八年级
What causes a seed to grow into a plant?
发布日期 : 2016-04-28浏览次数 : 来源 :
每到春天，种子都会发芽，可是你知道这是为什么吗？
A seed is already a tiny plant, and an embryo1 is ready to grow. It also has stored food to live on until it can put out green leaves and make its own food. And it usually has tough outer coat2 to protect it until it is time to grow.
How does a seed know when it is time to grow? First, something must happen inside to get the embryo ready. Most seeds need to wait until the next spring before they start to grow. Some just have to wait, some need to get cold, and some need to dry out before they are ready. After that, almost all seeds need the same things to start growing: water and warmth. So, that’s why you see little plants popping up3 from seeds on a warm spring day after the rain.
Notes: 1.胚胎；胚芽2.坚硬的外壳3.冒出
A seed is already a tiny plant, and an embryo1 is ready to grow. It also has stored food to live on until it can put out green leaves and make its own food. And it usually has tough outer coat2 to protect it until it is time to grow.
How does a seed know when it is time to grow? First, something must happen inside to get the embryo ready. Most seeds need to wait until the next spring before they start to grow. Some just have to wait, some need to get cold, and some need to dry out before they are ready. After that, almost all seeds need the same things to start growing: water and warmth. So, that’s why you see little plants popping up3 from seeds on a warm spring day after the rain.
Notes: 1.胚胎；胚芽2.坚硬的外壳3.冒出