養液氮和鉀濃度對沙漠玫瑰實生穴盤苗生長之影響

Effects of Nutrient Solution Nitrogen and Potassium Concentration on Growth of Plug Seedlings of Adenium obesum

沙漠玫瑰[Adenium obesum (Forssk.) Roem.& Schult.]具特別的株形和豐富的花型花色，深受歡迎；然而沙漠玫瑰實生苗之養分管理資訊匱乏，亟待研究以期加速整齊生產穴盤苗。本研究於沙漠玫瑰‘Harry Potter’實生穴盤苗之子葉完全展開後，每週施用不同氮(N)濃度、鉀(K)濃度之強生氏養液1次。結果顯示，缺N及低N (4 mM N)顯著延緩葉片展開時間，缺N處理者全株葉片黃化並且老葉症狀更為明顯，完全展開葉數少、葉面積小，根冠比高。養液N濃度由0增加至16 mM，會使莖徑、葉綠素計讀值、根與莖乾重隨之增加。缺K處理者老葉出現黃化、葉緣焦枯及落葉等徵狀，且根冠比最高，缺K或低K (2 mM K)處理皆會延緩穴盤苗葉片展開時間，養液K濃度由0增加至6 mM處理使莖徑、葉面積、葉綠素計讀值、植株乾重隨之增加。沙漠玫瑰穴盤苗乾重會隨植體N與K濃度增加而增加，均呈二次曲線關係。

Desert rose [Adenium obesum (Forssk.) Roem. & Schult.] is a popular flowering potted plant due to its attractive sculptural caudex with a wide range of flower colors and forms. However, information on nutrition management during slow and long plug production is presently limited. Plug seedlings of ‘Harry Potter’ were weekly applied with Johnson’s solution containing various nitrogen (N) or potassium (K) concentrations starting when the cotyledon had fully expanded. Results showed that N deficiency and low N (4 mM) treatments took longer time for third leaf pairs to expand. N deficiency resulted in small and chlorotic leaves especially in old leaves, reduced leaf number and leaf area, and the highest root to shoot ratio. Stem caliper, leaf SPAD-502 value, root and stem dry weights increased with increasing N concentration up to 16 mM. The K-deficient plants exhibited marginal necrosis in old leaves, reduced growth, and had the highest root to shoot ratio. K deficiency or low K (2 mM) treatments increased time for the third leaf pair to expand. Stem caliper, leaf area, leaf SPAD-502 value, and plant dry weight increased with increasing K up to 6 mM. Dry weight of plug seedlings increased quadratically with increasing tissue N and K concentrations, respectively.