Fig. 4

a Changes in PPO and POD activity in explants cultured in different media. Each value represents the mean ± S.E. of three biological replicates. The asterisks indicate significant difference according to Student’s t-test: **, P < 0.01. b Browning assays of JrPPO in explants together with 5 natural substrates: Sub 1 = gallic acid, Sub 2 = dopamine, Sub 3 = L-tyrosine, Sub 4 = 4-hydroxybenzoic acid, Sub 5 = protocatechuic acid. Freshly isolated protein extracts from 2 g of tissues under different treatments were incubated in the presence of substrates for the indicated time periods. The control-1 lane contains no enzyme, and the control-2 lane contains no substrates. The images were taken after 5 min, 2 h, 4 h. V72: samples from explants cultured in V for 72 h, V144: samples from explants cultured in V for 144 h, A72: samples from explants cultured in A for 72 h, A144: samples from explants cultured in A for 144 h