Question: Explain Variegation in Ivy (xiv): testing the theory: predicting the white margin
In this post I will try to explain the white margin. As opposed to a yellow centred cultivar having a mutated L3 layer, a white margined cultivar has a mutated L2 layer. Because the L2 layer is only sandwiched between the colourless epidermis, the margin will be white (eventually). The visible green patch is the actual section of cells the L3 layer contributed.
When you look closely at the green blotch you will often see the colour isn't uniform. Some regions are more of a lighter green or grey. There is no word about the cause of this by my sources. It is only mentioned (by Rose) that sectional chimeras can show interesting colour patterns. I think the way this pattern is constructed is similar to the construction of the mentioned colour ranges.
The explanation can be found in the distribution of the contributed cells of the L2 and L3 layers. Cells contributed by the L3 layer reside mainly in the regions around the larger veins. The L2 cells reside predominantly at the margin of the leaf. L3 cell layers are always sandwiched between L2 cell layers. At the centre of the leaf, where cells originated from L2 and L3 reside, one of these layers has the upper hand.
The palisade mesophyll of a Ivy leaf is about 3 cell layers thick. At places where the L3 cells reside there's only one layer of colourless L2 cells. This gives the darkest green colour possible. At the marginal region between the L2 and L3 layer it is possible the L2 layer occupies 2 or 3 layers of cells. This gives the lighter colours.
The distinct borders between the green blotches is caused, like the border between the green and white or yellow, by the vertical orientation of palisade cells. According to Rose Hedera helix 'Chester' is a cultivar with white margined leaves.
Leaves me only to predict the streaked and speckled patterns with the theory.
When you look closely at the green blotch you will often see the colour isn't uniform. Some regions are more of a lighter green or grey. There is no word about the cause of this by my sources. It is only mentioned (by Rose) that sectional chimeras can show interesting colour patterns. I think the way this pattern is constructed is similar to the construction of the mentioned colour ranges.
The explanation can be found in the distribution of the contributed cells of the L2 and L3 layers. Cells contributed by the L3 layer reside mainly in the regions around the larger veins. The L2 cells reside predominantly at the margin of the leaf. L3 cell layers are always sandwiched between L2 cell layers. At the centre of the leaf, where cells originated from L2 and L3 reside, one of these layers has the upper hand.
The palisade mesophyll of a Ivy leaf is about 3 cell layers thick. At places where the L3 cells reside there's only one layer of colourless L2 cells. This gives the darkest green colour possible. At the marginal region between the L2 and L3 layer it is possible the L2 layer occupies 2 or 3 layers of cells. This gives the lighter colours.
The distinct borders between the green blotches is caused, like the border between the green and white or yellow, by the vertical orientation of palisade cells. According to Rose Hedera helix 'Chester' is a cultivar with white margined leaves.
Leaves me only to predict the streaked and speckled patterns with the theory.
posted by Me, Myself and Ivy at 2:27 PM
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