鳳梨之切頂加速繁殖

The Decapitation Method for Rapid Multiplication of Pineapples

本研究報告鳳梨之加速繁殖方法三種：白化切頂法（Etiolation-decapitation method），切頂扦插法（Decapitation-cutting method）及分切法（Division method）。三者均由作者前次報告之發芽插加速繁殖法演變而來，既均自發芽插開始，應用切頂除去頂部優勢對發芽抑制之影響，而促成不定芽或側芽之形成及生長。白化切頂法係當葉芽插發芽形成之白化幼芽長及1-1.5公分時行切頂除去生長點部。切頂扦插法則當發芽長大長及4-5公分時，自基部0.5公分處切頂，作為插穗扦插。兩者之原葉芽插穗於再行插植後；在白化切頂法可促進不定芽之發生，在切頂扦插者可促基部葉腋側芽之發芽長大。如此兩者均可繼續分次切芽培養，約經6月餘，到插穗漸行萎枯為止。兩法中每葉芽插穗平均可得幼苗三株，在實用上以切頂扦插法較為節省時間並可保障得芽之數目。分切法係將由上法所得長及7-8公分時之幼苗經培養後從切為二，於重行插植後，可自葉腋之側芽發生幼苗，亦可切離培養，並可使繼續發生幼芽，平均第一原株亦可得幼苗三株，分切法因可用幼苗開始分切，故可縮短繁殖過程之循環。此三種方法對新品種原始株數有限時之加速繁殖有顯著之利點。

Three methods for rapid multiplication of pineapple Ananas comosus cv. Smooth Cayenne are described in this paper. The etiolation-decapitation method, the decapitation-cutting method and the division method; all are developed from the leaf bud cutting method of the author. These methods are based on the principle of decapitation; that is removing the shoot apex to force the growth of adventitious or lateral buds. Leaf-bud cuttings which consisted of a leaf attached with a piece of stem and a bud, were first taken from the crown of pineapples and striken in sand. After the buds grew to suitable size, they were decapitated. In the etiolation-decapitation method, the etiolated growing bud 15 cm in length obtained through deeper planting of the leaf-bud cutting was decapitated. In the decapitation-cutting method, the bud was allowed to grow to form a plantlet with green leaves 4-5 cm in length. The plantlet was then cut off the original cutting with a piece of stem attached at its base and planted as a cutting. In both cases the original leaf-bud cuttings were replanted to force the growth of adventitious and lateral buds. When these buds grew to a plantlets 4-5 cm in length they were harvested and the original cutting replanted the processes were repeated until the original cutting gradually become exhausted. For both methods, a single leaf-bud cutting in average produced 8 plantlets within a period of 6 months. In the division method young plantlets 7-8 cm in length obtained in the former methods were divided into halves by cutting longitudinally through its shoot apex and the halves planted. New plantlets developed from lateral buds in the leaf axile. The division method was considered to be effective to speed up the propagation cycle owing to the fact that the young plants soon attained suitable size which may further be divided. All the experiments were done in greenhouse, sand was used as rooting medium. Soil temperature around 28℃ was maintained during the winter months by soil heating cables. No disinfection of the cutting was used in this study and no trouble with rotting occurred. The role of apical dominance and the effect of decapitation in relation to these methods were discussed.