Nitrogen efficiency indexes for evaluating nitrogen uptake and use in ornamental bromeliad’s root system and tank

Abstract: The objective of this work was to evaluate if nitrogen use efficiency (NUE) indexes can elucidate functional differences in nutrient uptake between the root system and tank of epiphytic bromeliads. The bromeliads Guzmania lingulata and Vriesea 'Harmony' received fertilizers in their tanks or through their roots using modified Hoagland & Arnon solution, with 0.00, 2.62, or 5.34 mmol L-1 nitrogen, as urea. After 90 days, nitrogen contents in leaves and plant biomass were evaluated, and NUE indexes were calculated. Guzmania lingulata and V. 'Harmony' fertilized in their tanks with 5.34 mmol L-1 had the highest averages of nitrogen uptake efficiency and recovery efficiency; those fertilized with 2.62 mmol L-1 through their roots showed the highest averages of NUE, nitrogen utilization efficiency, nitrogen physiological efficiency, and biomass conversion efficiency. The NUE indexes, besides being an effective tool to assess the nutritional status of ornamental bromeliads, reveal that the root system of epiphytic bromeliads is functional for nitrogen uptake and use.

摘要：本研究旨在评估氮素利用效率（Nitrogen Use Efficiency, NUE）指标能否阐明附生凤梨科植物根系与贮水叶筒之间的养分吸收功能差异。供试凤梨科植物为匙叶果子蔓（Guzmania lingulata）与‘和谐’莺哥凤梨（Vriesea 'Harmony'），采用改良Hoagland & Arnon营养液作为肥料基质，以尿素为氮源设置0.00、2.62、5.34 mmol·L⁻¹三个氮浓度梯度，分别通过叶筒灌施或根系浇灌两种方式施加肥料。培养90天后，测定植株叶片氮含量与生物量，并计算各类氮素利用效率指标。结果显示，以5.34 mmol·L⁻¹浓度通过叶筒施氮的处理组，匙叶果子蔓与‘和谐’莺哥凤梨的氮吸收效率、氮回收效率均值最高；以2.62 mmol·L⁻¹浓度通过根系施氮的处理组，二者的氮素利用效率、氮生理效率与生物量转化效率均值最高。研究表明，氮素利用效率指标不仅可作为评估观赏凤梨科植物营养状况的有效工具，同时证实附生凤梨科植物的根系具备氮素吸收与利用的功能。