Morphological and physiological features of sweet cherry floral organ affecting the potential fruit crop in relation to the rootstock

The research concerning the evaluation of floral organ attributes affecting the potential fruit crop in relation to the rootstock was performed on sweet cherries cultivars - 'Burlat', 'Kordia' and 'Regina'. Potential fruit crop was estimated based on the following parameters: number of flowers, percentage of fruit-set and fruit mass. Moreover, morphological (flower biometrics, number of pollen in anther) and physiological features (flower phenology, viability and germination of pollen, sensitivity of flowers to winter frost damage) were assessed. Type of rootstock affected even several-day differences in the beginning of flowering period in particular cultivars. In the research of sweet cherry flowering, the stigma availability coefficient for pollinating insects (based on the sweet cherry flower biometry) was calculated for the first time. The coefficient indicates that flower's architecture and the optimal anther position relative to the stigma promotes the most effective collection and transfer of pollen on the insect's body. Sweet cherry flowers differed according to pollen efficiency depending on the type of cultivar and rootstock. 'Kordia' cultivar was characterized by a small number of pollen grains and its poor viability. Gisela 5 rootstock was highly rated in terms of potential crop, due to the large number of flowers on spur and high percentage of fruit setting. 'Regina' cultivar had higher winter frost resistance compared to 'Kordia'.