環境因子、養液濃度及穴格大小對洋桔梗穴盤苗生長之影響

洋桔梗[Eustoma grandiflorum (Raf.) Shinn.]為臺灣重要外銷切花，然其苗期生長速度緩慢，加速穴盤苗育成時間及提高品質之方法亟待建立。本研究探討播種後冷藏、苗期溫度、光積值及施肥濃度，對洋桔梗穴盤苗生長及移植後開花之影響，並探討穴格大小與苗齡及洋桔梗之幼年期，以供業者參考。洋桔梗‘克萊莉粉’播種後以5oC黑暗冷藏兩週與未冷藏處理，一同移至日夜溫35/30及25/20oC自然日照室。結果以栽培溫度對植株生長影響較顯著；於高溫35/30oC有較大葉寬、葉面積、比葉面積及簇生率，而於25/20oC者，有顯著較大之根乾重及抽苔率。播種後以5oC黑暗冷藏兩週無促進於高溫35/30oC生長者之抽苔率。洋桔梗‘克萊莉粉’於子葉展開後，置於日均溫18.3、21.0、25.1、29.3或32.5oC，搭配遮蔭0%、70%或90%處理。結果以25.1oC、未遮蔭者有顯著較高根活性、SPAD-502讀值、葉厚、葉面積、全株乾重及葉片分化速率。不論溫度為何，遮蔭均顯著不利植株生長。尤其以18oC、遮蔭90%處理者，生長顯著受抑制。以25.1oC、未遮蔭者有顯著較高之植體可溶性糖及澱粉濃度。洋桔梗‘克萊莉粉’於30/20oC、8 h光週期育苗至具6-8片本葉，栽培於高溫35/30oC與25/20oC之自然光照室，分別調查簇生與抽苔植株之生長差異。結果不論栽培溫度為何，莖乾重、第一對葉片總可溶性糖含量、第三對葉片澱粉含量及莖蔗糖、總可溶性糖、澱粉含量以抽苔者較簇生者高，SPAD-502讀值以簇生者較高。而不論抽苔與否，莖乾重、根乾重、葉片淨光合作用速率、第一對葉片蔗糖及總可溶性糖含量及莖蔗糖、總可溶性糖、澱粉含量以涼溫者較高。在涼溫下，不論抽苔與否，氣孔導度、細胞間隙二氧化碳濃度及蒸散速率無顯著差異，而於高溫下，則以簇生者較高。洋桔梗‘克萊莉粉’子葉完全展開後，於25/20oC以8 h、12 h、16 h三種光週，搭配100、150、200、300 μmol·m-2·s-1四種光強度，共8種光積值處理。穴盤苗葉片寬度、厚度、根活性隨光積值增加而上升，而比葉面積則下降，約於13.0 mol·m-2·d-1不再顯著變化；葉長、葉面積、地上部乾重、地下部乾重及全株乾重則隨光積值增加而上升。葉片分化速率隨光積值提高而增加，而自播種到可移植時間則減少且約於13.0 mol·m-2·d-1不再顯著變化。於穴盤苗具6-8片本葉時，置於光積值17.3 mol·m-2·d-1下繼續栽培，結果於12 h及16 h光週期下，花下葉片數及到花苞可見時間隨光強度提高而減少，而8 h光週期則否，以16 h光週期處理者較早開花。洋桔梗可能於育苗時期便結束幼年期，開始感應光週。洋桔梗‘克萊莉粉’於子葉展開後，置於25/20oC、12 h光週期，光強度100、200、300 μmol·m-2·s-1 (光積值4.3、8.6、13.0 mol·m-2·d-1)之人工光照室，每週施以50%、100%、200%之強生氏養液。於低光積值4.3 mol·m-2·d-1下提高養液濃度對穴盤苗多無顯著影響，而於高光積值13.0 mol·m-2·d-1，以200%強生氏養液有最大植株乾重及葉面積，而植株根冠比亦較低。不論光積值，以50%強生氏養液處理者螢光參數Fm及Fv/Fm值較低。將洋桔梗‘舞曲白’播種於128 (3.0×3.0×3.5 cm)、288及406穴盤中，於27oC、12 h光週期、200 μmol·m-2·s-1育苗並於不同苗齡時調查及定植至田間(日長10.5-12 h，日夜溫26.9/18.8oC)。結果顯示根活性、葉面積、葉片數及乾重隨苗齡增加而增加。定植七週後株高隨定植時苗齡增加而增加，並以406穴格育苗者較矮。定植後至開花所需天數以128及288格穴盤育苗63天再定植者較短，其定植時葉片數亦較多，隨定植時苗齡較小、葉片數亦較少，定植至開花所需天數較長。自播種至開花所需天數與定植時葉片數迴歸顯示洋桔梗幼年期可能在植株分化10-12片葉時結束。將洋桔梗‘克萊莉粉’間隔3-4天播種一次，置於23/16 oC，並以10 h及16 h長短光週處理，以驗證其對光週感應時期。結果植株於分化8片葉片前處於幼年期，葉片分化超過10片後結束幼年期並具感應光週能力，花下葉片數增加。此時約為播種後45-50天，肉眼可見6-8片葉時期。

關鍵字

日均溫；光積值；簇生化；幼年期

並列摘要

Lisianthus [Eustoma grandiflorum (Raf.) Shinn.] is an important cut flower for export trade in Taiwan. Production during plug stage period of lisianthus is crucial and might be hastened under appropriate environmental conditions and nutrional managements. This study aimed to determine the effects of cooling during seed imbibition, temperature, light integral, nutrient solution concentration, and plug cell size during plug production on seedling growth and flowering performance of lisianthus. Imbibed seeds of ‘Claris Pink’ were stored at 5oC in the dark for two weeks and then moved into phytotrons with growing day/night temperatures of 35/30 or 25/20 oC, while control seeds were not cool-stored. Results showed that growing temperatures, but not dark-cooling, affected seedling growth. Leaf width, leaf area, specific leaf area, and rosette percentage were higher for seedlings grown at 35/30oC, whereas root dry weight and bolting percentage were higher for those grown at 25/20oC. Dark-cooling for two weeks after sowing did not enhance bolting in seedlings subsequently grown at 35/30oC. Seedlings, with cotyledon unfolded, of ‘Claris Pink’ were grown at mean temperatures of 18.3, 21.0, 25.1, 29.3, or 32.5oC combined with 0%, 70%, or 90% shading. Results showed that seedlings grown without shading under 25.1oC had the highest root activity, SPAD-502 value, leaf thickness, leaf area, total dry weight, leaf initiation rate, total soluble sugar and starch concentrations. Shading reduced seedling growth, especially for those grown with 90% shading under 18oC. Seedlings of ‘Claris Pink’ were raised under 8 h photoperiod at 30/20oC until 3-4 leaf pairs were formed, and rosette and bolting plants were then moved into phytotrons of 35/30 or 25/20oC. Stem dry weight, total soluble sugar content of the uppermost unfolded leaves, starch content of the third unfolded leaf pairs, and stem carbohydrate content were higher in bolting than rosette plants, regardless of growing temperature. SPAD-502 value was higher for rosette plants. Stem and root dry weights, net photosynthesis of newly unfolded leaves, and carbohydrate content of the uppermost unfolded leaves and stems were higher in those grown at 25/20oC. Stomatal conductance, intercellular CO2 concentration, and transpiration were higher in rosette plants grown at 35/30oC, but did not differ in those grown at 25/20oC. Seedlings of ‘Claris Pink’ were grown at 25/20oC and received eight daily light integrals (DLI), resulting from 8 h, 12 h, or 16 h photoperiods combined with 100, 150, 200, and 300 μmol·m-2·s-1 PPF. Results show that leaf width, leaf thickness, and root activity increased, while specific leaf area and time to transplanting decreased with increasing DLI and plateaured at 13.0 mol·m-2·d-1. Leaf length, leaf area, shoot, root, and total dry weights increased linearly with increasing DLI. Leaf initiation rate increased with increasing DLI. Seedlings with 3-4 leaf pairs were received 17.3 mol·m-2·d-1 afterwards. Results show that leaf number below the flower and time to visible flower bud decreased with increasing DLI Flowering occurred earlier in seedlings raised under 16 h photoperiods, than 8 or 12 h photoperiods. Seedlings of ‘Claris Pink’ were grown at 25/20oC under 12 h of 100, 200, or 300 μmol·m-2·s-1 PPF (4.3, 8.6, 13.0 mol·m-2·d-1 DLI) and fertilized weekly with 50%, 100% or 200% Johnson’s nutrient solution (J). Rsults show that seedling growth was severely reduced under 4.3 mol·m-2·d-1. Seedlings receiving 200% J and 13.0 mol·m-2·d-1 had the highest total dry weight and leaf area, and lowest root to shoot ratio. Seedlings with 50% J had lower Fm and Fv/Fm value regardless of DLIs. Seeds of ‘Bolero White’ were sown at one-week-inteval and raised at 27oC under 12 h photoperiods of 300 μmol·m-2·s-1 PPF using 128- (3.0×3.0×3.5 cm), 288-, and 406-cell plug tray. Growth parameters at different plant ages were recorded and planted into the field (10.5-12.0 h daylenght, 26.9/18.8oC). Results show that root activity, leaf area, leaf number, and dry weight increased with increasing plant age, but seedlings were smaller when raised with 406-cell plug at the age of 49-63 d. Plant height at 35 d after planting increased with increasing plant age at planting, and were shorter when raised with 406-cells. Time from planting to flowering were shorter for 63 d-old seedlings raised with 128- and 288-cells, and more leaf number including leaf priomordia were recorded.Younger seedlings, with fewer leaf number, at planting required longer time from planting to flowering. Regression between time from sowing to flowering and leaf number including primordia at planting, indicated juvenile phase of lisianthus ended when 10-12 leaves were formed. Seeds of ‘Claris Pink’ were sown at 3-4-day-inteval and raised at 23/16oC under 10 h photoperiods and transferred together to 16 h photoperiods, in order to verify the ending of juvenility. Results show that juvenility persisted until plants initiated 8-10 leaves. After juvenility ends, seedling age 45-50 days after sowing and initiated 8-10 leaves, plants have competence to persive florally inductive stimuli.