Since growth is affected by so many factors, it'd be a difficult task to take an average conversion factor from shoot to root dry weight. The following links may provide clue to specific and useful literatures:

http://scienceflora.org/journals/index.php/cb/article/viewFile/1434/1420

http://www.agronomysociety.org.nz/uploads/94803/files/1990_13._Lentil_root-shoot_growth_relationships.pdf

http://www.arccjournals.com/uploads/articles/ijar2431001.pdf

http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3783788/

http://www.nrcresearchpress.com/doi/pdfplus/10.4141/CJPS08154

http://www.scielo.cl/pdf/chiljar/v74n3/at01.pdf

http://www.scitechnol.com/seasonal-dry-matter-accumulation-and-its-partitioning-trend-in-sweet-sorghum-genotypes-LfM8.pdf

https://www.jstor.org/stable/42881639

http://www.arb.ca.gov/fuels/lcfs/regamend14/stewart_rootshoot_10142014.pdf

http://publications.tamu.edu/CORN_SORGHUM/PUB_Sorghum%20Growth%20and%20Development.pdf

Hello,

The datawe are using in my institute for sunflower crop in French context are :

underground biomass represents 11% of the above-ground crop residues (above ground biomass, which does not include the harvested seeds).

The 'harvest index' - that is the share of harvested seeds in the total amount of above-ground biomass produced- is considered to be 33% for sunflower.

Hope this can help

Dear Madam,

Thank you so much.

Standard reference for your data will be useful for me.

The root/shoot ratio undergoes constant changes. At seedling stages the root is more favored while the shoot is more favored at grain filling. The root shoot ratio can reach a maximum at flowering or post flowering stages.(about 30%). But at maturity recoverable roots can come below 10% as the root death starts much before physiological maturity. Therefore the total root biomass incorporated in soil can exceed 25% not to mention the early root turnover and root exudates.

I attach the scan of article (Levin, 1977) with the table, which provides nice regresion equations for the steple crops, determined in European part of USSR. There is sunflower among these crops. I think the article will be usefull for those who can read in Russian.

https://www.researchgate.net/post/irrigation_deficit_and_pruning_missing_casued_extension_roots ?