Plants have evolved creative ways of dispersing their seeds, and one of the most effective ways is by using the wind. The main goal of wind dispersal is to let the seed fall in a place that is suitable for the plant to grow, but to move it far enough away from the parent that it does not compete for water, light and nutrients.
Dandelions (Taraxacum officinale) are a common weed in almost every habitat in North America. They demonstrate the parachute method of seed dispersal by wind. The tiny seeds are arranged in clusters on a mature flower head. Each seed, called an achene, is topped with a feather-like plume of fibres called a pappus in the shape of an umbrella. The mass of parachutes makes a flower head look like a big puffy ball. When the wind blows, the seeds are released and lifted up to drift in the breeze. Eventually they land, and a few find a favourable location to take root and grow. The parachute method is used for seed dispersal in many plants, especially the sunflower family.
Asian Climbing Gourd
Asian climbing gourds (Alsomitra macrocarpa) are tropical vines that are native to the rainforests of Southeast Asia. They grow high in the canopies of trees and have football-sized fruit. When the fruit opens, it releases up to 400 winged seeds that look like small gliders, about 5 inches from wing tip to wing tip. The wings are very thin, like a sheet of paper, with the seed acting as ballast weight in the centre. They allow the seed to glide in slow circles and land hundreds of yards away from the parent. When it lands, the wings decay, the seed germinates, and the vine climbs a nearby tree to start the process over again.
Maple tree seeds demonstrate the helicopter method of seed dispersal by wind. Each seed, called a samara, has one papery wing resembling a ceiling fan blade, with a seed on the bottom. When the samara drops from the tree in the wind, the wing causes it to spin in circles like a helicopter. A breeze will push the samara away from the parent and hopefully to a suitable growing location.
There are many different types of tumbleweed, but one of the most recognisable types in the American Southwest is Russian thistle (Salsola tragus), native to north-central Asia. It is a winter annual that forms a large ball that can reach 5 feet in diameter. When it is done flowering, the plant dies and dries up. It detaches from its roots and will blow around in the wind. As it rolls, it casts up to 50,000 tiny seeds along its path. Although the seeds do not take flight, they are dispersed by the wind as it causes the dried plant to roll around the desert.
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