Thorns, tendrils, underground stem and leaves are all modifications of the stem.
False
While in some plants the stem is modified into leafy structures, like tendrils which help in climbing and thorns which are axillary buds of stems that are modified into woody, straight and pointed elements. Thorns protect plants from browsing animals. However, the leaf is a not a modification of the stem. Leaves originate from shoot apical meristems and are present at nodes on the stem. They are the most important vegetative organs for photosynthesis.