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Sunday, February 15, 2015

Before there were flowers: Wind Pollination


Pine tassels. © Beatriz Moisset

Pine cones. © Beatriz Moisset
Maine’s state flower is rather unusual because it is not a flower in the real sense. It is the white pine’s (Pinus strobus) tassel and cone. These are not flowers but serve the same function: the tassels produce pollen that has to arrive at the small, immature cones to produce seeds. Only then the cones can grow and reach maturity. Maine residents must be mighty proud of their pines and for very good reasons. It is a handsome tree of great value, and the tassels and cones, although not as colorful as most true flowers, are quite handsome. I am delighted at this peculiar choice because it serves to illustrate a significant point of pollination.

Long before there were any animal pollinators, only the wind performed this function. Wind pollinated plants have to produce vast quantities of pollen so that just a few grains can arrive to their destination; the immense majority never even come near the female cones and simply goes to waste. Pines, firs, spruce, and other conifers belong to an ancient lineage that appeared long before pollinators entered the scene. Thus they were and still are pollinated by the wind. Despite its inefficiency, this method works well enough when many plants of the same species grow relatively close to each other. This is why conifer forests are composed of only a small number of species. This is also why corn, another wind pollinated plant, needs at least several rows of plants to produce seeds.

Pollen dispersal by wind. © Beatriz Moisset
Getting back to the pine, both the tassel and the cone are well-adapted to their functions, increasing the chances that wind-carried pollen finds its destination. The tassels are placed higher on the tree. The cones are aerodynamically shaped to create small air whirlpools that direct the pollen grains toward the seeds. For millions of years, the land was dominated by these plants, along with even older ones, the seedless ones that reproduce by spores. The more ancient dinosaurs never saw a flower, nor did they care. The flower revolution was yet to come, and once started it would take the land by storm and spread to distant corners. Nowadays, wind pollinated conifers are more common than flowering plants only in harsh and cold environments near polar regions. Most plants everywhere else produce flowers.

The great advantage of flowers and of animal pollinated plants is that pollinators are more efficient than wind alone in transporting pollen to the intended target, thus even if individual plants are far apart, they still succeed at being pollinated. In fact, forests of tropical regions are made largely of blooming trees with so many different species packed in the same space that a pollinator has to travel some distance between members of the same species. So pollinators contribute to biodiversity, which in turn contributes to a more efficient way of using all available ecological resources.

Now I can get on with the story of pollinators of state flowers.

Also see: Pollinators of Official State Flowers 

References 
Maine: White pine tassel and cone 

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