Effect of Elevated CO2 on the Photosynthesis, Respiration and Growth of Perennial Ryegrass

• Published in: Journal of experimental botany 1992-06, Vol.43 (6), p.811-818
• Main Authors: RYLE, G. J. A., POWELL, C. E., TEWSON, VERONICA
• Format: Article
• Language: English
• Subjects: Agronomy. Soil science and plant productions; Animal, plant and microbial ecology; Applied ecology; Biological and medical sciences; development; Ecotoxicology, biological effects of pollution; Effects of pollution and side effects of pesticides on plants and fungi; elevated CO2; Fundamental and applied biological sciences. Psychology; growth; Lolium perenne; photosynthesis; respiration; ryegrass
• ISSN: 0022-0957; 1460-2431
• DOI: 10.1093/jxb/43.6.811

Single, seed-grown plants of ryegrass (Lolium perenne L. cv. Melle) were grown for 49 d from the early seedling stage in growth cabinets at a day/night temperature of 20/15 °C, with a 12 h photoperiod, and a CO2 concentration of either 340 or 680μI 1−1 CO2. Following complete acclimation to the environmental regimes, leaf and whole plant CO2 effluxes and influxes were measured using infra-red gas analysis techniques. Elevated CO2 increased rates of photosynthesis of young, fully expanded leaves by 35–46% and of whole plants by more than 50%. For both leaves and whole plants acclimation to 680 μI−1 CO2 reduced rates of photosynthesis in both CO2 regimes, compared with plants acclimated to 340μl l−1. There was no significant effect of CO2 regime on respiration rates of either leaves or whole plants, although leaves developed in elevated CO2 exhibited generally lower rates than those developed in 340μI I−1 CO2. Initially the seedling plants in elevated CO2 grew faster than their counterparts in 340μI I−1 CO2, but this effect quickly petered out and final plant weights differed by only c. 10%. Since the total area of expanded and unexpanded laminae was unaffected by CO2 regime, specific leaf area was persistently 13–40% lower in elevated CO2 while, similarly, root/shoot ratio was also reduced throughout the experiment. Elevated CO2 reduced tissue nitrogen contents of expanded leaves, but had no effect on the nitrogen contents of unexpanded leaves, sheaths or roots. The lack of a pronounced effect of elevated CO2 on plant growth was primarily due to the fact that CO2 concentration did not influence tiller (branch) numbers. In the absence of an effect on tiller numbers, any possible weight increment was restricted to the c. 2.5 leaves of each tiller. The reason for the lack of an effect on tillering is not known.