Pollen and Spore Examination
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Transcript of Pollen and Spore Examination
POLLEN AND SPORE EXAMINATION
INTRODUCTION Pollen and spore information can be used to
determine the following: Was the body moved? Where did the crime take place? What season did the crime take place? Did the crime take place in the day or night?
Forensic Palynology – study of pollen and spore evidence to help solve a crime.
Pollen – reproductive structure that contains sperm from seed plants
Spore – reproductive structure that develops into an adult in algae, some plants, and fungi.
POLLEN PRODUCERS Pollen “fingerprint” – number and type of
pollen grains found in an area at a particular time of year.
Plant kingdom is divided into two groups based on how they reproduce: seeds or no seeds. Seeds: Gymnosperms (evergreens) and
Angiosperms (flowering plants) Nonseeds: Ferns, moss, liverworts, horsetails,
club mosses
GYMNOSPERMS Means “naked seed” – the seed is not
protected like they are in flowering plants Most numerous group of gymnosperms are
the conifers (evergreens) Produce their seeds within a cone. Here’s
how: Pollination occurs when pollen lands on a female
cone, grows and releases the sperm near the egg.
Once the egg is fertilized, a seed develops (containing an embryo)
ANGIOSPERMS Flowering plants Produce seeds within an enclosed fruit Parts of a flower:
TYPES OF POLLINATION Important in forensics in determining the
presence or absence of pollen in a place or on an object of a crime scene
Self pollination vs. Cross pollination Self – pollen transfer from anther to stigma
within the same flower. Cross – pollen transfer involving two distinct
plants Self pollinating plants has lower value because
they produce less pollen
METHODS OF POLLINATION Wind pollination – produce a lot of pollen (good
and bad) Good – well represented in the pollen profile of a
crime scene Bad – less effective in determining direct links Flowers are usually nonfragrant, lack color, small
Animal pollination – insects, birds, bats, monkeys Flowers are fragrant and “showy” Pollen grains are durable and can adhere to things Strong evidence of contact Produce less pollen
Dandelion – wind pollinated
Burs – animal pollinated (poor dog)
Notice the hooks on the ends of the spikes
Maple tree seeds – “helicopters”
METHODS OF POLLINATION CONTINUED Water pollination
Rarely preserved because it is composed of only a single layer cell wall made of cellulose
Pollen will decompose if removed from water Limited use, excepts for drowned victims…
contents of the lung can be emptied and analyzed.
SPORE PRODUCERS Algae
Adapted for dispersal in water or air Ferns and Mosses
Release spores into the air Because of this, forensics is most interested in these
Fungi Produce a large amount Mold, yeast, mushrooms Can be found practically everywhere
Bacteria (an exception) Some bacteria produce thick-walled, resistant spores
called endospores. Different in structure and aren’t used in reproduction Bacteria that causes anthrax and botulism are examples
SPORE DISPERSAL Wind Water Spore ejection Animal disperal (they eat the spore and
deposit it somewhere else in their feces)
Spore analysis has one advantage over pollen…it is possible to grow the organism and identify the species exactly.
POLLEN AND SPORE IDENTIFICATION IN SOLVING CRIMES Exine -- The hard outer layer of a pollen or
spore grain Has a unique and complex structure under the
microscope. Larger pollen grains can’t travel far (can only
drift with the wind ½ mile) (corn) Wind-dispersed pollen grains are simple,
have thin walls, easily preserved Animal-dispersed pollen grains are large,
sticky, highly ornamented, thick-walled and easily preserved
POLLEN AND SPORE IDENTIFICATION IN SOLVING CRIMES CONTINUED Identification of pollen and spore grains is
species specific Help determine season Help determine location If not native to the crime scene, body was
moved. Pollen and spores are difficult to eliminate by
the suspect because they are microscopic They are resistant to dehydration and
decomposition (can be found in sediment from millions of years ago)
Locard’s principle is easily applied (especially animal dispersed seeds)