Plants can exhibit albinism, a phenomenon that results in a complete absence of the green pigment chlorophyll. This rare occurrence is caused by a genetic mutation, resulting in seedlings that are pure white, cream, or pale yellow instead of the usual vibrant green. For a plant, this lack of color is significant because chlorophyll is the specialized molecule that harnesses light energy for food production. True albinism is an anomaly, representing a failure in the fundamental process that sustains nearly all plant life.
The Genetic Mechanism of Plant Albinism
Plant albinism results from a genetic mutation that interferes with the biochemical pathway of chlorophyll synthesis. This pathway involves numerous steps and requires the coordinated function of at least fifteen different enzymes. A single recessive mutation in a gene coding for any of these enzymes can halt the entire process, leading to the failure of chlorophyll production within the plant’s plastids, the organelles that develop into chloroplasts.
For example, a mutation in the GUN5 gene, which is involved in magnesium chelatase activity, can prevent a plant from creating the core structure of the chlorophyll molecule. Such a defect means the plant cannot properly form functional chloroplasts, resulting in achlorophyllous, or colorless, tissue. Since the mutated gene is often recessive, the albino trait only expresses itself when a seed inherits the defective allele from both parent plants.
Survival and Lifespan of Albino Plants
The inability to produce chlorophyll makes albino plants non-viable in the long term. A seedling that sprouts white is unable to perform photosynthesis, the process by which plants convert carbon dioxide and water into sugars. The albino seedling must rely entirely on the energy reserves stored in the seed’s endosperm or cotyledons.
Once these initial energy stores are depleted, usually within a few days or up to two weeks, the albino seedling dies. However, rare exceptions exist where albino plants can survive for years by becoming parasitic. Certain albino sprouts of coastal redwood trees, for instance, connect to the healthy root system of a neighboring redwood, drawing necessary sugars from the parent plant.
Distinguishing True Albinism from Variegation
True albinism, where the entire plant lacks chlorophyll, is distinct from variegation. Variegation describes a pattern where only certain parts of the leaves or stems are colorless, while other sections remain green. This coloration is not a fatal condition because the green tissue is capable of generating enough food to sustain the entire plant.
Variegation is caused by genetic chimerism, meaning the plant possesses two genetically different types of tissue growing side-by-side. One tissue type carries the genetic defect that prevents chlorophyll production, while the other is genetically normal and photosynthetically active. The resulting pattern is often patchy, sectoral, or streaked, creating a partially albino effect.
White Plants That Are Not Albino
Not all white or colorless plants result from a genetic defect like albinism; some have evolved to naturally lack chlorophyll. These species are known as heterotrophs, meaning they obtain nutrients from external sources rather than through photosynthesis. This group includes parasitic and mycoheterotrophic plants that have lost the need for green pigment.
A notable example is the Ghost Pipe, Monotropa uniflora, which appears translucent white or pinkish and has no green parts. This species does not parasitize other plants directly but instead relies on a specialized relationship with fungi in the soil. The plant draws its entire supply of carbohydrates and nutrients from these fungal networks, which are connected to the roots of nearby photosynthetic trees. This makes the lack of chlorophyll a successful adaptation rather than a debilitating mutation.