The separation between monocots and dicots was complete some 200 million years ago, and for some reason gene transfer is more difficult to achieve in monocots.
2 億年前，單、雙子葉在演化上就已經分了家，不知何故，單子葉植物在基因轉殖時困難度較高，余淑美猜測，或許與代謝物不同有關。