Heksenbezemverschijnselen : een pathologisch-morfologisch onderzoek

Infectious forms of witch's broom caused by a virus, were observed in Crotalaria spp. and other leguminous crops in Indonesia, and in Rubus idaeus and some herbaceous ornamentals, mainly Trqpaeolum majus, in the Netherlands. A detailed analysis of the abnormalities in Crotalaria and Tropaeolum was given. A plant infected during its early stages of development became a bushy dwarf. All potential buds developed into negatively geotropic sprouts and no flowers formed. A plant infected late had an almost normal growth habit, but inflorescences grew into complex leafy structures, thus producing broomy branch extremities. The younger their buds at the moment of infection, the more abnormal were the flowers. Thus a series of progressive floral abnormalities from a normal flower up to a completely vegetative leafy branch could be selected. The series of deviations was called antholysis. These abnormalities supported the theory that morphologically the flower must be regarded as a modified leafy branch.Large-scale virus-induced antholysis demonstrated the morphogenetic antagonism between floral initiation and vegetative growth. Many similar virus diseases were brought together in a group of witch's broom virus diseases. Other factors may cause related aberrations: certain parasitic plants, fungi, bacteria, mites and insects. However, they only incited restricted symptoms of witch's broom. The morphological analysis of witch's broom phenomena provided arguments that growth-hormonal disturbances were involved