For some JM, the variegation pattern won't appear until growth as slowed down, and the tree has some ramification. JM with finely cut leaves, will often have normal leaves until the branches are over 3 to 5 years old. Once the JM's growth rate slows down, the foliage will revert to the ''adult'' or mature foliage. The juvenile foliage of a Japanese maple looks pretty much like ''normal'' foliage of a ''normal'' Japanese maple. This is a process like Junipers having needle like foliage when juvenile, and scale like foliage when mature. Except - Japanese maples, when young, will often revert to juvenile foliage. Since the DAS is a far northern tree, mostly occurring north of the Canadian border, it is very likely that heat stress is contributing to the Maples (JM) - everything about witches brooms in conifers, ''mostly applies'' to Japanese maples. The Dwarf Alberta Spruce reverting to normal fairly regularly is likely a good indicator the original witches broom is from an epigenetic change, the underlying DNA of the Dwarf Alberta Spruce is still for the normal White spruce or normal Alberta spruce. So it is very seldom that it is really known which witches broom originated from which type of change. It is hard to tell epigenetic changes from genetic mutations, it takes time and lengthy testing to sort out which is which. This is not as common as the epigenetic change, but when it happens it will be stable for thousands of years, and it will be heritable through thousands of generations. This is where the DNA has changed, and it will never, or almost never change back. Some epigenetic changes in trees (and in humans) are known to persist through 2 or 3 generations.Ī second genetic form of mutation which forms a stable witches broom is an actual point mutation in the DNA. So the underlying DNA still has all the code for the normal form of the species, so when the epigenetic control is unblocked, the growth reverts to normal. Where it does you get the ''reversion'' to normal growth. This methylation process can be quite permanent, hand even be inherited through seed propagation. If it happens in the right spot, it creates what looks like a true genetic mutation, and can create dwarfs, contorted growth, variegated leaves, new flower color patterns, and all manner of other horticultural oddities. If the DNA at a specific location becomes methylated, the blocking control protein becomes semi-permanently bound to that portion of DNA. Many witches brooms are screw ups in this mechanism. This blocking and unblocking of the DNA Is called Epigenetic Control. Similarly the skin cell has proteins blocking the reading of directions for becoming a heart cell. There are proteins that block the reading of large parts of the DNA for each tissue type, this way the heart muscle cells only read the parts that tell it how to be a heart muscle cell, not the directions on how to be a nerve cell. Your skin cells and heart cells and brain cells all have the same DNA coding. There are 2 changes that cause relatively stable witches brooms, that can be stable long enough to be propagated.Įpigenetic changes - this is activating or deactivating the protective proteins that allow or prevent a segment of DNA from being read. Treat for downy mildew, the tree reverts back to normal. Many witches brooms disappear after you clean up the cause. There were 5 or more possible causes for witches brooms. I can not speak for the actual history of the cultivar ''Dwarf Alberta Spruce'', I don't know when or where it was found.
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