Fig. 1. Life cycle of Arabidopsis thaliana. The mature plant possesses primary and secondary roots, rosette and cauline leaves, and inflorescences. Flowers are composed of sepals, petals, stamens (male reproductive organs) and carpels (female reproductive organs). After pollination, the fertilized egg develops into an embryo inside the silique. The embryo possesses two meristems, a shoot meristem (SAM) and a root meristem (RAM), where new organs and tissues are initiated during post-embryonic growth. Seeds germinate and give rise to seedlings composed of the embryonically-formed hypocotyl and cotyledons. Further organogenesis depends on the action of shoot and root meristems.