长时间跑步后，他的脚底磨出了硬茧。

After running long distances, he developed a tough ___callus on the bottom of his foot.

植物切口处形成了一个硬化的愈伤组织。

A ___callus developed at the cut site of the plant.

弹吉他久了，手指会起茧子。

Playing guitar frequently will ___callous your fingertips.