Understanding plant variegations

Over the last few years, there has become a tremendous amount of interest and fascination over the variegation of plants. But do you really understand what causes the breaks in colour of a plant?

There are several reason a plant becomes variegated. All of the various reasons come back to the fact that the plant has experienced a mutation in the DNA. This mutation is almost always caused by an injury. The injury can be caused by a virus in the plant, insect damage, physical damage, and chemical damage. Plant cells are green because they contain chloroplasts, which the plant needs to make food. Sometimes damage can cause the cells to have mismatched DNA and therefore create cells that have no chloroplasts. Cells that have no chloroplasts are white or off colour, and therefore cannot produce food. Where the damage occurs is significant as to how the variegation will manifest itself. If the damage occurs, say on a flower from thrips, the flower will randomly have patches or streaks that contain no colour. This type of variegation will disappear as the plant continues to grow. It’s the same as if a leaf is damaged down to the plants’ molecular structure, the plant may repair itself by using cells that do not contain chloroplasts. In this case, you would see white streaks that again are unstable. As the plant matures and grows new leaves, they will revert back to green. The white streaking will not continue.

At the very tip of the growing section of the plant is called the meristem. The meristem is where all new growth for the plant begins. If the chromosomes are damaged variegation may occur. The new cells often have DNA that don’t match up. In this case, the cells without chloroplasts will still divide, however, the new cells will also lack chloroplasts and be albino cells. This becomes a more stable type of variegation if all three layers of tissue have been damaged at the chromosomal level. But does that mean that the seeds of that plant will be grow into variegated plants? Not usually. Seedlings that emerge that have no chloroplasts are not able to produce food for themselves (photosynthesize), and are weak and die. Therefore, most variegated plants are reproduced by cloning. When you see pink, yellow or pale green variegation or patches, it is because the cells have been mutated, but not down to the deepest level and still contain some chloroplasts.

All of this is extremely complex, and plant scientists are still working on fully understanding mutations. One thing we know for sure is that variegated plants will never be as tough as the non variegated plants and in nature will eventually die out to give way to their stronger counterparts.

Meanwhile, let’s marvel at the pink, purple, white and yellow plants that become available to us. I love all this colour!