Dear Ranatunga,

I can add: speed root growth, water content, turgor.

I would say the number of secondary roots and the overall volume of the roots

CALLUS SIZE, % OF CALLUSING CUTTINGS, % OF ROOTED CUTTINGS, NUMBER OF ROOTS PER OOTED CUTTINGS, SIZE OF ROOTS, % OF SURVIVAL CUTTINGS

If the method of propagation is by cuttings, I would add to your list the percentage of rooted cuttings and the speed of root formation. It can also depends on the species of plant. For some species cuttings can have a strong dominant root like Eucaliptus and the root lenght will represent better than number of secondary roots the success of this technique. 

i would also use root length distribution which depicts the frequency of root length classes. 

It depends on the relationship between regenerated plants and the desirable traits for the plants once grown a while in the field. For example, if you want a mature plant in the field with a larger taproot, your propagules should have the potential of growing these large taproots. What do you know concerning for example the quality of your tea leaf yield or the mechanical resistance to hurricanes in relationship with the mature root structure and the callus root structure.

More generally, a root system is not only a bulk of biomass, root length, root diameter distribution. It is highly organised, with structure. And with properties : for example Pinus pinaster, a pine tree, do not regenerate new roots on the old framework of roots and do not fork. Thus, the root system of an adult tree is largely dependant upon the root system of the seedling.

Jonathan P. Lynch worked a lot on relationships between root architecture and nutrient uptake, e. g. Amelia Henry a , Nestor F. Chaves b , Peter J.A. Kleinman c , Jonathan P. Lynch Field Crops Research 115 (2010) 67–78

Root architecture is very important for mechanical stability of the plant.

More about vegetative propagation vs. seeding :

Valdés-Rodríguez, O. A.; Sánchez-Sánchez, O.; Pérez-Vázquez, A.; Caplan, J. S. & Danjon, F. 2013 Jatropha curcas L. Root Structure and Growth in Diverse Soils. The Scientific World Journal Volume 2013, Article ID 827295 http://dx.doi.org/10.1155/2013/827295

Khuder H., Stokes A., Danjon F., Gouskou K., Lagane F. 2007. Is it possible to manipulate root anchorage in young trees? Plant & Soil 294:87-102 + erratum Plant Soil (2007) 295:293-295

Danjon, F., Stokes, A., Bakker, M. R. 2013 Root Systems of Woody Plants. In: Eshel, A., Beeckman, T., eds. Plant Roots: The Hidden Half, Fourth Edition. Boca Raton, Florida: CRC press, 29.1-29.21.

More about root architecture of trees in :

Danjon F, Khuder H, Stokes 2013 Deep phenotyping of coarse root architecture in R. pseudoacacia reveals that tree root system plasticity is confined within its architectural model. Plos One 8:e83548 DOI 10.1371/journal.pone.0083548

Danjon F, Reubens B 2008 Assessing and analyzing 3D architecture of woody root systems, a review of methods and applications in tree and soil stability, resource acquisition and allocation. Plant and Soil 303:1-34. DOI: 10.1007/s11104-007-9470-7

sincerely

frederic danjon

[email protected]

Dear All,

Thank you very much for your informative responses. They are really useful for my work.

Mahasen

Number of roots and total volumn of roots per plant