EFFECT OF DIFFERENT NITROGEN-FORMS AND IRON-CHELATES ON THE DEVELOPMENT OF STINGING NETTLE

The development of stinging nettle (Urtica dioica L.) grown on culture solution containing with either ammonium or nitrate ions, or urea, was investigated under iron deficiency conditions, and with added FeEDTA or FeCl3. Both seed-cultured and vegetatively-cultured stinging nettle plants produced normally developed green shoots when nitrate and 4 mu M FeEDTA or FeCl3 were supplied. Stinging nettle plants were able to utilize Fe-citrate, Fe-ascorbate, and Fe-malate effectively at the same concentration as well. When K3Fe(CN)6 was supplied, which is impermeable to the plasmalemma, and therefore is used to measure the reductive capacity of the roots, stinging nettle plants became chlorotic because the complex was stable at the pH of the culture solution. Urea did not induce chlorosis but inhibited growth. The plants died when ammonium was supplied as a sole N source. Applying bicarbonate and ammonium together prevented the plants from dying, but the plants became chlorotic. Total exclusion of iron from the culture solution resulted in iron-deficiency stress reactions as has been described for other dicotyledonous plants (Strategy II).