engleski

Low adaptive capacity of sunflower for nectar secretion under the changing climate in Eastern Croatia.

Whereas the sunflower is an allogamic plant, its succesful pollination largely depends on the presence of insects, especially honey bee, Apis mellifera carnica. The failure in nectar secretion was observed in recent years, which affected colonies of honey bees, and fertilization of sunflower. In our study, we set up a hypothesis that changes of weather conditions causing failure in nectar secretion during the sunflower’s blooming. An experiment was carried out in July 2009, at test field located southeast in the area of city of Osijek. Six hybrids of sunflower were grown in the block system, while the control group of blooming sunflower’s heads were covered by nets in order to prevent pollination by insect. Honey bees were transported in Langstroth-Rooth beehives to the site, and placed on three digital scales. A digital wireless weather station was installed at test field. The experiment showed that most favouring weather conditions for nectar secretion in sunflower are: daytime air temperatures of 22-26 oC, absence of rainfalls during the day, relative humidity of 65-75%, and winds from north and east directions. Weight drop of 8 kg was registered in beehives during the sunflower’s blooming. In the same period, lowest daily temperature was 26 oC, and highest 37 oC, the rain in quantity of 22, 6 mm was recorded during eight days (of total 15 days of blooming), and air humidity was 57-82%. It can be concluded that sunflower has low adaptive capacity in relation to climate parameters under the pronounced climate change. Specifically, increased temperature, more frequent rainfalls and wind from south direction negatively affected nectar secretion, and caused losses in honey yield

honey bee ; pollination ; sunflower ; climate change ; nectar secretion

nije evidentirano