Sunday, March 21, 2010

Getting the Kids to Leave Home

The successful propagation of any species requires dispersal- getting the kids to settle away from home, preferably a long way away.  The closer they live to you, the more food, drink and living space you have to share.  Your own success-think retirement-can be jeopardized if you run out of these resources.
Animals that nurture their young eventually encourage their young to move away to find their own food sources, dens, etc.  The boys have to travel to find a mate. In some insect species, hanging around too long may get you eaten by mom.
Plants have kids that can't move, once they have rooted, but they have evolved a number of ways to disperse their seeds long before they become teenagers.  Seeds may be spread by the wind (dandelion, winged maple seeds) or animals which eat the fruit and spread the seeds in their waste.  Plants such as the touch-me-not have even developed a catapult system for tossing their seeds away from the parent plant.  (see the February 8, 2010 entry)
The ferns and fungi seldom have these options.  Their spores require the wind to spread them over distant and hopefully fertile territory.  Once airborne, fungal spores infinitesimally small weight allows them to travel at high altitudes, possibly circumnavigating the globe before settling down to establish a new home.  However, leaving their mom (indelicately referred to as a "fruiting body") usually means a short fall from the gills under the mushroom to the ground under the cap, not an atmosphere known for breezes.
A field mushroom improves its odds by manic seeding, producing 16 billion spores that are released at a rate of 100 million an hour.  Some fungi have evolved methods to disperse spores a few inches higher, improving their odds of picking up a favorable breeze.   Puffball mushrooms launch their spores upward into the air when the fruiting body is pressed by a raindrop or the foot of an animal.  (See picture- Note cloud from Earth Star).  Recent research has identified ways some plants have developed to launch their spores.  Gibberella zeae, a fungal pathogen of wheat is currently the reigning champion in acceleration.  By producing chemicals that create high osmotic pressure in the cells, it is able to accelerate the spores to 870,000 times the acceleration of gravity, reaching 80 miles per hour.  This translates to traveling 2,000,000 spore lengths per second.  They are shot into the air to an amazing altitude of -are you ready for this?- quarter of an inch.  (Remember, they are infinitesimally light weight and therefore are rapidly stopped by the air pressure.)
There is a lot more detail available in this Natural History Magazine article.  However, none of it will help you to get the kids to move out on their own.

1 comment:

  1. Great article, especially the part about getting the kids to leave home! Thanks