Environmental effects on dry matter partitioning between shoot and root ofcrop plants: relations with growth and shoot protein concentration

The literature on environmental effects on dry matter partitioning in highe r plants, in particular crop plants, is reviewed focussing on changes in sh oot to root dry weight ratio (S:R). Of particular consistency is the findin g that S:R increases with increased nitrogen (N) supply. Relations between nitrogen (N) supply, growth, S:R and tissue N and protein concentration are examined. In some cases, the increase in S:R with increased N supply is li kely to have been at leaf in part an effect on growth and development, but there is unequivocal evidence that N affects S:R independently of growth an d development. A positive correlation between S:R and leaf protein concentr ation is highlighted. It is argued that the N effect on S:R outside the eff ect on growth and development is related to increased shoot protein concent ration. Specifically, shoot and root growth are colimited by local carbon ( C) and N (primarily protein) substrate concentrations and shoot growth will increase relative to root growth with increased N substrate availability d ue to the proximity of the shoot to the C source. It is further argued that results in the literature are consistent with the proposal that macronutri ent, water, irradiance, CO2 and temperature effects on S:R are often primar ily mediated through their effects on growth and development, and shoot pro tein concentration and hence shoot growth.