DARWIN’s theory of selection plus the realization, that the individuals of a species are not the image of a basic type, but represent the population instead, stimulated numerous zoologists and botanists to study the variability within a species, and the influence environmental factors have on the expression of a given feature.
The French botanist G. BONNIER (1853 – 1901) moved plants from valleys to high mountains and discovered, that 80 out of 200 species were unable to cope with the climatic conditions at high altitude. The surviving species displayed dwarfism and abnormalities. BONNIER performed, too, a classical experiment with Taraxacum officinalis. Its result became an integral part of textbooks on introductory biology and keeps being cited as the example for modification, i.e. a non-hereditary change of the phenotype.
During the seventies and eighties of the 19th century, the Austrian botanist A. KERNER von MARILAUN (1831 – 1898) carried out some systematic plant transplantation experiments. He cultivated a number of species in the Botanical Garden of Vienna and Innsbruck. At the same time, he set up an experimental station close to the top of an Alpine mountain at 2195 m altitude (the Blaser, above Trins in the Gschnitztal/Tirol). Many of the annuals, like Gilia tricolor, Hyoscyamus albus, or Trifolium incarnatum, that shooted regularly in Vienna, died in the high mountains due to night frosts occurring till June. Other species displayed a retarded growth, but flowered nevertheless at the end of August or the beginning of September (Lepidum sativum, Centaurea cyanus, Iberis amara, Satureja hortensis, Senecio vulgaris, Viola arvensis), but their flowers were smaller and fewer in number than that of the control group grown in the valley. Some of the annual plants did not flower or produce mature seeds, but became perennials instead (Poa annua, Senecio nebrodensis, Senecio vulgaris, Ajuga chamaepitys, Viola tricolor, Cardamine hirsuta, Medicago lupulina). Only 32 out of 300 perennial species transplanted to the Blaser flowered. In all cases, the body of vegetation was strongly compressed, the stem was short, the diameter of leaves and flowers was small, the inflorescences bore but few flowers and the flowers themselves only few stamens. The flowers of most species grown at high altitude were nevertheless more intensely coloured than their control plants in the Viennese botanical garden due to the intense, UV-rich radiation.
These changes induced by the cultivation at high altitude were not hereditary: progeny of plants with the typical high-altitude features kept these only, if grown at high altitude. When transplanted back into the valley, they assumed the species’ original characteristics. A. KERNER von MARILAUN summarized thus, that the variations in appearance and colour were caused by the changes of the soil and climate and were non-hereditary. He concluded, that features expressed under extreme environmental conditions are not constant.
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