The cultivated lettuce tends to flower in spring or early summer,and then drop its seeds which lie dormant on the soil whilst temperatures are high, only germinating once the temperature has dropped. This built-in dormancy protects the young plants from the risk of drying out in hot weather, but is a hindrance to commercial growers in hot regions.
In newly published work, a team of researchers led by a plant scientist at the University of California have identified the gene and its linked enzyme (abscisic acid) that are responsible for inhibiting hot weather germination. They were able to silence or mutate this gene, resulting lettuce that could germinate at high temperatures.
You can find out more at: http://news.ucdavis.edu/search/news_detail.lasso?id=10546
Story source: Science Daily, 28 May 2013
Journal Reference: H. Huo, P. Dahal, K. Kunusoth, C. M. McCallum, K. J. Bradford. Expression of 9-cis-EPOXYCAROTENOID DIOXYGENASE4 Is Essential for Thermoinhibition of Lettuce Seed Germination but Not for Seed Development or Stress Tolerance. The Plant Cell, 2013; DOI: 10.1105/tpc.112.108902