Adjunction of roots to unitriangular groups over prime finite fields

In this paper we study embeddings of unitriangular groups UT$_n(\mathbb{F}_p)$ arising under adjunction of roots. We construct embeddings of UT$_n(\mathbb{F}_p)$ in UT$_m(\mathbb{F}_p)$, for $n \geq 2$, $m=(n-1)p^s + 1$, $s \in \mathbb{Z}^+$, such that any element of UT$_n(\mathbb{F}_p)$ has a $p^s$-th root in UT$_m(\mathbb{F}_p)$. Also we construct an embedding of the wreath product UT$_n(\mathbb{F}_p) \wr C_{p^s}$ in UT$_m(\mathbb{F}_p)$, where $C_{p^s}$ is the cyclic group of order $p^s$.