Backyard Biology

Nature stories from my backyard and beyond

Nature Stories

Working for Clover

Wednesday, August 3, 2010

A hot summer day.  Sitting in an easy chair in the back yard thinking about fertilizing the lawn.  Certainly not feeling as ambitious as the bumblebee zigzagging low across the grass, stopping at each clover flower in search of nectar. 

The bumblebee must work for her food.  A single clover plant has many flowers joined together in a “head”.  Each individual flower must collect pollen from another flower to pollinate its eggs, and then pass its own pollen along to a third flower. This passing of the pollen from one clover flower to another is the bumblebee’s job.

The nectar that attracts the bumblebee to the clover is at the base of each flower.  To reach it, the bumblebee must stick her head deep within a flower*.  As she is hungrily lapping up the nectar, pollen sticks to her hairy body.  At the next flower she visits, some of this pollen will remain behind to pollinate the egg of that flower.  This process is repeated many times as the bumblebee travels from flower to flower, plant to plant.

The bumblebee works tirelessly pollinating the clover.  Her reward is a crop full of nectar she will bring back to her nest to feed her young. But she is not the only one working for the clover.  There are others working just as hard.  To see them, we must leave the warmth of the sun and venture below ground to the roots of the plant.

 As well as supporting the plant, the roots main job is to gather water and nutrients the plant needs for growth.  One of these nutrients is nitrogen.  Nitrogen is a necessary chemical in all plants and animals.  Life would not exist without nitrogen.  Fortunately for life (us included), nitrogen is a very common chemical.  80% of the air we breathe is nitrogen.  Unfortunately for life (us included again), it is in a form most living things cannot use. 

Since clover is a living organism, it needs nitrogen to grow.  And liroot noduleke most other living organisms, it is not able to use the nitrogen in the air.  So it must hire some help.  Somewhere in the distant past, it enlisted the help of a certain bacteria to process this unusable form of nitrogen into a useable form - ammonia.  These bacteria are housed in nodules growing on the roots of the clover.  Dig up a clover plant and, with the aid of a good magnifying glass, you can see these nodules.

Clover is not the only plant to enlist the help of bacteria.  Other related plants have this ability as well; plants such as alfalfa, soybeans, and peas. 

 The clover can use the nitrogen in ammonia for its growth processes.  When the clover dies, the nitrogen in its tissues is recycled into the soil to be used by other plants.    Or if a grazing animal eats the clover, that animal gets the benefit of the nitrogen for its growth processes.    In this way, the bacteria are really working for all of us.  The clover can be considered the middleman.

 A hot summer day.  Sitting in an easy chair fertilizing the lawn.  Thankful for the bumblebee pollinating clover and the bacteria converting nitrogen.  They may work for the clover, but the clover works for me!

All in all, a job well done.






*  It is much easier for humans to reach the nectar than the bumblebee.  Just pull a flower out of the clover head and suck the nectar from the bottom.  It is easy to see what attracts the bumblebee.