Eva Crossan, of Stirling, asks :-

What is inside a seed and how can something so hard and small grow?

David Burritt, a botanist at Otago University, responded.

The reason that even tiny seeds can grow into large plants is that each seed contains an embryo. Embryos are just tiny plants that just have to wait for the right conditions to germinate, or in other words begin to grow bigger. For the embryos of most crop plants, like the dry vegetable seeds that you can buy from a garden centre, the only thing that stops the embryos from germinating is a lack of water. This is why dry seeds only start to grow when they are planted in the soil and given plenty of water.

Seeds not only contain an embryo but also nutrients (food) that help the embryo begin to grow. Some plants such as coconut palms produce only a few very large seeds, each containing lots of food to help the embryo grow. Other plants such as orchids produce thousands of tiny seeds, less than 0.1 mm in diameter, which contain almost no food. In fact, the embryos of orchid seeds can only grow because they get help from a special fungus that provides them with some of the food they need to grow.

Because seeds contain food, plants that produce seeds are very important for many people all around the world who eat seeds or foods made from seeds almost every day. So the food contained with a seed can not only help a tiny embryo grow into huge a plant such as tree, but it can help people grow up to be strong and healthy.