- Details
- Written by: Tom Stapleton
Perhaps the most beautiful and fascinating of all redwood mutations is the Chimera Albino Redwood. What’s unique about chimeras is they consist of organized cells that have two visually distinguishable sets of DNA (genotypes) within the same plant. Genetically speaking, chimeras are essentially two trees in one. Caused by an extremely rare mutation within the meristematic cells of redwood buds, chimeras exhibit sectors of green & white foliage together in an array of very distinct patterns. Unlike their Nonchimeric Variegated Albino Redwood cousins, Chimeras display clear lines of delineation between the borders of each genotype. What’s interesting about chimeras that sets them apart from other mutations is they come in three different phenotypic subsets or color patterns know as: sectorial, mericlinal, & periclinal.
Not only noted for their beauty, Chimeras have been responsible for giving researchers the latest discoveries in redwood morphology. Because of the organized color differences between the cells of chimeric redwoods, scientists have been able to visually understand how redwood meristematic cell layers grow and interact with each other which previously hasn’t been understood within normal green redwoods. This research has allowed for a better interpretation of how redwoods develop and why we see such genetic variation within this species.
- Details
- Written by: Tom Stapleton
Albino redwood scientists consider the Periclinal Chimeric Albino Redwood one of the most intriguing of all redwood mutations. The reason for the attention is that this particular chimeric subset has yielded the most clues on understanding redwood morphology than any other redwood mutations known to date. It comes as no surprise that Periclinal Chimeras are currently at the heart of albino redwood research. What makes them unique is that they have two genetically distinct cell layers horizontally arced across the top of each redwood bud. This configuration otherwise known as a stratified meristem allows both normal green and mutated cells to divide and elongate at equal rates. In other words, as the apical meristem (tree leader) grows vertically, both layers of each genotype grow upward together at the same rate. This leads to a very stable, predictable, & long-lived chimera. As each genetic expression forms, scientists have been able to predict with relative accuracy which genotype is likely to occur next in the tree’s branching habit. The Periclinal color scheme has given scientists a virtual road map of how the inner & outer layers are expressed in Redwoods. Interestingly research has shown that all redwood have two genetically distinct layers which before now couldn’t be seen in genotypes with the same color scheme. Unlike Sectorial Chimeras that appear to be two trees sandwiched together, Periclinal Chimeras are literally one tree hidden inside another.
- Details
- Written by: Tom Stapleton
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.
- Details
- Written by: Tom Stapleton
The Sectorial Chimeric Redwood exhibits the showiest color pattern of the three chimeric subsets. Mutated cells extend vertically through all cell layers within the bud or meristem, see fig below. The border between each genotype is almost always parallel within the stem giving sectorial chimeras a candy cane-like appearance. Sometimes both genotypes (colors) are expressed together in individual needles giving them a beautiful split coloration pattern. Because sectorial buds have two different genotypes vertically aligned through the meristem, they tend to be unstable. In time one genotype will out-compete the other causing the tree to revert either completely green or white. This is why in nature; basal sectorial chimeras rarely exceed 15’ in height.
Here's a Sectorial Chimeric branch exhibiting heterophyllous needles. Notice how the white needles appear shorter than the green. On branches that are split between both phenotypes, you can see the normal green portion of the needle curving around the white causing the tips to look bent.