Fig. 4

The orthogonal partial least squares discriminant analysis (OPLS–DA) of physiological indices. (A) Blue and red lines indicate the distribution of the physiological data in HX and SH, respectively; (B and C) Black dashed lines represent the key nodes of VIP = 1. The numbers 1–3, 4–6, 7–9, 10–12, 13–15 and 16–18 represent three replicates after cold treatment 0, 1, 2, 4, 8 and 16 d, respectively