Luis Ruiz Valenzuela

Microclimatic-induced fluctuations in the flower and pollen production rate of olive trees (Olea europaea L.)

Abstract The possible impact of altitude and the related microclimatic conditions on the total production of fruiting branches, inflorescences, flowers and pollen grains of olive trees Olea europaea was analysed. A total of 90 Picual cultivar trees, the most extensive olive cultivar in the Iberian Peninsula, were studied for a three-year period (2007–2009). The study shows that production of flowers and pollen grains in a cultivar of the olive tree varies according to the microclimate. Our study also indicates that the olive trees frequently can have up to half a million flowers per tree. Moreover, the total flower production differs between years and study areas. In the Picual cultivar, the average production of pollen grains per anther is usually more than 60 000 grains. The total production of pollen per tree is around 72 000 million on average. The most favourable microclimatic conditions for reproduction in olive trees are found in years and olive growing areas with low temperature and high precipitation records during the months prior to flowering of the olive trees. We hypothesise that olive trees tend to increase their pollen production rate as altitude increases, which can be interpreted as a reproductive strategy to ensure fertilisation.

Time trend in the viability of pollen grains in the ‘Picual’ olive (Olea europaea L.) cultivar

The aim of this study was to evaluate the viability and longevity of the pollen grains of the olive cultivar ‘Picual’, the most extensive and important olive cultivar in the Iberian Peninsula. Over a 3-year period (2007–2009), viability of the pollen grains of 15 ‘Picual’ cultivar trees was measured using the Fluorochromatic Reaction (FCR). These olive trees were distributed along different altitudinal areas of the province of Jaen (southeast Iberian Peninsula). The percentages of viability did not show any geographical variability. In general, the percentage of viability did not vary from one year to another. With an average value of 49%, the viability of the pollen in the cultivar ‘Picual’ could be classified as medium-range. ‘Picual’ pollen grains have the highest viability after 24 hours of anther dehiscence. Viability declines rapidly with time. The longevity of the pollen grains was about seven days. The first three days after anthesis are the most important for fertilisation. A rapid decline in pollen viability may considerably reduce effective fertilisation and could negatively influence fruit production. For this reason, these findings should be considered for the improvement of olive fruit yields.