貯運後蝴蝶蘭氮素吸收之能力

蝴蝶蘭為臺灣重要的外銷花卉，本研究討論模擬黑暗貯運如何影響蝴蝶蘭氮素吸收能力。以大白花蝴蝶蘭Phalaenopsis Sogo Yukidian ‘V3’為植物材料，調查蝴蝶蘭植株在模擬貯運後之外觀品質、光合作用能力、乾重、氮含量，並以氮同位素示蹤技術探討蝴蝶蘭在貯運後的氮素吸收與分配。蝴蝶蘭‘V3’經20oC模擬貯運21天後，植株外觀良好、惟新葉暫停生長、成熟葉乾重減少，但植體儲存之氮素未被消耗，使地上部氮濃度由1.68%提升至1.93%，地下部氮濃度由1.75%提升至2.19%。此時植株淨光合作用速率為-0.31 μmol·m-2·s-1，蒸散速率與氣孔導度亦大幅降低。貯運後0.3天，蝴蝶蘭根系即具有氮素吸收能力，並能將吸收之氮素轉運至地上部，但此時氮素吸收與分配至地上部之氮素比率低於未貯運植株。在貯運後給予15天100 μmol·m-2·s-1光馴化與7天200 μmol·m-2·s-1光度栽培，新葉恢復生長，成熟葉乾重逐漸提升，根系生長則較為緩慢；光合作用能力逐漸恢復，並於貯運後第6天恢復穩定。於第22天試驗結束時，處理組植株之新葉、成熟葉與根系乾重與光合作用能力仍低於未貯運對照組。貯運後22天栽培期間，經貯運之蝴蝶蘭植株維持較高之氮濃度，新葉氮含量隨時間增加，但持續低於未貯運對照組；成熟葉與根系氮含量則沒有顯著變化，與未貯運對照組相近。模擬貯運剛結束時，給予蝴蝶蘭‘V3’氮同位素15N標識肥料，經貯運處理的植株在給予肥料後0.3天即可測得15N含量之增加，並在後續22天栽培期間持續吸收肥料氮，但地上部與地下部15N濃度在貯運後22天皆顯著低於未貯運對照組。除了貯運後第3天，處理組全株15N含量皆顯著低於對照組。在貯運後之2天內，經貯運植株將吸收的15N轉移至地上部之比率較未貯運植株低；隨後其15N含量分配比率提升至與對照組相近，在貯運後第22天，分配至地上部之15N含量佔38%，與未貯運對照組之41%無顯著差異。

Keywords

蝴蝶蘭；模擬貯運；光合作用；氮15 ； 15N ；氮素吸收

Parallel abstracts

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%).