 In Japanese persimmon ("Diospyros kaki") fruits, tannin is accumulated in the vacuole of tannin cells, which are idioblasts of parenchyma cells in the flesh.The convergent evolution of tannin-rich plant communities has occurred on nutrient-poor acidic soils throughout the world.Tannins were once believed to function as anti-herbivore defenses, but more and more ecologists now recognize them as important controllers of decomposition and nitrogen cycling processes.