Positive and negative phototropism in Schizophragma hydrangeoides and Parthenocissus tricuspidata

Abstract

We investigated phototropism in two liana species with different-climbing habits. The vines Schizophragma hydrangeoides and Parthenocissus tricuspidata use roots and adhesive-tendrils to climb, respectively. While these two species showed similar behaviors when exposed to light, illumination experiments detected very interesting responses when different stages of growth were studied. Short creeping shoots exhibited positive phototropism. Long creeping shoots appeared to show negative phototropism. This change in phototropism according to shoot length implies these climbing vines have adapted habits useful for climbing host trees. Soon after germination, their short shoots need to seek light for rapid growth, but their shoots need to explore the host trees after a certain period of growth. The base of a large host tree, the starting point for climbing, is usually in relatively dark forest floors. The vine's ability to change from positive to negative phototropism would be an essential habit for both types of vines which climb the planar surfaces of their hosts.