With the change of the components of MS which can be achieved by doubling the content of FeS04 or exorcize the miroelement, the degree of explant browning became more obvious and explant excreted lots of brown substances in medium.

• 无激素培养基使外植体黄化。 MS培养基中铁盐加倍和微量元素缺乏造成外植体严重褐变，培养基积累很多褐色物质；