LEVELS OF NITROGEN ASSIMILATION IN BROMELIADS WITH DIFFERENT GROWTH HABITS

Abstract

Bromeliads exhibit several growth habits, ranging from terrestrial to epiphytic and associated shoot and root architectures. Accordingly, they are probably exposed to different sources of supply and forms of nitrogen (N), including mineral and organic. Nitrogen uptake and assimilation could reflect this. We compared the activities of nitrate reductase (NR) and glutamine synthetase (GS) as well as NO₃ ⁻ contents in plantlets of two bromeliad species. Vriesea fosteriana, a C₃saxicolous tank-forming type, and Tillandsia pohliana, an atmospheric CAM epiphyte, were grown in vitro with NO₃ ⁻, NH₄ ⁺ or NH₄NO₃as the sole N sources (4 mM of N). Nitrate alone was a poor N source to support growth of both plant species but it was effective with NH₄ ⁺. Consistently, both bromeliads exhibited very low levels of NO₃ ⁻ assimilation. The tank-forming species presented GS activity 2.5–3.0 fold higher than T. pohliana. The low GS activity found in T. pohliana compared to V. fosteriana may be related to distinct photosynthetic pathways and may also reflect an adaptation to survival in a nutrient-limited habitat.

Keywords:

• Ammonium
• Bromeliaceae
• Epiphyte
• Glutamine synthetase
• Nitrate
• Nitrate reductase
• Nitrogen metabolism
• Tillandsia pohliana
• Vriesea fosteriana

ACKNOWLEDGMENT

The first author thanks the CAPES for a graduate-level scholarship.