光度、礦物營養及介質含水量對海南菜豆樹與山菜豆生長與光合作用之影響

Abstract

海南菜豆樹(Radermachera hainanensis)及山菜豆(R. sinica)以葉色深綠，具有光澤，能耐低光，而為臺灣重要的木本觀葉植物。然對其育苗及苗期後遮光及介質體積含水量管理資訊尚不清晰。因此本研究擬探討海南菜豆樹與山菜豆光度及養液濃度、養液氮濃度、養液氮素型態比率、養液磷濃度與養液鉀濃度對苗期生長之影響，以及苗期後遮光與介質含水量生長之影響，以供栽培參考應用。 於第一對本葉展開時將海南菜豆樹及山菜豆穴盤苗以3種光強度(100、200、300 µmol·m–2·s–1 PPFD)配合施用3種強生氏養液(50%、100%、150%)及自來水栽培。兩物種於100 µmol·m–2·s–1 搭配50%-150%強生氏養液，海南菜豆樹新葉具有皺縮徵狀，山菜豆新葉則具展開受阻，根系褐化受損之鹽害徵狀。當光度增加至200-300 µmol·m–2·s–1並搭配施用50%之強生氏養液，兩物種葉片及乾重生長表現已達到飽和，養液濃度再增加對生長無益。 於第一對本葉展開時將海南菜豆樹及山菜豆穴盤苗，每週施以含0-32 mM N之強生氏養液1次。兩物種葉色於缺氮處理較為淺綠、生長明顯受限以及光化學效率較低，隨著養液氮濃度增加至12-16 mM N，能使植株生長及光化學效率最大化，使根冠比降低。超過20 mM N處理會使生長及光化學效率降低，於28-32 mM N有介質鹽類累積情形，造成根系受損。 於第一對本葉展開時將海南菜豆樹及山菜豆穴盤苗，每週施以含16 mM N，銨硝比率為0:100、25:75、50:50、75:25和100:0之強生氏養液。海南菜豆樹葉色於全硝酸態氮處理具有褪綠徵狀，全銨態氮處理則具新葉皺縮徵狀。兩物種隨著銨態氮比率增加至銨硝比為50:50時生長表現達到飽和，銨態氮比率再增加，則會使葉面積降低，而養液銨硝比不影響兩物種株高、葉片數及Fv/Fm表現。 於第一對本葉展開時將海南菜豆樹及山菜豆穴盤苗，每週施以含0-4 mM P之強生氏養液1次。兩物種外觀於缺磷處理無明顯缺磷徵狀，但顯著降低生長及光化學效益，而隨著養液磷濃度增加至0.25-0.5 mM P時能使生長及光化學效率最大化，超過1 mM P時則會造成生長及光化學效益顯著降低。 於第一對本葉展開時將海南菜豆樹及山菜豆穴盤苗，每週施以含0-10 mM K之強生氏養液。兩物種葉片生長於0-2 mM K處理會受限，於4 mM K處理生長表現及光化學效益較佳，超過時生長表現已不再增加，於8-10 mM K處理則會使介質EC值提升，具有明顯鹽類累積，並且光化學效益顯著降低。 將株高15 cm的海南菜豆樹及山菜豆種於15 cm盆內，以四種遮光處理(0%、70%、78%及83%)。海南菜豆樹外觀表現於各遮光處理下無明顯差異，葉面積於70%遮光處理較大，隨著遮光增加葉片會變薄，光飽和點於70%遮光處理較大，為477.2 µmol·m–2·s–1。山菜豆於無遮光處理植株較矮，光飽和點較高，為540 µmol·m–2·s–1，株高、節間長及葉面積於70%遮光處理較大，葉片無明顯變薄。兩物種乾重於無遮光及70%遮光處理下無顯著差異，但當超過78%遮光時，生長會受限。並且隨著遮光增加光補償點可由42 µmol CO2·m–2·s–1。降至26 µmol CO2·m–2·s–1。 將株高15 cm之海南菜豆樹及山菜豆種於15 cm盆，給予4種介質含水量處理(20% VWC、20/70% VWC、40% VWC及70% VWC)。兩物種植株、葉片生長於20% VWC處理較差，為蒸散作用及氣孔導度降低，細胞間隙二氧化碳濃度較低，為氣孔因素及光合系統功能受損所致。兩物種生長表現皆於40% VWC處理較佳，但氣孔導度、蒸散作用及乾重變化與70% VWC處理間無顯著差異，且相對乾重與20% VWC處理相比降低較少，顯示兩物種為耐濕潤而不耐旱的作物。

Radermachera hainanensis and R. sinica are important indoor foliage plants with dark glossy green leaves, and low-light tolerance. However, the information on pulg production and subsequent management of shading and volumetric water content (VWC) of the medium after plug prodution is still unclear. Therefore, the objective of this study were to determine the effects of light intensity and nutrient solution strenght, nutrient solution nitrogen, phosphorus, potassium concentration, and nitrogen form on the growth of both speices during plug stage and the effects of shading and medium VWC on growth after transplant. R. hainanensis and R. sinica plug seedlings with the first expanded leaf pairs were grown under three light intensity level (100, 200, or 300 µmol·m–2·s–1 PPFD) with four Johnson's solution (J; 0%, 50%, 100%, 150%). When two species were supplied with full J strength higher than 50% at 100 µmol·m–2·s–1, new leaves and roots showed symptoms of salt damage. When light intensity level increased to 200-300 µmol·m–2·s–1 with 50% J was sufficient for growth of leaves and dry weights of the two species. No further growth was observed with increased J strength. Plug seedlings of two species with the first expanded of leaf pairs were supplied with Johnson's solution containing 0-32 mM N weekly. Results show that nitrogen-deficient treatment (0 mM N) resulted in light green leaf color, restricted growth and low photochemical efficiency fot both species. Maximum plant growth and photochemical efficiency were recorded for both species when nutrient solution concentration increased to 12-16 mM N, accompanied with lower root and shoot ratio. Treatmenet with 20 mM N, or higher reduced growth and photochemical efficiency. Salt accumulation in medium were observed at 28-32 mM N, causing damage to the root system. Plug seedlings of two species with the first expanded of leaf pairs were supplied with Johnson's solution containing 16 mM N in 0:100, 25:75, 50:50, 75:25 and 100:0 of NH4+:NO3-. R. hainanensis showed chlorotic leaves and shrinkage of new leaves when treated with full nitrate and ammonium J, respectively. Both species showed better when treated with J containing 50% nitrate and 50% ammonium. Further increase in NH4-N resulted in decreased leaf area. Nutrient solution ammonium to nitrate ratio did not affect plant height, number of leaves and Fv/ Fm value. Plug seedlings of two species with the first expanded of leaf pairs were supplied with Johnson's solution containing 0-4 mM P weekly. The two species did not express obvious symptoms of phosphorus deficiency in the P-deficiency treatment (0 mM P), however the growth and photochemical efficiency reduced. Maximum growth and photochemical efficiency of two speice recorded at 0.25-0.5 mM P. Treatment highter than 1 mM P reduced growth and photochemical efficiency. Plug seedlings of two species with the first expanded of leaf pairs were supplied with Johnson's solution containing 0-10 mM K weekly. Leaf growth of the two species was limited in 0-2 mM K treatments. the growth performance and photochemical efficiency were higher at 4 mM K, and no further increase was observed when exceeded 4 mM K. Significant salt accumulation and reduced the photochemical efficiency was recorded when treated with 8-10 mM K. R. hainanensis and R. sinica were planted in 15-cm pots and treated with 4 shading levels (0%, 70%, 78% and 83%). There was no significant difference in the appearance of R. hainanensis among treatments. Leaf area was larger at 70% shading. Leaves became thinner as the degree of shading increased. Light saturation point (LCP) was 477.2 µmol·m–2·s–1 in the 70% shading treatment and was larger than the other treatments. Full light had dwarfing effect on R. sinica. Plant height, internode length and leaf area were larger in 70% treatment. Leaf thickness did not change significantly with altering hight levels. LSP was 540 µmol·m–2·s–1 in the full light treatment and was larger than the other treatments. Growth of both species were limited when the shading was greater than 78% treatment. There was no significant difference in dry weight between full light and 70% treatment. The light compensation point (LCP) decreased from 42 µmol CO2·m–2·s–1 to 26 µmol CO2·m–2·s–1. R. hainanensis and R. sinica were planted in 15-cm pots and treated with four of medium volumetric water content (20% VWC, 20/70% VWC, 40% VWC and 70% VWC). Poor growth of both species was osbserved in the 20% VWC treatment, which was caused by both stomatal and non-stomatal limitation. The growth performance was better in 40% VWC treatment, but there was no significant difference in the stomatal conductance, evapotranspiration and dry weight in compared to the 70% VWC treatment, indicating that both species are moist-tolerant crops.