Adventitious Root Formation in Veronica Spp.

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Abstract
Species of the genus Veronica differ in habitat preferences, growth form and in adventitious root production. The annual species rarely or never produce adventitious roots in intact plants in the field but some, for example V. persica and V. arvensis will root vigorously from single node stem segments in culture. Others, such as V. agrestis require the presence of IAA for substantial levels of root formation to occur in cultured stem segments. Veronica hederifolia cuttings rarely produce roots. Stem cuttings of the perennial species, in general, rooted more vigorously than those of annual plants. Both V. fihiformis and V. serpyllifolia root very strongly. The position of root production from the stem cuttings differed from species to species. Roots arose either from the node, the region of the base or at some intermediate point. Veronica arvensis, V. chamaedrys and V. persica rooted mainly from the basal region whereas V. filiformis rooted mainly from the node. Veronica serpyllifolia cuttings rooted at both of these locations. Veronica filiformis, a perennial species that is infertile in Britain, produces root primordia in intact plants at nodes which are close to the shoot apex. Thus, even very young stem segments have ‘preformed’ root primordia. For this reason, detached stem segments of V. filiformis root very rapidly and this probably has been of great significance in its successful invasion and spread in lawns and short turf areas.