Pollen and Spore Examination

1. Pollen and Spore Examination

2. 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.

3. 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

4. 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)

5. Angiosperms • Flowering plants • Produce seeds within an enclosed fruit • Parts of a flower:

6. 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

7. 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

8. Dandelion – wind pollinated Maple tree seeds – “helicopters” Burs – animal pollinated (poor dog) Notice the hooks on the ends of the spikes

9. 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.

10. 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

11. 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.

12. 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

13. 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)