大白花蝴蝶蘭 ‘V3’ 對氮素之吸收、運移及利用

Abstract

為瞭解蝴蝶蘭營養及生殖生長階段對氮素型態的需求，本試驗以大白花蝴蝶蘭(Phalaenopsis Sogo Yukidian ‘V3’)之大苗與中苗為材料，施用五種氮素型態比例之肥料(NH4+：NO3- ＝ 0：100﹔ 25：75﹔50：50﹔75：25﹔100：0)，進行為期兩年之試驗。於兩個開花周期中，不同氮素型態比例對蝴蝶蘭大苗至抽梗、花苞可見、開花所需天數無顯著影響﹔然而於第二開花周期時，持續施用銨態氮比例超過50%之處理，會降低植株之總花朵數、花梗直徑及長度。至於營養生長，蝴蝶蘭大苗及中苗之鮮重、葉片數及葉面積會隨著銨態氮比例的增加而減少。根部對於陽離子的吸收於肥料中銨態氮比例超過50%時受到抑制，使得蝴蝶蘭植體中鈣、鎂濃度下降，並造成植株生長遲滯、葉片黃化及根部壞死等銨毒害現象。建議使用NH4+與NO3-比例為25：75之肥料，可使蝴蝶蘭有最高之抽梗率、鮮重及葉片數。 為瞭解蝴蝶蘭對氮素之吸收運移，各器官於不同時期之功能與角色，以及花梗之氮素來源，本研究利用氮同位素(15N)作為標定氮肥之示蹤原子，分別於大白花蝴蝶蘭(Phalaenopsis Sogo Yukidian ‘V3’)之營養或生殖生長時期、營養充足或缺乏狀況，以及植體不同部位施用。蝴蝶蘭之葉面與根部均具有吸收氮素之功能，且氮素吸收後會運往新生葉片與新生根這兩個強積儲。對氮素之吸收效率最佳者為新根，老根其次，葉片較差﹔葉片之上表皮與下表皮對於氮素之吸收效率並無差異。蝴蝶蘭於營養或生殖生長期，對於氮素的吸收無顯著差異，然植體對氮素之分配則隨當時各器官積儲之強弱而定。於營養生長時期，蝴蝶蘭對氮素最強之積儲為新生葉片，且積儲之強度隨葉齡之增加而下降﹔而生殖生長時期最強之積儲則為花梗。由花梗發育至花苞可見階段所需之氮素，在根域營養充足情況下，29%來自於先前儲存於植體的氮素，71%來自於花梗發育時植體所吸收之肥料氮。成熟葉與根部均具有儲存氮素與提供氮素給強積儲之功能，而兩者供應氮素之比例，則視植株當時營養狀況之不同而異。 綜合上述，蝴蝶蘭之成熟葉與根部具有儲存與供給氮素之功能，故短期之營養缺乏對植株生長的影響並不大，然而若使蝴蝶蘭長期處於缺乏或不適當之營養狀況，會使其生長不良，開花品質降低。使用NH4+與NO3-比例為25：75之肥料，並於營養與生殖生長時期持續給予充足之營養，可使蝴蝶蘭有良好之生長及開花品質。

In order to realize the demand of nitrogen form ratio during the vegetative and reproductive growth stages in Phalaenopsis Sogo Yukidian ‘V3’, five fertilizers with different nitrogen form ratio (NH4+: NO3- = 0:100, 25:75, 50:50, 75:25, 100:0) were applied to 8.5-cm and 10.5-cm pots for two flowering cycles. The days to spiking, visible buds, and anthesis were not affected by nitrogen from ratio during two flowering cycles. However, the number of flowers, the diameter and length of stalk in the second flowering cycle were decreased when plant received more than 50% NH4+-N. The fresh weight, leaf number and area decreased with the increase of NH4+-N ratio. When plants were provided with 50% or higher ratio of NH4+-N, the absorption of cations by roots was inhibited, the concentrations of calcium and magnesium in Phalaenopsis decreased, and the symptom of ammonium toxicity occurred, such as growth retardation, chlorosis leaves, and necrotic roots. It is recommended to provide Phalaenopsis with 75% nitrate and 25% ammonium nitrogen in order to have the highest percentage of spiking, fresh weight, and leaf numbers In order to understand the uptake and partitioning of nitrogen, the roles of organs in sink and source relationship during different stages, and the nitrogen sources of stalks in Phalaenopsis, the isotopic nitrogen (15N) was used as a tracer. Isotopic nitrogen was applied to Phalaenopsis Sogo Yukidian ‘V3’ during the vegetative or reproductive growth stage, in a nutrition deficiency or abundance situation, and different parts of plants. Both leaves and roots were able to utilize nitrogen, and the absorbed nitrogen was distributed to two major sinks: newly grown leaves and newly grown roots. Nitrogen uptake efficiency was highest in new roots, lower in old roots, and lowest in leaves. No difference of nitrogen uptake efficiency was found in the upper or lower epidermis of leaves. The absorption of nitrogen did not differ between the vegetative and reproductive growth stages, and the partitioning of nitrogen depended on the sink strength. During the vegetative growth stage, newly grown leaves were the major sinks. Strength of sink decreased with the increase of leaf age. Stalk was the major sink during the reproductive growth stage. For the nitrogen demand of stalks from spiking to visible buds stage, 29% were provided from the nitrogen previously stored, and 71% from the recent fertilizer applications. Mature leaves and roots were the major sources where nitrogen stored. However, the percentage of nitrogen supply from these two organs depended on the nutrition situation of plants. In summary, mature leaves and roots had the functions of nitrogen store and supply, therefore, a short-term nutrient deficiency did not retard the growth of Phalaenopsis. However, a deficient or improper nutrition level for a long period reduced plant growth and flowering quality. Providing fertilizer with the ratio of 75% nitrate and 25% ammonium nitrogen throughout the vegetative and reproductive growth stages to Phalaenopsis will result in the best product quality.