Limited carbohydrate availability as a potential cause of fruit abortion in Rubus chamaemorus

Fruit abortion can be caused by a range of abiotic and biotic factors. To g ain a better understanding of the causes of the high fruit abortion frequen cy in cloudberry (Rubus chamaemorus L.), me manipulated different sources o f carbon, that is, leaves and rhizome, We also manipulated flower number to see if competition between floral ramets explained fruit abortion in cloud berry. Reducing the number of flowers had no impact on fruit abortion frequ ency. In fact, the species forms an extensive rhizome network with only a f ew ramets per clone and competition between floral ramets is unlikely. Rame t defoliation had limited impact on fruit abortion, but successful fruit de velopment was affected by rhizome length. The longer the rhizome, the highe r the chances to mature a fruit. These results suggest that current photoas similate production by the reproductive ramet alone is insufficient to insu re fruit development. Carbon can come from other ramets but distances are u sually high between ramets, Fruit production might thus depend on the use o f stored carbohydrates in the rhizome to balance insufficient photosyntheti c contribution during fruit production.