The effect of the heavy metal barium on the growth rate of your plants.
for the above title i have to complete my P-skill for the coursework but i was unsure of what type of scientific information i should include.
I would suggest that you need something on the environmental effects of heavy metals in general, and some specific information about barium specifically. I've had a quick look and it's not all that easy to find information about barium and plants. Barium is a toxin but is quite common in the environment, but at low levels. Problems may arise when it reaches higher levels. Some useful information can be found at http://www.lenntech.com/Periodic-chart-elements/Ba-en.htm but I think you'll need to look further. What I would not recommend is a whole load of information about plant growth in general - keep any discussion of growth in the context of the effects of heavy metals.