Coefficients of the logistic regression for dry matter translocation to tubers (HI, X0 and R2) and maximum tuber growth or bulking rate (TGmax).

Where: HI is the maximum value that α reaches, X0 is the point in thermal time (°Cd), where the maximum speed of translocation of assimilates is given, TGmax is the Maximum tuber growth or bulking rate (g m−2 °Cd−1). SE is the Standard error; R2 is the determination coefficient at P<0.01 (**).