Any wrinkling in lettuce is a result of oxygen deficiency

• Bluish colouration of skin due to poor circulation
• A bluish discoloration of the skin and mucous membranes
• A sign that oxygen in the blood is dangerously diminished (as in carbon monoxide poisoning)

WordNet Word definitions in WordNet
n. a bluish discoloration of the skin and mucous membranes; a sign that oxygen in the blood is dangerously diminished (as in carbon monoxide poisoning)

The Collaborative International Dictionary Word definitions in The Collaborative International Dictionary
Cyanosis \Cy`a*no"sis\ (s?`?-n?"s?s), n. [NL. See Cyanic .] (Med.) A condition in which, from insufficient a[eum]ration of the blood, the surface of the body becomes blue. See Cyanopathy .

Douglas Harper's Etymology Dictionary Word definitions in Douglas Harper's Etymology Dictionary
"blue disease," the "blue jaundice" of the ancients, 1820, Medical Latin, from Greek kyanosis , from kyanos "dark blue color" (see cyan ) + -osis .

Wiktionary Word definitions in Wiktionary
n. (context pathology English) A blue discolouration of the skin due to the circulation of blood low in oxygen.

Wikipedia Word definitions in Wikipedia
Cyanosis is the appearance of a blue or purple coloration of the skin or mucous membranes due to the tissues near the skin surface having low oxygen saturation. Based on Lundsgaard and Van Slyke's work, it is classically described as occurring if 5.0 g/dL ...