SEEDLING GROWTH OF 4 FIRE-FOLLOWING MEDITERRANEAN PLANT-SPECIES DEPRIVED OF SINGLE MINERAL NUTRIENTS

1. Anthyllis vulneraria, Cistus creticus, Hippocrepis unisiliquosa and Pious brutia are frequent post-fire colonizers whose seedlings are su bjected to the mineral conditions imposed by ash in the early stages o f growth. We test the hypothesis that the effective internal supply of mineral elements in the seeds of these species may complement the ext ernal availability of specific nutrients, 2. Newly germinated seedling s were grown in nutrient solutions, each deficient in one of the follo wing elements: nitrogen, phosphorus or potassium. Control treatments c onsisted of full nutrients and distilled water, Seedling growth was mo nitored over 12 weeks. The final dry masses of the seedlings were take n as a measure of the availability of each element from the seeds' own stored reserves. 3. For the two legume species nitrogen was the most limiting element followed by phosphorus. Potassium deficiency had no e ffect on the final legume dry biomass. For Cistus, the order was nitro gen followed by potassium, while phosphorus deprivation had no effect on growth during the 12 weeks of the experiment. Deprivation of single minerals had no significant effect on seedling growth of Pinus over t he same period. The two legumes and Cistus when denied nitrogen had re latively greater relative root ratios than control plants. 4. The rela tive seedling requirements of each species for early external supplies of the various nutrients for establishment in the field are discussed with reference to the adaptation of the four species to post-fire reg eneration.