Citrus fruit originated in Southeast Asia but quickly became a staple of diets on all continents after it spread through trade during the Middle Ages. It is an ideal fruit for trade and consumption because of its unique structure and long shelf life.
The Facts
The genus citrus is part of the rue family, or rutaceae, and has 60 species of fruit, 10 of which are used in agriculture. The rue family consists of approximately 1,500 species and 150 genera, most of which are trees or shrubs.
Structure
Citrus fruits are easily damaged and, as a result, are intolerant to freezing. They have thorny twigs and often vary in size from shrubs to trees. Their foliage is evergreen and aromatic, and leaves are arranged alternatively on the twigs. Because citrus trees do not develop root hairs, they are highly dependent on mutual symbiosis with mycorrhizal (soil fungi) for their mineral nutrition.
Features
Citrus trees have small white or purple scented flowers that produce nectar. Ripe fruit is classified as a hesperidium (a type of berry), which has multiple seeds and is fleshy. The fruits typically have a leathery outer shell and a thick rind that is rich in aromatic oil glands that give it its particular smell.
According to culturesheet.org, citrus fruit range in diameter from 1.6 inches (lime) to more than 10 inches (pummelo). The shape is globose to ovoid, and the fleshy endocarp is divided into 10 to 14 sections containing pulp, juice and seeds (often referred to as "pips").
Function
Because many animals seek out citrus fruits for their flavor and often consume both the pulp and the seed, they have become the main source of seed dispersal, primarily through feces excretion.
Geography
Citrus originated in southern and southeastern Asia and are cultivated in many subtropical and tropical countries in the Americas, Africa and Asia for their edibility, and the sweet orange (citrus sinesis) is the most popular citrus species that is cultivated.
Tags: Structure Citrus