Root size, form and architecture
For a discussion of the significance of and protocols to measure specific root length, fine root diameter, and root depth and distribution see: Cornelissen JHC, Lavorel S, et al. (2003) A handbook of protocols for standardised and easy measurement of plant functional traits worldwide. Australian Journal of Botany 51(4), 335-380. Click here for PDF.
Several excellent resources for root structure and architecture are available:
A more comprehensive summary on Root size, form and architecture is currently being prepared by Louise Comas.