樟樹體胚發生與植株再生

Somatic Embryogenesis and Plant Regeneration in Camphor Tree Cinnamomum camphora (L.) Presl

樺樹（Cinnamomum camphora（L.）Presl）未成熟胚（1.5～5.0mm）培養在WPM基本培養基，添加BA 1mg/l或BA、GA各1mg/l，經過8～12週，會形成含有8～10片子葉狀物（或稱次生子葉，secondary cotyledons），叢生在胚軸上。未成熟胚先行5°C處理1或2週，再培養於上述的培養基，則發育成正常的植株，部分植株的子葉節（cotyledon node）部位會產生粒狀體胚（somatic embryos）。此粒狀體胚移到含2,4-D 0.2mg/l、Kinetin 0.1mg/1或2,4-D 1mg/l、Kinetin 0.5mg/l、10% coconut milk的培養基上，顯著發育成白色肥厚子葉。在子葉的基部會附著少量黃色緊密的胚性癒合組織（embryogenic callus）。移胚性癒合組織到數種不同生長素組合的培養基上，可誘導體胚發生，形成子葉狀物，但不能長成正常的植株。將胚性癒合組織從固體培養基移到相同成份不含洋菜、但加入GA 0.1、0.2和0.5mg/l的液體培養基中，一些顆粒狀體胚會正常發育成有根的植株或無根的綠色枝條。在含GA的液體或固體培養基，配合5°C低溫處理2週後繼續培養，則體胚發育成植株或綠色枝條的效果更佳。此現象顯示樟樹未成熟有性胚和體胚皆具休眠性，可用GA或低溫處理打破休眠，使其發育成正常植株。

Immature embryos (1.5-5.0 mm) of camphor tree (Cinnamomum camphora (L.) Prel) from fruits without 5°C treatment were cultured on WPM basal medium supplemented with BA 1 mg/l or BA 1 mg/l and GA 1 mg/l. Clusters of cotyledon-like structures (secondary cotyledons) appeared on the embryonic axis after 8-1 2 weeks in culture. Immature embryos from fruits received 5°C cold treatment for 1 or 2 weeks exhibited normal germination on the above media, and occasionally produced granular somatic embryos arround the cotyledon node. Somatic embryos developed into cotyledon structures after transferred onto media containing 2,4-D 0.2 mg/l and kinetin 0.1 mg/l or 2,4-D 1.0mg/l, kinetin 0.4 mg/l, and coconut milk 10% (v/v). Embryogenic callus also appeared on the basal part of cotyledon of somatic embryo. The embryogenic callus subcultured on different media formed somatic embryos with cotyledon-like structures but without shoot formation. Normal germination and plantlets formation only occurred in somatic embryos resulting from embryogenic callus subcultured in liquid media with the addition of GA (0.1, 0.2, and 0.5 mg/l). Culturing somatic embryos in liquid or solid media containing GA in combination with 5°C cold treatment for 2 weeks could more efficiently produce normal plantlets or green shoots. These results suggest that the dormancy of zygotic and somatic embryos of camphor tree can be overcome by either GA or 5°C treatment, and more efficiently by combined GA with 5°C treatment.