Ontogeny, Anatomy, and Reproductive Biology of Vegetative Reproductive Organs of Diodia virginiana L. (Rubiaceae)

Adventitious buds formed on the hypocotyl and roots of Virginia buttonweed (Diodia virginiana L.) approximately 2-4 wk after germination. Buds arose either singly or in clusters from within the phellogen in the outer starch storage parenchyma. Many of the buds were spatially associated with lateral roots. Adventitious root primordia arose endogenously from caudexes and aerial shoots. Survival of adventitious roots required contact of the nodal region with soil or a moist surface. Shoot emergence and the number of shoots emerged per root segment increased with temperature and were greatest at 35 C, while time to shoot emergence decreased below 35 C. Maximum rooting of stem segments occurred at 30 C. No rooting from stem segments or shoot emergence from root segments occurred after 1 h or more exposure to - 10 C, and 100% regeneration occurred after 0 C at all exposure periods. Shoot emergence from root segments following 1 h exposure at -5 C was 95%, compared with 15% after 8 h. Root segments failed to produce shoot growth after drying for 4 h at 30 C. Shoot emergence from buried root segments increased as rootsegment length increased and planting depth decreased.