Open Access

Gerhard Wiegleb

• Die Geschichte des Lebens- und Wuchsformenbegriffes wird kurz dargestellt, soweit sie die Anwendung auf Wasserpflanzen betrifft. Die Einteilung geschah bisher hauptsächlich nach den Gesichtspunkten "Anpassung", "Form" und "Dynamik". Als "Lebensformen" werden 5 Gruppen von Pflanzen mit vergleichbarem Grad der Anpassung an das Wasserleben unterschieden. Da die einzelnen für das Leben im Wasser vorteilhaften Merkmale unabhängig voneinander auftreten, ist eine exakte Trennung zwischen Wasser- und Landpflanzen nicht möglich. Für die Definition der "Wuchsform" wird die phänotypisch realisierte morphologische Struktur verwendet. Auf diese Weise können 20 Wuchsformen unterschieden werden. Aufgrund der Dynamik einzelner demograpischer Einheiten kann der "Lebenszyklus" einer Pflanze beschrieben werden. Innerhalb einer Art können verschiedene Einheit unterschiedliche Lebenszyklen haben. Abschließend wird auf die Bedeutung der Lebens- und Wuchsformen in verschiedenen Bereichen der Pflanzenökologie hingewiesen.
• The general history of life-form and growth-form concepts in plants is briefly outlined with special reference to their application in aquatic ecological studies. Three basic viewpoints are distinguished which are related to the concepts of adaptation, form and dynamics. The first approach emphasizes the aspect of adaptation to the aquatic environment. Life forms are conceptualized as groups of plants with a similar degree of adaptation. It is shown here that an exact delimitation between "aquatic" and "terrestrial" plants fails. An ultimate grouping of aquatic plants is difficult because characters usually regarded as "adaptations" are distributed independently among plant species. Thus, a pragmatic grouping is presented distinguishing five classes of plants, more or less adaptated to the aquatic environment. The second approach emphasizes plant form, which can be described in morphological terms. Form can be regarded both from a genotypical (potential growth form) and a phenotypical viewpoint (realized growth form). A strictly phenotypical system of growth forms is presented distinguishing appr. 20 categories that are found in waters of the temperate regions. Some quantitative descriptors of growth form are discussed, and the close relation to the concepts of "resource allocation" and "spatial heterogeneity" is shown. The third approach emphasizes the dynamics of various demographic entities as a reaction to changes in the environment in ecological time. This concept of life form refers to life cycles or complete life histories. As an example some results on the life spans of various Potamogeton species are presented. The life cycle of different entities may differ within one species, according to ecological circumstances. Variation within the genus may be used for reconstructing evolutionary trends. Finally, the relation of life form and growth form concepts to several other ecological disciplines (classification of aquatic communities; functional morphology; production ecology; population biology, demography and life history theory) is discussed. The need for a unified but pluralistic approach is pointed out.