碳氮濃度及碳氮比對蝴蝶蘭及春石斛開花之影響

Abstract

蘭花為臺灣最重要的外銷花卉，本研究以屬單莖型蘭花的蝴蝶蘭 (Phalaenopsis spp.) 與屬複莖型蘭花的春石斛 (Dendrobium spp.) 為代表，探討不同生育階段之植體碳氮養分變化，以及碳氮對蘭科植物開花之影響。植體中碳和氮的比例稱為碳氮比 (C/N ratio)，碳氮比假說認為高C/N促進生殖生長，低C/N則促進營養生長甚至抑制開花。涼溫為促進蝴蝶蘭與春石斛開花之主要因子，然探討碳氮對其開花影響之研究甚少，甚至結果互相衝突。 分析白色大花蝴蝶蘭 (P. Sogo Yukidian ‘V3’) 新葉及第一、二、三、五、七片成熟葉之碳氮濃度，氮濃度隨葉齡增加而下降，新葉有最高的氮濃度2.72%，第二、三、五片成熟葉氮濃度無顯著差異，第七片成熟葉氮濃度1.48%最低，碳氮比則隨葉序增加而上升。進一步分析第二片成熟葉片內不同位置之碳氮濃度，顯示葉片內碳氮濃度非均值，葉片中段氮濃度1.96%、碳氮比22.3，最接近全葉片均值。綜上所述，以蝴蝶蘭第二片成熟葉中段做為葉片營養分析取樣部位，可獲得具代表性且適當之乾重與碳氮測值。 分析白色大花蝴蝶蘭 (P. Sogo Yukidian ‘V3’)、紫色小花蝴蝶蘭 (P. Sogo Lotte ‘F2510’)、雜交春石斛 (D. Lai’s Yukisakura) 於不同生育階段之植體碳氮濃度。白色大花蝴蝶蘭由瓶苗發育至開花株，全株氮濃度由4.63%逐漸下降至1.63%，全株碳氮比則由9.1上升至26.7；紫色小花蝴蝶蘭氮濃度、碳氮比變化趨勢與白色大花蝴蝶蘭相同，數值亦相當接近。雜交春石斛當代假球莖在停心至成熟期間，氮濃度由1.12%下降至0.53%，碳氮比由41.8上升至85.6。參試兩蝴蝶蘭品種與春石斛的植體氮濃度皆隨植株成熟而下降，此趨勢有普遍性，顯示氮濃度有做為成熟度指標之潛力。 關於高或低氮肥是否能延遲或促進蝴蝶蘭開花，目前研究結果多有分歧。本試驗分析白色大花蝴蝶蘭 (P. Sogo Yukidian ‘V3’)、紫色小花蝴蝶蘭 (P. Sogo Lotte ‘F2510’) 兩品種，自最後8週營養生長期 (30/28˚C) 並接續生殖生長期 (20/18˚C) 給予不同氮肥處理：高氮肥 (28.6 mM N)、正常氮肥 (14.3 mM N)、低氮肥 (1.4 mM N)、無氮肥 (0 mM N)。兩品種蝴蝶蘭在營養生長期結束時，施用氮肥濃度越高，莖葉、根部氮濃度越高。於生殖生長期，缺氮逆境下 (0 mM、1.4 mM) 蝴蝶蘭根部總氮含量增加速率為負值，顯示花序發育會消耗儲存性氮。所有參試植株皆抽梗開花，然處理間的抽梗時間與開花品質略有差異：與正常氮肥處理組相比，高氮肥延遲小花品種抽梗達8.9天，但對於大花品種則無影響；低氮肥或無氮肥處理會使兩品種提早1-2天抽梗，並使小花品種花朵數分別下降2與3朵，但對大花品種花朵數則無影響。儲存性氮含量會影響短期氮肥施用的效應，迷你型蝴蝶蘭（小花品種）的開花表現較易受到氮肥施用而改變，而標準型蝴蝶蘭（大花品種）則幾乎不受影響。 涼溫與光照是蝴蝶蘭抽梗開花之必要環境條件，本試驗比較涼溫光照、涼溫黑暗、高溫光照及高溫黑暗等四種栽培環境下，白花蝴蝶蘭 (P. amabilis) 第二片成熟葉碳水化合物濃度的變化。溫度不影響葉片葡萄糖與果糖濃度，然高溫處理下葉片有較高的蔗糖濃度，又以高溫光照處理濃度最高；而黑暗處理下有較高的葡萄糖與果糖濃度。葉片澱粉濃度不受溫度影響，光照組有較高的澱粉濃度。本試驗結果與前人研究結果趨勢不同甚至相反，可能受取樣部位效應、機械傷害及品種差異等因素影響。

Orchids are the major flower crops for export in Taiwan. In this research, monopodial phalaenopsis (Phalaenopsis spp.) and sympodial nobile dendrobium (Dendrobium spp.) are used to investigate the changes in carbon (C) and nitrogen (N) composition of tissues during various developmental stages. How C and N affect their flowering was also studied. The ratio of tissue C and N concentration is called C/N ratio (C/N). In the literature, high tissue C/N promotes reproductive growth and low C/N increases vegetative growth or even inhibits flowering. Cool temperatures is the main factor that controls the flowering of phalaenopsis and dendrobium. However, literatures on how C and N affect the growth and flowering of orchids are limited and even controversial. Tissue analysis of new leaf and 1st, 2nd, 3rd, 5th, 7th mature leaves of large, white-flowered phalaenopsis (P. Sogo Yukidian ‘V3’) demonstrated that N concentration decreased as leaf matured. As leaf position progressed from new leaf to 7th mature leaf, N concentration decreased from 2.72% to 1.48% and C/N therefor increased. There were no significant differences among N concentrations of 2nd-5th mature leaves. Analysis of various sections of the 2nd mature leaf indicated that C and N were not evenly distributed in the leaf. The N concentration and C/N of middle part from 2nd mature leaf were 1.96% and 22.3, respectively, which are very close to the average of whole leaf. The middle part of 2nd mature leaf is the appropriate tissue for sampling to obtain the representative N concentration and dry weight values. To investigate the changes in the C and N in tissues through various developmental stages, this research compared large, white-flowered phalaenopsis (P. Sogo Yukidian ‘V3’), small, purple-flowered phalaenopsis (P. Sogo Lotte ‘F2510’), and hybrid dendrobium (D. Lai’s Yukisakura) by performing tissue analysis. As the large, white-flowered phalaenopsis grew from deflasked plantlet to mature plant in 10.5-cm pot, N concentration of whole plant decreased from 4.63% to 1.63% and C/N increased from 41.8 to 85.6. The N concentration and C/N of small, purple-flowered phalaenopsis had similar values and trends. From terminal leaf emerged to pseudobulb matured, the N concentration of current psudobulb decreased from 1.12% to 0.53% and C/N increased from 41.8 to 85.6. The N concentration of both phalaenopsis cultivars and hybrid dendrobium decreased as plant matured. It indicates that N concentration has the potential of becoming a maturity index. Results in the literature regarding whether growers can delay or advance spiking of phalaenopsis by high or low N level, respectively, have been controversial. Nutrient solutions with four N levels, namely, high (28.6 mM N), normal (14.3 mM N), low (1.43 mM N), and deficient (0 mM N), were applied to large, white-flowered phalaenopsis (P. Sogo Yukidian ‘V3’) and small, purple-flowered phalaenopsis (P. Sogo Lotte ‘F2510’) in their last 8 weeks of vegetative growth at 30/28 oC. The same fertilization regimen was carried onto their reproductive growth stage at 20/18 oC. A significant difference of tissue N concentration is detected in both cultivars 8 weeks after treatment: Higher N level in nutrient solution resulted in higher shoot and root N concentration and lower C/N. The root and shoot both had a negative N gain in the low N and deficient N treatments during the reproductive stage of the two cultivars, indicating that stored N was utilized for inflorescences development when N supply was limited. All plants spiked and flowered but differed slightly in time and quality of flowering. High N delayed the spiking of the small-flowered phalaenopsis ‘F2510’ by 8.9 days but did not affect the large-flowered phalaenopsis ‘V3’. Plants in low N and deficient N treatments spiked only 1-2 days earlier than the normal N treatment in both cultivars. Nitrogen levels did not affect flower count of the large-flowered ‘V3’ but number of flowers in the small-flowered ‘F2510’ was reduced by 2 and 3 in the low N and deficient N treatments, respectively. It is concluded that effects of short-term N application on spiking and flowering of phalaenopsis mainly depend on the size of stored N pool. Flowering performance of miniature-type phalaenopsis is more likely to be lightly manipulated by short-term N application but not those of standard-type phalaenopsis. Cool temperature and light are essential factors that stimulate phalaenopsis to flower. This research compared carbohydrate concentrations of the 2nd mature leaf of a white-flowered phalaenopsis (P. amabilis) at four different cultivation environments: cool in light, cool in dark, warm in light, and warm in dark. Temperature did not affect concentrations of glucose and fructose. Plants in dark treatments had higher concentrations of glucose and fructose. Plants with warm treatments had higher concentrations of sucrose. Sucrose concentration of warm in light treatment was higher than that of warm in dark. Temperature did not affect the concentration of starch; light treatments resulted in higher leaf starch concentration. Many results in this research are different from previous literatures, even with conflicts. These differences might be attributed to the effects of sampling position, mechanical stress, and cultivar difference.