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M. jalapa hails from tropical South America, but has become naturalised throughout tropical and warm temperate regions. In cooler temperate regions, it will die back with the first frosts, regrowing in the following spring from the tuberous roots. The plant does best in full sun. It grows to approximately 0.9 m in height. The single-seeded fruit are spherical, wrinkled and black upon maturity (see picture), having started out greenish-yellow. The plant will self-seed, often spreading rapidly if left unchecked in a garden. Some gardeners recommend that the seeds should be soaked before planting, but this is not totally necessary. In North America, the plant perennializes in warm, coastal environments, particularly in USDA Zones 9–10.
Around 1900, Carl Correns used the four o’clock as a model organism for his studies on cytoplasmic inheritance. He used the plant’s variegated leaves to prove that certain factors outside the nucleus affected phenotype in a way not explained by Mendel’s theories. Correns proposed that leaf color in Mirabilis was passed on via a uniparental mode of inheritance.
Also, when red-flowered plants are crossed with white-flowered plants, pink-flowered offspring, not red, are produced. This is an exception to Mendel’s Law of Dominance, because in this case the red and white genes are of equal strength, so neither can dominate the other.
Source: http://en.wikipedia.org/wiki/Mirabilis_jalapa
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