The Rainforest Biome is a great resource to learn about tropical plants. Check it out to learn about plant adaptations, economic plants, and plants from many parts of the world. It's the Great Plant Escape, created by the University of Illinois. This site is an elementary program for 4th and 5th grade students. Each of the lessons in this program is interdisciplinary, designed to introduce students to plant science and increase their understanding of how foods grow.
Activities enhance student's math, science, language arts, social studies, music and art.
The first page gives general information, and you can click on to find more specific details about each type of plant. Use these sites with discretion.