Levels of free proline in a number of higher plants on collection from the field and after wilting

Proline levels and percentage water content of the leaves were measured for a wide range of plant species from several habitats classified as either drought-prone or drought-free. Little differences in initial proline levels or maximum proline levels after wilting intact in the laboratory were found between species taken from the two habitat types .Similar measurements were made for six species of each of the families, Compositae and Cruciferae. Little differences in initial or maximum proline levels after wilting were found between species of the two families. Results indicate that proline accumulation is genetically controlled by species. Species which accumulate proline may be more frequent in habitats liable to drought.