Effects of Elevated Temperature and CO2 on Photosynthesis and Rubisco Activity and Amount in Meadow Fescue Leaves

Heliö, R.; Hakala, Kaija; Mela, Timo

doi:10.1007/978-94-009-0173-5_1136

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“…Earlier investigations and reviews have reported increases in plant biomass of between 20% and 209% at CO, levels double those of the ambient level (Lawlor andMitchell 1991,Bowes 1993). Even though the photosynthetic rate of meadow fescue in the present experiment was 40-60% higher in elevated than in ambient C0 2 at both ambient and elevated temperatures (Heliö et al 1995), the increase in photosynthesis was not translated into an equal increase in biomass. Similar results have been reported previously with grasses, and the lack of a greater effect of elevated C0 2 on the yield has been attributed to low sink strength due to limited tiller formation capacity (Ryle et al 1992, Gay and Hauck 1994.…”

Section: Discussioncontrasting

confidence: 75%

The effects of prolonged exposure to elevated temperatures and elevated CO2 levels on the growth, yield and dry matter partitioning of field-sown meadow fescue

Hakala¹,

Mela²

1996

AFSci

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Field-sown meadow fescue (Festuca pratensis, cv. Kalevi) stands were exposed to elevated temperatures (+3°C) and elevated CO2, (700 ppm) levels in two experiments conducted in 1992-1993 (experiment 1) and in 1994-1995 (experiment 2). Total aboveground yield was, on average, 38% higher at elevated than at ambient temperatures. At ambient temperatures elevated CO2 increased the number of tillers by 63% in 1992, 24% in 1993, 90% in 1994 and 14% in 1995. At elevated temperatures, the increase in tiller number in elevated CO2 was seen only in the first growing seasons after sowing. The total yield in a growing season was about 10% higher in elevated CO2 in experiment 1. In experiment 2 the yield was more than 20% higher in elevated CO2 at elevated temperatures, whereas at ambient temperatures the rise in CO2 level had no effect on the yield; the root biomass, however, increased by more than 30%. In elevated CO2 at ambient temperatures the root biomass also increased in experiment I, but at elevated temperatures there was no consistent change. The soluble carbohydrate content of above-ground biomass was 5-48% higher in elevated CO2 at most of the measuring times during the growing season, but the nitrogen content did not show a clear decrease. The reasons for the lack of a marked increase in biomass in elevated CO2 despite a 40-60% increase in photosynthesis are discussed.

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