ECOTYPE DIFFERENTIATION IN TEUCRIUM SCORODONIA WITH RESPECT TO SUSCEPTIBILITY TO LIME‐INDUCED CHLOROSIS AND TO SHADE FACTORS

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Abstract
Summary: A study has been made of populations of Teucrium scorodonia from Britain and Europe. Edaphic ecotypes have been found to occur with respect to lime‐induced chlorosis. Chlorosis‐susceptible populations were found to be from acidic and non‐calcareous sites whilst chlorosis‐resistant populations were invariably from calcareous sites. The severity of the chlorosis and the retardation of growth in the laboratory suggests that in the field chlorosis‐susceptible populations would be at a great disadvantage compared with resistant ones, on many calcareous soils. In limited field‐experiments, however, seedling failure was found to be due to catastrophic effects such as drought, frost and animal depredation which eliminated both green and chlorotic seedlings. It was found, however, that seedlings of populations from shaded habitats had considerably larger cotyledons than had those from unshaded habitats. This was also true under controlled conditions, irrespective of the shade and nutritional regime given. The seedlings with large cotyledons formed their leaves more rapidly than did those with small cotyledons. Other morphological differences occurred which also appear to be of an adaptational nature. These differences were independent of the soil types from which the populations originated. A study of populations from within a very small area indicated that ecotypic differentiation can take place rapidly and precisely within such an area.