Induced twining in Convolvulaceae climbing plants in response to leaf damage

Plant responses to herbivory include slow changes in growth patterns and biomass distribution. A recent study, however, showed that a convolvulaceous vine began twining sooner around a stake after 25% of the plant was defoliated (damaged). We evaluated whether this induced response is widespread within the Convolvulaceae, and made preliminary studies of its underlying mechanisms. Leaf damage was applied to seven twining vine species from the genera Convolvulus, Calystegia, and Ipomoea. We compared the twining rate (proportion of plants successfully climbing at a given time), growth rate, and twining geometry in the control and in damaged plants. We further evaluated the consequences of jasmonic acid application on the twining rate of Ipomoea purpurea (L.) Roth. Five out of the seven species tested showed an enhanced twining rate after leaf damage. Growth rate did not differ between damaged and undamaged plants in any species. The angle of ascent of the twining stem was lower in damaged plants during the first gyres. Jasmonic acid increased twining rate in I.apurpurea, as did leaf damage. The induced twining was not due to increased growth, but to changes in the climbing process, and further mechanistic approaches should consider the jasmonate pathway. Induced twining may be common in the Convolvulaceae, and its occurrence in other families should be tested.