|關鍵字： 百香果；果實品質；巨量營養元素；微量營養元素；passion fruit；fruit quality；macronutrients concentration；micronutrients concentration
|摘要： 本研究目的探討鉀對‘台農1號’（Passiflora edulis x P. edulis f. flavicarpa）百香果生長之影響，並藉由調查台灣百香果主要產區：南投縣埔里鎮大坪頂地區之10果園，了解在台灣慣行栽培模式下百香果葉片礦物元素與果實品質之週年變化。由於埔里地區的土壤多為紅土，性質偏酸，同時許多前人研究指出，百香果在酸性的土壤環境中生長較佳，且營養吸收與土壤酸鹼值高度相關，因此利用水耕栽培系統控制酸鹼值，探討酸鹼值對百香果生長之影響。結果顯示以pH 5.5在葉片數、株高、側芽數、莖鮮重、葉鮮重、根乾重、莖乾種、葉乾重顯著高於pH 7.0。 進一步探討鉀濃度對百香果生長之影響，以水耕栽培系統調整鉀濃度為6（對照）、4.5（花後增加為9 mM）、3.0、1.5、0.75與0 mM的水耕液栽培百香果，比較不同濃度鉀溶液對百香果生長量及果實品質之影響。結果顯示，以0 mM處理後3週在老葉出現缺鉀徵狀，莖長、葉片數及側芽數隨鉀濃度降低，顯著低於對照組。葉綠素a、b、總葉綠素及類胡蘿蔔素含量隨鉀濃度降低而降低，且葉片過氧化物酶活性下降，植株根、莖及葉片之乾鮮重，隨鉀濃度降低而降低。9 mM之葉片可溶性糖、澱粉濃度顯著高於其他處理。上、中、下位葉之葉片鉀濃度與水耕液之鉀濃度皆呈正相關，缺鉀處理葉片鉀、鐵含量顯著低於對照組。缺鉀處理之平均果實鮮重、大小、總可溶性固形物含量、果實乾重、果皮相對含水量皆顯著低於對照組。第二年度試驗以缺鉀配方為基礎添加氯化鉀配置之鉀濃度為12、6（對照）與0 mM的水耕液栽培百香果。結果顯示，0 mM處理表現與第一年度試驗結果相符，在植株生長量、開花、果實品質等各方面生長表現皆顯著低於其他處理。而整體生長上以12 mM的鉀含量處理在各方面生長表現較佳，其果實品質如果實重、總可溶性固形物、可滴定酸含量、果皮鮮重、果皮含水率皆顯著高於缺鉀（0 mM）處理。在相同濃度下以硫酸鉀搭配磷酸二氫鉀作為鉀源之處理，在莖鮮重、莖乾重、葉乾種及果皮全可溶性糖含量上顯著高於以氯化鉀作為鉀源之處理，而在果汁總可溶性固形物、可滴定酸含量上顯著低於氯化鉀處理。本研究結果顯示缺鉀對百香果營養生長及果實品質均有負面影響，且植株缺鉀易誘導新葉黃白化缺鐵症，進而影響葉綠素含量。 基於在鉀濃度試驗中觀察到鉀缺乏誘導鐵缺乏之表現，因此進一步探討鐵缺乏對百香果生長之影響。結果顯示缺鐵直接抑制百香果生長，0.04 mM（每週添加3次EDTA-Fe）處理在株高、側芽數、莖乾重、葉片鐵、錳含量上顯著高於缺鐵（0 mM）處理。同時0 mM處理之果汁總可溶性固形物含量顯著低於其他處理。本研究結果顯示鉀肥對百香果營養生長及果實品質影響皆巨，須審慎使用。為提高‘台農1號’百香果生長並生產高品質果實，應控制土壤酸鹼值於4.5至5.5間，並自營養生長期即施用鉀，同時注意鐵的補充。The purpose of this study was to investigate the impact of potassium on the growth of ‘Tainung No.1’ passion fruit (Passiflora edulis x P. edulis f. flavicarpa). For understanding the annual changes in leaf mineral elements and fruit quality during passion fruit growth and development, 10 orchards in the main producing area of Taiwan located in Dapingding area, Puli Township, Nantou County were selected. In the second part of this research, the effect of pH value on passion fruit growth was investigated. The soil in Puli area is mostly red soil and slightly acidic. Many previous studies have pointed out that passion fruit grows better in an acid soil environment, and nutrient absorption is highly related to soil pH. Our results showed that in pH 5.5, the number of leaves, plant height, number of lateral buds, stem fresh weight, leaf fresh weight, root dry weight, stem species, leaf dry weight were significantly higher than those in pH 7.0. To further explore the effect of potassium concentration on the growth potential and quality of ‘Tainung No.1’ passion fruit, the hydroponic cultivation system was used to adjust the potassium concentration to 6 (control), 4.5 (increased to 9 mM after flowering), 3.0, 1.5, 0.75 and 0 mM. Results from this study showed that potassium deficiency symptoms appeared in the old leaves three weeks after treatment, the stem length, total number of leaves and number of lateral buds decreased as potassium concentration decreased, with a level significantly lower than that of the control group. The contents of chlorophyll a and b, total chlorophyll, carotenoids, the activity of leaf peroxidase (POD) and root, stem and leaf fresh/dry weight decreased as potassium concentration decreased. Leaf sugar and starch contents were significantly higher in 9 mM K treatment compared to other treatment. The potassium concentration in the upper, middle and lower leaves was positively correlated with the potassium concentration in the hydroponic solution. The potassium and iron content in the leaves treated with 0 mM was significantly lower than the control group. The average fruit fresh weight, size, total soluble solid content, dry weight of fruit and relative water content of the fruit shell in 0 mM K treatment were significantly lower than those of the control group. To understand the effect of higher potassium concentration on passion fruit, the Hoagland nutrient solution was adjusted by using a potassium concentration of 6 mM as the control in the 2nd year’s experiment. Potassium chloride was used to prepar the nutrient solution with various potassium concentrations including 12, 6 and 0 mM. Our results showed that the tested resulted in the 0 mM K treatment was consistent with those observed in the first year, with the growth performance, flowering, fruit quality and other aspects of plant growth significantly lower than other treatments. Overall growth performance was better, and the fruit quality such as solid weight, total soluble solids, titratable acid content, fresh peel weight, and peel moisture content was significantly higher in the 12 mM K treatment than those of 0 mM. Treatment by using potassium sulfate and potassium dihydrogen phosphate as the potassium source, the stem fresh and dry weight, leaf dry weight and total soluble sugar content in husk were significantly higher, but the soluble solids content and titratable acid were significantly lower than those treated with same concentration of potassium chloride as the potassium source. Results from this study showed that potassium deficiency has a negative effect on the vegetative growth and fruit quality of passion fruit, and that potassium deficiency in plants can easily induce iron deficiency, revealed by the yellowing of new leaves which in turn affects chlorophyll content. Based on the observation that potassium deficiency may induce iron deficiency in the potassium concentration test, we next discuss the effect of iron deficiency on passion fruit growth. Our results confirmed that iron deficiency directly inhibited the growth of passion fruit. The plant height, number of lateral buds, stem weight, leaf iron and manganese contents were significantly higher in the treatment with 0.04 mM (EDTA-Fe, added 3 times a week) than those in the treatment with 0 mM. Meanwhile, the soluble solid content in the 0 mM treatment was significantly lower than those in the control group (0.02 mM) and 0.04 mM treatment. Results from this study showed that potassium fertilizer has a huge impact on the vegetative growth and fruit quality of passion fruit and must be used with caution. In order to improve the growth of ‘Tainung No.1’passion fruit and produce high-quality fruits, the soil pH should be controlled between 4.5 and 5.5, and potassium should be applied during the vegetative growth phase by paying attention to iron supplementation.