Fig. 1. Morphological and developmental responses of 10 Indonesian rice varieties to chromium (Cr) stress and gibberellic acid (GA3) treatment under in vivo and in vitro conditions. A, Seedling elongation observed 7 d after germination under in vivo conditions. Scale bars, 1 mm. B, Callus induction from rice explants cultured under controlled in vitro conditions. Scale bars, 1 mm. C, Callus regeneration under Cr treatment. Scale bars, 1 mm. D, Cytochemical staining indicating callus viability and cellular activity. Acetocarmine stained nuclei and chromosomes red, indicating cells with active nuclear activity and division, whereas Evans blue penetrates only cells with damaged plasma membranes, staining non-viable cells blue. Scale bars, 1 mm. E, Plantlet formation from regenerated calli. Scale bars, 1 mm. The 10 Indonesian rice varieties were Batang Ombilin, Bayar Putih, Bengawan, Getik, Grogol, Leukat Medan, Pandan Wangi, Sampit, Sirendah, and Sukamandi.

Fig. 2. Relative expression profiles of gibberellin-related genes under chromium stress in 10 Indonesian rice varieties. Genes including OsAmy1A, OsAmy1C, OsAmy3C, OsCPS1, OsKS1, OsKAO, OsGA2ox1, OsGA2ox3, and OsGA2ox9 were analyzed using callus tissue with OsActin as the internal control. Data are mean ± SD (n = 3). Different lowercase letters indicate significant differences among varieties within each gene (P ≤ 0.05) as determined by Duncan’s multiple range test.