Twisty Cucumbers, All Alike
September 7, 2012 As if gardening isn't hard enough, a home gardener needs to know genetics; well, at least the folklore version of genetics passed from one generation of gardeners to another. Summer squash, including zucchini, is a member of the Cucurbita pepo species, of which pumpkins and gourds are also members. This means that there's a possibility of cross-pollination between these plants. This is no real problem in any single year, but seeds saved to the next year may not give you what you expect. To prevent problems, distances of a kilometer or greater are advised between extensive planting of different species. Folk knowledge is not perfect, since it's often thought that cucumbers and squash will cross-pollinate. They don't. tendrils, those plant runners that attach to objects to elevate the leaves to regions with more sunlight (see photograph, below). Since plant fibers do not contract as well as animal muscle, the way that these tendrils draw the plants upwards is by forming a spiral/helical structure. The overall structure, however, is unusual. The tendrils form a right hand helix on one end, and a left hand helix on the other. This was noted by Charles Darwin in 1865. As a result of this structuring, there's a transitional region in the center of the tendril that Darwin called a "perversion." it's a strange use of the word, today, but "perversion" actually derives from the Latin adjective, "perversus," which means slanted, crooked, or cross-eyed.
 |
| Tendrils of the cucumber plant, Cucumis sativus. In the top image, the tendril has just grasped an object and it hasn't formed the dual helix structure. The dual helix structure is shown in the lower image. (Top image by Kropsoq, via Wikimedia Commons). Lower image, Harvard SEAS image by Joshua Puzey and Sharon Gerbode).[1] |
 | Cells in a cucumber tendril's core fiber. The thick cell walls containing lignin, are visible. (Harvard SEAS image by Joshua Puzey and Sharon Gerbode).[1] |
"The advantage of using a tendril is that the plant saves on complex machinery to build structural supports such as trunks and branches. The disadvantage is that it must depend on other species to build these supports. Thus, tendrils are an adaptation that is likely to develop only in regions replete with vegetation that can provide supports and where competition for resources is intense."[1]This new type of spring seems to offer some technological advantage, so a patent application has been filed.[1] A report on this research, which was funded by the MacArthur Foundation and other sources, is published in a recent issue of Science.[2] Some readers may have noticed the allusion of the title of this article to the phrase, "You are in a maze of twisty little passages, all alike," found in the 1980 computer game, Zork I. I rarely play games, but I do miss the simplicity of text games such as Zork, and subsequent text based games overlaid with a thin graphics background.
References:
- Uncoiling the cucumber's enigma, Harvard School of Engineering and Applied Sciences Press Release, August 30, 2012.
- Sharon J. Gerbode, Joshua R. Puzey, Andrew G. McCormick and L. Mahadevan, "How the Cucumber Tendril Coils and Overwinds," Science, vol. 337 no. 6098 (August 31, 2012), pp. 1087-1091.
- Emily Underwood, "Video: How Cucumber Tendrils Curl," Science Now, August 30, 2012.
- Sharon J. Gerbode, Joshua R. Puzey, Andrew G. McCormick and L. Mahadevan, "How the Cucumber Tendril Coils and Overwinds," Science, vol. 337 no. 6098 (August 31, 2012), pp. 1087-1091.