Live Colours

LIVE COLOURS

Looking around me, I find thousands of colours in nature. Various shades of green leaves, yellow flowers, multi-coloured butterflies, fishes etc! None of the shades in my colouring-set can give the exact hue of the flowers in the garden. So how does nature bring about such a variety (hundreds of shades in red, blue, green etc) of never fading, live colours??

The answer lies in the tiny cells (typical animal cell: 10µm to 30µm, plant cell: 10µm to 100µm) which make up all living organisms. Body of every living organism has its share of colour or pigment producing cells called ‘chromatophores’. So first of all what is a ‘colour’, it is nothing but light of a particular wavelength, which falls within the visible spectrum of sunlight (390nm to 780nm). Pigments are compounds which selectively absorb certain wavelengths of light and reflect the rest, which our eyes can perceive as specific colour of the object.

The most common plant pigment is ‘chlorophyll’, which is synthesised within special organelles inside a plant cell called ‘chloroplast’. It is chlorophyll which impart green colour (by strong absorption of red and violet colours of incident sunlight) to the leaves and are tools for trapping solar energy during photosynthesis. Other common plant pigments are carotenoids which give yellow or orange colour (eg: xanthophyll, they act as antioxidants and also assist in photosynthesis by absorption of blue light not easily absorbed by chlorophyll). Anthocyanin gives purple blue colour, seen in black grapes, and has nutritional benefits. Among animal cells, melanin is the pigment responsible for colours of skin (among human races), hair, iris of the eye, feathers of birds etc. Melanin is dark brown or black in colour, but depending on its chemical state can impart other colours like red (pheomelanin). Melanin producing cells are called ‘melanocytes’. It absorbs ultra violet (UV) rays (280nm to 400nm) and protects the cell from UV induced damage. Greying of hair, albinisms etc are result of reduction in melanin synthesis (find out more about albinism!). Thus colours not just make our world look alive, but are essential for the living beings to carry out various biological processes.

Coming to occurance of numerous shades, it happens due to different combinations in which pigments are produced. Further differences in concentration leads to absorption of different regions of visible spectra and thus reflection of rest, giving rise to very subtle differences in colours perceived by our eyes!

Sneha