Arrangement of Reproductive Elements in Some Temperate Deciduous Tree Species

In adult woody plants, there is a division of labour between innovation and reproduction: One particular group of meristems, buds or shoot sections guarantees the vegetative continuation, another one only functions for a short period of pollination or diaspore production. The reproductive elements originate from the purely vegetative shoot sections by different ways of segregation. The unit of extension (UE) is used as the reference matrix to describe different types of allocation: (1) terminal flowering in competition with the vegetative apex, (2) lateral inflorescence shoots occupying a vacant UE section, (3) "mixed" structure of 1 and 2, (4) partial or full displacement of strong lateral shoots, (5) accessory buds developing into both vegetative and reproductive organs, (6) long-term reproductive capacity by accessory or prophyll shoots which is widespread in tropical families, (7) alternation between a reproductive and a non-reproductive UE form, (8) insertion of an additional short-shoot-like reproductive UE. Also a change of arrangement is possible because the UE programme undergoes a regressive metamorphosis during tree ageing or at subordinate branches. At the branch level, the allocation is described by the "shoot chain" in terms of monopodial, ananthic-sympodial or anthetic-sympodial. Research is based upon temperate species but the results can be extrapolated to some tropical species.