Plant Variegation
Variegated plants have stripes, blotches, streaks, or other pigmentation patterns on their leaves, flowers, or fruit. The patterns can exhibit white, cream, yellow, or other colors that make the variegated plant stand out. Numerous plant species can be observed with variegation including hosta, canna, Dieffenbachia, spider plant (Chlorophytum comosum), and philodendron, to name a few.
Causes of variegation
There are several factors that can cause variegation in plants. Differential gene regulation occurs in some variegated plants where the plant cells contain the same genomic sequence, but different cells of the plant express the gene(s) at different rate(s). This type of variegated plant will grow true to seed and can be observed in striped watermelon rinds, petunias with bicolor flowers, or the face on a pansy (Marcotrigiano 1997).
Physical structures of the plant leaf can also cause variegation. In this case, leaf cells physically separate from the layers above or below them, forming in essence, a plant blister (Hara 1957). This type of physical variegation causes silver spots or streaks and can be observed with Pilea cadieri, the aluminum plant.
The presence of viruses also causes variegation and other leaf or flower patterns. Virus induced variegation is observed in two popular mint varieties with golden veins, ‘golden ginger mint’ and ‘emerald mint’. These varieties have been shown to contain several viruses (Tzanetakis et al 2010). Eliminating the viruses from these cultivars also eliminates the presence of the attractive golden veins (Tzanetakis et al 2010). The presence of novel variegation and leaf distortion in some hosta spp. has also been attributed to the presence of a virus called Hosta virus X or HVX (Currier and Lockhart 1996; Blanchette and Lockhart 2003).
Hosta with virus caused leaf pattern. White edges are normal in this variety.
Genetic mosaicism or chimeras are also a cause of plant variegation. Plants with chimeric variegation may be transient and present in only one plant section, or stable and able to be passed down to progeny. A chimeric plant has genetically different cells in different regions. This type of variegation can arise by transposable genetic elements (Doodeman et al 1984), spontaneous mutations, or induced mutations in the nuclear or chloroplast genome (Tilney-Bassett 1986). Chimeric variegation can be stable and easily propagated or can be unstable and present in only an isolated portion of a plant.
Pepper plant with a transient chimeric leaf variegation in young leaves.
Stable chimeric variegation observed in variegated spider plant, Chlorophytum comosum. Yellow tint due to artificial lighting.
Differentiating between virus induced symptoms and natural genetic mutations in some plant species is challenging, time consuming, and requires laboratory testing. New hosta varieties are now vigorously tested to verify new leaf color patterns are caused by chloroplast mutations and not viruses.
Plant variegation is an interesting pattern of pigmentation in plants that can be caused by viruses, but in many cases is simply differential gene regulation, physical deformity, or a genetic mutation.
All photos taken by Sara Bratsch. For non commercial use only.
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Cite this article:
Bratsch, Sara. "Plant variegation". Web article. 27 February 2017. http://plantpathlesstraveled.com/plant-variegation/
Citations
Blanchette, B., & Lockhart, B. (2003). Hosta virus X: A three-year study. Hosta J, 35, 19-23.
Currier, S., & Lockhart, B. E. L. (1996). Characterization of a potexvirus infecting Hosta spp. Plant disease, 80(9), 1040-1043.
Doodeman, M., Boersma, W., Koomen, W., Bianchi, F. (1984). Genetic analysis of instability in Petunia hybrida l. A highly unstable mutation induced by a transposable element inserted at the An1 locus for flower colour. Theor. Appl. Genet. 67:345-455.
Hara, N. (1957). Study of the variegated leaves with special reference to those caused by air spaces. Jap. J. Bot, 16, 86-101.
Marcotrigiano, M. (1997). Chimeras and variegation: patterns of deceit. HortScience, 32(5), 773-784.
Tilney Bassett, R. A. (1986). Plant chimeras. Cambridge, UK: CUP.
Tzanetakis, I. E., Postman, J. D., Samad, A., & Martin, R. R. (2010). Mint viruses: Beauty, stealth, and disease. Plant disease, 94(1), 4-12.