Plants & Human Affairs (BIOL106)  -  Stephen G. Saupe, Ph.D.; Biology Department, College of St. Benedict/St. John's University, Collegeville, MN 56321; ssaupe@csbsju.edu; http://www.employees.csbsju.edu/ssaupe

Pollen Analysis

Objectives:  Upon completion of this lab you should be able to:

1. recognize some common pollen grains
2. describe how pollen counts are made
3. describe the characteristics of plants that are wind-pollinated
4. prepare a standard pollen count

Introduction: 
    Airborne pollen, which is the major cause of hay fever, is shed from wind-pollinated plants.  The flowers of these plants are well adapted for this mode of pollination.  Among their characteristics, wind pollinated plants typically:

• have small (highly reduced) petals and sepals (perianth) since these structures are primarily to attract a pollinator
• have little color or odor (again, these features are designed to attract pollinators)
• produce copious amounts of pollen to insure that at least some pollen finds its way to the stigma
• have feathery, antenna-like stigmas to catch the pollen

    As a result, wind-pollinated plants have inconspicuous flowers that are often not observed by the casual botanist.  Among the common wind-pollinated plants are oaks, birches, maples, pines, grasses, ragweed, sage, pigweed, and lamb's quarters.

    The amount of pollen in air can be measured a variety of ways.  At the CSB/SJU Center for Pollen Studies we use a Rotorod sampler.  This is an impact sampler that has two grease-coated rods that spin around and catch pollen.  The pollen grains on the rods are then identified and counted.  Based on the area of the rods, the time the rods are left in the field, and the speed at which the rods are spun, we can calculate the pollen per cubic meter of air.  In this lab we will analyze a pollen sample collected by the Rotorod sampler.  For more information about pollen sampling, check out the CSB/SJU Center for Pollen Studies web site and the links cited, especially articles from Multidata Inc.

Analysis of a Rotorod Pollen Sample.

1. Place a tiny drop of pine pollen stained with Calberla's solution on a standard microscope slide.  Put on a cover slip.  Find a single grain.  On a clean, separate sheet of paper, write your name on the top.  On the bottom of the page, write Fig 1.  Pine pollen (400x).  Then, sketch 2 or 3 grains showing various views.
2. Place a tiny drop of ragweed pollen stained with Calberla's solution on another slide.  Then on the back of the page, sketch several ragweed grains.  Give this figure an appropriate label at the bottom of the page.
3. Repeat with a pollen sample from a grass.  Label this figure appropriately.
4. Obtain a rod from the Rotorod sampler.  You will be given a rod that was previously collected.  Record the duty cycle and sample time on your data sheet in Table 1.  You will not be told the date the sample was made.
5. Mount the rod in a slide holder, greased side up, and then put two drops of Calberla's stain on the rod. 
6. Put on a coverslip and then analyze your slide under the microscope. 
7. Focus on the slide and look for pollen grains.  Like the reference samples we examined, pollen grains will stain reddish.  (Although we will not study these, as you scan your slide for pollen, notice the numerous and varied mold spores. And, be on the lookout for algae which typically appear as clumps of green balls)
8. Now count the number of pollen grains on your slide.  To begin, move the stage so that the field of view is in one corner of the slide.  Then, sweep across the slide counting each grain that you see.  Put a tick mark in the left column of Table 2 to keep track of your pollen.  When you reach the end of coverslip, move the field of view down and sweep back in the opposite direction.  Repeat until you count the entire slide.
    
9. Calculate the number of grains per cubic meter of air using the following equation:

where:  3.12 m³ = the calculated volume of air Rotorod Sampler measures in standard conditions (1440 minutes, 10% Duty Cycle and 100% of rod counted)

Last updated:  07/29/2005 / � Copyright  by SG Saupe