Variegation occurs when some part of
the leaf loses the ability to produce enough chlorophyll to maintain
the solid green color. When this happens, either a yellowish or
whitish color of the underlying cells shows through giving the leaf
the variegated appearance that is so distinctive on many cultivars.
In hostas, it has been determined that there
are three layers of cells in the leaf tissue which seem to control
the colors in the leaf. There are many other cell layers present but
these three seem to be unique and the loss of chlorophyll may occur
in one, two or all three of these layers. Depending on which layer
is affected, the leaf will show one of the characteristic patterns
we associate with variegation in hostas.
Layer 1 (L1) - one cell thick at the
epidermis of the plant and is especially important in the formation
of color pigment at the leaf margins i.e. at the edges.
Layer 2 (L2) - located beneath L1 but
does not extend all the way out to the edge of the leaf. This layer
has more to do with the color in the center of the leaf.
Layer 3 (L3) - beneath L2 in the leaf
and also the only layer that extends down into the roots.