環境因子與室內維管對女王鹿角蕨光合作用及生長之影響

女王鹿角蕨(Platycerium wandae Racif.)為體型最大之鹿角蕨，因姿態優美且觀賞期長，若栽培環境適宜，深具庭園或室內綠美化之價值；然而其育苗期長，且目前關於鹿角蕨生理特性之學術研究仍不足，因此本研究分別探討溫度、光度及養液濃度對女王鹿角蕨小苗光合作用及生長之影響，並於模擬室內低光環境下探討最適介質體積含水量、氮濃度及強生氏養液濃度。將帶有2-3片營養葉之女王鹿角蕨小苗栽培於遮光50%環境，以日/夜溫35/30、30/25、25/20、20/15及15/13℃處理3個月，結果顯示苗期對溫度適應性廣，以25/20℃有利植株生長，其淨光合作用速率、全株乾重及葉面積最大。35/30°C或15/13°C處理之地上部乾重、全株乾重、葉面積及淨光合作用速率低，而細胞間隙CO2濃度高。而35/30°C處理之植株不僅受到非氣孔因素限制，還伴隨著光系統II的損傷，最大螢光值(maximum fluorescence, Fm)及PSII最大光化學量子效率(maximum PSII photochemical quantum efficiency, Fv/Fm)下降。栽培於15/13°C者則遭受寒害，生長受阻。於日夜溫23/16°C環境，將帶有2-3片營養葉之女王鹿角蕨小苗置於光度37、79或194 μmol•m-2•s-1下，結果顯示，2個月後，各處理之淨光合作用速率、氣孔導度、細胞間隙CO2濃度及蒸散作用速率無顯著差異。以79 μmol•m-2•s-1處理者葉片數、葉面積、地上部乾重、地下部乾重較高，且隨光量子通量(photosynthetic photo flux, PPF)由0上升至2000 μmol•m-2•s-1時，氣孔導度增加，促使淨光合作用速率高達8.18 µmol CO2•m-2•s-1，並於200 μmol•m-2•s-1 PPF達50%最大淨光合作用速率。具有2-3片平展狀營養葉或具有螺旋狀營養葉之女王鹿角蕨，栽培於溫度25/20℃，以光度100、200或300 μmol•m-2•s-1搭配施用0%、25%、50%或100%強生氏養液處理131天。結果顯示，僅具2-3片平展狀營養葉之女王鹿角蕨以高光300 μmol•m-2•s-1搭配100%強生氏養液處理，淨光合作用速率、氣孔導度、蒸散作用速率、光飽和點及暗呼吸速率高，且有最佳葉片長及葉片寬。高光300 μmol•m-2•s-1搭配未施肥處理者之Fv/Fm下降。葉片數隨光度或養液濃度下降而減少；SPAD-502讀值隨光度下降或養液濃度提高而上升。而具螺旋狀營養葉之女王鹿角蕨光度適應性廣，光合參數主要受養液濃度影響，高光300 μmol•m-2•s-1搭配100%強生氏養液處理，淨光合作用速率及暗呼吸速率高，而細胞間隙CO2低。未施肥之植株置於高光300 μmol•m-2•s-1，其類囊體之非光化學粹熄係數(nonphotochemical quenching, Qn)及天線系統之非光化學粹熄係數(nonphotochemical quenching, NPQ)顯著高於其他處理。葉片長度及SPAD-502讀值，隨養液濃度提高而增加。模擬室內低光55 μmol•m-2•s-1下，將帶有2-3片營養葉之女王鹿角蕨栽培於25℃環境，以20%介質體積含水量(volumetric water content, VWC)處理、30% VWC處理、70% VWC潮濕處理及20%/70% VWC乾旱復水處理3個月，結果顯示，以20% VWC處理不利植株生長，乾重與葉面積最低，淨光合作用速率因氣孔因素而下降；以30%或70% VWC處理者生長量與光合參數無顯著差異；以20%/70%VWC處理之植株乾重、葉面積、淨光合作用速率與氣孔導度最高，而細胞間隙CO2濃度最低，顯示乾溼交替使植株有效代謝細胞間隙CO2，營養葉快速生長且彎曲成螺旋形。各VWC處理下，光系統II參數及SPAD-502讀值無顯著差異。模擬室內低光55 μmol•m-2•s-1下，以具有2-3片營養葉之女王鹿角蕨作為參試植株，栽培於27℃環境，每週施用一次含有0、4、8、12、16、20或24 mM N之強生氏營養液。處理6個月後，結果顯示氮肥施用濃度以4-8 mM較適當，光合作用速率、地上部乾重、葉面積及SPAD-502讀值較12-24 mM N處理高；當養液N濃度大於12 mM，光合作用受非氣孔因素限制而下降，根冠比提高，葉片焦枯無觀賞價值；以24 mM N處理者除了受非氣孔因素之影響，Fv/Fm顯著降低，營養葉基部褐化。模擬室內低光55 μmol•m-2•s-1下，以具有2-3片營養葉之女王鹿角蕨作為參試植株，栽培於27℃環境，每週施用一次0%、25%、50%或100%強生氏完全養液。處理8個月後，結果顯示以25%強生氏養液處理之淨光合作用速率、乾重及葉面積最大；以0%或50%強生氏養液處理，生長量無顯著差異，但50%強生氏養液處理者部分葉片褐化；以100%強生氏養液處理，淨光合作用受氣孔因素限制，葉片壞疽並脫落，使葉片數顯著降低。模擬室內低光環境下，健康之女王鹿角蕨小苗光補償點約為21-23 μmol•m-2•s-1。綜上所述，僅具營養葉之女王鹿角蕨生長適溫為25/20℃，以高光300 μmol•m-2•s-1栽培，並搭配100%強生氏養液施用，可促進植株生長；當女王鹿角蕨作為室內觀賞植物，生長於低光(55 μmol•m-2•s-1 )環境下，以20%/70% VWC乾溼交替的方式給水，並施用4-8 mM N或25%強生氏養液，有助於植株維持良好觀賞品質。

關鍵字

鹿角蕨；光合作用

並列摘要

Platycerium wandae Racif, the largest staghorn fern, has been used extensively in many areas for outdoor and indoor landscaping, with great potential for markets’ demands. However, production time was long and could be hastened by manipulating environmental conditions and nutrient management for young plants growth. The first objective of the study was to determine the effects of temperature, irradiance, and nutrient solution concentration on photosynthesis and growth during production period. The second objective of the study was to determine the effects of volumetric water content (VWC), nutrient nitrogen concentration, and Johnson’s solution concentration on photosynthesis and growth of young plants under interior low light conditions. Platycerium wandae young plants with 2-3 sterile fronds were grown in phytotrons with various day/night temperatures of 35/30, 30/25, 25/20, 20/15, and 15/13℃ for three months. Results showed that plants at 25/20°C had maximum dry weight, frond area, and net photosynthesis. Plants at 15/13°C or 35/30°C had lowest plant dry weight, frond area, and exhibited lower net photosynthesis accompanied with higher intercellular CO2 concentration. Apart from non-stomatal limitation, plants at 35/30°C also exhibited the lowest Fm and Fv/Fm values. Plants at 15/13°C expressed chilling injury symptoms as brown at the base of sterile fronds. Young plants with 2-3 sterile fronds were grown under 37, 79, and 194 μmol•m-2•s-1 photosynthetic photo flux (PPF) for two months. Results showed that all plants did not differ in net photosynthetic rate, stomatal conductance, intercellular CO2 concentration, and transpiration rate. Frond number, frond area, shoot dry weight, and root dry weight were higher for young plants grown under 79 μmol•m-2•s-1. Plants grown under 79 μmol•m-2•s-1 PPF were exposed with 0 to 2000 μmol•m-2•s-1, and the sampled fronds exhibited increased stomatal conductance and net photosynthetic rate up to 8.18 µmol CO2•m-2•s-1, with 50% maximum net photosynthetic rate at 200 μmol•m-2•s-1 PPF. Young plants with 2-3 sterile fronds or bending sterile fronds were grown under three irradiances (100, 200, or 300 μmol•m-2•s-1) with four Johnson’s solution (J) concentration (0%, 25%, 50%, or 100%) for 131 d. Results showed that young plants with 2-3 sterile fronds supplied with 100% J and grown under 300 μmol•m-2•s-1 had highest net photosynthetic rate, stomatal conductance, transpiration rate, light saturation point (LSP), dark respiration (Rd), frond length, and frond width. Plants grown under 300 μmol•m-2•s-1 without fertilization had higher Qn, and NPQ, and decreased Fv/Fm. Frond number decreased as irradiance or J decreasing. SPAD-502 value increased as J increased from 0% to 100% or irradiances decreased from 300 to 100 μmol•m-2•s-1. Young plants with bending sterile fronds with 100% J and 300 μmol•m-2•s-1 had highest net photosynthesis, Rd, and lowest intercellular CO2 concentration. Plants grown under 300 μmol•m-2•s-1 without fertilization had highest Qn and NPQ. Frond length and SPAD-502 value increased as J increased from 0% to 100%. Growth and photosynthesis were measured in young plants under interior low light intensity (55 μmol•m-2•s-1) conditions with 30% volumetric water content (VWC), 70% VWC (moisture), 20% VWC (drought), and 20%/70% (drought/moisture) VWC treatments for three months. Results showed that plants under 20% VWC exhibited poor growth and lowest net photosynthetic rate through stomatal limitation. Plants under 30% VWC and 70% VWC did not differ in growth and photosynthesis. Plants under 20%/70% VWC had the highest dry weight and net photosynthetic rate, and the largest frond area due to the appearance of rapidly bending sterile fronds. Chlorophyll fluorescence measurements and SPAD-502 value did not differ among the four VWC treatments. Young plants were supplied with J containing various nitrogen (N) concentrations weekly under interior low light (55 μmol•m-2•s-1) conditions for six months. Resulted showed plants at 4-8 mM N had higher net photosynthetic rate, shoot dry weight, frond area, and SPAD-502 value than those at 12-24 mM N. Plants exhibited higher root to shoot ratio and lower net photosynthetic rate through non-stomatal limitation as solution N increased from 12 to 24 mM. Apart from non-stomatal limitation, plants at 24 mM N also had the lowest Fv/Fm values. Plants expressed salt injury symptoms as fronds (12 mM N), and brown at the base of sterile fronds (24 mM N). Young plants were supplied with four J concentration which were 0%, 25%, 50%, and 100% under interior low light (55 μmol•m-2•s-1) conditions for eight months. Resulted showed that plants supplied with 25% J had the largest dry weight, frond area, and the highest net photosynthetic rate. Plants supplied with 0% J and 50% J did not differ in growth, while frond necrosis appeared with 50% J treatment. Plants supplied with 100% J exhibited lowest frond number and net photosynthetic rate through stomatal limitation. The light compensation point for young plants with 0% J and 25% J treatments were estimated to be 21-23 μmol•m-2•s-1. In conclusion, Platycerium wandae young plants should be supplied with 100% J and grown under 300 μmol•m-2•s-1 at 25/20°C to promote its growth. When young plants been used as indoor plants grow under low light intensity (55 μmol•m-2•s-1) conditions, they should be treated with 20%/70% VWC (alternating between dry and wet) and fertilized with 4-8 mM N or 25% J to maintain indoor performance.