養液氮濃度對洋桔梗穴盤苗生長及後續開花之影響

Effects of Nutrient Solution Nitrogen Concentration on Growth of Plug Seedlings and Subsequent Flowering in Eustoma grandiflorum

養液氮濃度可能影響洋桔梗【Eustoma grandiflorum（Raf.）Shinn.】穴盤苗之生長及後續開花。本研究取洋桔梗三品種之種子分別於夏季與冬季在日／夜溫25/20℃環境下播種於穴盤，自子葉完全展開後，每週施用含不同氮（N）濃度之強生氏養液一次。結果顯示每週施含4-8mM N養液之穴盤苗皆生長慢、定植後生長停滯期較長而延遲開花。早生的‘克萊利粉’穴盤苗於16-20mM N處理已有最佳的葉片生長與植株乾重表現；而晚生之‘禮儀彩藍’則需以20-24mM N處理，才能加速葉片展開與植株生長。每週施含20-24mM N之養液使參試三品種穴盤苗展葉較快，葉面積、乾重、植體碳濃度與根活性較大，植體之巨量元素濃度多介於前人之推薦值範圍，且移植後較低N育苗者提早抽莖與開花。養液N濃度再提高（28-36mM）對苗期生長與定植後之開花已不再有顯著助益。 Nitrogen (N) may affect plug seedling growth and subsequent flowering in lisianthus [Eustoma grandiflorum (Raf.) Shinn.]. We determined the effects of various nutrient N concentrations, applied weekly from cotyledon unfolded to the third leaf-pairs fully expanded, on plug seedlings growth and subsequent flowering of three Eustoma cultivars. Results showed that all seedlings with 4-8mM N grew slowly, required longer time for post-transplant recovery, and thus delayed flowering and harvesting. Leaf and plant growth saturated in early cultivar Claris Pink with 16-20mM N, but growth peaked in late cultivar Ceremony BlueFlash with higher N (20-24mM). All plug seedlings with 20-24mM N had higher plant dry weight, carbon concentration and root activity, and earlier post-transplant flowering than those with lower N treatments. Plant analysis revealed that the concentrations of macro-elements in seedlings received 20-24mM N were within the range as recommended for Eustoma. Further increases in N concentration to 28-36mM did not enhance seedling growth and subsequent flowering as compared with those with 20-24mM N.