Vines Climb to New Heights

Recent research in Amazonian forests has suggested that the abundance of woody vines is increasing relative to tree species, possibly as a result of increasing carbon dioxide concentration and increasing forest fragmentation.

Climbing plants have fascinated biologists, including Charles Darwin, who wrote a provocative essay on the subject in 1865; however, many questions remain to be answered. A recent article by Dr. Sandrine Isnard and Dr. Wendy Silk in the July issue of the American Journal of Botany explores the logistics of this incredible ability. A greater knowledge of these fascinating plants is warranted as we begin to understand the important ecological role they play in forest dynamics, structure, and composition.

Root-climbers and other clinging climbers often adhere to a supporting structure through viscous secretions, allowing them to crawl up very large tree trunks. Hook-climbers are rather less sophisticated. They use their hooks to lean on their source of support without firmly attaching to it, a notable difference from the other types of climbers.

Although it is possible to observe the superficial differences among the vines in their climbing methods, it is more difficult to observe structural traits of the stems that play an integral role in the plants' climbing ability. Because climbing plants rely on their other supportive structures as they reach toward the sky, they do not need to invest their energy into building huge tree trunks to support heavy branches. Not only are they able to be flexible, but flexibility is an asset that makes a vine less prone to mechanical stresses while detaching from support or during fall of the support itself. Many anatomical traits of vines, such as the significant development of parenchyma and high frequency of wide water transport vessels, allow them to maintain this flexibility and withstand breakage while still effectively transporting water and nutrients throughout the plant.