2172:
The Uptake and Partitioning of Nitrogen In Phalaenopsis Sogo Yukidian

Tuesday, July 28, 2009: 2:45 PM
Lewis (Millennium Hotel St. Louis)
Yao-Chien Alex Chang , Dept. of Horticulture, National Taiwan University, Taipei 10617, Taiwan
Ying-Chun Peng , Dept. of Horticulture and Landscape Architecture, National Taiwan University, Taipei, Taiwan
Shui-Cheng Lee , Institute of Nuclear Energy Research, Atomic Energy Council, Taoyuan County, Taiwan
The low growth rate and slow response to fertilizer application of Phalaenopsis make it difficult to understand its nutrient requirement. In this study, we used stable nitrogen isotope, 15N, to trace nitrogen absorption and partitioning in Phalaenopsis. Mature Phalaenopsis Sogo Yukidian ‘V3’ plants were potted in sphagnum moss and fertigated with modified Johnson’s solution. The KNO3 in the solution was partially substituted by K15NO3. Both roots and leaves were capable of taking up nitrogen; the uptake efficiency was highest in new roots, lower in old roots, and lowest in leaves. There was no difference on nitrogen uptake efficiency between upper and lower leaf surfaces. After one single 15N application, tissue 15N content reached a plateau about 8 weeks after treatment. These results indicated that sphagnum moss is a substrate good for retaining fertilizer and Phalaenopsis has a high efficiency for nutrient utilization. Growing young leaf is the major sink during vegetative growth stage and stalk during reproductive phase. The sink strength of leaves decreased as the leaf age increased. Data revealed that mature leaves and roots act as storage organs and are able to translocate nitrogen to stalks during reproductive phase; this explains why well-grown Phalaenopsis can still flower after months of fertilizer cessation.