變葉木扦插技術及六種變葉木光合特性之研究

Abstract

摘要 變葉木(Codiaeum variegatum)又名彩葉木、錦葉木，屬於大戟科(Euphorbiaceae)、變葉木屬(Codiaeum)，為多年生木本觀葉植物，目前主要應用於庭園景觀，但如能提高苗木品質，很有潛力成為室內盆栽作物。因此，插穗品質的提升及植物耐陰性的評估，為重要的研究課題。本試驗目的在建立變葉木插穗的取穗標準、扦插條件以及研究光度對變葉木不同品種之生長與光合作用特性之影響。以黃龜甲‘Andreanum’及彩霞‘MacArthurii’變葉木為試驗材料，在取穗部位對發根的影響試驗中，變葉木的發根情形皆是以取自枝條上部位的插穗發根較佳，明顯地比下部位枝條的發根情形佳。插穗長度對插穗發根的影響，皆是以長插穗的發根情形優於短插穗。直徑對插穗發根的影響，結果顯示在處理間並無差異（0.48~0.95cm），顯示試驗中插穗直徑於此範圍中對發根沒有影響，觀察不定根品質，顯示0.5 cm左右的穗粗已符合取穗標準。插穗上留葉片數之多寡對於‘黃龜甲’變葉木發根的影響，試驗結果顯示，插穗上所留存的葉片數至少要四片葉。在變葉木插穗的取穗標準試驗中，試驗結果顯示，取穗時應取枝條上部位且較長，至少帶有4片葉的插穗。外施IBA對於兩品種變葉木插穗發根之影響，因品種其效果並不相同，增加施用IBA濃度，能增加‘黃龜甲’插穗的發根數目，但根長度、最長根長及根乾重等，則是有隨著施用濃度的增加而下降的趨勢；但 ‘彩霞’ 對IBA處理的效應並不存在。在15/13℃、20/15℃、25/20℃、30/25℃與35/30℃不同日夜溫下進行‘黃龜甲’變葉木扦插試驗，結果顯示當日夜溫在25/20℃時，有較高的根數；而日夜溫在30/25℃時，根長度、最大根長、根乾重等皆有較佳的表現。冬季的根部加溫試驗，結果顯示出有地底加熱至23∼25℃，能增進插穗發根的情形。本試驗六品種變葉木在遮光環境下，葉面積、比葉面積會增加，比葉重會下降，葉片柵狀組織及葉片厚度會變薄，氣孔數減少；此外在遮光下，葉片的葉斑比例較高。光強度對植株的影響，在遮光下變葉木的節間長度會增加，但株高則無明顯的影響，新生葉片數會較多。變葉木的光飽和點及光補償點皆隨著遮光程度的增加而下降，在80%的高度遮光下，六品種變葉木的光補償點約為13.63至20.12μmol m-2s-1，顯示變葉木為陽性植物，但可遮陰馴化；發展為室內盆栽植物的潛力，因品種而異。

Summary Croton(Codiaeum variegatum) is a perennial woody foliage plant, which is used landscaping commonly. However, by improving the cutting quality and accommodating to lower light, croton can be potentially developed to be indoor plants. The objective of this study was to build a standard cutting procedure and evaluated the lower light tolerance of the common cultivars in Taiwan. In the study of the effect of nodal position on rooting of the cuttings of ‘Andreanum’ and ‘MacArthurii’, the data suggested that leaves at apical position, cutting length may resulted in better rooting. Besides, due to the diameters of the cuttings we selected were larger than ~0.5cm, the effect of cutting diameter on rooting was not observed. The result of the effect of leaf retention number on the rooting of ‘Andreanum’ cutting indicated that the cuttings with more than 4 leaves were preferred for rooting. The effect of IBA application on rooting was cultivar dependent. Application higher concentration of IBA to ‘Andreanum’ cuttings resulted in more rooting, shorter root length and less weight. However, the effect was not observed in ‘MacArthurii’cutting. The result of rooting experiment in the phytotron indicated that 25/20℃ resulted in more roots and 30/25℃ resulted in longer roots with higher dry weight. Besides, heating up the soil temperature to 23-25℃ was also suggested for winter production. The six croton varieties expressed higher leaf area and specific leaf area, longer internodes, lower specific leaf weight, thinner leaf due to the decreased length of palisade tissues, and decreased number of stomata under shading. Besides, leaf variegation ratio was observed higher under shading. In general, croton is sun plant, and their light saturation and compensation points were decreased in response to shading. Under 80% shading, light compensation point of the 6 cultivars were about 13.63 to 20.12 μmol m-2s-1, which indicating croton is sun-shade plant and potentially an indoor pot plant depending on cultivar.