Growth and nitrogen metabolism of Catasetum fimbriatum (orchidaceae) grownwith different nitrogen sources

Citation
N. Majerowicz et al., Growth and nitrogen metabolism of Catasetum fimbriatum (orchidaceae) grownwith different nitrogen sources, ENVIR EXP B, 44(3), 2000, pp. 195-206
Citations number
50
Categorie Soggetti
Plant Sciences
Journal title
ENVIRONMENTAL AND EXPERIMENTAL BOTANY
ISSN journal
00988472 → ACNP
Volume
44
Issue
3
Year of publication
2000
Pages
195 - 206
Database
ISI
SICI code
0098-8472(200012)44:3<195:GANMOC>2.0.ZU;2-L
Abstract
Catasetum fimbriatum is an epiphytic orchid from South America that has bee n used for 15 years as a model plant for metabolic and developmental studie s in our laboratory. In this work, C. fimbriatum plants were aseptically gr own with 6 mol m(-3) of either glutamine or inorganic nitrogen forms (NO3-: NH4+ ratios). The highest biomass accumulation was found in plants supplied with glutamine; no significant difference was observed in plants incubated in the presence of inorganic nitrogen sources. Nitrogen assimilation was l imited in the presence NO3- as a sole nitrogen source. C. fimbriatum did no t accumulate NO3- and very low rates of in vivo nitrate reductase activity were observed. Most nitrate reductase activity (70%) was detected in the 2 cm apical roots. Nitrate-treated plants exhibited relatively lower amounts of free amino-N, chlorophyll and free NH4+ contents and higher soluble suga r contents than the NH4+-treated plants. While shoot glutamine synthetase a ctivity was only slightly affected by nitrogen sources, root glutamine synt hetase activity was not modified by any nitrogen form. Glutamate dehydrogen ase-NADH activity in shoot tissues was not influenced by any nitrogen sourc e. However, the glutamate dehydrogenase-NADH activity in roots was enhanced when NH4+ tissue contents was augmented by increasing NH4+ in the medium a nd by the presence of glutamine. Our results strongly suggest that organic nitrogen and NH: are probably the most important nitrogen sources to C. fim briatum plants. (C) 2000 Elsevier Science B.V. All rights reserved.