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The aim of the present paper is to study the influence of air temperature on the start of Quercus pollination in Córdoba (Andalusia, Spain). Sixteen years of pollen counts were used. The start date of the pollen season in this period varied between 26[sup th] February and 7[sup th] April. Chilling requirements and heat accumulation were taken into account although no significant correlation between chilling hours and the start date was observed. Five different predictive methods based on heat accumulation were compared in this paper: 1) Number of days over a threshold; 2) Heat Units (accumulated daily mean temperature after deducting a base temperature); 3) Growing Degrees Days (Snyder 1988), as a measure of physiological growing time; 4) Accumulated maximum temperatures; and 5) Mean maximum temperature. Results indicated that the optimum base temperature for heat accumulation was 11 C[sup o]. This threshold was used in the first three methods mentioned above. Good statistical results were obtained with the five methods, yielding high levels of explanation (p~99%). Nevertheless, the most accurate method appeared to be the Growing Degree Days (GDD[sup o]) method, which indicated that a mean of 127.3 GDD[sup o] must be accumulated from the end of the chilling period up to the beginning of the Quercus pollen season in Córdoba (South West Spain). Results were tested for predicting start dates in 1999 and 2000. The predicted dates were only one day after the actual dates. [ABSTRACT FROM AUTHOR]

The use of meteorological autocorrelation variables and pollen concentrations from previous days, coupled with classification of meteorological data according to multivariate analysis techniques, is shown to improve the predictive power of multiple regression models for daily pollen forecasts. This paper presents an investigation of the meteorological and autocorrelation variables which influence pollen counts in Cartagena, from 1995 to 1999, as a basis for the development of predictive models. The analysis of total pollen concentrations, and especially Chenopodiaceae-Amaranthaceae, was determined. Initially, forecasting models for total pollen counts were developed, using data from 1995 to 1998, and autocorrelation and meteorological variables. Secondly, predictive models were developed for different meteorological situations, which improved the results by decreasing the number of predictive parameters. Finally, data from 1999 were used to validate the predictive models. [ABSTRACT FROM AUTHOR]

The pollen of nine endemic taxa of the Gonospermum Less., Lugoa DC. and Tanacetum L. complex and of T. parthenium L. (introduced species from the Canary Islands) was studied using light and scanning electron microscopy with the aim of extending the knowledge of their morphology and to investigate whether pollen morphology may help clarifying the controversial taxonomy of these taxa. Twenty six populations in the Canary Islands (Spain) were studied and the following parameters were measured: polar axis (P), equatorial diameter (E), polar exine thickness (Ex1), length (L) and thickness (A) of the spines in the meridional optical section, exine thickness at the centre of the mesocolpium in the interapertural area (Ex2) and distance between spines (De) in the equatorial optical section. The studies show that the pollen of the three genera is very similar regarding shape, apertures, and ornamentation, but may be distinguished by size and exine thickness. [ABSTRACT FROM AUTHOR]

The timing of pollen appearance in the atmosphere provides a general idea of the flowering onset of plants over a wide area. Woody plants in temperate regions have evolved mechanisms to preserve cells from the risk of frost during adverse weather conditions in the period prior to flowering regulated mainly by temperature. A number of indices have been developed to quantify the rest and heat requirements of temperature, which will enable the plant to adapt to environmental conditions. However, flowering is a dynamic and complex phenomenon and it is difficult to separate individual effects of different meteorological parameters. The use of modified bioclimatic indices could be a major step forward. In this study the Alnus glutinosa flowering in four different areas in north-western Spain in the period 1995-2003 is examined, and trends identified by means of information gathered by Hirst pollen traps. Temperature plays an important role in the maturation of reproductive organs and pollen production. Comparison with bioclimatic indices showed that temperature during the 25-55 days preceding pollen release was the main controlling factor, and that relationship between flowering time and bioclimatic indicator values differs according to local conditions. In colder areas, rest and heat temperature requirements are greater because the trees need protection over a longer period; in the Mediterranean region of north-western Spain, the rest temperature requirement and the threshold temperature are both higher than in Eurosiberian areas. Ombrothermic, Continentality and Thermicity indices are thus useful tools for characterizing the various bioclimatic areas of north-western Spain. [ABSTRACT FROM AUTHOR]

A preliminary study to compare Poaceae pollen data and to determine possible differences in pollen productivity and/or seasonality was performed at six locations in Catalonia (Spain): Barcelona, Bellaterra, Girona, Lleida, Manresa and Tarragona over a 6-year period (1996-2001). In the study area, Poaceae pollen grains are an important cause of respiratory allergies. Being present in the atmosphere all year round, the grass pollen concentrations are especially significant between May and August. The absolute peak occurs in June, except in Lleida where the peak comes earlier, possibly due to the early flowering of particular steppe species. Even if there are differences between different years, Girona and Lleida (inland locations) usually present the highest annual grass pollen index with, on average, 2177 pollen grains per year. Barcelona and Tarragona (the coastal sites) show the lowest levels, with around 1140 grass pollen grains per year. The respective local climates are very different, and pollen grains may originate in different grass species. A decreasing trend in the Poaceae annual pollen index was found over the period of the present study. [ABSTRACT FROM AUTHOR]

Temperature is one of the main factors affecting the start of flowering in tree species that flower at the beginning of spring. Knowledge of the chilling and heat needs required by plants to overcome the period of dormancy enables us to determine the onset of pollination, which is of great importance to allergy sufferers. This study attempted to obtain behaviour models with a view to determining both the onset of the olive pollen season and daily pollen concentrations during the pollination period in Vigo. Monitoring was carried out using a Lanzoni VPPS 2000 pollen trap, from 1995 to 2002 inclusive. Olea pollen is mainly detected during the spring, principally in May. Given the geographical location, the very limited presence of this tree in the study area and the low Olea pollen concentrations detected in northern Spain as a whole, the values recorded here in the atmosphere of Vigo are particularly striking. A strong correlation was observed between total quantity olive pollen collected over the season and rainfall recorded during the second fortnight in February. According to the proposed model, an average of 680 Chilling Hours (CH) are necessary to overcome the chill period and break the state of bud dormancy, and 481 Growth Degree Days (GDD) °C are needed to induce flowering. Models for predicting daily mean pollen concentrations combine temperature and the previous days' pollen concentrations as predictor variables to provide a high level of prediction. [ABSTRACT FROM AUTHOR]

The study of potential pollen emission in the genus Cupressus was carried out in the city of Córdoba (Spain). Pollen production of 227 trees of the represented species of Cupressus in the area (Cupressus sempervirens, C. macrocarpa and C. arizonica) was studied by counting the number of pollen grains per flower, the number of flowers per branch, and the number of branches per m[sup 2] of surface area. Total surface area was estimated by considering the shape of the tree as a cone and estimating the average height and radius of each species. Results indicated that there was little variation in the number of pollen grains produced by a flower within each species. Equally, there were few differences in the number of grains per flower among the species, although C. arizonica had slightly fewer than the other species because it possessed fewer stamens per flower. However, there were clear differences in the number of flowers per branch, with C. macrocarpa having the highest floral density, considerably lower in C. arizonica and even lower in C. sempervirens. All of this indicates that the pollen contribution of C. macrocarpa to the atmosphere is far greater than that of C. arizonica and C. sempervirens. The results indicate a different potential emission in each species, and this must be taken into account when determining the quantity of pollen present in the atmosphere. The maximum amount of pollen grains that one individual can spread is provided in this study and would provide useful data in the development of an airborne forecasting system. [ABSTRACT FROM AUTHOR]