empowerment was conveyed as essential to actualize positive changes in their child's behavior. DISCUSSION: Teachers of tribally affiliated ECE centers are important stakeholders in promoting the health and well-being of young American Indian children. Additional efforts are needed to more effectively integrate teachers and nurses in order to create effective interventions. We propose a stakeholder partnership to guide the development of future interventions.

Health Care Provider's Role in Obesity Prevention and Healthy Development of Young American Indian Children.

INTRODUCTION: Health care providers (HCPs) serving American Indian (AI) populations are critical stakeholders in promoting healthy weight-related behaviors of young AI children. The purpose of this study is to develop an understanding of how HCP perceive their role in the healthy development of young AI children, and how they envision working with early care and education teachers and parents to enhance children's health. METHOD: Twenty HCP that serve young AI children in Oklahoma participated in individual interviews. Thematic analysis was conducted on coded transcripts and three main themes, each with two to four subthemes were identified. RESULTS: HCP had limited contact with teachers, felt family health was equal or more important than child health, and parental empowerment and gradual change was essential for success. CONCLUSION: Creating ways to involve HCP, early care and education teachers, and parents together in multilevel and multisector interventions has the potential to improve the health of young AI children.

Expression of functional traits during seedling establishment in two populations of Pinus ponderosa from contrasting climates.

First-year tree seedlings represent a particularly vulnerable life stage and successful seedling establishment is crucial for forest regeneration. We investigated the extent to which Pinus ponderosa P. & C. Lawson populations from different climate zones exhibit differential expression of functional traits that may facilitate their establishment. Seeds from two populations from sites with contrasting precipitation and temperature regimes east (PIPO dry) and west (PIPO mesic) of the Oregon Cascade mountains were sown in a common garden experiment and grown under two water availability treatments (control and drought). Aboveground biomass accumulation, vegetative phenology, xylem anatomy, plant hydraulic architecture, foliar stable carbon isotope ratios (δ(13)C), gas exchange and leaf water relations characteristics were measured. No treatment or population-related differences in leaf water potential were detected. At the end of the first growing season, aboveground biomass was 74 and 44% greater in PIPO mesic in the control and drought treatments, respectively. By early October, 73% of PIPO dry seedlings had formed dormant buds compared with only 15% of PIPO mesic seedlings. Stem theoretical specific conductivity, calculated from tracheid dimensions and packing density, declined from June through September and was nearly twice as high in PIPO mesic during most of the growing season, consistent with measured values of specific conductivity. Intrinsic water-use efficiency based on δ(13)C values was higher in PIPO dry seedlings for both treatments across all sampling dates. There was a negative relationship between values of δ(13)C and leaf-specific hydraulic conductivity across populations and treatments, consistent with greater stomatal constraints on gas exchange with declining seedling hydraulic capacity. Integrated growing season assimilation and stomatal conductance estimated from foliar δ(13)C values and photosynthetic CO2-response curves were 6 and 28% lower, respectively, in PIPO dry seedlings. Leaf water potential at the turgor loss point was 0.33 MPa more negative in PIPO dry, independent of treatment. Overall, PIPO dry seedlings exhibited more conservative behavior, suggesting reduced growth is traded off for increased resistance to drought and extreme temperatures.

Session RPE following interval and constant-resistance cycling in hot and cool environments.

PURPOSE: This study examined effects of heat gain, circulatory adjustment to temperature regulation (HR), and [La] consequent to interval (INT) and constant-load (CON) cycling on session RPE (S-RPE). METHODS: Male volunteers (N = 10) completed a cycle ergometer VO2peak test and then, in a randomized, counterbalanced order, four cycling bouts, including constant load (approximately 45% VO2peak) (CON) and interval (8 x 1 min at about 90% VO2peak, 1 min between intervals) (INT), in hot (approximately 32.5 WBGT) (HOT) and cool (approximately 21.0 WBGT) (COOL) environments. Trials included a standardized warm-up and cool-down (10 min each: 0 W, 60 rpm). Total external work was equated among all trials, with blood lactate ([La]), heart rate (HR), rectal temperature (Tre), and acute RPE recorded at 10, 13, 17, 21, 25, and 36 min. S-RPE was recorded 20 min after each session. RESULTS: HOT (CON and INT) resulted in significantly (P < 0.05) greater heat gain (Tre), HR, and RPE-O, whereas INT had significantly elevated [La] versus CON (HOT and COOL). HOT yielded significantly higher S-RPE versus COOL for CON (HOT = 5.6 +/- 2.1, COOL = 4.3 +/- 1.3) and INT (HOT = 7.0 +/- 1.9, COOL = 5.1 +/- 2.0). S-RPE was significantly higher for INT/HOT than CON/HOT. CONCLUSIONS: Heat gain and cardiac strain (Tre, HR) and [La]) were manipulated with environment and exercise type while holding total work constant. The added strain of HOT was reflected in elevated S-RPE for both CON and INT. S-RPE linkage with [La] was limited to HOT trials, indicating only a loose association. These data indicate that under the conditions of this study, S-RPE is similar to acute RPE in that no single mediator seems universally dominant.