For today’s image in the series on plant colour, I am focusing on pigmentation in fruit. I would like to thank 3Point141@Flickr for today’s image of three different Mangifera indica (mangoes). From left to right, they are: the wild species, Mangifera indica ‘Rosigold’ and Mangifera indica ‘Cogshall’. Magnifera indica is native to the tropical forests of Asia, although it is now cultivated all over the tropical world. The highly-varied colour seen on the left and centre mangoes are caused by the accumulation of carotenoid pigments, mainly beta-carotene, in the epidermis. The deep red colours seen on ‘Cogshall’ are caused by the production of anthocyanins, and where the skins appear green is where the production of chloroplasts has persisted.
In nature, fruit colour is a trait that is often the product of co-evolution with the animals that eat the fruit and disperse the seed. Fruits that are more likely to be seen by their animal dispersers are more likely to be eaten, thus their seed is more likely to be spread. Different species of animals have different sensitivities to colour. Birds are highly sensitive to red and black colours, and studies have shown that the majority of fruits that are bird dispersed are black and/or red. Terrestrial mammals, including most primates, are highly perceptive of blues and greens (not reds), therefore larger fruits (such as the mango or the durian) are commonly green in their wild form.
Homo sapiens interaction with plant colour is not so different. As consumers of fruit with a keen eye for colour (in the visible spectrum), we have selected and created varieties of fruit with spectacular colour and spread them far and wide from their native ranges. In the process we have created vast expanses of new, ideal and competition-free habitat (i.e. orchards, farms and gardens) for these species. The mango is a prime example of such a species; it is thought to have been first cultivated outside its native range roughly 4,000 years ago in India. A more classic example, one that is used by both Michael Pollan and David Lee, is the apple. (see: Pollan’s The Botany of Desire or Lee’s Nature’s Palette).
Domestication of formerly wild species often produces a fruit that has a more saturated colour than its ancient relatives. This is certainly the case for Malus ‘Red Delicious’ (‘Red Delicious’ apple); in fact colour became such an important trait for ‘Red Delicious’ that quality of taste was sacrificed in the efforts to produce a skin with higher concentrations of the deep-red anthocyanins. It is interesting to think that the modern forms of food plants are still evolving (due to our selection) to attract consumers.