鎂含量為‘台中二號’梨果實冷藏後褐變之評估指標

Magnesium is the Major Index to Internal Browning Disorder after Cold Storage in 'Tai-Chung No. 2' Pears (Pyrus pyrifolia (Burm.) Nak.)

果肉褐變為‘臺中二號’梨（Pyrus pyrifolia）採後生理障礙，冷藏後果肉呈水浸狀及褐化病症，導致果實品質下降。本試驗在瞭解不同枝條類型上之葉片養分、土壤肥份與梨果實發生生理障礙癥狀嚴重程度之關連。試驗於2011年六月從10個‘臺中二號’梨果園中採取結果短果枝、無結果短果枝、徒長枝及橫向枝之葉片，分析葉片鉀、鈣、鎂、磷、氮含量，以及分析果園表土（土面下0-15cm）和底土（土面下16-30 cm）中氧化鉀、氧化鈣、氧化鎂、磷酐含量。果肉褐變程度以果實於2℃冷藏6週後果實內褐化情形作為代表。結果顯示果肉褐變程度與短果枝葉片中鉀含量（r = 0.65）呈正相關，但與鎂含量（r = -0.65）呈負相關；此外，短果枝葉片中鉀含量對鎂含量之比值與果肉褐變程度具正向線性迴歸關係。其他各部位葉片內營養元素則與果肉褐變程度無相關性。結果短果枝葉片內鎂含量是唯一與表、底土中氧化鎂含量皆有關之元素，而結果短果枝葉片內鉀含量僅與表土中氧化鉀含量有關。因此，結果短果枝葉片和土壤中鎂缺乏是影響‘臺中二號’梨果肉褐變最有關之因子。 Internal browning disorder is a postharvest disorder in 'Tai-Chung No. 2' pear (Pyrus pyrifolia). The flesh of fruit becomes water-soak and browning after cold storage, and the incidence declines the quality of fruits. The objective of this study was to clarify the relationships between the nutrition of leaves on different branches and the soil nutrition condition with the incidences of fruit browning disorder. The leaves from 4 kinds of shoots were collected, including spurs with bearing fruits (fruiting spurs), spurs without bearing fruits (non-fruiting spurs), lateral shoots, and water sprouts, from 10 'Tai-Chung No.2' pear orchards in June 2011. Potassium (K), Calcium (Ca), magnesium (Mg), phosphorus (P), and nitrogen (N) contents of leaves were investigated. The contents of potassium oxide (K_2O), calcium oxide (CaO), magnesium oxide (MgO), and phosphorus pentoxide (P_2O_5) of top (0-15cm) and subsurface (16-30 cm) soil in all orchards were also analyzed. The levels of internal browning disorder of fruits from all orchards were investigated after 6 weeks cold storage at 2°C. The results showed that the browning severity level was positively correlated with K content (r =0.65), and negatively correlated with Mg content (r=-0.65) in fruiting spur leaves. In addition, a positive liner regression between K/Mg ratio in fruiting spur leaves and the browning severity level of fruit was found. There were no correlation showed among browning severity level and other nutrients in all kinds of shoots' leaves. Moreover, Mg is the only nutrient of fruiting spur leaves that correlated with the related nutrient in both top and subsurface soil. Relatively, K in fruiting spur leaves only correlated with K_2O in subsurface soil. Consequently, Mg deficiency in fruiting spur leaves and soil was most important nutrition factor that related to internal browning disorder level after cold storage in Asian pears.