GROWTH AND GDH AND AAT ISOENZYME PATTERNS IN TERRESTRIAL AND EPIPHYTIC BROMELIADS AS INFLUENCED BY NITROGEN SOURCE

Abstract

Seedlings of three bromeliad species, Pitcairnia flammea, Vriesea philippo-coburgii and Tillandsia pohliana, with different growth habits were in vitro cultured for 6 months in a modified knudson medium containing 8mM nitrogen, such as $N{O_3}^ - $, $N{H_4}^ + $, NH₄NO₃, glutamine or urea. Growth analysis showed that all species presented a very efficient uptake and utilization of glutamine and NH₄NO₃. The presence of $N{O_3}^ - $ substantially stimulated root development. To examine some possible effects of different nitrogen sources on nitrogen assimilation, protein was extracted from leaf shoots of three species and glutamate dehydrogenase (GDH) and aspartate aminotransferase (AAT) activities were determined by gel electrophoresis. Effects of nitrogen source were shown most clearly by the different mobility of GDH observed in samples which had been supplied with Ca(NO₃)₂ compared to those found in samples supplied with (NH₄)₂ SO₄. Urea as a nitrogen source depressed AAT activity in the terrestrial species Pitcairnia flammea but enhanced it in the epiphyte Tillandsia pohliana. The latter species and the other epiphyte examined, Vriesea philippo-coburgii, were distinguishable from P. flammea through their AAT mobility, while the two epiphytes differed between themselves principally in the level of their AAT activity.