Distribution of the Post‐illumination CO2 Burst Among Grasses1

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Abstract
Evolution of CO2 upon transition of leaves from light to darkness was studied in 44 species of grasses, mostly from genera possessing the 4‐carbon dicarboxylic acid cycle of CO2 fixation. Attached leaves were placed in small acrylic plastic chambers and illuminated at 6,500‐7,000 ft‐c. Ten to 15 min after steady rates of photosynthesis had heen attained, the lights were turned off and CO2 evolution was measured for at least 5 min thereafter. Species that exhibited a post‐illumination CO2 burst (PIB) had a peak CO2 output at slightly less than 0.5 min after the lights were extinguished. Species lacking the PIB required about 1 min to reach the maximum respiration rate. The PIB was lacking in all species tested in the tribe Andropogoneae. Of 22 species in the tribe Paniceae, none possessed the PIB except those in the Panicum genus. All 10 Panieum species exhibited a burst. Five species in the tribe Chlorideae exhibited a PIB, as did Eragrostis curvula (Schrad.) Nees of the Eragrosteae tribe and Uniola paniculata L. of the Unioleae tribe.Well‐developed grana were observed in parenchyma sheath chloroplasts of the species that possessed the PIB. Species lacking the PIB also lacked well‐developed grana in parenchyma sheath chloroplasts. There was a fairly close association between the existence of a PIB and location of the parenchyma sheath chloroplasts against the centripetal walls of the sheath cells.

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