Meristems are located wherever the plant grows from. You can use root tips, leaf tips, eyes, nodes etc. However, the quality of the meristem depends on where you take it. Root meristems are not as good as leaf meristems, you are likely to get much higher mutation rates. The more stable the tissue, such as node or leaf tip, the lower your mutation rates.Originally Posted by jono
It may also interest you to know that what people call meristems etc, are not meristems whatsoever. They are only using meristematic cells for propagation. The meristem is much much smaller than the piece of tissue that is cultured.