3 research outputs found
Warming and wetting signals emerging from analysis of changes in climate extreme indices over South America
Here we show and discuss the results of an assessment of changes in both area-averaged and station-based climate extreme indices over South America (SA) for the 1950-2010 and 1969-2009 periods using high-quality daily maximum and minimum temperature and precipitation series. A weeklong regional workshop in Guayaquil (Ecuador) provided the opportunity to extend the current picture of changes in climate extreme indices over SA.Our results provide evidence of warming and wetting across the whole SA since the mid-20th century onwards. Nighttime (minimum) temperature indices show the largest rates of warming (e.g. for tropical nights, cold and warm nights), while daytime (maximum) temperature indices also point to warming (e.g. for cold days, summer days, the annual lowest daytime temperature), but at lower rates than for minimums. Both tails of night-time temperatures have warmed by a similar magnitude, with cold days (the annual lowest nighttime and daytime temperatures) seeing reductions (increases). Trends are strong and moderate (moderate to weak) for regional-averaged (local) indices, most of them pointing to a less cold SA during the day and warmer night-time temperatures.Regionally-averaged precipitation indices show clear wetting and a signature of intensified heavy rain events over the eastern part of the continent. The annual amounts of rainfall are rising strongly over south-east SA (26.41. mm/decade) and Amazonia (16.09. mm/decade), but north-east Brazil and the western part of SA have experienced non-significant decreases. Very wet and extremely days, the annual maximum 5-day and 1-day precipitation show the largest upward trends, indicating an intensified rainfall signal for SA, particularly over Amazonia and south-east SA. Local trends for precipitation extreme indices are in general less coherent spatially, but with more general spatially coherent upward trends in extremely wet days over all SA. © 2012 Elsevier B.V
Post-weaning feeding levels on feeding behavior, growth and development in Holstein dairy heifers
Hormonal and Nutritional Changes in the Flavedo Regulating Rind Color Development in Sweet Orange [Citrus sinensis (L.) Osb.]
The objective of this research was to determine the changes in the levels of endogenous gibberellins GA(1) and GA(4), abscisic acid (ABA), and ethylene during fruit coloring of on-tree fruits of sweet orange. The time course of carbohydrates and nitrogen content in the flavedo prior to fruit color break and during peel ripening were also studied. To identify nutritional and hormonal changes in the fruit, 45 days before fruit color break the peduncles of 15-30 fruits per tree of 'Washington' navel, 'Navelate,' and 'Valencia Delta Seedless' sweet orange, located in single-fruited shoots, were girdled to intercept phloem transport. A set of 15-30 fruits per tree remained intact on the peduncle for control. Girdling significantly delayed fruit coloration for more than 2 months; the delay paralleled higher GA(1) and GA(4) concentrations in the flavedo and retarded the rise of ABA concentration prior to color break. Girdling also reduced carbohydrate concentrations and increased N concentrations in the flavedo compared to control fruits; no ethylene production was detected. Therefore, in sweet orange, fruit changes color by reducing active gibberellin concentrations in the flavedo, which are involved in regulating sugars and ABA accumulation and in reducing N fraction concentration as rind color develops. This was demonstrated in vivo without removing the fruit from the tree. Comparable results were obtained with experiments carried out over four consecutive years in two countries (Spain and Uruguay).This study was partially supported by the Programme ALssan, EU Programme of High Level Scholarships for Latin America (IN E03D15012UR), and Comision Sectorial de Investigacion Cientifica (Univ. de la Republica, Uruguay). The authors thank Dra. 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