Fig. 1: S is involved in nodule senescence.

a Mineral concentration in nodule symbiosomes. Nodules were treated with low nitrogen (CK) or high nitrogen (H-N) for 3 d. b Mineral alteration in symbiosomes by H-N supply. Percentage difference (100× (element content in H-N - element content in CK)/element content in CK) of minerals is shown. c Response of S concentration in symbiosomes to H-N. Soybean nodules at 25 dpi were transplanted to H-N (10 mM NH₄NO₃) for 0, 1, 2 or 3 d, and harvested for symbiosome isolation and mineral determination by ICP-AES. d LA-ICP-TOF-MS analysis of S in nodules. Upper panels show bright field, lower panels show S intensity and distribution. Soybean nodules at 25 dpi were transplanted to H-N for 0, 1, 2 or 3 d, and then sectioned for LA-ICP-TOF-MS observation. A representative result of 3 repeated tests is shown. Effects of S on nodule SNF and senescence under H-N conditions. e Ureide export rate of nodules. f nodule color after transfer to low S. Soybean nodules at 25 dpi, which experienced low S (2.5 μM sulfate) for 0, 3, 6, 9, 12 or 15 d, were treated with H-N for 3 d, and then used for ureide extraction and nodule color observation. Data are means + SD in (a, c). The boxes in (e) indicate the first and third quartiles, and the whiskers indicate the minimum and maximum values. The lines within the boxes indicate the median values. n = 3 (a–c), 6 (e, f) biologically independent replicates. The P values in (a, e) were calculated using two-sided t-test. Source data are provided as a Source Data file.