Acclimation of Photosynthesis to Elevated CO2under Low-Nitrogen Nutrition Is Affected by the Capacity for Assimilate Utilization. Perennial Ryegrass under Free-Air CO2 Enrichment

Abstract

Acclimation of photosynthesis to elevated CO 2 has previously been shown to be more pronounced when N supply is poor. Is this a direct effect of N or an indirect effect of N by limiting the development of sinks for photoassimilate? This question was tested by growing a perennial ryegrass (Lolium perenne) in the field under elevated (60 Pa) and current (36 Pa) partial pressures of CO 2 (pCO2) at low and high levels of N fertilization. Cutting of this herbage crop at 4-to 8-week intervals removed about 80% of the canopy, therefore decreasing the ratio of photosynthetic area to sinks for photoassimilate. Leaf photosynthesis, in vivo carboxylation capacity, carbohydrate, N, ribulose-1,5-bisphosphate carboxylase/ oxygenase, sedoheptulose-1,7-bisphosphatase, and chloroplastic fructose-1,6-bisphosphatase levels were determined for mature lamina during two consecutive summers. Just before the cut, when the canopy was relatively large, growth at elevated pCO 2 and low N resulted in significant decreases in carboxylation capacity and the amount of ribulose-1,5-bisphosphate carboxylase/oxygenase protein. In high N there were no significant decreases in carboxylation capacity or proteins, but chloroplastic fructose-1,6-bisphosphatase protein levels increased significantly. Elevated pCO 2 resulted in a marked and significant increase in leaf carbohydrate content at low N, but had no effect at high N. This acclimation at low N was absent after the harvest, when the canopy size was small. These results suggest that acclimation under low N is caused by limitation of sink development rather than being a direct effect of N supply on photosynthesis.Acclimation of photosynthesis to growth in elevated pCO 2 has frequently been shown to be more marked under suboptimal N supply (Drake et al., 1997). Growth in low N limits the development of the shoot and root, and therefore the capacity for utilization of the additional photoassimilate formed under elevated pCO 2 . Low N may therefore exacerbate the accumulation of carbohydrate observed under elevated pCO 2 (Webber et al., 1994; Drake et al., 1997). Alternatively, nitrate accumulation within the plant can alter gene expression (Paul and Driscoll, 1997; Scheible et al., 1997), and could lead to different patterns of acclimation to elevated pCO 2 depending on the N supply. Wheat grown under limiting N supply showed a greater loss of Rubisco in response to elevated pCO 2 than plants grown with free access to N (Rogers et al., 1996). This appeared to result from an accumulation of soluble carbohydrates in leaves, resulting in sugar repression of the expression of the genes encoding the LSU and the small subunit of Rubisco (rbcL and rbcS, respectively) (Stitt, 1991; Sheen, 1994; Krapp and Stitt, 1995; Koch, 1996).Most studies of acclimation to elevated pCO 2 under different levels of N nutrition have been conducted in containers in the laboratory. However, Arp (1991) demonstrated that such restriction of rooting volume might accentuate acclimation to elevated pCO 2 . In addition to the p...

The nitrate and ammonium nitrate supply have a major influence on the response of photosynthesis, carbon metabolism, nitrogen metabolism and growth to elevated carbon dioxide in tobacco

“…In a recent free-air CO 2 enrichment study of ryegrass, Rogers et al (1998) also observed that elevated [CO 2 ] leads to a marked decrease of Rubisco large subunit when the nitrogen supply was restricted, but not when more nitrogen fertlizer was supplied. In ryegrass, the decrease of Rubisco was associated with an increase of the leaf-sugar level, and both reverted after cutting to increase the sink-source ratio (Rogers et al 1998).…”

“…In ryegrass, the decrease of Rubisco was associated with an increase of the leaf-sugar level, and both reverted after cutting to increase the sink-source ratio (Rogers et al 1998). The different response of sugars in limiting nitrogen in rye grass and tobacco might be due to the larger amounts of starch synthesized in the latter.…”

“…Acclimation is accompanied by alterations in gas exchange characteristics that are indicative of a decreased capacity for carboxylation (Stitt 1991;Sage 1994) and by a decrease of Rubisco activity in tobacco Sicher, Kremer & Rodermel 1994), tomato (Van Oosten, Wilkins & Besford 1994), Arabidopsis (Cheng, Moore & Seeman 1998), Scirpus olneyi (Jacob et al 1995), wheat (Nie et al 1995;Rogers et al 1996b;Sicher & Bunce 1997), barley (Sicher & Bunce 1997), rice (Vu et al 1997), Panicum laxum (Ghannoum et al 1997), loblolly pine (Tissue, Thomas & Strain 1993, 1997, cherry (Atkinson et al (1997), oak (George, Gerant & Dizengremel 1996) and cork oak (Faria et al 1996). Acclimation of photosynthetic rate (Wong 1979;Oberbauer et al 1986;Tissue et al 1993;Pettersson et al 1993;Sage 1994;Pettersson & MacDonald 1994;El-Kohen & Mousseau 1994;Miglietta, Giuntoli & Bindi 1996;Rogers et al 1998) and the decrease of Rubisco activity in elevated [CO 2 ] (Wong 1979;Tissue et al 1993;Delgrado et al 1994;Webber, Nie & Long 1994;Riviere-Rolland, Contard & Betsche 1996;Rogers et al 1996a) is more marked in nitrogen-limited than in nitrogen-sufficient plants.…”

Nitrogen fertiliser rate affects the frequency of nitrate-dissimilating Pseudomonas spp. in the rhizosphere of Lolium perenne grown under elevated pCO2 (Swiss FACE)

“…The influence of elevated pCO 2 on NDP frequency was not as strong as hypothesised. It is possible that the 9 y exposure to elevated pCO 2 resulted in an acclimation of the soil-plant system to function under these conditions (Rogers et al, 1998). Previous experiments have shown that the type of nitrate reductase enzyme carried by the NDP differed under ambient and elevated pCO 2 (Roussel-Delif et al, in press), suggesting that NDP populations may respond to elevated pCO 2 by altering both the enzyme type, and probably its activity.…”

Influence of an Elevated Atmospheric CO 2 Content on Soil and Rhizosphere Bacterial Communities Beneath Lolium perenne and Trifolium repens under Field Conditions

“…Consequently, the main influence is thought to occur by the intermediation of the plants. Indeed, because of the competitive inhibition by O 2 of the ribulose-1,5-bisphosphate carboxylase, which is responsible for CO 2 fixation during photosynthesis [7], the C 3 plant photosynthetic rate increases under a CO 2 -enriched atmosphere [28,47,51]. An increased root biomass under CO 2 enrichment has been shown by several authors [25,30,47,52,53].…”