Colour means different things to different people and the perception of colour depends on individuals. Naturally, the female folks tend to be more colour sensitive than the male folks, I could be wrong though. First, there is this idea about primary colours (red, yellow and blue, hope I'm right) and then secondary colours which happen to be different combinations of primary colours. At another level, there is what is generally known as rainbow colours consisting of red, orange, yellow, green, blue, indigo and the violet colour.
All these known colours aside, there are several other colours I have heard ladies talk about, especially when there is an occasion or celebration to attend. I have heard colours such as fuschia red, burgundy black, creamy blue, burnt yellow and all sorts of ridiculous colour taxonomy. Well, that is not the subject of today's discussion.
Colours tend to speak even though they do not have a voice. Sociologists will call this kind of communication a non-verbal communication. If I will not too hasty, I believe virtually everyone understands that red could mean danger, blue signifies love (though people wear red on valentine's day?) and of course, green signifies life.
Why does green signifies life?
I want to believe each colour symbols has a story behind it. The green colour symbolizing life has to do with the general idea that life would not have existed without plants and vegetation which happen to be green in colour. Even deserts have plants in them, at least I know of desert cacti that are well adapted to very low water and high insolation nature of the desert.
Plants derived their green colours from the component of their cells known as plastids, a name that was coined by Ernest Henckel in 1866. Plastids generally developed from precursors known as proplastids. The proplastids have the ability to divide, differentiate and give rise to various forms of plastids namely:
- leucoplasts
- chromoplasts; and
- chloroplasts
Leucoplasts are colourless/whitish plastids found mainly in the storage organs of plants such as fruits, seeds, tubers etc. They could take different shapes such as oval, rod-like or they could as well occur in filaments. There are different types of leucoplast in nature - amyloplasts found in potato tubers, rice, wheat etc. which specializes in the storage of starch grains, aleuronoplast found mostly in maize grains which specializes in the storage of proteins and elaioplast found in the endosperm of castor oil which specializes in the storage of lipids.
Chromoplasts are plastids that are coloured but differ in some ways from chloroplasts. They contain carotenoids mainly which is a fat-soluble yellow, red or orange pigments. Chromoplasts gives the attractive colour to petals of flowers to attract pollinators and to fruits to attract biological agents of dispersal. Leucoplasts or chloroplasts serve as the precursor in the synthesis of chromoplasts. Lycopin develops from chloroplasts thereby making fruits such as that of tomato to turn from green to red while leucoplasts in carrots are replaced by lycopene to give carrots its characteristic colour.
The chloroplasts are plastids that are mainly green in colour, a characteristic imposed by the presence of chlorophyll. It is an important organelle of the green plants and perhaps more important for all aerobic organisms, including humans. This due to the fact that chloroplast happens to be the site where the conversion of CO2 and H2O to carbohydrate and oxygen gas, the latter being used for respiration in aerobic organisms.
The chloroplast is present in all green tissues of plants, though especially concentrated in the parenchyma cells of the tissues of plant's leaves and gives the luscious green colour to vegetations. It is a double membrane organelle of the plant cell of about 1–2 μm in thickness and 5–7 μm in diameter. Between the outer and inner membrane of the chloroplast is the inter-membrane space and the inner membrane is extensively folded and associated with coin-like discs known as thylakoids or thylakoid membrane. These thylakoids are arranged in stacks known as grana, especially in most higher plants and they are connected by an extension that runs from one granum to Granum, the stroma lamellae. The core of the organelle is the stroma which is a matrix containing a mixture of enzymes, starch granules and some DNA/RNA strands that constitute the genome of the organelle itself.
What makes the chloroplast green: The chlorophyll
The green pigment that constitutes chlorophyll was first isolated and given its nomenclature by Joseph Bienaimé Caventou and Pierre Joseph Pelletier in the year 1817. The chlorophyll molecules are arranged in the photosystem of the thylakoid membranes of the chloroplast. It is an important pigment necessary for photosynthesis and apart from chloroplasts of algae and higher plants, it is also found in cyanobacteria. The molecule of the chloroplast is known to be a poor absorber of the green component of white light. It reflects and produces the characteristic green colour in the various chlorophyll-containing tissues in nature. It specializes in absorbing light in the blue and red portion of the electromagnetic spectrum.
There are basically two types of chlorophyll in green plants - chlorophyll A and chlophyll B. Other types of chlorophyll are found in nature in algae, such as chlorophyll C in diatoms or brown algae, chlorophyll D in red algae, chlorophyll E and chlorophyll F as found in several lower organisms. The general structure of chlorophyll is made up of central magnessium atom within a nitrogen containing porphyrin ring. A long carbon-hydrogen side chain otherwise known as phytol chain is attached to the the porphyrin ring. The differrent chlorophyll differs only due to minor modification of the side chain. Interestingly, the structure of chlorophyll and that of haemoglobin in the red blood cells of mammals and vertebrates share remarkable resemblance.
Green signifies energy
Without the green chlorophyll content of plants, there is no doubt that life would either not have existed or perhaps there would have been an alternative ways to get energy to drive various processes that sustain life. The energy from the sun constitutes the primary source of energy for all living organisms. This is made possible by the chlorophyll's capacity to absorb energy from the sun and the chloroplast's ability to convert this energy into chemical energy that is then locked up in the various tissues of the plant.
Organism that consume these energy-locked plants, through their own life processes such as respiration, would be able to unlock the energy in the plant and use it to drive the life-sustaining processes in their body. Hence, the green plants are generally referred to as primary producers while organisms that feed on them are known as consumers. The energy trapped by the chlorophyll moves through the various level of the food chain and keeps the ecosystem alive.
Thank you all for reading.
References
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