洋桔梗之幼年期及育苗期間光處理對穴盤苗生長與後續開花之影響

Juvenile Phase and Effects of Lighting during Plug Stage on Growth and Subsequent Flowering of Eustoma grandiflorum

洋桔梗育苗期長，了解幼年期與育苗光環境之影響，有利加速生產高品質之穴盤苗。本研究取洋桔梗‘Claris Pink’間隔3-4天播種一次，並置於23/16℃、每日提供200 μmol·m-2·s-1光照10 h環境，之後將16批次不同苗齡之植株同時移入16 h光週環境，調查其花下葉數的改變，以測定幼年期。結果顯示分化少於8片葉的植株仍處於幼年期，分化超過10片葉後的植株已結束幼年期，具感應光週能力。取子葉完全展開的小苗，於25/20℃以8 h、12 h、16 h三種光週期，搭配100、150、200或300 μmol·m-2·s-1四種光強度，共8種日光積值(2.9-17.3 mol·m-2·d-1)處理，結果顯示穴盤苗根活性、葉面積、葉片厚度、乾重、葉片分化速率隨日光積值增加而上升。而自播種到可移植大小的時間則隨日光積值上升至13.0 mol·m-2·d-1而縮短。將這些於不同光積值處理之穴盤苗生長至具6-8片肉眼可見葉片大小（含葉原體共8-12總葉數）時，分別移植於每日光照16 h、光積值17.3 mol·m-2·d-1下繼續栽培，結果顯示育苗期間以12 h搭配300 μmol·m-2·s-1與以16 h光週搭配150-300 μmol·m-2·s-1處理者（日光積值≥ 8.6 mol·m-2·d-1）顯著減少花下葉片數並縮短到花苞可見日數。

Production of lisianthus [Eustoma grandiflorum (Raf) Shinn.] is time consuming due to slow growth of plug seedlings. A better understanding of juvenile period and cultural light conditions facilitates to enhance plug seedling growth and quality. The duration of juvenile development was measured by transferring plants from less-inductive photoperiods to inductive photoperiods and using a change in leaf number as the indication for the end of juvenility. Sixteen batches of Eustoma ‘Claris Pink’ seeds were sown at intervals of 3-4 days and raised to various sizes with 2-18 leaves (including leaf primordium) at 23/16℃ under 10 h (less-inductive) photoperiods. Seedlings were then transferred together to 16 h (inductive) photoperiod conditions. Results showed that juvenility persisted until plants initiated 8 leaves, and became photoperiod-inductive when 10 or more leaves initiated. After cotyledon unfolded, seedlings were raised at 25/20℃ with daily light integrals (DLI) between 2.9 and 17.3 mol·m-2·d-1, resulting from 8 h, 12 h, or 16 h photoperiods combined with 100, 150, 200, or 300 μmol·m-2·s-1 photosynthetic photon flux density. Results showed that root activity, leaf area, leaf thickness, plant dry weights, and leaf initiation rate increased with increasing DLI, while time to transplant decreased and plateaued at 13.0 mol·m-2·d-1. When these plug seedlings pretreated with various DLI produced 6-8 visible leaves (8-12 total leaf number including leaf primordium), they were then transplanted and grown under 16 h photoperiod with 17.3 mol·m-2·d-1 DLI conditions. Results showed that the lowest leaf number below the flower and the shortest time to flower bud visibility were recorded in pretransplant plug seedlings raised with DLI ≥ 8.6 mol·m-2·d-1, namely from 12 h photoperiod combined with 300 μmol·m-2·s-1, and 16 h photoperiod combined with 150-300 μmol·m-2·s-1 conditions.