Effect ofErwinia carotovora subsp.atroseptica on yield of potatoes from cut and uncut seed tubers in Valencia

Summary The effect on the development of blackleg symptoms and on yield of inoculating seed tubers of 15 cultivars withErwinia carotovora subsp.atroseptica (Eca) was investigated. Tubers were planted either whole or as pieces. Eca inoculation reduced the mean yield per plant by 8% for whole tubers and by 12% for cut tubers. There was no correlation between blackleg symptoms and yield loss.     

Interrelated effects of temperature, light and oxygen on Amaranthus caudatus L. seed germination

The aim of this study was to investigate the effects of temperature, light and oxygen on the germination of Amaranthus caudatus (var. viridis) seeds. At the highest temperature studied (35°C), seed germination was found to be most rapid and highest in both the dark and the light. Germination was inhibited by continuous white light. The lower the temperature, the greater the inhibitory effect of light. The far-red and blue spectral regions were the most effective in light inhibition. The light effect was also dependent on the percentage of oxygen in the atmosphere around the seeds; it was less marked in O₂-enriched atmospheres. Light/ oxygen dependency resulted from the action of the seed coat and endosperm. Scarified seeds were much less sensitive to light and hypoxia than non-scarified seeds. Effets combinés de la température, de la lumière et de I'oxygène sur la germination des graines d'Amaranthus caudatus L. Le but de ce travail était d'étudier les effets de la température, de la lumiere et de I'oxygène sur la germination des graines d'Amaranthus caudatus (var. viridis). A la temperature la plus élevée utilisée (35°C), la germination était la plus rapide et la plus complète tant à la lumière qu'à 1'obscuritè. La germination était inhibée par la lumière blanche continue. Plus la temperature était basse, plus 1'effet inhibiteur de la lumière était important. Les radiations rouge sombre et bleues du spectre étaient les plus in-hibitrices. L'effet de la lumière dépendait aussi de la teneur de 1'atmosphère en oxygène; il était moins marqué dans des atmosphères enrichies en oxygène. L'interaction lumière/oxygène provenait du tégument et de 1'albumen. Les graines scarifiées étaient beaucoup moins sensibles à la lumière et a 1'hypoxie que les graines non scarifiées. Wechselwirkungen von Temperatur, Licht und Sauerstoff auf die Keimung der Samen von Amaranthus caudatus L. Sowohl im Dunkeln als auch im Licht keimten die Samen von Amaranthus caudatus (var. viridis) bei 35°C, der höchsten Temperatur der Versuche, am schnellsten und meisten. Durch weiβes Dauerlicht wurde die Keimung gehemmt. Je niedriger die Temperatur, desto hölier die Hemmung durch Licht. Im entfernt roten und blauen Spektralbereich war die Lichthemmung am stärksten. Die Wirkung des Lichts hing auch vom Sauerstoffgehalt der die Samen umgebenden Luft ab: Bei O₂₅-Anreiche-rung war sie weniger deutlich. Die Licht/ Sauerstoff-Wechselwirkung wurde von der Samenschale und dem Endosperm beeinfluβt: Geritzte Samen waren gegenüber Licht und O₂-Mangel viel weniger empfindlich als ganze.     

Dormancy of Bromus rubens L. seeds in relation to temperature, light and oxygen effects

Freshly harvested mature Bromus rubens L. seeds are dormant. This dormancy corresponds to the inability of seeds to germinate in the dark at temperatures above 15°C, but is practically not apparent at temperatures between 5 and 15°C. Continuous white light markedly inhibits germination of dormant seeds, even at low irradiances, and reinforces their sensitivity to oxygen deprivation. However, prolonged illumination with white light does not alter subsequent germination in the dark. Breaking of dormancy during dry storage at 20°C results in a widening of the temperature range within which a high rate of germination occurs, and in almost complete disappearance of sensitivity of seeds to light. The structures surrounding the embryo (glumellae, caryopsis envelopes and possibly endosperm) are mainly responsible for dormancy and photosensitivity of whole seeds, probably because they limit the oxygen supply to the embryo. However, the embryo itself appears to play a role in dormancy. The results obtained are discussed in relation to dormancy of cereal seeds, and in relation to field establishment of B. rubens as a weed. La dormance des semences de Bromus rubens L. en relation avec les effets de la température, de la lumière et de l'oxygène Les semences mûres de Bromus rubens L. fraîchement récoltées sont dormantes. Leur dormance correspond à une inaptitude à germer à l'obscuritéà des températures supérieures à 15°C, mais elle ne se manifeste pratiquement pas entre 5 et 15°C. La lumière blanche continue inhibe nettement la germination des semences dormantes, même à de faibles énergies, et renforce leur sensibilitéà la privation d'oxygène. Cependant, un éclairement prolongé n'a aucune conséquence sur la germination ultérieure à l'obscurité. L'élimination de la dormance pendant la conservation au sec, à 20°C, se traduit par un élargissement de la gamme thermique qui assure une bonne germination et par la disparition presque complète de la sensibilité des semences à la lumière. Les structures qui entourent l'embryon (glumelles, enveloppes du caryopse et peut-être albumen) sont, en grande partie, responsables de la dormance et de la photosensibilité des semences entières, sans doute parce qu'elles limitent l'apport d'oxygène à l'embryon. Toutefois, l'embryon lui-même semble participer à la dormance. Les résultats obtenus sont discutés par comparaison avec la dormance des semences des céréales et en relation avec l'implantation, dans les cultures, de B. rubens en tant que mauvaise herbe. Dormanz der Samen von Bromus rubens L. in Bezug auf Temperatur, Licht und Sauerstoffversorgung Frisch geerntete Samen von Bromus rubens L. sind im Dunkeln bei Temperaturen über 15°C dormant, während diese Dormanz bei Temperaturen zwischen 5 und 15°C praktisch nicht vorliegt. Ständiges weißes Licht hemmt die Keimung dormanter Samen deutlich, sogar bei niedriger Intensität, und verstärkt ihre Empfindlichkeit gegenüber Sauerstoffmangel. Ständige Beleuchtung mit weißem Licht verändert jedoch nicht die folgende Dunkelkeimung. Das Brechen der Dormanz während der trockenen Lagerung bei 20 °C führt zu einem vergrößerten Temperaturbereich, in dem die Samen gut keimen, und läßt ihre Lichtempfindlichkeit fast vollständig verschwinden. Die Strukturen um den Embryo (Spelzen, Schale der Caryopse und möglicherweise Endosperm) sind hauptsächlich für die Dormanz und die Lichtempfindlichkeit des ganzen Samens verantwortlich, vermutlich deshalb, weil sie die Sauerstoffversorgung des Embryos einschränken. Aber auch der Embryo selbst scheint bei der Dormanz eine Rolle zu spielen. Die Untersuchungsergebnisse werden im Vergleich zur Dormanz von Getreidesamen und hinsichtlich des Vorkommens von Bromus rubens als Unkraut diskutiert.     

Diversity of global fisheries governance: Types and contexts

Fisheries governance systems designed to regulate fishing are often described as being highly diverse across countries. However, there is little systematic work that directly examines and describes the (dis)similarities across such systems, and how socio-political and economic contexts drive such variation at a global scale. In this paper, we use 68 indicators from a novel dataset to examine the fisheries governance systems in place to constrain overfishing in national waters across 142 countries. We found that countries cluster in just two distinct governance groups which display different traits to constrain overfishing. Where one group takes a tougher stance on aspects regarding access to its fisheries resources, the other is more focused on gathering fisheries information and publicizing the data. The 10 greatest differences between groups relate to the gathering of information and monitoring of their fisheries, the effectiveness of compliance systems and the existence of policies around sustainability. On these key differences, one group consistently displays more far-reaching governance traits. The overall governance capacity of a country and the national socio-economic importance of fisheries are identified as potential drivers of this variation. Despite their differences, the two groups show substantial overlap for many indicators, particularly those that are inexpensive, but also for certain costly policies. These patterns prompt hypotheses of policy transfer or convergence across fisheries governance systems, most notably regarding ‘low-hanging fruit’ policies.     

Undernutrition During Foetal and Post‐Natal Life Affects Testicular Structure and Reduces the Number of Sertoli Cells in the Adult Rat

To test whether undernutrition during foetal to pre‐pubertal life would have long lasting effects on testicular histology in adult male offspring, eleven adult Sprague–Dawley pregnant rats were divided into two groups: Control group, n = 4, fed ad libitum, during gestation and lactation (until 25 day post‐partum). Underfed group pregnant females (n = 7) were kept in cages where only dams had access to food (standard rat chow, 33.5% of ad libitum intake of Control group pregnant dams). After parturition, litters were adjusted to either 14 (Underfed group) or eight (Control group) pups. Mothers were weighed weekly. At 25 day of age pups were weaned, housed at four animals per cage, fed ad libitum and weighed weekly until euthanized at 100 day of age. Testes were processed for standard histology and morphometrical evaluation. At weaning, mother weight was lower in Underfedthan in Control group (mean ± SD): 214.1 ± 26.2 g vs 361.9 ± 33.1 g. Body weight at 100 days of age (254 ± 26.9 g vs 342.4 ± 10.2 g, p ≤ 0.001), testicular weight (1.29 ± 0.16 g vs 1.45 ± 0.13 g, p = 0.03), number of Sertoli cells per seminiferous tubule cross section (18.2 ± 1.2 vs 20.2 ± 1.3, p ≤ 0.01) and per testis (30.5 ± 4.2×10⁶ vs 36.0 ± 5.4×10⁶) were lower (p < 0.05) in Underfed than in Control group. This is the first report stating that foetal to pubertal subnutrition is accompanied by changes in testicular structure and lower Sertoli cell numbers in adult life, strongly suggesting lower daily sperm production.     

聚丙烯酰胺防治坡地水土流失田间试验研究

坡地篱用聚丙烯酰胺可以减少地表径流,提高土壤含水量,促进土壤沉降,增强土壤结构性和水稳性,因而提高了土壤的持水性和抗蚀性,减少了土壤侵蚀量和肥力流失量,有利于作物增产。施用聚丙烯酰胺可使产量增加１８．７％～３２．４％。施用聚丙烯酰胺对环境无不良影响,而且投入费用较低,是一条值得探索的防治坡地水土流失的新途径。     

Effect ofErwinia carotovora subsp.atroseptica alone and withAlternaria solani orVerticillium dahliae on disease development and yield of potatoes in Israel

Summary Tubers of 17 cultivars were inoculated withErwinia carotovora subsp.atroseptica (ECA) and planted in 1986 and 1987 in the Negev in randomised plots in three blocks where eitherVerticillium dahliae orAlternaria solani were present or where both were absent. ECA reduced the yield in the control block and exacerbated the yield losses in the disease blocks, but the intensity of symptom expression did not always accord with the extent of yield loss. ECA had a greater effect on plants infected withA. solani than on those withV. dahliae. It was possible to categorise the cultivars as resistant, intermediate or susceptible with respect to ECA and early blight, but resistance toV. dahliae could not be differentiated from foliage maturity.     

Emissions from in situ burning of crude oil in the arctic

The results of an exploratory study of the effects of in situ crude oil spill burning on air quality in the Beaufort Sea region of the Arctic are presented. A scenario is postulated defining the amounts of oil released, the size and number of burnable oil pools, and the duration of the burning period. Estimates are made of the likely emissions of soot, CO, SO₂ and metals based on literature and some experimental work. Assumptions are made about plume rise and dispersion which permit downwind concentrations of emissions to be calculated and compared with air quality objectives. Although the calculated concentrations may contain significant error because of the many assumptions, it is believed that the data demonstrate that concentrations of SO₂ and CO will be acceptably low, concentrations of soot and metals will often be undesirably high within 10 km of the fires, but will be acceptably low at greater distances. It is concluded that burning may be a method of substantially reducing the adverse environmental impact of oil spills in the Arctic.