Text this: Mean values (n = 4, +  SE, %) of carbon (C) contents per leaf and tuber dry mass (<i>C</i>_L, <i>C</i>_T, A and B) and nitrogen (N) contents per leaf and tuber dry mass (<i>N</i>_T, <i>N</i>_T, C and D) in purple sweet potato cultivar in N0, N50, N100 and N150 treatments in different planting dates.