Also found in: Dictionary, Thesaurus, Medical, Acronyms, Idioms, Wikipedia.
a sugary exudate that forms primarily on the leaves of some hardwood trees and on spruce needles. It appears at night and in the morning. Its formation is increased by sharp fluctuations in temperature or humidity. Bees sometimes collect manna instead of nectar. Although manna is similar in composition to nectar, its sugar is not as easily digested by the bees. Honey made from this exudate is of a lower quality than floral honey, and, like honeydew honey, it can make wintering bees ill and lead to their death. Sometimes the word “manna” is used erroneously to designate the sweetish excretions of aphids and leafhoppers, as well as the sweet liquid exuded by the conidium generation of the fungus Claviceps purpurea (which causes ergot of grains).
in certain plants, the juice that exudes from damaged bark and from punctures made in the bark by insects; it congeals upon exposure to air. Manna is characteristic of flowering ash (Fraxinus ornus) and F. rotundifolia of the family Oleaceae, which are native to the Mediterranean region, and Tamarix mannifera of the family Tamaricaceae, which is native to South-west Asia and the Arabian Peninsula. It is a yellowish pellet that contains sugar and manitol. Manna was formerly used as a laxative.