megagametophyte

例句：

1. 1. The giant kelp forests are a vital part of the marine ecosystem.
   巨大的海带森林是海洋生态系统的重要组成部分。
2. 2.The researchers found that the megagametophyte plays a crucial role in nutrient cycling.
   研究人员发现，巨型藻类植物在营养物质循环中起着至关重要的作用。
3. 3.The meadows were once dominated by giant gametophytes, but now they are mostly replaced by grasses.
   曾经，这些草地主要由巨型藻类植物占据，但现在它们大多被草取代了。