Calli were induced from internode segments of the methionine resistant plantlets of astragalus melilotoides . the highest yield of protoplasts ( 2 . 1 x 106 / g f . wt . ) was obtained from 8 - day - old friable calli after subcultured on fresh medium 用草木樨状黄芪甲硫氨酸抗性变异系植株茎切段诱导的松软愈伤组织为材料，通过酶法分离出大量有活力的原生质体。
