Figure 1 Germination and sowing of rice seeds, and the way of seedling culture (A) Germination of rice seeds; (B) Placement of germination seeds in 96-well plates without bottom; (C) Trefoil stage seedlings (Bar=2 cm)

Figure 2 The diagram of low temperature water bath treatment of rice seedlings (A) The temperature of water bath within 24 h; (B) Seedlings under chilling treatment in 4°C water bath; (C) Partially enlarged detail of the seedlings in the cold water bath tank; (D) A diagram of the fixation pattern of seedlings in cold water bath

Figure 3 Effect of submerged depth of cold water on low temperature tolerance of rice Red arrow indicated the site of shoot apical meristem under different water depth in chilling treatment I, II and III. Dotted lines represent the water surface. The survival rates were indicated on the top of the seedlings recoveried for 7 days. Treatment with 28oC water was used as control (left). Bars=6 cm

Figure 4 The evaluation of cold tolerance for different rice varieties at seedling stage (A) Phenotypic response to chilling in DJ, NIP and MH86, the survival rate was determined after cold-water treatment at 4°C for 96 h and subsequent recovery at 28°C for 7 days (means±SD, n≥30, three replicates); (B) The phenotype for seedlings of ZH10 and OX8 after the chilling treatment at 4°C for 120 h, subsequently at 28°C for 50 days. Bars=2 cm