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Bleached centers of leaf spot lesions on a diseased palm, caused by a plant-pathogenic fungus. These lesions are also surrounded by yellow halos.

Gramozone (herbicide) spray injury to this banana (Musa sp.) leaf resulted in the formation of non-expanding, bleached lesions.

Bleached leaf of the shade-loving plant (Piper methysticum), due to sunburn.

Definition

Bleaching is a plant disease symptom in which affected plant tissue turns white after disease developement.

Etymology. E. blęcan, from P.Gmc. *blaikos "white," from PIE *bhleg- "to gleam," root of blanche, blank, bleak and probably black. The connection seems to be "burning, blazing, shining, whiteness." That the same root yielded words for "black" and "white" is probably because both are colorless, and perhaps because both are associated with burning. Bleachers (1889, Amer.Eng.) were so-named because the boards were bleached by the sun.

Discussion

Bleaching is a common phtytoxic plant response to chemcial injury and is characterisitc of some fungal leaf spot diseases.