Question

As the plant matures , the outer layer epidermis is replaced by bark tissues. why is it so?

Answer 1

As the plant grows and matures, its need for food and water increases and to supplement it, the plant grows in girth or thickness giving rise to more phloem and xylem (vascular tissues) from already existing phloem and xylem elements and further as the girth increases, the outermost layer also gets pushed away and matured giving rise to bark.