Plant Pigments

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Abstract

Interesting facts on Sunlight

Sunlight and Reflector

Pigments as Reflectors

Experiments

Summary

Spectrophotometer

Bibliography and Acknowledgement

There are 3 prime pigments found in plants:

Chlorophyll

Carotenoid

Phycobilins

Click on the underlined pigment names to know more about them.

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Chlorophyll

They are greenish in color.
Often found in leaves, stem cells of the plant. They are also found in sepals (green, leaf like structures that protect the bud prior to opening) of the flower.
The Chlorophyll makes the plant leaves look green as they do not absorb green color.
These pigments are located in the chloroplasts of the plant.
The energy of sunlight is captured by chlorophyll pigments to make food during the process of photosynthesis.
Equation for Photosynthesis, in a simple form would be:
Water + Nutrients in soil + Carbon dioxide + sunlight ----- > food for plants + Oxygen
There are 3 kinds of Chlorophyll:
- Chlorophyll "a": mainly responsible for photosynthesis. Found in all plants, algae and cyanobacteria carrying out photosynthesis.
- Chlorophyll "b": found only in green algae and in plants.
- Chlorophyll "c": found only in photosynthetic kind of organisms found in aquatic ecosystem e.g. Chromista and dinoflagellates.

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Carotenoid

They are generally red, orange or yellow pigments. Familiar carotene gives a carrot their color.

They do not mix completely in water.

They pass the absorbed sunlight energy to Chlorophyll, and so assist in the process of photosynthesis.

The pigment found in carrot is beta carotene.

Lycopene gives a red colour to a ripe tomato or to a red bell pepper.

Other fruits and veggies where these pigments found are: mango, melon, apricot, sweet potatoes, parsley and spinach… to name a few.

There are 2 kinds of caroteniods :

carotenes
xanthophylls

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Phycobilins

They dissolve in water.

They are found in specific kinds of plants: Rhodophyta or single cell bacteria: Cyanobacteria.

When the strong light falls on phycobilins they absorb light energy and release this energy by emitting light of shorter wave length, giving a fluorescent effect. Due to these property these pigments are used as a research tool.

The picture at the left shows the two classes of phycobilins.
The vial on the left contains the bluish pigment phycocyanin, extracted from the Cyanobacteria. Click on the underlined word to know more.
The vial on the right contains the reddish pigment phycoerythrin, extracted from red algae. Click on the underlined word to know more.
Image source: http://www.ucmp.berkeley.edu/glossary/gloss3/pigments.html

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Cyanobacteria

....(1)

....(2)

Cyanobacteria live in water and they can prepare their own food by photosynthesis. They are the oldest, largest and most important bacteria on the earth. e.g.

(1) Nostoc (Image source: http://www.ucmp.berkeley.edu/bacteria/nostoc.gif) and

(2)Oscillatoria (Image source:http://www.ucmp.berkeley.edu/bacteria/oscillatoria2.jpg )

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Red algae

(Image source: http://www.ucmp.berkeley.edu/protista/rhodophyta.html)

The red algae look red due to presence of pigment phycoerythrin. These pigments reflect red light and absorb blue light , which penetrates deep into the sea. Some red algae have very little of phycoerythrin so they look blue or greenish due to chlorophyll of some other pigments.

In Asia, Rhodophyta are important source of food. They are rich in Vitamins and protein contents, e.g. nori. They are easy to grow so Japan started growing them more then 300 years ago. Some red algae help in reef-building.

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