Download Survival Advantages (Purpose) of Plant Pigments

Survival Advantages (Purpose) of Plant Pigments
TANNINS
Tannins (brown color) act as a defense mechanism in plants against pathogens, herbivores and hostile environmental
conditions. Generally, tannins induce a negative response when consumed. These effects can be instantaneous like
astrigency or a bitter or unpleasant taste or can have a delayed response related to antinutritional/toxic effects.
The presence of tannins in food sources for monogastric animals (like humans), is generally viewed adversely, though
their contribution to red wines is certainly an exception. However, in ruminants (sheep, cows, goats), tannins can induce
beneficial effects. For example,
 Higher retention of nitrogen has been observed in sheep and cattle with low to moderate levels of tannins in forages.
In these cases, the lower apparent and true digestibility of nitrogen was compensated for by reduced urinary loss of
hydrogen,
 Moderate levels of tannins (less than 4% ) in forage legumes can have beneficial responses, resulting in higher growth
rates and milk yield. However, even in ruminants, levels of tannins exceeding 6% of the diet result in negatively
affect growth rates and milk yield.
Plant parts containing tannins include bark, wood, fruit, fruitpods, leaves, roots, and plant galls. Examples of plant
species used to obtain tannins for tanning purposes are wattle (Acacia sp.), oak (Quercus sp.), eucalyptus (Eucalyptus sp.),
birch (Betula sp.), willow (Salix caprea), pine (Pinus sp.), quebracho (Scinopsis balansae).
ANTHOCYANINS
The red coloration found in bromeliads, cranberries, carnivorous plants, etc., is caused by plant pigments known as
anthocyanins. Anthocyanins are members of a class of nearly universal, water-soluble, terrestrial plant pigments that can
be classified chemically as both flavonoid and phenolic. They are found in most land plants, with the exception of the
cacti and the group containing the beet. They contribute colors to flowers and other plant parts ranging from shades of red
through crimson and blue to purple, including yellow and colorless. (Every color but green has been recorded).
Anthocyanins apparently play a major role in two very different plant processes: for one, attracting insects for the
purpose of pollination. Advantage is made of the fact that the pigments absorb strongly in the UV (ultraviolet), visually
attracting insects but with light wavelengths that are invisible to humans. These pigments play a major role in plant
pollination - and in predation in carnivorous plants, attracting insects into the trap apparatus. (Anthocyanins play a very
versatile role in pollination, especially in the Bromeliaceae. Certain bromeliads turn a vivid red just before and during
pollination but soon revert to the original green color characteristic of the photosynthesis pigment, chlorophyll.
Anthocyanins are not a biochemical dead end but rather a dynamic signaling device that can be switched on when needed
by the plant to assist in pollination. They are then degraded by plant enzymes when no longer needed to attract pollinators
to flowers.)
In their second major role, anthocyanin-related pigments serve as a UV screen and are produced in response to
exposure of the plant to UV radiation, protecting the plant's DNA from damage by sunlight. (UV causes the paired strands
of genetic material in the DNA double helix to become cross-linked, preventing cell division and other vital cellular
processes like protein production).
And in a third, and no less significant role, anthocyanins serve as anti-feedents, their disagreeable taste serving to deter
predatory animals. In a related defense mechanism, anthocyanin production can be induced by ionizing radiation, which
can damage DNA as readily as UV can. Chemical messengers apparently signal the damage to DNA and induce
anthocyanin production in these plants.
Anthocyanines occur in all higher plants, mostly in flowers and fruits but also in leaves and roots. In these parts, they
are found predominantly in outer cell layers such as the epidermis. The amounts are relatively large: one kilogram of
blackberry for example contains approximately 1,15 gram, from red and black legumes it is possible to obtain between 20
mg per 1 gram. Rich in anthocyanines are for example chokeberry, cherry, aubergine, blue grape, Vaccinium and red
cabbage and also the Usambara-violet. Anthocyanins are less abundant in banana, asparagus, pea, fennel, pear and potato.
Most frequent in nature are the glycosides of cyanidine, delphinidine, malvidine, pelargonidine, peodine and petunidine.
Roughly 2 percent of all hydrocarbons fixated in photosynthesis are converted into flavonoids and their derivatives such
as the anthocyanines. This is no less than 109 tons per year.
CAROTENOIDS
Any of a group of yellow, orange, red, or brown pigments found in many living organisms, particularly in the chloroplasts
of plants. There are two main types, the carotenes and the xanthophylls. Both types are long-chain lipids (fats).
Carotenoids are a class of natural fat-soluble pigments found principally in plants, algae, and photosynthetic bacteria,
where they play a critical role in the photosynthetic process. They also occur in some non-photosynthetic bacteria, yeasts,
and molds, where they may carry out a protective function against damage by light and oxygen. Although animals appear
to be incapable of synthesizing carotenoids, many animals incorporate carotenoids from their diet. Within animals,
carotenoids provide bright coloration, serve as antioxidants, and can be a source for vitamin A activity
Chloroplasts also contain carotenoids. These are also pigments with colors ranging from red to yellow.
Carotenoids absorb light most strongly in the blue portion of the spectrum. They thus enable the chloroplast to trap are
larger fraction of the radiant energy falling on it. In animals, carotenoids are often the major pigments in flowers and
fruits. The red of a ripe tomato and the orange of a carrot are produced by their carotenoids.
In leaves, the carotenoids are usually masked by the chlorophylls. In the autumn, as the quantity of chlorophyll in the leaf
declines, the carotenoids become visible and produce the yellows and reds of autumn foliage.
Carotenoids are responsible for many of the red, orange, and yellow hues of plant leaves, fruits, roots, and flowers, as well
as the colors of some birds, insects, fish, and crustaceans. Some familiar examples of carotenoid coloration are the
oranges of carrots and citrus fruits, the reds of peppers and tomatoes, and the pinks of flamingoes and salmon Some 600
different carotenoids are known to occur, and new carotenoids continue to be identified.
In human beings, carotenoids can serve several important functions. The most widely studied and well-understood
nutritional role for carotenoids is their provitamin A activity. Deficiency of vitamin A is a major cause of premature death
in developing nations, particularly among children. Vitamin A, which has many vital systemic functions in humans, can
be produced within the body from certain carotenoids, notably beta-carotene.
Carotenoids also play an important potential role in human health by acting as biological antioxidants, protecting cells and
tissues from the damaging effects of free radicals and filtering out high-energy blue light (known to cause organ damage).
Other health benefits of carotenoids that may be related to their antioxidative potential include enhancement of immune
system function protection from sunburn and inhibition of the development of certain types of cancers.
CHLOROPHYLL
Chlorophyll is the molecule that absorbs sunlight and uses its energy to synthesize carbohydrates from CO2 and water.
This process is known as photosynthesis and is the basis for sustaining the life processes of all plants. Since animals and
humans obtain their food supply by eating plants, photosynthesis can also be said to be the energy source of our life.
The great abundance of chlorophyll in leaves and its occasional presence in other plant tissues, such as stems, causes these
plant parts to appear green. In some leaves, chlorophyll is masked by other pigments. In fall, chlorophyll wanes in the
leaves of trees, and other pigments predominate.
Two types of chlorophyll are found in plants and the green algae.
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
chlorophyll a (Blue Green)
chlorophyll b (Yellow Green)
Both chlorophylls absorb light most strongly in the red and violet parts of the spectrum. Green light is absorbed poorly.
Thus when white light shines on chlorophyll-containing structures like leaves, green light is transmitted and reflected and
the structures appear green.