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C4 Photosynthesis in Smooth Pigweed

Published online by Cambridge University Press:  12 June 2017

David T. Patterson*
Affiliation:
Dep. Bot. Duke Univ., Durham, NC 27706

Abstract

The response of net photosynthetic rate to temperature and light, the rate of photorespiration, the compensation concentration for CO2, and the pathway of CO2 fixation in smooth pigweed (Amaranthus hybridus L.) were investigated using infrared gas analysis and 14CO2. Maximum net photosynthetic rates of whole shoots were 45 mg CO2 dm-2 hr-1 at 30 C and 7.8 klux. Intact whole shoots were not light saturated at 10 klux. The optimum temperature for net photosynthesis was between 30 C and 40 C. Photorespiration was low and the CO2 compensation concentration was 7 ppm. After a 5-sec exposure to 14CO2 in the light, label was detected in oxaloacetate, malate, and aspartate. It was concluded that smooth pigweed has the gross photosynthetic characteristics and CO2 fixation pathway typical of C4 or Hatch-Slack plants.

Type
Research Article
Copyright
Copyright © 1976 by the Weed Science Society of America 

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