Circumnutation behavior of an exotic honeysuckle vine and its native congener: influence on clonal mobility

Virtually all plant parts rotate slightly about a central axis, a movement called circumnutation, but vines show exaggerated circumnutation. This study contrasts circumnutation in two congeneric twining vines, specifically focusing on differences in erect and prostrate shoots, and examines the impact of circumnutation on exploitation of available climbing supports and exploration for more distant ones. Elongating shoots of Lonicera japonica and L. sempervirens growing in a common garden were classed as (1) erect but not climbing, (2) climbing on a trellis, or (3) prostrate, and their circumnutation quantified by tracking the compass direction of shoot tips. To quantify the impact of different circumnutation behaviors, the climbing success of erect shoots and the maximum dispersion and rooting success of prostrate shoots were measured. Erect shoots of both species circumnutated at similar rates (averaging 31°/h), and did not differ in their success rate of exploiting trellises (averaging 76.8%). Prostrate shoots differed, with those produced by L. japonica having reduced circumnutation. In contrast, prostrate shoots of L. sempervirens continued to circumnutate as much as erect shoots. The specialized circumnutation behavior of the prostrate shoots of L. japonica results in increased rooting success and maximum dispersion compared to the unspecialized shoots of L. sempervirens.