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Plant Physiology 76:1060-1064 (1984)
© 1984 American Society of Plant Biologists

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Articles

Detection of Chemicals Inhibiting Photorespiratory Senescence in a Large Scale Survival Chamber

David T. Manning, Andrew J. Campbell, Tsong Meng Chen1, N. E. Tolbert and E. Wayne Smith2

Union Carbide Agricultural Products Company Inc., P. O. Box 12014, Research Triangle Park, North Carolina 27709, Department of Biochemistry, Michigan State University, East Lansing, Michigan 48824

A large scale survival chamber was developed as a screen for detecting chemical treatments that extend the survival time of illuminated soybean seedlings at CO2 concentrations below the compensation point. In theory, extended survival should indicate potential for improved crop performance via decreased photorespiration and increased photosynthetic efficiency. An automated control system regulated CO2 concentrations, temperature and plant watering during a continuous CO2-removal photoperiod of 72 hours. An endogenously controlled circadian rhythm of net photosynthesis occurred throughout the continuous light treatment.

Spray applications of 3.49 millimolar 2-(4-chlorophenoxy)-2-methylpropanoic acid (CPMP) significantly decreased leaf chlorophyll loss, compared with the control, after 72 hours of subcompensation-point stress. Treatment with CPMP also consistently increased leaf chlorophyll per unit area under nonstress greenhouse conditions. These effects may be due to increases in specific leaf weight produced by CPMP although the compound did not consistently act as a height retardant. The compound, 3-butyl-2-hydroxy-4H-pyrido[1,2-a]pyrimidin-4-one (BHPP), inhibited senescence under low CO2 conditions but did not decrease leaf light transmission at ambient CO2 levels. The cytokinin N6-benzyladenine (BA) retarded low CO2 stress senescence although greening effects were not observed. Neither 2-hydroxy-3-butynoic acid (HBA) nor its butyl ester, inhibitors of glycolate oxidase, influenced low CO2 survival. Cyclohexanecarboxylic acid (CHCA) and sodium naphthenate had no effect upon subcompensation-point senescence.

Antisenescence effects of CPMP, BHPP, and BA do not appear to be directly attributable to effects upon the competing carbon paths of photosynthesis and photorespiration. Protection against low CO2 stress and increased chlorophyll synthesis under nonstress conditions may represent separate effects upon plastids by some of the compounds. This screen will identify compounds which inhibit photorespiratory senescence without decreasing the CO2 compensation point.

1 Present address: FMC Corporation, P. O. Box 8, Princeton, NJ 08540.

2 Present address: Smith and Associates, 1014 S. 11th Avenue, St. Charles, IL 60174.






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ASPB Publications PLANT PHYSIOLOGY THE PLANT CELL
Copyright © 1984 by the American Society of Plant Biologists