seed coat

例句：

1. 1. The seeds are encased ina protective layer of wax.
   种子被一层蜡质的保护层所包围。
2. 2. The plant's seed coat is designed to protectthe embryo during germination.
   植物的种子外层设计用来在发芽过程中保护胚芽。
3. 3. The researcher found that theseed coat plays a crucial role in determiningthe plant's ability to survive andreproduce.
   研究者发现，种子外层在决定植物能否生存和繁殖方面起着关键作用。