Naturespeak A naturalist's view of the world

April 19, 2008

Spring is Up in the Air

Filed under: Uncategorized — wykes @ 8:20 pm

  From the title of this piece you might assume that I am going to say that the status of this spring is somewhat doubtful – you know, as in yet to be decided or debatable.  Well nothing could be further from the truth. This spring season is charging ahead full force. It is neither late nor early, but definitely proceeding at its usual rapid pace. What I really wanted to say with this title is that the essence of spring is literally up in the air in the form of pollen and that the first pollen-producing spring wildflowers are located up in the air as well. In other words, ‘tis the time to suck in some tree dust and blow it out again (maybe that would have been a better title, eh?).  

  Trees, such as Black Alders and Red Maples are among the earliest of bloomers yet they are little appreciated for this effort. I was reminded of this the other day when I went up in the air aboard a helicopter.  We were engaged in deer counting again, but found it a difficult task without the neutralizing effect of background snow.  We did spot a few deer but only the ones that were flashing their white tummies in the morning light.  Doing an April survey wasn’t my idea – I can blame that on the Univ. of Michigan but don’t have time to explain why I was involved in this particular scheme.  Whilst airborne I got a spectacular view of the flowering red maples.  These trees added a crimson wash to a canopy otherwise dominated by gray. The view shown above is out my side of the cockpit over Oakland County and the chance to see it was a blessing – with or without deer sightings. The white pines poking through the canopy can be temporarily ignored because they are always green, whereas the maples are only vibrantly attired in red twice a year (during flowering and autumn leaf blush). O.K., you don’t have to ignore the pines. Go ahead and say “ooh” and “ahh” and “aren’t they great, etc.” and then let’s get back to the maples.

  You can see these trees blooming from down here on earth but you have to look up. Forget the late appearing daffodils and hibiscus and peer skyward in order to appreciate these much larger flowering plants.  The maples have been blossoming for several weeks and right now the red female flowers are at their peak. The male blooms started much earlier and a few are still out (see here). Each bunch of flowers consists of a cluster of five-parted florets sporting five individual yellow anthers.  Each anther is coated with grains of pollen whose sole function is to fertilize the female flowers.

 The Black Alder is another early tree flower that expresses itself in the form of a dangling pollen wand known as a catkin (see here). This is a low tree which really has to be appreciated from the ground level.  An individual male alder flower is not very impressive, but there are dozens that make up each catkin and together they make up a fascinating structure. The catkins open and relax downward when prompted by the first warming rays and shed their pollen load to the four winds.

  Since both the Red Maple and Alder are primarily wind pollinated they are called anemophilous plants (a term which literally means “wind loving”). They rely on the wind to distribute their pollen. Since the breeze is a haphazard postal service, such plants need to shed trillions of very light pollen grains in the hopes that some of them make their goal. It so happens that we are unintentionally sticking our noses into their love life by interrupting that pollen stream.

  A pollen grain is essentially a sperm packet surrounded by a tough outer coat. Most are round and elaborately ornamented and all are extremely tiny. Take a look here and you can see what the pollen grains of Red maple and Black Alder look like. Yes, that is my hand in the photo and yes, these are models.  Thank God, eh? Imagine sucking one of these things up your nose! In actual scale, the Alder grain (on the left) would be only 15 microns wide and the Maple (on the right, in case you weren’t paying attention) would be about 20 microns in diameter.

  A micron, or micrometer, is one-thousands of a millimeter, so you get an idea of just how small these grains are. If my photo were to scale, I would be only a few millimeters tall and my hands would be so tiny that I wouldn’t be able to type on a keyboard (I would, in fact, fall between the spaces in the keys and have to live off all the food crumbs found there).

  The air is now full of tree pollen and nearly all of it is wasted since very little makes it to the intended destination. Those that find their mark – being a female flower of the right species –immediately sprout a tubule which penetrates to the ovary and delivers the precious cargo. Those that are wasted end up in places such as your nose where they initiate sneezing. All maple pollen is allergenic to humans and some folks are allergic to alder pollen.

  If you are they type that gets seasonal allergies, you likely have been keenly aware that the trees have been flowering for some time. Perhaps this essay will give you something to look for in the Kleenex next time you blow your nose. For those of you who don’t feel the effects of tree dust, it’s time to stop and look up at our largest wildflowers and take in a deep breath of spring.

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