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Published in Crop Sci 8:441-445 (1968)
© 1968 Crop Science Society of America
677 S. Segoe Rd., Madison, WI 53711 USA
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Growth Response of Orchardgrass (Dactylis glomerata L.) to Different Light and Temperature Environments. II. Leaf Age and Photosynthetic Activity1

K. J. Treharne, J. P. Cooper and T. H. Taylor2

The variation in rate of apparent photosynthesis (PR) with leaf age in three populations of orchardgrass, grown in two different temperature environments, was investigated using a Warburg manometric technique. Fully expanded leaves maintained a high PR for 15 to 20 days but the rate rapidly declined thereafter. PR (oxygen evolution) per unit leaf area closely paralleled the synthesis and degradation of the chlorophyll pigments; PR per unit chlorophyll changed very little throughout the life of the leaf. These results were confirmed by the pattern of assimilation of C14O2 by leaves of different ages. The Portuguese ecotype had a significantly higher photosynthetic rate at 21 C than the cultivars ‘S.143’ and ‘Boone’ in both growth environments. Plants grown at 21 C day/13 C night temperatures had a significantly higher rate at 21 C than plants grown at 29 day/21 night temperatures, but when measured at 29 C plants grown in the higher temperature regime had a significantly higher rate of PR. The relative pattern of change of PR with leaf age was unaffected by the temperature at which the plants were grown.

Key Words: cocksfoot • chlorophyll • leaf area • cultivars • Warburg technique • C14O2 • photosynthetic rate • dactylis

1 Cooperative investigation of the University of Kentucky and the Welsh Plant Breeding Station. The work reported in this paper (67-3-127) was supported by a project of the Kentucky Agricultural Experiment Station and the Kentucky Research Foundation and is published with the approval of the Directors.

2 Research officers, Welsh Plant Breeding Station, Aberystwyth, Wales and Professor, Department of Agronomy, University of Kentucky, Lexington, Kentucky 40506.

Received for publication December 4, 1967.




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