Transcript 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)
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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
Maple tree
seeds –
“helicopters”
Burs – animal
pollinated (poor
dog)
Notice the hooks on
the ends of the spikes
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.
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SPORE PRODUCERS

Algae

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Adapted for dispersal in water or air
Ferns and Mosses
Release spores into the air
 Because of this, forensics is most interested in these

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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
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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
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POLLEN AND SPORE IDENTIFICATION IN
SOLVING CRIMES CONTINUED
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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.
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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)
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