Leaf structure and ultrastructure changes induced by heat stress and drought during seed filling in field-grown soybean and their relationship with grain yield.

Studies focusing on terminal drought combined with heat impacts on plants of agronomic value remain scarce, and even less under field conditions. The objective of this study was to investigate leaf structural and ultrastructural changes induced by heat stress (HS) and drought stress (DS) during seed filling and their relationship with physiological variables and yield determination. Two soybean cultivars were grown in field conditions. During seed filling four treatments were applied, including a control (without manipulation, at ambient temperature and field capacity), HS (episodes exceeding 32°C for 6 h d-1) during 21-d, DS (20% of field capacity soil water content) during 35-d, and HS×DS. Drought principally reduced leaf area, whereas heat decreased leaf thickness, possible as acclimation strategies, but also irreversible reducing CO2 assimilation sites. Both stresses damaged the outer and inner membranes of chloroplasts, causing swollen chloroplasts and accumulation of plastoglobules, loss of chlorophyll content, and negatively affecting chlorophyll fluorescence. Thus, the performance and integrity of the photosynthetic machinery were reduced. Through a morpho-functional perspective and a holistic multiscale approach, our results provide evidence of photosynthesis impairment and yield drops under stressful conditions which were associated with structural and ultrastructural (particularly at the level of chloroplasts) modifications of leaves.

Co-occurrences between adolescent substance use and academic performance: school context influences a multilevel-longitudinal perspective.

A growing body of literature has linked substance use and academic performance exploring substance use as a predictor of academic performance or vice versa. This study uses a different approach conceptualizing substance use and academic performance as parallel outcomes and exploring two topics: its multilevel-longitudinal association and school contextual effects on both outcomes. Using multilevel Confirmatory Factor Analysis and multilevel-longitudinal analyses, the empirical estimates relied on 7843 students nested in 114 schools (Add Health study). The main finding suggests that the correlation between substance use and academic performance was positive at the school level in contraposition to the negative relationship at the individual level. Additional findings suggest a positive effect of a school risk factor on substance use and a positive effect of academic pressure on academic performance. These findings represent a contribution to our understanding of how schools could affect the relationship between academic performance and substance use.

Ecological factors and adolescent marijuana use: results of a prospective study in Santiago, Chile.

PURPOSE: Despite the growing evidence that ecological factors contribute to substance use, the relationship of ecological factors and illicit drugs such as marijuana use is not well understood, particularly among adolescents in Latin America. Guided by social disorganization and social stress theories, we prospectively examined the association of disaggregated neighborhood characteristics with marijuana use among adolescents in Santiago, Chile, and tested if these relationships varied by sex. METHODS: Data for this study are from 725 community-dwelling adolescents participating in the Santiago Longitudinal Study, a study of substance using behaviors among urban adolescents in Santiago, Chile. Adolescents completed a two-hour interviewer administered questionnaire with questions about drug use and factors related to drug using behaviors. RESULTS: As the neighborhood levels of drug availability at baseline increased, but not crime or noxious environment, adolescents had higher odds of occasions of marijuana use at follow up, approximately 2 years later (odds ratio [OR] = 1.39; 95% CI = 1.16-1.66), even after controlling for the study's covariates. No interactions by sex were significant. DISCUSSION: The findings suggest that "poverty", "crime", and "drug problems" may not be synonyms and thus can be understood discretely. As Latin American countries re-examine their drug policies, especially those concerning decriminalizing marijuana use, the findings suggest that attempts to reduce adolescent marijuana use in disadvantaged neighborhoods may do best if efforts are concentrated on specific features of the "substance abuse environment".

Can the school context moderate the protective effect of parental support on adolescents' alcohol trajectories in urban Chicago?

BACKGROUND: Research explaining school effects on alcohol use is scare. This study examined the interactive effect between family support and school characteristics (size, poverty, and sector) on adolescents' alcohol use trajectories in Chicago. METHODS: Longitudinal and multilevel data were from the Project of Human Development in Chicago Neighborhoods and the Common Core of Data (National Center for Educational Statistics). The sample consisted of 2205 adolescents in 558 schools. A three-level hierarchical linear model was used to estimate multilevel growth curve models and school effects on alcohol trajectories. RESULTS: In addition to the strong relationship between parental support and alcohol trajectories; the results also found school effects on the average baseline of alcohol use and the rates of change across time. Interestingly, high levels of parental support were more effective in preventing alcohol use in public schools, while adolescents attending private schools with low levels of parental support were more likely to consume alcohol. Similarly, students attending public schools with higher rates of poverty who enjoy higher levels of parental support were less likely to consume alcohol compared to students with lower parental support attending lower rates of schools poverty. CONCLUSION: Key findings highlight the importance of the interaction between parental support and school characteristics meaning that protective factors provided by parents could be reinforced or diminished by the school context.

The Role of Religiousness on Substance-Use Disorder Treatment Outcomes: A Comparison of Black and White Adolescents.

This study compares 41 Black and 124 White adolescents at intake and discharge from a residential treatment program for substance-use disorders. Study data were obtained as part of a larger study (N = 195) that sought to assess the relationship of helping behavior and addiction recovery. This post-hoc analysis aims to identify cultural strengths that may be associated with recovery from substance-use disorders among Black adolescents. Using regression analyses and controlling for the severity of substance use and background variables that distinguish racial groups, religious practices and behaviors at intake were examined. Specifically, Black youth and White youth were compared on treatment outcomes, including alcohol or drug use during treatment, drug craving, 12-Step work, and 12-Step helping. The burden of health and socioeconomic disparities at intake did not disproportionately disfavor Black adolescents. Outcomes related to 12-Step measures were similar between Black and White youth. White adolescents reported higher craving scores at discharge, and Black adolescents were more likely to use drugs during treatment. High levels of religiousness at treatment intake were linked to greater 12-Step work and greater 12-Step helping at discharge. High levels of religiousness at intake were not related to drug use during treatment or to craving scores at discharge. The relationship between intake levels of religiousness and treatment-related outcomes did not differ by race.

Racial/ethnic differences in the longitudinal progression of co-occurring negative affect and cigarette use: from adolescence to young adulthood.

AIMS: This study examined the longitudinal progression of the co-occurrence of cigarette use and negative affect among the general population of U.S. adolescents and young adults and between racial/ethnic groups. METHODS: Data for this study consisted of Waves 4, 6, and 8 of the NLSY97 longitudinal study containing a nationally representative sample of U.S. adolescents and young adults. A total of 7979 adolescents (Mean age at Wave 4=17.98, SD=1.44, 49% female) were included in the analyses. To investigate the co-morbidity between negative affect and cigarette use, a latent factor of negative affect and single indicator of cigarette consumption were examined at each wave. A three wave Bivariate Autoregressive Cross-Lagged Effect Model was estimated to test the conjoint trajectory of negative affect and smoking. RESULTS: For all racial/ethnic groups prior negative affect status influenced future negative affect between waves and prior negative affect was positively related to increases in smoking in subsequent waves. The longitudinal trajectory of negative affect for the three racial/ethnic groups was the same, but racial/ethnic group differences were observed in the strength of the longitudinal relationship between previous and future cigarette use. Specifically, the following racial/ethnic differences were observed, even after controlling for the effect of SES; White young adults were found to exhibit the strongest association between cigarette use in the first two waves, followed by Hispanic individuals and lastly by African Americans. In the last two waves, African American young adults were found to have the strongest association between cigarette use at the latter two waves, followed by White individuals. CONCLUSIONS: Both negative affect and cigarette consumption influence each other during the transition between late adolescence and young adulthood but the magnitude of the associations between cigarettes use across waves differed between racial/ethnic groups. Implications for prevention and treatment programs include considering both cigarette use and negative affect as two factors that jointly impact each other and that should be targeted simultaneously.

[Neighborhood Systematic Social Observation; The Case of Chile and its Perspectives for Social Work.] / La Observación Sistemática de Vecindarios: El caso de Chile y sus perspectivas para Trabajo Social.

The study of neighborhood characteristics and their effects on individuals has become an area of increasing attention by scholars from various disciplines in developed countries. Although there are various methods to study neighborhoods and their impact on human populations, one of the most used is the Systematic Social Observation -Observación Sistemática de Vecindarios (OSV), in Spanish-because it allows the collection of information about various features of the physical, social, environmental and economic characteristics of neighborhoods. The purpose of this article is to (i) briefly present some research on neighborhood effects influential in the U.S., ii) describe how they Systematic Social Observation was designed and implemented in the city of Santiago, Chile, iii) discuss some facilitators and obstacles of the implementation process and, finally iv) list possible contributions and limitations this approach would offer the profession of social work in Chile.

Quantitative trait loci for grain moisture at harvest and field grain drying rate in maize (Zea mays, L.).

Hybrids with low grain moisture (GM) at harvest are specially required in mid- to short-season environments. One of the most important factors determining this trait is field grain drying rate (FDR). To produce hybrids with low GM at harvest, inbred lines can be obtained through selection for either GM or FDR. Thus, a single-cross population (181 F (2:3)-generation plants) of two divergent inbred lines was evaluated to locate QTL affecting GM at harvest and FDR as a starting point for marker assisted selection (MAS). Moisture measurements were made with a hand-held moisture meter. Detection of QTL was facilitated with interval mapping in one and two dimensions including an interaction term, and a genetic linkage map of 122 SSR loci covering 1,557.8 cM. The markers were arranged in ten linkage groups. QTL mapping was made for the mean trait performance of the F (2:3) population across years. Ten QTL and an interaction were associated with GM. These QTL accounted for 54.8 and 65.2% of the phenotypic and genotypic variation, respectively. Eight QTL and two interactions were associated with FDR accounting for 35.7 and 45.2% of the phenotypic and genotypic variation, respectively. Two regions were in common between traits. The interaction between QTL for GM at harvest had practical implications for MAS. We conclude that MAS per se will not be an efficient method for reducing GM at harvest and/or increasing FDR. A selection index including both molecular marker information and phenotypic values, each appropriately weighted, would be the best selection strategy.