養液氮、磷及鉀濃度與溫度對仙客來生長及開花之影響

Abstract

仙客來(Cyclamen persicum Mill.)為世界重要盆花；但小苗發育不整齊、育苗期與栽培期長，且於高溫下生長不良，故生產高品質穴盤苗、縮短栽培期，並篩選耐熱品種為重要課題。本研究探討早期施肥與養液氮(N)、磷(P)及鉀(K)濃度對仙客來‘Laser Synchro Scarlet’穴盤苗生長及後續開花之影響。另評估溫度對11個仙客來品種種子發芽、生長及開花之影響。 仙客來‘Laser Synchro Scarlet’於胚根突出後，每週施用50%或100% Johnson’s solution 1次者之穴盤苗葉片展開天數，與本葉開始生長後才施用100% Johnson’s solution者無顯著差異；然而提早於胚根突出後施肥之穴盤苗葉片及乾物重較大，且定植後提早約2週開花，花朵數較多。 於1-3片葉生長期間，每週施用含0-28 mM N之Johnson’s solution 1次。缺N (0 mM)者之全株淨光合作用速率低且暗呼吸作用高，生長遲緩，葉片較小、葉色黃化，根活性及植株乾重低。而16-20 mM N處理之全株淨光合作用速率最高。葉面積、葉綠素計讀值及植株乾重隨養液N濃度由0提高至20 mM而增加，再提高至24-28 mM則不再顯著增加。提高養液N濃度，植體碳(C)、N、P及鈣(Ca)濃度隨之增加，缺N處理之植體鎂(Mg)濃度顯著最低，而植體K濃度則於各養液N濃度處理間無顯著差異。苗期施用24-28 mM N者定植後最早開花且花朵數最多。 於1-3片葉生長期間，每週施用含0-4 mM P之Johnson’s solution 1次，結果顯示缺 P處理者光合作用速率最低，其他養液P濃度處理間則無顯著差異。缺P之植株矮小、葉片較厚且濃綠。葉面積及植株展幅隨P濃度自0提高至1 mM而增加，但於0.5-4 mM P處理間無顯著差異，植株及葉片乾重於各養液P濃度處理間無顯著差異。植體P濃度隨養液P濃度增加而上升，植體C濃度則隨著養液P濃度增加而逐漸下降，而植體N、K、Ca及Mg濃度於各養液P濃度處理間無顯著差異。苗期施用1 mM P者定植後最早開花，且花朵數最多。 於1-3片葉生長期間，每週施用含0-10 mM K之Johnson’s solution 1次，對植株淨光合作用速率及生長均無顯著影響。植體K濃度隨養液K濃度增加而上升，植體C、N及P濃度於各養液K濃度處理間無顯著差異，而植體Ca及Mg濃度則隨養液K濃度增加而逐漸下降。苗期K濃度對定植後開花天數無顯著影響，以6-10 mM K處理者定植後之花朵數最多。 仙客來11品種播種於5.2-30.1oC環境，三種花型大小仙客來種子發芽之基本溫度(cardinal temperature)相似，介於-0.6-35.6oC，最適溫度(optimal temperature, To)介於14.1-16.3oC。迷你型仙客來於To之發芽速率(50%種子發芽時間之倒數)較中花型及大花型快。另將11品種仙客來定植於9 cm塑膠盆，分別置於20/15及30/25oC栽培70天。各品種於30/25oC處理之單葉葉面積較大且葉色較淡、花朵數減少、植株較不緻密。除了30/25oC使迷你型‘Silverado Scarlet’之淨光合作用速率顯著下降外，其餘品種於兩溫度處理之淨光合作用速率無顯著差異。迷你型仙客來於30/25oC處理之氣孔導度及蒸散速率均顯著較中花型及大花型高，葉片溫度也顯著較低。於30/25oC處理，迷你型‘Smatiz Rose’、‘Super Serie Vareno Dark Violet’及‘Metis Light Pink With Eye’能有較佳的外觀品質，花朵花苞數及完全展開葉片數減少比例低，亦能維持相對植株乾重，為相對耐熱品種；而迷你型‘Silverado Scarlet’、大花型‘Latina Success Deep Magenta’、‘Halios HD Salmon’、‘Sierra Synchro White’及‘Snowridge Maxi Purple’於30/25oC處理之外觀品質、葉片及花芽分化能力差，花芽夭折率高，且相對植株乾重較低，為熱敏感品種。 綜合以上結果，仙客來‘Laser Synchro Scarlet’於胚根突出後每週施用50%或100% Johnson’s solution，或於1-3片葉生長期間，每週施用含24-28 mM N、1 mM P及6-10 mM K之養液1次，穴盤苗生長表現佳，且定植後能提早開花，花朵數較多，縮短栽培期約2週。於高溫30/25oC，相對耐熱之迷你型‘Smatiz Rose’、‘Super Serie Vareno Dark Violet’及‘Metis Light Pink With Eye’蒸散速率高降低葉溫，維持葉片及花芽分化能力，且有較佳的外觀品質。

Cyclamen (Cyclamen persicum Mill.) is one of the most popular potted flowers worldwide, while slow and aberrant growth of plug seedlings and poor growth under high temperature condition are major production problems. It is important to produce high quality seedlings, reduce production period, and screen heat-tolerant cultivars. This study aimed to determine the effects of early feeding and optimum solution nitrogen (N), phosphorus (P), and potassium (K) concentration during plug stage on growth and subsequent flowering of Cyclamen ‘Laser Synchro Scarlet’. Effects of temperature on seed germination, plant growth, and flowering of eleven cyclamen cultivars were studied. Days from sowing to the third leaf unfolding of Cyclamen ‘Laser Synchro Scarlet’ did not differ between seedlings applied weekly with 50% or 100% Johnson’s solution at root emergence and those applied with 100% Johnson’s solution when true leaves grew and developed. Seedlings with early feeding at root emergence had higher leaf area and dry weight, more flowers, and 2 weeks earlier to flowering than those applied when true leaves grew and developed. Seedlings were applied with Johnson’s solution containing 0-28 mM N weekly from the first to the third leaf-stage. Results showed that N deficiency (0 mM) reduced whole plant net photosynthesis rate (Pn) and increased dark respiration rates, which resulted in poor growth, small and chlorotic leaves, low root activity and plant dry weight. Seedlings applied with 16-20 mM N had the highest Pn. Leaf area, SPAD-502 value, and plant dry weight increased with increasing N concentration from 0 to 20 mM, and did not increase significantly with increased N to 24-28 mM. Tissue carbon (C), N, P, and calcium (Ca) concentration increased with increasing solution N concentration. N-deficient seedlings had the lowest tissue magnesium (Mg) concentration, while solution N concentration did not affect tissue K concentration. After transplanting, seedlings applied with 24-28 mM N took the shortest time to flowering, and had the most flowers. Seedlings were applied with Johnson’s solution containing 0-4 mM P weekly from the first to the third leaf-stage. Results showed that P-deficient seedlings had the lowest Pn, while there were no significant differences between P concentration treatments. P deficient seedlings were small, and had thicker and dark-green leaves. Leaf area and plant width increased with increasing P concentration from 0 to 1 mM, and did not differ between seedlings applied with 0.5-4 mM P. Plant and leaf dry weight did not differ between P concentration treatments. Increasing solution P concentration increased tissue P concentration, decreased tissue C concentration, but did not alter tissue N, K, Ca, and Mg concentrations. After transplanting, seedlings applied with 1 mM P took the shortest time to flowering and had the most flowers. Seedlings were applied with Johnson’s solution containing 0-10 mM K weekly from the first to the third leaf-stage. Results showed that solution K concentration did not affect Pn and growth. Increasing solution K concentration from 0 to 10 mM increased tissue K concentration, decreased Ca and Mg concentration, but did not affect tissue C, N, and P concentrations. Days from transplanting to flowering were not affected by K concentration treatments. Seedlings applied with 6-10 mM K had the most flowers. Eleven cyclamen cultivars, categorized in mini, midi, and maxi flower sizes, were sown at 5.2-30.1oC. Regardless of cultivar, the base and maxium temperatures for seed germination were similar as -0.6 and 35.6oC, respectively. The optimum temperature (To) for germination was 14.1-16.3oC, and the germination rate (the reciprocal of time to 50% seed to germinate) at To of mini cyclamen was faster than midi and maxi type. Eleven cyclamen cultivars were also cultivated in 9 cm pots, and grown at 20/15 and 30/25oC for seventy days. All cultivars at 30/25oC had bigger leaves, fewer flowers, and less compact than those at 20/15oC. Except that mini ‘Silverado Scarlet’ at 30/25oC had lower Pn than at 20/15oC. Pn of other cultivars did not differ between 30/25oC and 20/15oC treatments. As compared with midi and maxi type, mini cyclamen had higher stomatal conductance and transpiration rate (E), which resulted in lower leaf temperature at 30/25oC. Heat-tolerant mini ‘Smatiz Rose’, ‘Super Serie Vareno Dark Violet’, and ‘Metis Light Pink With Eye’ at 30/25oC maintained acceptable quality, with only slightly reduced flower and leaf numbers. Heat-sensitive mini ‘Silverado Scarlet’, maxi ‘Latina Success Deep Magenta’, ‘Halios HD Salmon’, ‘Sierra Synchro White’, and ‘Snowridge Maxi Purple’ at 30/25oC had poor quality and initiation ability of leaf and flower, more blasted flowers, and lower relative plant dry weight. In conclusion, Cyclamen ‘Laser Synchro Scarlet’ applied weekly with 50% or 100% Johnson’s solution at root emergence or applied weekly with Johnson’s solution containing 24-28 mM N, 1mM P, and 6-10 mM K from the first to the third leaf-stage had good plug performances, more flowers, and took the shortest time to flowering. At 30/25oC, heat-tolerant mini ‘Smatiz Rose’, ‘Super Serie Vareno Dark Violet’, and ‘Metis Light Pink With Eye’ had higher E and lower leaf temperature, and maintained leaf and flower initiation, and quality.