The European Space Agency, Noordwijk, The Netherlands
Title: Seeds, dispersal and biomimicry
Seeds provide the vital genetic link and dispersal agent between successive generations of plants. Without seed dispersal as a means of reproduction, many plants would quickly die out, and it is the last important step before the new offspring finally establish independence on their own. Because plants lack any sort of mobility and remain in the same spot for their entire lives, they rely on seed dispersal to transport their offspring throughout the environment. This can be accomplished either collectively or individually. But because seeds ultimately abdicate their movement, they are at the mercy of environmental factors. There are a number of reasons why seed dispersal is integral to the survival of a plant species, and the methods of dispersal are varied.
Seed dispersal is important to reduce competition. Plants that accrue all in one area will have to fight for resources, but seeds that are spread out are much more likely to find success in favourable environments without the danger of interbreeding in local habitats near the parent plant. Sometimes it is not competition that is the problem for the seed, but just the right growing conditions. Older plants can survive in areas where seedlings may struggle to live. Dispersal allows seeds to move to locations where better growing conditions exist, at least temporarily.
Plants have evolved seeds that take advantage of animals, wind, water, fire and even explosions to distribute the seeds and give them a chance to reach a favourable environment. In order to deal with the realities of dispersal, plants have evolved specific structures and strategies to carry their seeds throughout the environment. Some seeds have two lateral wings to help them glide; dandelions use umbrella-like parachutes instead. Maple seeds are known as “helicopters” because they are wing-shaped, and as they fall from the tree, they flutter toward the ground and can be spread farther when caught by the wind. But the wind is not the only method for seed dispersal. Seeds also can hitch rides on animals, preferably winged animals such as insects, bats and birds, as they usually travel the greatest distances; or light seeds can rely on water or there may be fluff that helps buoyancy. Explosive dehiscence is a ballistic form of dispersal that flings seeds far from the parent plant. A notable example is the Sandbox Tree (Hura crepitans L.), which can fling seeds 100 meters and has been called the “Dynamite tree” due to the loud sound of its explosive dehiscence.
All these time-tested strategies are pure wonders and plants are the consummate engineers who designed them. They have found what works, what is appropriate, and most importantly, what lasts here on Earth, and they exhibit many examples of efficient design and specialized functionality. One of the first designs derived from them is Velcro, emulating the minute hooks on the seed of the hitch hiker burdock plants. Nowadays, scientists are looking at many aspects of seeds dispersal such us the airfoil of autorotation Mable seeds, the anti-fouling surface of a palm tree species dispersed by water, or the small parachute of dandelions.
Nature provides a wonderful database from which to borrow ideas, concepts and designs. Investigation of natural samples leads to the discovery of ideas and designs which have been optimised for distinct biological functions. Investigation of natural samples leads to the discovery of ideas and designs which have been optimised for distinct biological functions and we are likely to see more bio-inspired seeds designs, devices and technologies in the near future.
Contribution to the Workshop “Smart Solution from the Plant Kingdom”