| Summary: | 碩士 === 國立臺灣大學 === 園藝暨景觀學系 === 107 === Phalaenopsis is the major floral crop for export in Taiwan. The objective of this research was to evaluate the nitrogen uptake ability of Phalaenopsis after simulated dark shipping (SDS). In this research, Phalaenopsis Sogo Yukidian ‘V3’ was used to investigate the appearance quality, photosynthetic ability, changes of dry weight and nitrogen content before and after shipping. In addition, 15N tracing technology was used to investigate the nitrogen uptake ability and partitioning in Phalaenopsis after SDS.
After 21 days of SDS at 20oC, the plants maintained normal appearance, while new leaves stopped growing and dry weight of mature leaves decreased. The nitrogen content of plants did not decrease, and the nitrogen concentration of shoot and roots increased from 1.68% to 1.93% and from 1.75% to 2.19% after SDS, respectively. The net CO2 uptake rate of the plants was -0.31 μmol·m-2·s-1. The transpiration rate and stomatal conductance of the plants also decreased rapidly. The roots of Phalaenopsis still had the ability to absorb nitrogen and transport the nitrogen to shoots, 0.3 d after SDS. But the absorption of nitrogen and the nitrogen distribution percentage to shoots were still lower than those of non-shipped plants.
Giving Phalaenopsis Sogo Yukidian ‘V3’ 100 μmol·m-2·s-1 light acclimation for 15 days and cultivation under 200 μmol·m-2·s-1 for 7 days after the SDS, new leaves resumed growing, dry weight of mature leaves increased, but roots grew slowly. The ability of photosynthesis gradually recovered and became stable 6 days after SDS. The dry weight of new leaves, mature leaves, and roots and the photosynthetic ability of the treated plants were still lower than those of control plants after 15 days light acclimation and 7 days cultivation. During the 22 days of acclimation and cultivation after SDS, the treated plants maintained a higher nitrogen concentration than controls. The nitrogen content of new leaves increased gradually, but it was still lower than non-shipped plants. The nitrogen content of mature leaves and roots had no significant difference compared with non-shipped plants.
When SDS completed, a 15N-label fertilizer was applied to Phalaenopsis. The 15N content of treated plants rose significantly in 0.3 days and continued to absorb nitrogen toward Day 22. However, the 15N concentrations of shoot and roots in the treated plants were continuously lower than those of control plants. Except for Day 3 after the end of SDS, the accumulation of 15N in the whole plant was significantly lower than that of the control. The nitrogen distribution percentage to shoots was lower than non-shipped plants in the first 2 days and then became similar to that of control plants. At the end of the experiment (Day 22), the 15N content distributed to the shoot of the treated plants was 38%, which did not differ from the control plants (41%).
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