淀粉降解代谢与种子萌发、叶片光合作用、块茎和块根贮藏及肉质果实的发育密切相关。体外酶学实验普遍认为 ,β 淀粉酶是催化淀粉水解的重要酶之一 ,然而由于其在生活细胞中经常定位于叶绿体或质体之外 ,与淀粉基质在亚细胞水平上相互隔离 ,所以该酶在植物活体内的生理功能至今尚不清楚。我们最近首次发现 ,苹果果实生活细胞中的 β 淀粉酶主要定位于质体内 ,与其淀粉基质居于同一亚细胞区域 ,但尚不清楚这一现象是否具有普遍性。本研究利用胶体金免疫电镜定位技术证明 ,甘薯块根生活细胞中的 β 淀粉酶也是主要定位于质体内 ,围绕淀粉粒分布较多 ,其他亚细胞区域内 β 淀粉酶分布很少 ,说明该酶主要分布于其功能区域。质体内胶体金分布密度随着块根发育的推进显著增加 ,但 β 淀粉酶区隔于质体内的亚细胞分布特点在块根整个生长发育期没有变化。这些结果明确地展示出甘薯块根生活细胞中 β 淀粉酶与其淀粉基质居于同一亚细胞区域内 ,为 β 淀粉酶普遍参与植物生活细胞或贮藏器官生活细胞中的淀粉水解提供了证据。 Starch degradation and metabolism are closely related to seed germination, leaf photosynthesis, tuber and root tuber storage and fruit development. In vitro enzymatic experiments generally believe that β-amylase is one of the important enzymes that catalyze the hydrolysis of starch. However, β-amylase is often isolated from chloroplast or plastid in the living cells at the subcellular level because of its isolation from the starch matrix The physiological function of the enzyme in the plant body remains unclear. We recently found for the first time that β-amylase in apple fruit living cells is mainly located in the plastid and resides in the same subcellular area as its starch substrate, but it is not clear whether this phenomenon is universal. In this study, using colloidal gold immunoelectron microscopy localization technology, β-amylase in sweet potato root cells was mainly located in the plastid, with more starch granules distributed around other subcellular regions, indicating that the enzyme mainly Distributed in its functional area. The distribution density of colloidal gold in plastids increased significantly with the development of tuberous roots. However, the subcellular distribution of β-amylase in plastids did not change during the whole growth and development of tuberous roots. These results clearly demonstrate that β-amylase resides in the same subcellular area as its starch matrix in the root tuber of living sweet potato, providing evidence for the widespread involvement of β-amylase in starch hydrolysis in plant living cells or in living cells of storage organs.