## 4 Discussion
Specifically, regarding sunshine, the mostly positive correlation results found in this study can be supported by the fact that the increase in hours of sunshine during the day can cause the release of pollen from the anthers as a consequence of the dehydration of the walls of the anthers, but this meteorological variable is also related to temperature and photoperiods, so the increase in hours of sunshine leads to the release of gibberellins and cytokins, which ultimately cause flowering [11]. Precipitation in the city of Granada obtained results of negative sign with all pollen types [12] (the same occurs with the sub-variable PT with _Olea_ in this study, but a result contrary to what occurs with _Populus_, with which a positive correlation is given, was seen). A negative value of \(\rho\) can be associated with the effect of washing by dragging, which rain produces in aerobiological particles [12]. Relative humidity in Granada also gave negative correlations in all cases, except with Cupressaceae and Urticaceae (there is a coincidence in these results with those obtained in this study) [12]. Significant negative correlations of relative humidity with most pollen types are frequent, as is the case in other areas of Europe with a temperate continental climate [12]. On the other hand, abrupt changes in relative humidity indices can cause the breakage of pollen grains and the release of submicron particles, which can more easily affect the lower respiratory tract with a more negative effect on the health of patients affected by pollinosis. Furthermore, in the study carried out in the city of Granada, the Cupressaceae pollen type was the most strongly correlated with the meteorological variables, specifically with the minimum and maximum daily temperature and the global insolation [12]. In the case of this study, there is a coincidence in the results, in terms of Tmax and TMin, since within the thermal sub-variables, Cupressaceae is the pollen type (among the six studied) that achieves the highest correlations, although these are negative, followed by _Olea_. It is _Olea_ that correlates more strongly with global radiation (GR); in fact, it reaches the highest value of \(\rho\) (0.8132) of the whole study. The value of TMin is of particular importance in that its variations come to cause the onset of the vegetative period after the stoppage caused by the autumn season of deciduous plant species upon reaching the temperature threshold necessary for this and thus being able to resume the reproductive period [12]. The solar radiation that plants receive, accumulated over time, also causes, as already mentioned, the stimulation of biological activity, and, together with insolation, both meteorological variables lead to an increase in the values of pollen concentration in the atmosphere, even beyond the time of peak pollen emission [12,15]. Thus, in the present study, as already mentioned, there are significant correlations, mainly positive (except in the case of Cupressaceae, with radiation, and _Ulmus_, with insolation). Regarding current results, a positive relationship between global radiation and _Platanus_ pollen concentration was observed in Valladolid during the three years of the study (2009-2011) [11]. In this study, higher correlation occurs with monthly data because the main pollen season does not usually overpass this period of time. The analysis based on monthly data provides relevant information that is missing in the analysis based only on daily values. It is also interesting to analyze the behavior of the variables, their inter-relationship, outside and inside the MPP. The statistically significant correlation results between the two study variables are only 19.05%, compared to 64.44% obtained from monthly values. As with the results obtained from monthly data, the significant correlations obtained for Cupressaceae, from daily data, with the temperature and radiation variables are negative.