|MadSci Network: Botany|
Yes, this can be true, although in real research we usually do not use a whole leaf. Plants have some fascinating characterestics that different from animal cells, one of them is that plants have stronger regenerative capabilities than most of higher animals. A whole plant can grow from a single cell, a little piece of leaf ( leaf disk ), or even a pollen cell. Ususally plant cells are at first phisically wounded, a patch of soft cell called a callus will grow from the cell. These callus are moved to culture with nutrition and hormone, then will grow into kind of suspension tissues. After plated out, new callus will form and followed by regenerating into new plant. The whole process should be sterile. Some parts of plant body is easier than others to regenerate. This technique has been used for about 100 years and has been very helpful for plant biologist. From above you can see, cloning of plant is much earlier than cloning of Doly, right?
Try the links in the MadSci Library for more information on Botany.