Question

do sieve cells arrise from pre-existing cells​

Answer 1

Answer:

All cells arise from pre- existing cells if we consider RBC and Sieve tubes.

Answer 2

Answer:

Theodor Schwann

By the late 1830s, botanist Matthias Schleiden and zoologist Theodor Schwann were studying tissues and proposed the unified cell theory. The unified cell theory states that: all living things are composed of one or more cells; the cell is the basic unit of life; and new cells arise from existing cells.