The Biological Cycle
Truffles must grow in symbiosis with shrubs or trees in order to produce the precious sporocarp; the exchanging of substances between the two partners (the truffle and the plant) takes place at the roots, in special formations known as mycorrhizae, which are structured differently for each species. The mycorrhizae are a sort of sleeve, formed by several layers of small septate tubes called hyphae; these twist themselves around the apexes of the terminal rootlets of the tree, forming a reticulum - or netlike structure - by working their way in-between the first layers of root-cells. The plant provides the fungus with various substances by way of this association, receiving mainly water and mineral salts in return. A large number of these hyphae - known collectively as mycelium - branch out from the reticulum into the ground in search of nutritive substances.
Later, when all the environmental conditions are right, some of the hyphae intertwine to create the fruiting body in which the spores differentiate. The spores then germinate to form a new mycelium, which will itself create new mycorrhizae by combining with the young apexes of the roots. Unlike the fruiting bodies of epigean fungi, which grow above the ground, hypogean - or underground - fungi are not able to exploit air currents to scatter their spore. Evolution has therefore equipped them with a strong smell that becomes noticeable when the spores ripen, attracting insects and mammals which feed on the truffle and scatter its spores.
