EFFECT OF THE FORM AND CONCENTRATION OF N ON THE GROWTH AND MINERAL COMPOSITION OF OLIVE SEEDLINGS
The best growth was obtained in in vitro culture through the applications of NH4NO3, in concentrations of 10 and 20 mM of N. Addition of (NH4)2SO4 clearly damaged the seedlings and increased the contents of S in the seedlings' tissues. All the treatments led to a direct relationship between concentration of N in the medium and N in the seedling tissues, however the N-increases were lowest for KNO3 and highest for ammonium applications, especially for NH4NO3.
In greenhouse conditions all the N-treatments significantly increased the growth of the seedlings but no significant differences between N-salts were observed except for (NH4)2SO4 at the highest concentration. Treatment with (NH4)2SO4 did not induce any symptom of toxicity in the seedlings, in contrast to the behaviour of in vitro seedlings. The treatments did not cause significant changes in the mineral composition of the seedling tissues. These circumstances were related to the fact that an oxidation process (nitrification) was produced from N-NH4 to N-NO3 in the nutritive solutions in the containers.