杜鵑花耐陰性指標評估

Evaluation of Shade Tolerance Index in Azaleas

許雅婷(Ya-Ting Hsu)

指導教授 ： 張育森

國立臺灣大學/生物資源暨農學院/園藝暨景觀學系/碩士(2017年)

https://doi.org/10.6342/NTU201703150

摘要

杜鵑花為臺灣北部地區重要的景觀花木，本研究主要目的為比較不同杜鵑花品種長期遮陰下生長及開花之反應、探討不同光度對平戶杜鵑生長及開花之影響，並評估具有潛力的耐陰指標與光合作用之相關性，期望提供生產應用、品種選擇以及耐陰指標提供綠化景觀使用參考。
以平戶杜鵑‘Hirado’、西洋杜鵑‘Night Paris’、‘Pink Bubble’、‘Ripples’共4種杜鵑花品種為材料，於塑膠布溫室內進行一般光度及遮陰栽培。夏季(2016/5-2016/9)平均光度分別為641和145 μmol·m-2·s-1，冬春季(2016/10-2017/3)平均光度為300和56 μmol·m-2·s-1。遮陰下‘Hirado’及‘Ripples’形態變化量較高，包含枝條長度增加幅度較高、植株總葉面積顯著增加。遮陰下‘Hirado’葉綠素a/b比值顯著下降，‘Ripples’顯著上升。乾重方面，遮陰下’Night Paris’、‘Pink Bubble’及‘Hirado’乾重沒有顯著差異；‘Ripples’乾重顯著降低。長期遮陰(19個月)下，4品種杜鵑花之總花朵數、花朵鮮重、乾重皆顯著降低，其中以‘Ripples’下降幅度最高，‘Night Paris’在遮陰下之花徑及花色明度(L*)及彩度(C*)和一般光度栽培比較沒有顯著差異。
以盆栽平戶杜鵑‘艷紫’為材料，以不同透光程度針織網進行5種光度處理，相當於100%、81%、54%、32%及13%全日照，夏季 (2016/7/12-9/10)平均光度分別為1321、1029、525、393及166 μmol·m-2·s-1，冬春季(2016/11-2017/3)平均光度為355、288、198、140及70 μmol·m-2·s-1。32%及54%日照，在夏季具有較佳的生長表現，具有最大的葉面積及葉綠素計讀值(chlorophyll meter readings, CMR)，生理上具有最高的光飽和點(light saturation point, LSP)及最大光合作用速率(saturation rate of net photosynthesis, Asat)；13%日照，具有最低的總枝條數、葉乾重、最大光合作用速率。開花部分，32%日照以上具有較高總花朵數、花徑、花朵乾重及鮮重，花色較鮮艷飽和；13%日照處理，花芽發育初期長度、花朵數量及品質顯著較低。
以8種杜鵑花和參考植物朱槿、白鶴芋及火鶴為材料，測量光合作用曲線及高光下(450至550 μmol·m-2·s-1)葉溫氣溫差值(ΔT)，並比較其相關性，結果顯示ΔT與光飽和光合作用速率(Asat)、光飽和點(LSP)、光補償點(light compensation point, LCP)及暗呼吸速率(dark respiration rate, Rd)顯著相關，相關係數r分別為−0.69*** 、−0.61** 、−0.46* 及−0.49*，顯示ΔT為評估植物光需求、耐陰能力的潛力指標。以9種杜鵑花為材料，測量光合作用曲線、葉片葉綠素計濃度、葉綠素計讀值(CMR)、比葉重(leaf mass per leaf area, LMA)及葉片厚度，並比較其相關性，結果顯示Asat與LMA顯著相關(r=−0.58*)，其他特性與光合作用沒有顯著相關。以26種常綠杜鵑花品種為材料，調查其冠層葉片ΔT值，結果顯示平戶杜鵑ΔT值顯著較其他皋月杜鵑、久留米杜鵑及西洋杜鵑低。
綜合上述研究，4品種杜鵑花評估其生長及開花表現，在遮陰下‘Night Paris’、‘Pink Bubble’為較耐陰品種，‘Hirado’可以適應低光環境，而‘Ripples’生長及開花品質下降較多，不適合遮陰下長期栽培。艷紫杜鵑夏季適度遮陰(平均光度393至525 μmol·m-2·s-1)具有較佳的生長表現，長期遮陰以32%日照(夏季平均光度393 μmol·m-2·s-1，冬季平均光度140 μmol·m-2·s-1)以上具有較佳的花朵數量及品質。以多種杜鵑花和參考植物為材料，不同品種間ΔT值與Asat、LSP、LCP、Rd顯著負相關，LMA與Asat顯著負相關，顯示ΔT及LMA是具有潛力的光需求或耐陰指標，杜鵑花品種中，以平戶杜鵑ΔT值顯著較低，推測其光需求偏向陽性植物。

關鍵字

杜鵑花 ； 光合作用 ； 光補償點 ； 植物形態 ； 葉溫氣溫差值

並列摘要

Azalea (Rhododendron spp.) is an important ornamental plant in green spaces of northern Taiwan. The objective of this study was to compare effect of shading on different azalea cultivars, to understand the effects of shading on growth and flowering of R.pulchrum and to evaluate the correlation between potential shade tolerance index and photosynthesis.
The four azalea cultivars,including hirado azalea, belgian azalea ‘Night Paris’, ‘Pink Bubble’ and ‘Ripples’, were in non-shade and shade treatment in PVC covered green house. The average light intensities were 641 and 145 μmol·m-2·s-1 in summer(2016/5-2016/9), while 300 and 56 μmol·m-2·s-1 in winter (2016/10-2017/3). Under shade treatment, ‘Hirado’ and ‘Ripples’ had higher increasing rate in shoot length and total leaf area, while ‘Night Paris’ and ‘Pink Bubble’ had lower morphology plasticity. The decrease of chlorophyll a/b under shading was considered as the ability of shade tolerance. Under shading, chlorophyll a/b of ‘Hirado’ was significantly decreased while ‘Ripples ’ was significantly increased. Dry weight of ‘Night Paris’, ‘Pink Bubble’, and ‘Hirado’ had no significant differences under shading, while ‘Ripples’ significantly decreased. With long term shading treatments (19 months), flower number, flower fresh weight, dry weight of 4 cultivars were significantly decreased and ‘Ripples’ had the greatest decreasing rate. Lightness (L*) and Chroma (C*) of ‘Night Paris’ had no significant differences under shading.
Potted R.pulchrum was grown under 100%, 81%, 54%, 32% and 13% of sunlight with various shading clothes. The average light intensities were 1321、1029、525、393and166μmol·m-2·s-1 in summer (2016/7/12-9/10), and 355、288、198、140 and 70 μmol·m-2·s-1 in winter(2016/11-2017/3). The highest chlorophyll meter readings (CMR), light saturation rate of net photosynthesis (Asat) and light saturation point (LSP) was observed in plants grown under 32% and 54% of sunlight and were considered to have best growth performances. The lowest shoot number, leaf dry weight and Asat was observed in plants grown under 13% of sunlight. Plants got higher total flower number, flower width, flower fresh weight, dry weight and saturation color with light intensity of 100% to 32% of sunlight.
Leaf canopy temperature minus air temperature (ΔT) along with Asat, LSP, light compensation point (LCP) and dark respiration rate (Rd)was conducted in 8 azalea cultivars, hibiscus, peace lilies and anthurium to evaluate the correlation between each other. Results showed that ΔT had significant negative correlation with Asat , LSP, LCP and Rd. The correlation coefficients were −0.69*** 、−0.61** 、−0.46* and−0.49* respectively. ΔT might be a potential index in evaluating light requirement and shade tolerance of plants. Leaf chlorophyll concentration, CMR, leaf mass per leaf area (LMA) along with Asat , LSP, LCP and Rd was conducted in 9 azalea cultivars. Results showed that LMA had significant negative correlation with Asat (r=−0.58*). ΔT of 26 azalea cultivars was investigated. Results showed that hirado azaleas had lower ΔT value than satsuki azalea, kureme azalea and belgian azalea.
In conclusion, ‘Night Paris’, ‘Pink Bubble’ were shade tolerant, ‘Hirado’ was able to adapt in lowlight, but ‘Ripples’ was not shade tolerant with overall evaluation of growth and flower performance. R.pulchrum had the best growth performance with moderate shading in summer (average light intensity of 525 to 393 μmol·m-2·s-1) and best flower quality with light intensity more than 32% of full sun (average 393μmol·m-2·s-1 in summer and 140 μmol·m-2·s-1 in winter). Asat, LSP, LCP and Rd had neganive correlation with ∆T in several azalea cultivars and reference plant. LMA had neganive correlation with Asat. ∆T and Asat were potential indexes in evaluating light requirement or shade tolerance of plants. ∆T was used to compare the differencesamong 26 azalea cultivars.Result showed that hirado azaleas had a lower ∆T than satsuki azaleas, kurume azaleas and belgian azaleas, indicated that hirado azaleas were inclined to light-demanding plants.

並列關鍵字

Azalea ； Photosynthesis ； Light compensation point ； Plant morphology ； ΔT

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