溫度、遮光與無機養分對彩葉鳳梨穴盤苗光合作用與生長之影響

Abstract

彩葉鳳梨(Neoregelia sp.)之花苞片顏色鮮豔且觀賞期可長達半年，深具戶外景觀及室內觀賞潛力，然而育苗期長且目前仍缺乏光度、溫度及養分需求之研究。因此本研究主要目的為瞭解溫度、光度及養液濃度、氮及鉀營養對彩葉鳳梨雜交實生穴盤苗光合作用與營養生長之影響。 將彩葉鳳梨四個雜交組合之種子播於日夜溫20/15、25/20、30/25及35/30oC下，以25/20、30/25oC處理者達50%種子發芽時間少，20/15oC處理延後發芽，而35/30oC處理不僅延後發芽且使最大發芽率下降。將三個彩葉鳳梨雜交組合、具4-5 張本葉之小苗栽培於15/13、20/15、25/20、30/25及35/30oC下，亦以25/20、30/25oC處理者具較高全株淨光合作用速率、地上部、地下部乾重、葉片數、葉面積及葉綠素計讀值，20/15oC處理者各項調查參數較25/20及30/25oC處理者低，而15/13oC處理對植株造成冷害，35/30oC處理則使植株死亡。 將彩葉鳳梨‘Pink Sensation’ × ‘Gold Fever’第一張本葉展開之實生苗以3種遮光程度(20%、50%、77%，中午平均光度分別為858、561、258 μmol•m-2•s-1)配合3種強生氏養液濃度(50%、100%、200%)與自來水栽培。結果顯示施用100%強生氏養液下，以77%遮光處理之光補償點、光飽和點、最大光合作用速率、暗呼吸速率較低。於20%遮光下，以200%強生氏養液處理之全株淨光合作用、光補償點、光飽和點、最大光合作用速率、暗呼吸速率較高。遮光程度與養液濃度處理間對植株生長具交感效應，以20%遮光程度搭配200%強生氏養液處理之地上部、地下部乾重、葉片數、葉面積、葉綠素計讀值較高；施用自來水者植株無明顯生長。 於彩葉鳳梨‘Pink Sensation’ × ‘Gold Fever’實生苗第一張本葉展開時，每週施用一次含0、4、8、12、16、20、24、28、32 mM N之強生氏養液。結果顯示隨養液N濃度由0增加至20-28 mM時，穴盤苗全株光飽和點、最大光合作用速率上升，光補償點無顯著變化。隨養液N濃度由0增加至20-24 mM，地上部、地下部乾重、葉片數、葉面積、葉綠素計讀值增加，養液N濃度再提高至24-32 mM則不再顯著增加。隨養液N濃度增加植體C及N濃度增加，養液N濃度對植體P及K濃度無顯著影響。養液N濃度由0增加至8 mM 植體Ca濃度增加，由12至32 mM N處理則下降。隨養液N濃度增加，植體Mg濃度下降。 於彩葉鳳梨‘Pink Sensation’ × ‘Gold Fever’實生苗第一張本葉展開時，每週施用一次含NH4+:NO3-比例為0:100、25:75、50:50、75:25及100:0之強生氏養液。結果顯示25:75、50:50處理者之全株最大光合作用速率較高，光補償點較低。以25:75處理之地上部及地下部乾重、葉長、葉寬、葉片數、葉面積明顯較高。以0:100及25:75處理者植體C濃度較高，25:75、50:50處理者植體N濃度較低，全銨態氮或全硝態氮處理者植體N濃度較高，0:100、50:50、100:0處理者植體P及K濃度較25:75及75:25處理者低，養液氮型態對植體Ca及Mg濃度無顯著影響。 於彩葉鳳梨‘Pink Sensation’ × ‘Gold Fever’實生苗第一張本葉展開時，每週施用一次含0、2、4、6、8、10 mM K之強生氏養液。結果顯示以0-2 mM K處理之光補償點、光飽和點、暗呼吸速率較高，4-10 mM K處理之光補償點、光飽和點、暗呼吸速率較低。養液K濃度由0增加至6-8 mM時，地上部、地下部乾重、葉片數、葉片長、寬、厚度增加，葉綠素計讀值降低。隨養液K濃度增加，植體C、N濃度下降，隨養液K濃度由0增加至4-6 mM植體P濃度增加，養液K濃度再提升則下降。隨養液K濃度增加，植體K濃度上升。養液K濃度對植體Ca、Mg濃度無顯著影響。

Neoregelia species have long - lasting showy bracts and have been widely used in outdoor and indoor landscaping. Production was long and could be hastened by manipulating environmental conditions and nutrient management to for seedling growth. The objectives of the study were to determine the effects of temperature, light and nutrient solution concentration, and nitrogen and potassium nutrient requirement on leaf growth and photosynthesis. Hybrid seeds of four Neoregelia cross combinations were sown under day/night temperatures of 20/15, 25/20, 30/25, and 35/30oC. Results showed that the time for seeds to reach 50% germination was earlier at 25/20 and 30/25oC than 20/15 and 35/30oC. Maximum germination percentage were lower when sown at 35/30oC. Hybrid seedlings with 4-5 leaves of three Neoregelia cross combinations were grown under various temperatures. Results showed plants had higher whole plant net photosynthesis, shoot and root dry weights, leaf number, leaf area, and SPAD-502 reading value at 25/20 and 30/25oC than at 20/15oC. Plants at 15/13oC showed cooling injury, and all died when grown at 35/30oC. Neoregelia ‘Pink Sensation’ × ‘Tricolor’ seedlings with the first expanded true leaf were grown under three shading levels (20%, 50%, and 77%, ca. 859, 567, and 258 μmol•m-2•s-1 averaged noon time PPF) with four Johnson’s solution (J) strength (0%, 50%, 100%, and 200%). When supplied with 100% J, plants grown under 77% shading had lower light compensation point (LCP), light saturation point (LSP), light saturated photosynthesis rate (Amax), and dark respiration (Rd). Plants supplied with 200% J under 20% shading, had the highest whole plant net photosynthesis, LCP, LSP, Amax, and Rd, shoot and root dry weights, leaf number, leaf area, and SPAD-502 value. Seedlings were stunt when supplied with tap water only. Neoregelia ‘Pink Sensation’ × ‘Tricolor’ seedlings with the first expanded true leaf were supplied with various nitrogen (N) concentrations weekly. Results showed LSP and Amax increased with increasing N from 0 to 20-28 mM. Light compensation point did not differ between treatments. Shoot and root dry weights, leaf number, leaf area, and SPAD-502 value increased as N concentration increased from 0 to 20-24 mM, and saturated thereafter. Plant C and N concentration increased with increasing solution N concentration. Plant K and P concentration did not differ between solution N concentration treatments. Plant Ca concentration increased when solution N concentration increased from 0 to 8 mM, but decreased as solution N increased from 12 to 32 mM. Plant Mg concentration decreased with increasing solution N concentration. Neoregelia ‘Pink Sensation’ × ‘Tricolor’ seedlings with the first expanded true leaf were supplied with 0 : 100, 25 : 75, 50 : 50, 75 : 25, and 100 : 0 NH4+ : NO3- weekly. Result showed plants had the heighest Amax and lowest LCP when supplied with 25 : 75 and 50 : 50 NH4+ : NO3-. Plants had the heighest shoot and dry weights, leaf length, leaf width, leaf number, leaf area and plant C concentration but lowest plant N concentration when supplied with 25 : 75 NH4+ : NO3-. Plant P and K concentration were lowest when supplied with 0 : 100, 50 : 50, 100 : 0 NH4+ : NO3-. Solution nitrogen form did not alter plant Ca and Mg concentrations. Neoregelia ‘Pink Sensation’ × ‘Tricolor’ seedlings with the first expanded true leaf were supplied with 0, 2, 4, 6, 8, 10 mM K. Result showed plants at 0-2 mM K had higher LCP, LSD, and Rd than those at 4-10 mM K. Amax increased with increasing K concentration from 0 to 8 mM, but decreased with further increased K concentration to 10 mM. Shoot and dry weights, leaf number, leaf length, leaf width, and thickness increased, but SPAD-502 decreased, when K concentration increased from 0 to 6-8 mM. Plant C and N concentration decreased with increasing solution K concentration. Plant P concentration increased with increasing solution K concentration from 0 to 4-6 mM, but decreased when solution K concentration further increased. Plant K concentration increased with increasing solution K concentration. Solution K concentration did not alter plant Ca and Mg concentration.