營養元素對洋桔梗生長與開花之影響

Abstract

洋桔梗原生於美國南部，主要分布在內布拉斯加州、科羅拉多州及德州之石灰岩草原地帶，屬龍膽科之宿根草本花卉，傳入日本經由民間及企業育種家將之發揚光大，栽培品種超過400個。由於花型、花色豐富及瓶插壽命長深受消費者喜愛，並名列世界十大切花之一。田間栽培洋桔梗常會發生下位葉出現黃斑症狀，本研究將由探討營養元素的缺乏、氮濃度和型態、氮鉀濃度及養分需求對洋桔梗生長及開花影響，以瞭解洋桔梗的營養管理。 分別調配缺乏氮、磷、鉀、鈣、鎂、硼、錳或鐵的養液，進行水耕栽培洋桔梗‘Umihonoka’56天後，缺氮處理者僅多形成1-2對葉，葉面積、葉綠素計讀值及淨光合作用速率(Pn)較低。缺磷處理者生長停滯、Pn較低，但地上部無明顯缺乏症狀。缺鉀處理對葉片數影響不顯著，但株高及Pn較低，下位葉出現黃褐色小斑點和/或葉尖壞疽。缺鈣處理造成植株停止生長，莖頂及根分生組織壞疽或死亡。缺鎂及缺硼處理皆未影響洋桔梗生長或光合作用，但缺鎂處理者偶爾可於下位葉觀察到脈間黃化，而缺硼處理者可觀察到根尖壞死及次生根增加。缺錳處理者地上部及地下部乾重減少，Pn及細胞間隙二氧化碳濃度下降，但地上部無明顯缺乏症狀。缺鐵處理者新葉脈間黃化，生長及Pn皆減少。 於夏季長日高溫期間，以含0-32 mM氮之養液，水耕栽培洋桔梗‘Umihonoka’，結果顯示氮濃度顯著影響生長和開花，養液氮濃度由4提高至8-16 mM，葉綠素計讀值增加，葉面積隨著氮濃度提高而減少，8 mM氮處理組的切花壽命和花朵直徑可達最大。>20 mM氮處理之植株出現下位葉出現黃斑及壞疽。根部生長隨養液氮濃度提高而出現抑制的趨勢，>24 mM氮處理者的根部於試驗結束前全數褐化。不同氮型態及比例處理的結果顯示，洋桔梗穴盤苗期及移植後以含17%-25%銨態氮養液處理者葉長、葉寬、葉片厚度及葉綠素計讀值較高，株高、節數、莖徑、地上部乾重、根乾重較大。以相同氮型態比例養液進行水耕栽培顯示，不論冬季或夏季，以17%-25%銨態氮處理者株高、葉片厚度、葉面積、乾重較大，全銨態氮處理者生長不良。Pn以全硝酸態處理者較高，全銨態氮處理者氣孔導度低、細胞間隙二氧化碳濃度高、光系統II最大潛能下降。 以含不同氮(8或16 mM)及鉀濃度(0、3、6或9 mM)比例之養液水耕栽培洋桔梗‘Umihonoka’，結果顯示以8 mM氮處理者雖葉片厚度及葉綠素計讀值較16 mM氮處理者低，但葉面積較大、根部生長較佳且較重，切花長度、鮮重及花苞數較多，其中以6 mM鉀處理者有較大葉面積、根重、切花鮮重、分枝數。另以含8 mM氮及不同鉀濃度(0、2、4、6或8 mM)之養液水耕栽培，除2 mM鉀處理者較矮，鉀濃度為4 mM時，生長較佳。 洋桔梗‘Engage White’在水耕133天的生長期中，依株高、節數、生物量和植體元素含量增加的速率可以分為四個階段，第一階段為3-4至4-6對葉(水耕後第21天)，此時為抽莖期；第二階段為4-6對葉至9對葉(水耕後第42天，此時進入花芽分化期)；第三階段為9對葉至出現可見花苞(水耕後第84天)，第四階段則為花苞發育到開花(水耕後第133天)。以所測得植體葉片營養元素濃度推估計算，於可見花苞出現時，每株植體的營養元素含量分別為，100 mg氮、9.2 mg磷、63.5 mg鉀、10.5 mg鈣、11.2 mg鎂，開花時對營養元素需求均大幅增加，於花開時分別為，638.9 mg氮、38.6 mg磷、303 mg鉀、104.5 mg鈣、76.7 mg鎂。 綜合以上試驗結果，建立洋桔梗缺乏特定營養元素之症狀資訊，農民可以依對照組養液成分調整為田間生產施肥濃度，以減少土壞連作障礙，並可於溫室內全年連續生產。洋桔梗在可見花苞出現後，對營養元素需求大增，其中對於氮和鉀的需求量大於其他營養元素；養液中氮型態比例以17%-25%銨態氮可以使洋桔梗生長和開花表現最佳；水耕栽培洋桔梗時，養液最適氮：鉀濃度比為2 (8 mM氮、4 mM鉀)。

Eustoma grandiflorum (Raf.) Shinn, a perennial plant of Gentianaceae, is native to semi-arid limestone prairie region of the southern part of the United States, mainly inhabits in Nebraska, Colorado, and Texas. There are more than 400 cultivars bred in Japan. Because of various flower types and colors and long vase life, Eustoma is one of the most popular cut flowers worldwide. In Taiwan, Eustoma plants are often see to exhibit yellow spots in lower leaves, suggesting nutritional problems. The purpose was to determine the nutrient management, included function of nutrient elements, the nitrogen forms and ratios, the concentration of nitrogen and potassium, and the requirement of nutrient elements. Effects of deficiencies in nitrogen (N), phosphorus (P), potassium (K), calcium (Ca), magnesium (Mg), boron (B), iron (Fe), or manganese (Mn) on growth and photosynthetic parameters were studied in Eustoma ‘Umihonoka’ grown hydroponically for 56 d. The N-deficient plants had increased one to two leaf-pairs only and had consistently lower leaf area, leaf SPAD-502 reading, and net photosynthetic rate (Pn) than those plants with complete nutrition. The P-deficient plants grew slowly with lower Pn, but no deficiency symptoms were visible on leaves. Potassium-deficient plants had similar node number with the control but reduced plant height and Pn, and many yellow specks developed on the lower leaves and/or tip necrosis. Calcium-deficiency resulted in stunt growth after treatment, and necrosis or death of both shoot and root meristem. Both Mg- and B-deficiency did not cause significant reduce in plant growth or photosynthesis, but occasional interveinal chlorosis was expressed on lower leaves in Mg-deficiency plants, whereas root tip necrosis and more lateral roots were seen in B-deficient plants. Manganese-deficient plants had lower shoot and root dry weights, Pn, and intercellular carbon dioxide concentration, but no visual symptoms on leaves. Interveinal chlorosis was expressed on young leaves in the Fe-deficient plants, and growth and Pn were significantly reduced. Plug seedlings of Lisianthus ‘Umihonoka’ were grown hydroponically under summer long day and high temperature conditions with solution containing 0-32 mM nitrogen (N) to evaluate the growth and flowering responses. Results showed the growth and flowering were affected significantly by N concentration. SPAD-502 reading increased, whereas leaf area decreased when solution N concentration increased from 4 to 8-16 mM. The 8 mM N treatment had the longest vase life and the biggest flower dimater. Plant supplied with high (>20 mM) N exhibited yellow spots and necrosis on lower leaves. The root growth was depressed with increased solution N concentration, and the roots were brown at 28 mM or higher N. Plug seedlings had higher leaf growth, and higher post-transplanting height, node number, stem diameter, and plant dry weights when supplied with 17%-25% ammonium-N, irrespective of winter or summer seasons. Plants with 100% ammonium-N grew poorly, with lower stomatal conductance and Fv/Fm value, and higher intercellular CO2 concentration. Lisianthus ‘Umihonoka’ plants with 3-4 leaf pairs were hydroponically grown with solution containing various N (8 or 16 mM) and K (0、3、6 or 9 mM) concentrations. Results showed that, higher leaf area, root growth, cut flower length, flower bud number, and lower leaf thickness and SPAD-502 reading were recorded in plants with 8 mM N than 16 mM N. Plants with 6 mM K had higher leaf area, root weight, cut flower fresh weight, and branches. Plants of Lisianthus ‘Umihonoka’ were also hydroponically grown with solution containing 8 mM N and various K (0, 2, 4, 6, or 8 mM) concentrations. Results showed that the best growth was recorded in plants with 8 mM N in combination with 4 mM K. Lisianthus ‘Engage White’ with 3-4 pairs of leaves was hydroponically cultured with 1/2 Johnsons’s solution in the greenhouse. During 133 d of the experiment, four growth stages could be divided according to the rates of increase in plant height, node number, and biomass. The first stage was from 3-4 to 4-6 leaf pairs (Day 21 after treatment), during which bolting occurred. The second stage was from 4-6 to 9 leaf pairs (Day 42, when flowers having initiated). The third stage was from 9 leaf-pairs to flower visibility (Day 84). The fourth stage was from flower visibility to anthesis (Day 133). Plants contained 100 mg N, 9.2 mg P, 63.5 mg K, 10.5 mg Ca, and 11.2 mg Mg at flower visibility and 638.9 mg N, 38.6mg P, 303.0 mg K, 104.5 mg Ca, and 76.7 mg Mg at anthesis by leaf analysis. In conclusion, a diagnostic key to N, P, K, Ca, Mg, B, Mn or Fe deficiency, which should be a valuable diagnostic tool to identify the nutritional deficiencies of Eustoma. Growers may adopt the complete hydroponic nutrient solution for an alternative production for Eustoma to avoid soil sickness, resulting from successive cropping in greenhouses all year round. The nutrient requirement significantly increased after flower buds visibility. Nitrogen and K were the two major nutrient elements, and with 8 mM N and 4 mM K as optimum for hydroponic culture. Eustoma with 17%-25% ammonium-N showed the best growth and flowering performances, as comparaed with other nitrogen form and ratio. The optimum nitrogen: potassium ratio was 2 (8 mM N and 4 mM K) for Eustoma grown in hydroponic culture.