Mourning form
The mourning form or pendula form is a specific growth form of trees that deviates from the usual habitus . Different tree species such as red beech , birch , ash or willow occasionally develop shapes that are characterized by a short main axis. From this short main axis, there are many side branches with increased length but little growth in thickness.
The long side branches hanging lug-like down. Such mourning or pendula forms usually survive in the shelter of the woods. The leaves positioned on the umbrella-like overhanging branches can make better use of the scattered radiation penetrating through the upper stand. Changes of light, for example because the upper hand by wind damage is reduced, such grief forms usually develop a steeply upright engine, but which often depends again after a corresponding linear growth from dormant buds. Such naturally occurring forms have been reinforced by breeding interventions and are occasionally found as solitary trees in parks and green spaces .
Parallel mutations
Due to the fact that in species with different degrees of relationship there are genetic variations with the same characteristics , the Russian botanist Nikolai Iwanowitsch Wawilow formulated the "law of homologous series" in 1920. This law is still in force. He cites the pendular shape as an example , along with other genetic variations such as albinism and dwarfism . One speaks here of parallel variations or, if caused by mutation , of parallel mutations . Albinism and dwarfism occur throughout flora and fauna. These widespread parallel variations are usually a mutative loss of features. It is mainly somatic mutations that do not affect the germ cells and are therefore not inherited, but only affect individual life. The different forms of mourning in trees also indicate parallel mutations.
literature
- Dietrich Böhlmann: Why trees don't grow into the sky. An introduction to the life of our trees. Quelle & Meyer Verlag, Wiebelsheim 2009, ISBN 978-3-494-01420-3
