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Identifying N sources that affect N uptake and assimilation in Vanda hybrid using 15N tracers

Panjama, Kanokwan, Ohyama, Takuji, Ohtake, Norikuni, Sato, Takashi, Potapohn, Nuttha, Sueyoshi, Kuni, Ruamrungsri, Soraya
Horticulture, environment and biotechnology 2018 v.59 no.6 pp. 805-813
Vanda, absorption, alanine, ammonium, glutamine, hybrids, leaves, nitrate fertilizers, nitrates, nitrogen, nitrogen content, roots, shoots, stable isotopes, stems, tracer techniques, tyrosine, Thailand
Vanda is an aerial tropical orchid native to Thailand and nitrogen (N) fertilizer is mainly used to promote its growth and quality. However, little is known about the characteristics of N absorption and assimilation in Vanda. The objective of this study was to determine the appropriate source of N for Vanda cultivation. In this experiment, shoots and roots of Vanda ‘Ratchaburi Fuchs-Katsura’ were sprayed weekly with 100 ml of ¹⁵N tracer solution (1) 10 mM of ¹⁵NO₃⁻, (2) 5 mM of ¹⁵NO₃⁻ plus 5 mM of NH₄⁺, (3) 5 mM of NO₃⁻ plus 5 mM of ¹⁵NH₄⁺ and (4) 10 mM of ¹⁵NH₄⁺. The results indicated that plants fed with a combined N fertilizer gave the highest of ¹⁵N use efficiency (¹⁵NUE) of about 21.8%, 30 days after the first feeding (DAF), compared with those fed sole sources of ¹⁵NO₃⁻ (21.0%) and ¹⁵NH₄⁺ (16.6%). However, a sole nitrate fertilizer or combination fertilizer did not significantly affect the total N and labelled N content. Alanine was a major amino acid found in leaves and roots at 7 DAF, whereas glutamine was mainly found in stems. At 30 DAF, tyrosine and alanine became major components in the leaves, and glutamine decreased in stems when plants were fed with a single ¹⁵NH₄⁺source.