Responses of CO2 Assimilation, Transpiration and Water Use Efficiency to Long-Term Elevated CO2 in Perennial C3 Xeric Loess Steppe Species

Two cultivars (Katy and Erhuacao) of apricot (Prunus armeniaca L.) were evaluated under open-field and solar-heated greenhouse conditions in northwest China, to determine the effect of photosynthetic photon flux density (PPFD), leaf temperature, and CO 2 concentration on the net photosynthetic rate (P N ). In greenhouse, Katy registered 28.3 μmol m -2 s -1 for compensation irradiance and 823 μmol m -2 s -1 for saturation irradiance, which were 73 and 117 % of those required by Erhuacao, respectively. The optimum temperatures for cvs. Katy and Erhuacao were 25 and 35 ºC in open-field and 22 and 30 ºC in greenhouse, respectively. At optimal temperatures, P N of the field-grown Katy was 16.5 μmol m -2 s -1 , 21 % less than for a greenhouse-grown apricot. Both cultivars responded positively to CO 2 concentrations below the CO 2 saturation concentration, whereas Katy exhibited greater P N (18 %) and higher carboxylation efficiency (91 %) than Erhuacao at optimal CO 2 concentration. Both cultivars exhibited greater photosynthesis in solar-heated greenhouses than in open-field, but Katy performed better than Erhuacao under greenhouse conditions.

Section: Discussionmentioning

confidence: 99%

Photosynthetic responses of apricot (Prunus armeniaca L.) to photosynthetic photon flux density, leaf temperature, and CO2 concentration

Wang¹,

Wang²,

Wang³

2007

“…Most species occurring in these habitats are typically drought tolerant monocots or dicots with reduced shoots and thick leaves, more or less considered as xerophytes. Beside the specific morphology due to the regulation of water balance, they developed mechanisms for protection against the harmful effects of excess absorbed photons at the level of both their leaf surfaces and chloroplasts so that the most efficient CO 2 assimilation could be performed (Kalapos 1994, Nagy et al 1994, Tuba et al 1996.…”

Section: Introductionmentioning

confidence: 99%

Carotenoid composition and photochemical activity of four sandy grassland species

Veres¹,

Tóth²,

Láposi³

et al. 2006

The photosynthetic pigments and photochemical efficiency of photosystem 2 (PS2) were studied in four constitutive species (Achillea millefolium L., Festuca pseudovina Hack. ex Wiesb., Potentilla arenaria Borkh., and Thymus degenianus Lyka) of a semiarid grassland in South-eastern Hungary. Every species displayed typical sun-adapted traits and substantial plasticity in the composition and functioning of the photosynthetic apparatus. The contents of chlorophylls (Chls) and carotenoids (Cars) on a dry matter basis declined from May to July, however, the amount of total Cars on a Chl basis increased. This increase was the largest in Potentilla (48 %) and the smallest in Achillea (14 %). The pool of xanthophylls (VAZ) was between 25 % and 45 % of the total Car content and was larger in July than in May. The content of β-carotene increased by July, but lutein content did not change significantly. The Chl fluorescence ratio F v /F m was reduced by 3-10 % at noon, reflecting the down-regulation of PS2 in the period of high irradiance and high temperature. The occurrence of minimal values of ΔF/F m ' showed close correlation to the de-epoxidation rate of violaxanthin. Hence in natural habitats these species developed a considerable capacity to dissipate excess excitation energy in the summer period in their photosynthetic apparatus through the xanthophyll cycle pool and a related photoprotective mechanism, when the photochemical utilization of photon energy was down-regulated.

“…The CO 2 exposure was carried out in the Global Climate Change and Plants Long-Term Experimental Ecological Research Station (Gödöllő) for 15 months using open top chambers (Tuba et al 1996). Monoliths (50×50×30 cm) were extracted from the grassland and transplanted into the open top chambers described by Tuba et al (1996).…”

Section: Methodsmentioning

confidence: 99%

“…An upward regulation of photosynthesis results in an increase of net photosynthetic rate, P N (Arp andDrake 1991, Chen et al 2000). The increased P N is usually accompanied by accumulation of soluble sugars in the upward acclimated plants (Tuba et al 1996). In the case of downward acclimation, accumulation of starch is often observed (e.g.…”

Section: Introductionmentioning

confidence: 99%

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Role of fructose-1,6-bisphosphatase, fructose phosphotransferase, and phosphofructokinase in saccharide metabolism of four C3 grassland species under elevated CO2

Nádas¹,

Balogh²,

Kiss³

et al. 2008

We studied the effects of 15-months of elevated (700 μmol mol -1 ) CO 2 concentration (EC) on the CO 2 assimilation rate, saccharide content, and the activity of key enzymes in the regulation of saccharide metabolism (glycolysis and gluconeogenesis) of four C 3 perennial temperate grassland species, the dicots Filipendula vulgaris and Salvia nemorosa and the monocots Festuca rupicola and Dactylis glomerata. The acclimation of photosynthesis to EC was downward in F. rupicola and D. glomerata whereas it was upward in F. vulgaris and S. nemorosa. At EC, F. rupicola and F. vulgaris leaves accumulated starch while soluble sugar contents were higher in F. vulgaris and D. glomerata. EC decreased pyrophosphate-D-fructose-6-phosphate l-phosphotransferase (PFP, EC 2.7.1.90) activity assayed with Fru-2,6-P 2 in F. vulgaris and D. glomerata and increased it in F. rupicola and S. nemorosa. Growth in EC decreased phosphofructokinase (PFK, EC 2.7.1.11) activity in all four species, the decrease being smallest in S. nemorosa and greatest in F. rupicola. With Fru-2,6-P 2 in the assay medium, EC increased the PFP/PFK ratio, except in F. vulgaris. Cytosolic fructose-1,6-bisphosphatase (Fru-1,6-P 2 ase, EC 3.1.3.11) was inhibited by EC, the effect being greatest in F. vulgaris and smallest in F. rupicola. Glucose-6-phosphate dehydrogenase (G6PDH EC 1.1.1.49) activity was decreased by growth EC in the four species. Activity ratios of Fru-1,6-P 2 ase to PFP and PFK suggest that EC may shift sugar metabolism towards glycolysis in the dicots.