Homeotic changes played a considerable role during the evolution of flowers, but how floral homeotic mutants initially survive in nature has remained enigmatic. To better understand the evolutionary potential of floral homeotic mutants, we established as a model system Stamenoid petals (Spe), a natural variant of Capsella bursa-pastoris (Brassicaceae). In the flowers of Spe plants, petals are transformed into stamens, whereas all other floral organs are unaffected. In contrast with most other homeotic mutants, the Spe variant occurs in relatively stable populations in the wild. In order to determine how the profound change in floral architecture influences plant performance in the wild, we performed common garden experiments running over 3 years. Here, we show that Spe and wild-type plants attract the same assemblage of floral visitors: mainly hoverflies, wild bees and thrips. However, floral visitation is about twice as frequent in wild-type plants as in Spe plants. Nevertheless, the numbers of seeds per fruit were about the same in both variants. Wild-type plants produced more flowers, fruits and seeds per plant than Spe plants, whereas the germination capacity of Spe seeds was higher than that of the wild-type. Determination of volatile composition revealed monoterpenes and 3,4-dimethylbenzaldehyde, which were detected only in wild-type flowers, presumably because they are produced only by petals. Our data indicate that the similar fitness of Spe and wild-type C. bursa-pastoris in the field results from complex compensation between plant architecture and germination capacity. In contrast, flower structure and floral visitation are only of minor importance, possibly because C. bursa-pastoris is mainly self-pollinating.
In the USA, 858 million tonnes of coal was used in 2013 for electricity production. With an average content of ppm uranium and ppm thorium, US coal-fired electricity generation in that year gave rise to 1100 tonnes of uranium and 2700 tonnes of thorium in coal ash. In Victoria, Australia, some 65 million tonnes of brown coal is burned annually for electricity production. This contains about ppm uranium and - ppm thorium, hence about 100 tonnes of uranium and 200 tonnes of thorium is buried in landfill each year in the Latrobe Valley.
Of course, radon is in the natural outdoor air as well, but it is diluted by all the air that is available. The Environmental Protection Agency (EPA) did a national survey in the United States and determine that the average indoor air concentration ( picocuries of radon per liter of air) is about three times higher than the average outdoor air concentration ( picocuries per liter). The average indoor air concentration is three times less than the recommended limit ( picocuries per liter). Even though, on average, we could expect our house to have about picocuries per liter of radon, the EPA estimates that nearly 1 out of every 15 homes in the United States has elevated radon levels.