Natheniel Mollett, of Ngahere School, asks :-

How do trees grow from their seed?

David Burfitt, a botanist at Otago University, responded.

There are two things that have to happen to make a seed develop into a tree. First, the seed has to begin to grow or "germinate", and then the newly formed "seedling" has to break through the surface of the soil and start to make its own food. The seed takes care of the first part all by itself. It contains an "embryo", which is just a miniature tree, with a stem, roots and the first leaves. The seed also contains all the food the embryo needs to begin growing.

Often to make a seed germinate, it just takes soil, water, and warm temperatures, but the seeds of most trees require a period of inactivity or "dormancy" before they will germinate. If you were to take a fresh apple seed and give it the right conditions for germination, the seed would not germinate immediately. In the wild, apple seeds need to be exposed to the cold temperatures of winter before they can germinate. Often two or three winters are needed. A quick way to get fresh apple seeds to germinate is to put them in a refrigerator for 3 to 6 months, before planting them.

Following germination the seedling quickly exhausts the supply of food provided by the seed, and it must make its own by "photosynthesis". Photosynthesis is the process that plants use to make sugars out of carbon dioxide and water, using the energy contained in sunlight. Once the seedling can make its own food it just grows larger and larger, becoming a tree that can eventually produce its own seeds.