Monoecy often co-occurs with anemophily,[2] because it prevents self-pollination of individual flowers and reduces the probability of self-pollination between male and female flowers on the same plant.[4]: 32
The term monoecy was first introduced in 1735 by Carl Linnaeus.[2]Darwin noted that the flowers of monoecious species sometimes showed traces of the opposite sex function, suggesting that they evolved via hermaphroditism.[7] Monoecious hemp was first reported in 1929.[8]
Maize is monoecious since both pistillate (female) and stamenate (male) flowers occur on the same plant. The pistillate flowers are present on the ears of corn and the stamenate flowers are in the tassel at the top of the stalk. In the ovules of the pistillate flowers, diploid cells called megaspore mother cells undergo meiosis to produce haploid megaspores. In the anthers of the stamenate flowers, diploid pollen mother cells undergo meiosis to produce pollen grains. Meiosis in maize requires gene product RAD51, a protein employed in recombinational repairofDNA double-strand breaks.[18]
Inamaranths monoecy may have evolved from hermaphroditism through various processes caused by male sterility genes and female fertility genes.[20]: 150
Monoecy may be an intermediate state between hermaphroditism and dioecy.[21] Evolution from dioecy to monoecy probably involves disruptive selection on floral sex ratios.[22]: 65 Monoecy is also considered to be a step in the evolutionary pathway from hermaphroditism towards dioecy.[23]: 91 Some authors even argue monoecy and dioecy are related.[2] But, there is also evidence that monoecy is a pathway from sequential hermaphroditism to dioecy.[23]: 8