Premium
Effects of NO 3 − , NH 4 + and urea nutrition on endogenous levels of IAA and four cytokinins in two epiphytic bromeliads
Author(s) -
MERCIER H.,
KERBAUY G.B.,
SOTTA B.,
MIGINIAC E.
Publication year - 1997
Publication title -
plant, cell and environment
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.646
H-Index - 200
eISSN - 1365-3040
pISSN - 0140-7791
DOI - 10.1046/j.1365-3040.1997.d01-72.x
Subject(s) - cytokinin , urea , zeatin , epiphyte , nitrogen , shoot , botany , biology , riboside , auxin , horticulture , chemistry , biochemistry , organic chemistry , gene
The long‐term effects of different nitrogen sources on the endogenous IAA and cytokinin levels in two bromeliad species were investigated. In nature, Vriesea philippocoburgii is a tank‐forming epiphytic bromeliad which uses the tank water reservoir as a substitute for soil, whereas Tillandsia pohliana is a tankless atmospheric epiphytic species. A culture was established from seeds germinated in aseptic condictions, and the plantlets were grown for 6 months in a modified Knudson medium to which was added 8 mol m −3 of nitrogen in the form of NO 3 − , NH 4 + or urea. The hormonal contents of the bromeliad shoots were determined by means of high‐performance liquid chromatography (HPLC), coupled to an enzyme‐linked immunosorbent assay (ELISA) for indole‐3‐acetic acid (IAA), isopentenyladenine (iP), isopentenyladenosine ([9R]iP), zeatin (Z) and zeatin riboside ([9R]Z). Nitrogen supplied in the form of urea gave the highest values of fresh and dry weights for both species, and this was positively correlated to IAA levels. The cytokinin patterns showed that isopentenyladenosine was the predominant form for both species in all samples. However, urea induced the highest level of this riboside form and also the highest level of total cytokinins for V. philippocoburgii , while NH 4 + had the same effect on the atmospheric species. These results are discussed in terms of the different growth habits of these two species in nature. It is suggested that urea may be an important source of nitrogen often found inside the tank of V. philippocoburgii. NO 3 − treatment increased the IAA/Cks balance, mainly for V. philippocoburgii , while urea and NH 4 + shifted this ratio in favour of cytokinins, thus apparently inhibiting root development in both species.