Articles
THE EFFECT OF TEMPERATURE ON POLLEN TUBE GROWTH AND FRUIT SET ON PLUM TREES
Since plums are early flowering, it is obvious to presume that the yearly fluctuations in yield are mainly determined by the weather during the bloom period.
In this study, we examined the influence of the temperature on one hand on the yield, and on the other hand on the growth of the pollen tube.
A significant correlation between temperature during the bloom period and the yield has been established for the varieties Stanley, Monsieur Hâtif, Magna Glauca and Reine Claude d’Althan.
By means of a linear regression, it is shown that between 64 and 82% of the variance of the yield could be explained by the variance of the temperature.
The varieties Bleue de Belgique and Sanctus Hubertus did not show any significant relation between yield and temperature during the bloom.
Especially for the varieties the production of which is largely determined by the temperature during the bloom period, it is important that they are pollinated by varieties with a quick growth of the pollen tube.
Measurements of the speed of pollen tube growth at different temperatures have shown reliable patterns that reveal the connection between the swiftness of growth and the temperature.
Especially with low temperature, differences were important.
Sanctus Hubertus, Reine Claude d’Althan and Monsieur Hâtif showed a slow pollen tube growth with low temperature, in contrast with Opal.
At high temperature, the pollen tube in Czar growed quickly, while growth was clearly slower in Reine Claude d’Althan and Sanctus Hubertus.
Under normal circumstances of temperature and for all examined varieties, the quickest pollen tube growth was observed with Opal and Czar.
Provided that no symptoms of incompatibility occur, we may expect a better fruit set and thus a higher production after pollination with Opal and Czar than after pollination with the other examined varieties.
This statement has been regularly confirmed by hand pollination.