遮陰與矮化劑對馬拉巴栗綠苗編種苗生育與品質之影響

Effects of Shading and Growth Retardant on the Growth and Quality of Green Braid 'Pachira macrocarpa' Seedlings

利用馬拉巴栗實生幼苗，生產迷你株型之18 cm綠苗編產品，深受日本、美國及歐洲市場喜愛。本研究探討遮陰與矮化劑對馬拉巴栗綠苗編種苗生育與品質之影響，結果顯示，60%（中午光度800μmol．m^(-2)．s^(-1)PPF）及80%（中午光度400μmol．m^(-2)．s^(-1)PPF）遮陰處理與無遮陰處理對照組（中午光度2000μmol．m^(-2)．s^(-1)PPF）相比，使下胚軸的長度伸長4-5 cm以上，可達到下胚軸長度12 cm之商業取苗標準，且下胚軸直徑也隨著遮陰程度增加而減少，達到5.2-5.7 mm之商業標準；但節間則過度伸長，隨著矮化劑濃度的增高及使用次數的增加，總節間長度與株高顯著縮短，其中又以巴克素（Paclobutrazol）處理對縮短節間長度效果較為顯著，且不會影響節數，以巴克素葉面噴施二次較適合綠苗編植株高度外觀品質。矮壯素（Chlormequat Chloride, CCC）處理則以346 mg．L^(-1)噴施二次為佳。二種矮化劑處理時機，無論是拔苗前或是編辮上盆後處理皆具相同矮化效果；實務操作於種子苗下胚軸長度達12 cm標準長度葉面噴施一次，再於完成編辮上盆後再噴施一次為佳。巴克素濃度高於15 mg．L^(-1)或噴施次數多於三次，皆會造成過度矮化與畸形葉的產生，影響觀賞品質。 Using the young seedlings of malabar chestnut [Pachira macrocarpa (Cham. & Schl.) Schl.] to produce mini-plant types of 18-cm green braid seedlings is popular for Japan, the U.S., and Europe markets. This study aimed to investigate the effects of shading level and growth retardants on the growth and quality of green braid seedlings. Results showed that 60% (800 μmol．m^(-2)．s^(-1) PPF at noon) and 80% (400 μmol．m^(-2)．s^(-1) PPF at noon) shading treatments caused hypocotyl to elongate by 4-5 cm, resulting in 12-cm shoot length for salable standard. Shadings reduced the hypocotyl diameter by 5.2-5.7 mm and increased internode length causing undesirable stretching shape. Internode length and plant height decreased as retardant concentration and spraying frequency increased. Foliar spraying twice at 15 mg．L^(-1) Paclobutrazol (PBZ) could reduce internode length, but did not affect node number and quality. However, the best effect of reduced plant height and maintained quality was foliar-spray with 346 mg．L^(-1) chlormequat chloride (CCC) twice. These two retardants had the same dwarfing effect regardless applied before digging seedlings or after braiding and then planted in 9-cm plastic pot. We suggested the first spray time when the hypocotyl length of seedlings reached 12-cm length, and the second spraying at the recently braided seedlings. Plants would be too short and produced abnormal leaves when applied growth retardants higher than the suggested concentration or sprayed more than three times.