Sunday, April 10, 2011

Ah-choo! The Necessity of Pollen

As yellow powder envelopes every outdoor surface, sneezes abound and allergy medicine supplies dwindle on store shelves.  With such a monumental dump of this stuff, people have got to wonder “What good is this stuff?  What is it used for ... and why is there so much of it?”

Pollen bearing flowers of Pinus virginiana

Pollen is essential to the fertilization of flowers.  If the pollen from the male parts of a flower cannot reach the female parts, seeds and fruit will not develop and the plant will not be able to reproduce, reducing food for wildlife and for us.

Types of pollination include biotic pollination (by animals) and abiotic pollination; the most common form of abiotic pollination is anemophily which is pollination by wind.  Wind-pollinated flowers produce lighter (in weight) pollen, and they produce it in great quantities to ensure that at least some pollen grains can reach the other flowers.  So you see, all of that pollen flying around is just part of the natural process!

Southern red oak, Quercus falcata

 Look at these Oak and Carex flowers and notice that they don't really have any petals - they are not needed to attract insects and in fact petals might hinder the flower's ability to capture some of the pollen flying around.  On the oak picture to the left, the flowers are the structures dangling down; the stuff growing above the flowers are the new leaves emerging.

Carex laxiculmis

Only a small percentage of plants (as a percentage of total species) are wind-pollinated (one estimate that I found is 10%).  However, the wind-pollinated plants make up a larger percentage of the total plants when you consider that many trees are included plus the important agricultural grasses like wheat, corn and rice.

It should come as no surprise to those who are sensitive to pollen that plants which are wind pollinated include trees like pines and oaks (spring) and grasses (summer).  According to Atlanta Allergy – which maintains a daily count online – the most prevalent pollens right now are pine, oak and mulberry.  Despite the fact that pine pollen is so very visible – you can see it blowing off the trees – it does not cause as many allergic reactions as oak pollen.

Post oak, Quercus stellata

I found it amusing that Atlanta Allergy’s website has a picture of Goldenrod (Solidago sp.).  Goldenrod is often blamed for fall pollen allergies. However, Goldenrod’s pollen is too heavy to be blown about on the wind; it is an insect-pollinated plant.  Ragweed (Ambrosia sp.) is the culprit, and it's plain, green-colored flowers are often overlooked by those looking for a plant to blame!

Goldenrod (Solidago sp)

Pollen counts are reported on local news, weather sites and allergy websites like the Atlanta one I mentioned earlier.  These counts are meant to give people some warning about what to expect outside – although I suspect true sufferers are already aware of high pollen conditions.  The definition of pollen count is: the number of pollen grains in a standard volume of air over a twenty-four hour period.  This past week the counts were 3301 on Monday, 2293 on Tuesday and then 685 on Wednesday after we got thunderstorms on Tuesday night.  By Friday, the count was back up to 1032.  Any count over 90 is considered "High", with counts over 1500 being "Extremely high".  This same week in 2010 saw counts in excess of 5000 for several days.

So be careful out there if you're sensitive.  And even if you're not, don't stand still too long or you'll be covered in a fine yellow powder too!

Buddy after being outside

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