Got milk? The secret life of laticifers.

Laticifers are specialized cells that occur in over 20 plant families in several unrelated angiosperm orders. Although laticifers are likely to be of polyphyletic origin, their occurrence is considered a morphological indicator of relatedness among species. The classification of laticifers is based on developmental patterns and overall morphology. The cytoplasmic latex exuded in response to damage often includes specialized metabolites, such as cardenolides, alkaloids and natural rubber. Laticifers provide an effective location to store defense metabolites, although not all latex-bearing plants accumulate bioactive natural products. Ecophysiological studies have shown that latex and its associated metabolites are vital for the defense of plants against insects. The anatomy, development and physiology of laticifers are discussed with a focus on evolutionary and ecological perspectives.