Mericlinal chimeras are similar to the Sectorial subset with a few distinct differences. Within Mericlinal chimeras, normal or mutated cells do not extend through all layers within the bud or meristem. Usually one genotype (whether green or white) occupies a small portion of the meristem’s outer layers, see diagram. The ratio of one genotype tending to be much larger than the other is characteristic of Mericlinal chimeras. Unfortunately, this causes them to be inherently unstable & short lived. In the wild it’s not unheard of to have a Mericlinal chimera appear in one year & than completely disappear in the next. On some occasions Mericlinal chimeras have been known to successively disappear & reappear again. This is caused by normal or mutated cells growing within the meristem to surface from time to time.
What’s also interesting about Mericlinal chimeras is they come in two opposite color arrangements: green over white & white over green.
White cells from the inner mutated layer have erupted to the surface on this right lateral bud.
In this green over white Mericlinal chimera, notice how short lived the white mutation is. After only a few cm of growth the mutation has completely disappeared.
Here we have white over green Mericlinal chimera exhibiting the same characteristics. Only this time the green genotype loses out.
This is a rare picture of two needles that are Mericlinal. The needle in the upper portion of the photo barely exhibits the white mutation.
Diagram of a Mericlinal chimera: