Why do you think some plants have woody stems and some have soft stems?​

Dear student, 

Plants with large, woody and hard stem are called shrubs and trees. While, plants with with soft and green stems are called as herb. When the stem is young, the epidermal cells remain fresh, alive and green. As the cells turn towards maturation they become brownish due to the cellulose deposition and hardening. When matured, the cells become dead and appeared woody.

Regards