Effects of Exogenous Amylases and Metal Ions on the Amylase Specific Activities and Starch Degradation of the Upper Leaves of ‘KRK_(26)' during Flue-curing

外源淀粉酶和金属离子对烘烤中烤烟‘KRK_(26)’上部叶淀粉酶比活力和淀粉降解的效应

Objective] The aim of this study was to investigate the effects of exoge-nous amylases and Ca2＋, Mn2＋ and K＋ on the amylase specific activities and starch degradation of the upper leaves of ＇KRK26＇ planted in Yunnan Province during flue-curing. [Method] The amylase specific activities and starch degradation of the leaves were determined by using spectrophotometry. [Result] The 8 U/g exogenous α-amy-lase could improve the specific activity of the leaf α-amylase at yel owing and color-fixing stages, but could not at stem-drying stage, and similarly, the 80 U/g exoge-nous β-amylase could improved the specific activity of the leaf β-amylase at the yel owing stage and the early period of color-fixing stage. The leaf starch could be enhanced to degrade by the exogenous α- or β-amylases and the enhancing effect of the former was stronger than that of the later. 1.50 mg/ml Ca2＋ improved the specific activity of the leaf （α＋β）-amylase mainly due to its enhancing effect on the leaf α-amylase, and increased the starch degradation. 4 mmol/L Mn2＋ inhibited the leaf α-amylase from yel owing to the early period of color-fixing and the β- and （α＋β）-amylases from the yel owing to the later period of color-fixing, but enhanced the leafα-amylase from the later period of color-fixing to the later period of stem-drying and the β- and （α＋β）-amylases at the later period of stem-drying. Meanwhile, Mn2＋ ham-pered the starch degradation during yel owing, but promoted it from the early period of color-fixing to stem-drying. 1 mg/ml K＋ enhanced the leaf α-, β- and （α＋β）-amy-lases during the yel owing stage, but lowered them from the early period of color-fix-ing to the later period of stem-drying, and always inhibited the leaf starch degrada-tion. [Conclusion] The exogenous α-, β- amylases and Ca2＋ of suitable concentra-tions could be used to treat the tobacco leaves before flue-curing to improve the leaf starch degradation during the curing.

[目的]探究外源淀粉酶和Ca2+、Mn2+、K+对烘烤中烤烟‘KRK26’上部叶淀粉酶比活力和淀粉降解的效应。[方法]用分光光度法检测烟叶的淀粉酶比活力和淀粉含量。[结果]8 U/g用量的外源α-淀粉酶能在变黄和定色阶段提高烟叶α-淀粉酶的比活力,但在干筋阶段不能,80 U/g用量的外源β-淀粉酶类似地能在变黄阶段和定色早期提高烟叶β-淀粉酶的比活力;烟叶淀粉的降解被外源α-或β-淀粉酶强化,前者的效果优于后者的。1.50 mg/ml Ca2+主要因其对烟叶α-淀粉酶的强化效应而强化烟叶总淀粉酶的比活力,并促进的淀粉降解。4 mmol/L Mn2+在变黄至定色早期抑制烟叶α-淀粉酶、在变黄至定色晚期抑制烟叶β-和总淀粉酶,但在定色晚期至干筋早期促进烟叶α-淀粉酶、在干筋晚期促进烟叶β-和总淀粉酶。同时,Mn2+在变黄阶段妨碍淀粉降解,但在定色早期至干筋期促进。1mg/ml K+在变黄阶段提很高烟叶α-、β-和总淀粉酶比活力、但在定色早期至干筋晚期降低,并总是抑制淀粉降解。[结论]适当浓度的外源淀粉酶和Ca2+能用于在烘烤前处理烤烟叶片以促进叶片淀粉在烘烤中的降解。