Wednesday, October 24, 2012
The rugged rose
Species name: Rosa rugosa
Common name: Japanese rose, wrinkled rose
This species of "wild" rose (it is also cultivated and sold in garden stores, so most plants probably aren't truly wild) is incredibly popular across the world for a diverse number of reasons. The native range of this plant is enormous, ranging from western Europe all the way east to Japan and Korea, as far south as Turkey, and as far north as the southern edge of Siberia. It has adapted to a wide range of habitat types, but prefers areas that have moderate levels of disturbance, low nutrient levels in the soil, and full sunlight (for those reasons it does very well on sand dunes and in sandy soil but also roadside ditches). It can often be seen as a garden escape growing in very shrubby areas, where it can dominate (at least for a short time, until buckthorn comes in) the area quickly.
The genes determining flower colour in this plant are very similar to each other. What I mean by that, is that for every single gene in our genome, we have two copies of that gene. One we inherited from our mother, and one we inherited from our father. Each of these copies of genes we call "alleles". If you read the DNA sequence of each of these alleles, they will be different from each other, and that's why they can result in very different physical characteristics of an organism (we call this the organism's "phenotype"). The different copies of a gene arise through gene mutation, and depending on the gene as little as a single mutation can cause a drastically different phenotype, depending on where in the gene or gene product (usually a protein) the mutation occurs. The allele for the white flower colour is incredibly similar to the allele for the purple (or pink, depending on who you ask) flower colour; so much so, that sometimes in the plant as it grows, one branch will generate a new mutation (a regular occurrence that happens in all biological organisms; this is how we evolve over time) that causes the exact same change in flower colour that having a different allele would. You might be looking at a single plant that has mostly pink flowers, then all of a sudden a short branch with 3 or 4 white flowers on it. It's amazing how our DNA works sometimes!
Aside from the colour-changing ability of the flowers, these flowers are highly praised for other reasons. They have incredibly high resistance to disease, including two fungal diseases that cause huge financial devastation in the ornamental rose industry: black spot of rose and rose rust. Many species of rose readily hybridize, so hybridizing the Japanese rose with any other species of rose can sometimes confer the benefits of increased disease resistance. Because it also has high salt resistance, it's a popular hedge plant for beside busy roads that get heavily salted during the winter. The rose petals retain their scent when dried, and so are a popular source of potpourri in Japan and China.