Figure 7.

ROS-mediated OsSGR expression and chlorophyll degradation. A, The effects of exogenous addition of H₂O₂ and ROS scavengers on OsSGR expression in mid-aged leaves. Rice seedlings were grown in +Mg or −Mg nutrient solution for 8 d and treated with H₂O₂, DMTU, DCMU, or mannitol for 12 h. B, Time-dependent expression of OsSGR in response to H₂O₂. C, The effects of H₂O₂ and DMTU on leaf chlorosis. Rice seedlings were grown in +Mg solution with or without H₂O₂, or −Mg solution with or without DMTU addition. D and E, H₂O₂ concentrations in different Mg-deficient times (D) and in different leaves (E). F to H, Effects of light intensity on OsSGR expression (F), H₂O₂ concentration (G), and SPAD values (H) in mid-aged leaves. Rice seedlings were exposed to light intensities of 1,000, 650, or 350 μmol m⁻² s⁻¹ with or without Mg supplied. Gene expression is shown relative to expression of CK (+Mg) in (A), 0 h in (B), and 1,000 PPFD (+Mg) in (F). H₂O₂ concentration was quantified by the FOX method. SPAD values were measured using a chlorophyll meter. Data are means ± sd (n = 3). The asterisk in (A), (C), (D), (E), and (H) shows a significant difference compared to CK (A), wild type (WT; C), (D), and (H), and +Mg (E; P < 0.05 by Tukey’s test). Means with different letters in (F) and (G) are significantly different (P < 0.05 by Tukey’s test). FW, fresh weight.