Large Environmental Variation Research Articles

Clothing and exercise. I: Biophysics of heat transfer between the individual, clothing and environment.

Despite large environmental variations, the human body maintains a tightly regulated core temperature. Effective thermoregulation must balance the interaction between skin surface, clothing and ambient air. Indices of thermal stress (wet bulb globe temperature, heat stress index, maximum evaporation rate, required evaporative rate and wind chill) provide valuable information concerning the heat exchange between the individual and the environment, and serve as protective guidelines while working in environmental extremes. The role of clothing, as an interactive barrier, greatly affects thermal balance. Clothing is varied according to prevailing environmental conditions, metabolic heat production, gender and age differences, fabric thermal properties, garment design and intended use. Models (static, dynamic and human) have investigated the biophysical transfer of heat between the skin surface area, clothing and ambient air. Additionally, the role of metabolic heat production during exercise can greatly influence tolerance to thermal stress during a variety of environmental conditions.

Genotype‐by‐Environment Interactions of Barley in the Mediterranean Region

In the Mediterranean region, progress in selection for yield in harsh environments is hampered by large environmental variation between seasons and locations. This study analyzes the genotype‐by‐environment (GE) interaction of 36 two‐rowed genotypes of barley (Hordeum vulgare L.), grown in 14 environments in Syria and North Africa. It assesses the effect of growth type (winter or spring type) and heading date on the GE interaction and determines whether or not high‐yielding (HY) environments are representative of low‐yielding (LY) ones. Average grain yield per environment ranged from 7 to 513 g m−2. Genotypes and environments were classified by a cluster analysis and the interaction was analyzed with an additive main effects and multiplicative interaction model. Genotypes were classified into four clusters, related to their growth type and earliness of heading. Environments were clustered in a HY and LY group; this classification was related to seasonal rainfall and temperature. Medium‐early heading winter types had a positive interaction with LY environments and a negative interaction with HY environments, whereas late heading genotypes (spring and winter types) had the opposite interaction pattern. Early heading spring types had above‐average mean yields; the highest‐yielding among them tended to have a low interaction with environments. High‐yielding environments did not discriminate well between genotypes with high or low yields in LY environments, and may thus have limited value for yield selection for LY environments. For a breeding program aimed at improving yield in environments where favorable conditions are rare, selection for yield should be done in representative less‐favorable environments.

Free amino acid concentrations in Mytilus edulis L. From different locations in the southwestern part of the netherlands: Their possible significance as a biochemical stress indicator

1. 1. During an annual cycle, concentrations of free amino acids were determined in mussels, Mytilus edulis L., collected monthly from 10 different locations in the Delta area (southwest part of the Netherlands). 2. 2. The applicability of suggested biochemical stress indices, i.e. the ratio of the taurine/glycine concentrations and the sum of the threonine and serine concentrations, was investigated. 3. 3. It is shown that, due to large seasonal and environmental variations (reproduction, salinity etc.), these stress indices should be used with much care.

Comparison of Stability Statistics as Criteria for Cultivar Development in Peanut1

Abstract Means of yield and qualitative traits are assessed in multi-location tests in the final stages of breeding line evaluation. Due to large environmental variation and genotype x environment interactions, it is often desirable to compare stability of lines over a range of environments. The objective of this study was to use various stability parameters to try and determine the stability of experimental breeding lines. Using data from regional advanced peanut (Arachis hypogaea L.) breeding line yield trials conducted over 3 years and four locations in Virginia and North Carolina, the stability of peanut cultivars and breeding lines was compared. Stability variance was found to be highly correlated (0.91–1.00) with covariate adjusted stability variance. In many instances, the stability-variance parameters produced similar results to pairwise regressions and dissimilarity measures when compared with standard cultivars. However, the distance parameters and regressions provided more precise information on relative responses in varying environments of two advanced breeding lines being considered for release. This allowed for direct comparison to cultivars targetted for replacement. NC 18411 had equal mean yields and qualitative traits but better stability than breeding line NC 18423. Regression analysis indicated that NC 18423 performed best in good environments but worse than most other cultivars in poor environments. Means and stability of value per kilogram and value per hectare were highly correlated with percentage of sound mature kernels and yield (0.92–0.99), respectively. A comparison of means and stability parameters was effective in discerning superiority of peanut breeding lines for potential release and use by growers.

X-ray fluorescence yields for light emitter atoms: fluorine

By explicitly taking into account the critical configuration-dependent covalency which may occur in ionic systems such as solid fluorides, a dense and comprehensive picture is devised of radiative and non-radiative decay of highly excited states carrying a single vacancy in the F K shell. Besides reproducing the pertinent spectroscopic findings, at least at a semi-quantitative level the authors predict surprisingly large environmental variations of X-ray fluorescence yields which are available now for experimental verification. Moreover, in the formal treatment of covalent effects on inner-hole filling processes they have encountered a new possibility for 'interatomic' vacancy-transferring transitions which will prove significant, particularly in explaining chemical effects on X-ray satellite spectra.

Selection for Sucrose Yield in Stressed Sugarbeet Seedlings

Progress in improving sucrose yield in sugarbeet (Beta vulgaris L.) has been slow, due to large environmental variation associated with root yield and a negative correlation between root yield and sucrose concentration. Appropriate stress applied on segregating populations could increase performance differences among genotypes and increase the genetic variance. Stress that forces defoliated plants to grow new leaves from their stored root reserves logically ought to select for increased photosynthate storage and, therefore, increased sucrose yield. Stress was imposed in greenhouse tests by trimming the leaves from 3‐ to 4‐wk‐old sugarbeet seedlings and covering them with black plastic, thereby forcing the plants to grow new leaves from their stored root reserves. When this stress was imposed on seedlings of a series of cultivars varying in root yield and sucrose potential, those cultivars with the highest potential sucrose yield had the greatest survival rate (fewest plants dying). The correlations between percent survival after stress and total sucrose yield were 0.96 and 0.90 for field and greenhouse replicated trials, respectively. Open‐pollinated seed increases of the surviving plants in two heterogeneous populations resulted in increases in field root yield, sucrose concentration and total sucrose yield. These increases, although in a favorable direction, were not always at the desired probability of significance. Data combined over 2 years of testing gave significant increases in total sucrose yield for the two new stress selection populations over their parents at the 0.07 and 0.14 probability levels. This method shows promise as a quick, inexpensive technique for improving both root yield and sucrose concentration.

Year Effects on Partitioning of Dry Matter into Cotton Boll Components1

The distribution of dry weight in cotton boll walls, seeds, and fibers was investigated through the boll developmental period for one flowering date each year in 1979 and 1980. Previous experiments on patterns of fiber development encountered large environmental variation, so this experiment with four diverse cottons was undertaken to measure the effect of years on dry weight distribution into boll components. There was a large difference between years in temperature and moisture, with 1980 being hot and dry. Associated with differences in weather between the years was a large difference in dry weight distribution and boll development. In 1980, cotton matured in 88% of the time, individual boll dry weight was reduced 25%, boll wall dry weight per boll was reduced 17%, seed dry weight per boll was reduced 15%, and fiber dry weight per boll was reduced 41% compared to 1979. In addition, bolls developed in 1980 had fewer but larger seeds and fewer but larger fibers than in 1979. Total lint yield was reduced only 7% in 1980 vs. 1979, so more bolls were produced in 1980. At the individual boll level, the differences between years had the greatest effect on fiber dry weight. The effect on fiber dry weight per boll demonstrated the vulnerability of fiber development to environmental variation.

VARIABILITY IN POD FILLING CHARACTERISTICS OF PEAS (Pisum sativum L.) UNDER FIELD CONDITIONS

The average rates of pod dry weight increase, final pod weights and durations of pod growth were estimated for peas (Pisum sativum L.) growing in the field. The effects of plant genotype, field location and the time of season on these characters were studied in several populations of pea genotypes. Rate of pod filling and final pod weight were both affected by genotype, year and initiation time during the season. Effective duration of pod filling was not affected by any of these factors and final pod weight was always strongly related to the rate of filling. For 46 genotypes, the rate of pod filling ranged from 16 to 75 mg∙day−1 in a single location. Despite the large environmental and seasonal variation, the interactions with genotype were small and estimates of broad sense heritability were high. Across genotypes, rate of pod filling was correlated with weight per 100 seeds and final seed yields. The large changes in rate of pod filling during the season were similar in pattern in 2 yr. However, because this pattern was similar in populations with different flowering times, and because of the significant relationship to the changes in irradiance during both seasons, it is suggested that these seasonal changes in pod filling are of environmental rather than developmental origin.Key words: Pod bulking, seed development, pod development, seasonal changes, growth rate, duration