Lime Chlorosis as a Factor in Seedling Establishment on Calcareous Soils

SUMMARY The water relations of a number of species affected by lime‐chlorosis have been studied by following the development of leaf water deficits in detached leaves gravimetrically. It has been found, both for material collected in the field and for material raised under controlled laboratory conditions, that chlorotic leaves invariably lose water more rapidly than do green leaves of the same species. The rate of transpirational loss of individuals of a species is directly related to the degree of chlorosis they exhibit. Addition of iron chelate to soil in which a chlorosis‐susceptible plant grows alleviates the chlorosis and the rate of transpiration is also greatly reduced. The age of the material and intrinsic soil factors also influence rates and patterns of transpirational loss. Both the stomatal and cuticular phases of transpiration appear to be affected in chlorotic material, where the larger leaf water deficits may be due either to more rapid loss during the stomatal phase, coupled with later stomatal closure, or to more rapid cuticular loss, or both. The percentage of dry matter in chlorotic leaves is reduced compared with that in green leaves. The ecological significance of the overall findings is discussed in relation to the potential survival of species invading calcareous soils as seedlings. Such seedlings are very often subjected to annual droughts.