The Biology of Plants by Missouri Botanical Gardens
A wealth of age appropriate information about plants.
If plants, their parts and their lifecycle is your science topic then all the information you need is here.
Germination, pollination, seed dispersal and the way different plants have adapted to suit their environment is all covered.
This is good old fashioned textual information interspersed with appropriate diagrams, images, animations and video clips – ideal for a research project in upper Key Stage 2 (9-11 years)
There is also a section detailing the importance to life on Earth.