Drought and leaf damage limit the search for support in the climbing plant Ipomoea purpurea (L.) Roth (Convolvulaceae)

Abstract

There is evidence that some climbing plants increase their twining rate after leaf damage, thus avoiding ground herbivores, and that drought limits this induced response. However, it is unknown whether leaf damage and drought affect the search for support, an ecologically relevant process for climbing plants. We evaluated the combined effect of drought and leaf damage on support searching in the twining vine Ipomoea pupurea (Convolvulaceae). Plants were assigned to a combination of three watering treatments (regular watering, moderate drought, and severe drought) and two damage treatments (control and 50% defoliation). We placed a stake at 15 cm from the stem and recorded the time to successful twining (360° turn). We also measured some plant functional traits to explore possible mechanisms. Leaf damage decreased time to successful twining in all treatments with the exception of severe drought. Severe drought decreased plant growth, particularly when combined with leaf damage. In nature, climbing plants are usually not in contact with a support in the early stages. The searching behavior seems to increase with leaf damage, but it is restricted by water shortage. Plants experiencing both leaf damage and severe drought will be less likely to find a support, resulting in higher probability of further leaf damage.