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Formation of chloroplast protrusions and catalase activity in alpine Ranunculus glacialis under elevated temperature and different CO2/O2 ratios.

Buchner O, Moser T, Karadar M, Roach T, Kranner I, Holzinger A - Protoplasma (2015)

Bottom Line: We investigated in the alpine plant Ranunculus glacialis L. treated under various CO2 concentrations if CP formation is related to photorespiration, specifically focusing on hydrogen peroxide (H2O2) metabolism.The same relationship was found for CAT activity, which decreased from 34.7 nkat mg(-1) DW under low CO2 to 18.4 nkat mg(-1) DW under high CO2, while APX activity did not change significantly.In summary, CP formation and CAT activity are significantly increased under conditions that favour photorespiration, while in darkness or at high CO2 concentration under light, CP formation is significantly lower, providing evidence for an association between CPs and photorespiration.

View Article: PubMed Central - PubMed

Affiliation: Institute of Botany, Functional Plant Biology, University of Innsbruck, Sternwartestrasse 15, 6020, Innsbruck, Austria. Othmar.Buchner@uibk.ac.at.

ABSTRACT
Chloroplast protrusions (CPs) have frequently been observed in plants, but their significance to plant metabolism remains largely unknown. We investigated in the alpine plant Ranunculus glacialis L. treated under various CO2 concentrations if CP formation is related to photorespiration, specifically focusing on hydrogen peroxide (H2O2) metabolism. Immediately after exposure to different CO2 concentrations, the formation of CPs in leaf mesophyll cells was assessed and correlated to catalase (CAT) and ascorbate peroxidase (APX) activities. Under natural irradiation, the relative proportion of chloroplasts with protrusions (rCP) was highest (58.7 %) after exposure to low CO2 (38 ppm) and was lowest (3.0 %) at high CO2 (10,000 ppm). The same relationship was found for CAT activity, which decreased from 34.7 nkat mg(-1) DW under low CO2 to 18.4 nkat mg(-1) DW under high CO2, while APX activity did not change significantly. When exposed to natural CO2 concentration (380 ppm) in darkness, CP formation was significantly lower (18.2 %) compared to natural solar irradiation (41.3 %). In summary, CP formation and CAT activity are significantly increased under conditions that favour photorespiration, while in darkness or at high CO2 concentration under light, CP formation is significantly lower, providing evidence for an association between CPs and photorespiration.

No MeSH data available.


Related in: MedlinePlus

Experimental set-up for determining the effect of different CO2 concentrations on the formation of chloroplast protrusions (CPs) in leaves of R. glacialis. On 15 August 2013, a potted plants (n = 5) were placed inside cylindrical exposure chambers made of highly transparent Plexiglas and exposed to natural solar irradiation with the exception of (3) which was kept in darkness. During the 2.5 h exposure, air with different CO2 concentrations was streamed through the chambers. 1 10,000 ppm, 2 38 ppm, while 3 and 4 had normal CO2 concentration (380 ppm). b Mean leaf temperature (red line; n = 16) and photosynthetically active photon flux density (PPFD; black line) for the whole duration of the exposure. c Typical CPs in leaf mesophyll of R. glacialis immediately after the 2.5 h exposure at 38 ppm CO2 and at natural solar irradiation. The DIC microscopy image clearly shows CPs as broad and beak-like, stroma-filled extensions of the chloroplast envelope. d Schematic drawing of c; light blue areas indicate CPs. Horizontal bars 2 μm
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Fig1: Experimental set-up for determining the effect of different CO2 concentrations on the formation of chloroplast protrusions (CPs) in leaves of R. glacialis. On 15 August 2013, a potted plants (n = 5) were placed inside cylindrical exposure chambers made of highly transparent Plexiglas and exposed to natural solar irradiation with the exception of (3) which was kept in darkness. During the 2.5 h exposure, air with different CO2 concentrations was streamed through the chambers. 1 10,000 ppm, 2 38 ppm, while 3 and 4 had normal CO2 concentration (380 ppm). b Mean leaf temperature (red line; n = 16) and photosynthetically active photon flux density (PPFD; black line) for the whole duration of the exposure. c Typical CPs in leaf mesophyll of R. glacialis immediately after the 2.5 h exposure at 38 ppm CO2 and at natural solar irradiation. The DIC microscopy image clearly shows CPs as broad and beak-like, stroma-filled extensions of the chloroplast envelope. d Schematic drawing of c; light blue areas indicate CPs. Horizontal bars 2 μm

Mentions: To determine the impact of different CO2 concentrations on CP formation under natural solar irradiation or darkness, four experimental conditions (ECs) were applied for 2.5 h. The CO2 concentrations in EC1 and EC2 were controlled to stimulate and prevent photorespiration, respectively. EC1 and EC2 comprised CO2 concentrations of 38 and 10,000 ppm, respectively, under natural solar irradiation. EC3 and EC4 comprised atmospheric CO2 concentrations (380 ppm) either kept in the dark using metal cylinders or under natural solar irradiation, respectively (Fig. 1a). Environmental conditions were maintained using highly transparent Plexiglas cylinders (200 × 350 mm, XT 29070, Röhm, Darmstadt, Germany; spectral transmittance: see Suppl. 1). Each cylinder contained five individuals of R. glacialis that were provided with variable CO2 concentrations (Airliquide, Schwechat, Austria) at a constant flow rate of 4000 ml min−1. Leaf temperatures of four individual leaves in EC1, EC2 and EC4 were monitored every 5 s by software-controlled heat tolerance testing system (HTTS; Buchner et al. 2013) to enable regulating EC3 to the same temperature of EC1, EC2 and EC4.Fig. 1


Formation of chloroplast protrusions and catalase activity in alpine Ranunculus glacialis under elevated temperature and different CO2/O2 ratios.

Buchner O, Moser T, Karadar M, Roach T, Kranner I, Holzinger A - Protoplasma (2015)

Experimental set-up for determining the effect of different CO2 concentrations on the formation of chloroplast protrusions (CPs) in leaves of R. glacialis. On 15 August 2013, a potted plants (n = 5) were placed inside cylindrical exposure chambers made of highly transparent Plexiglas and exposed to natural solar irradiation with the exception of (3) which was kept in darkness. During the 2.5 h exposure, air with different CO2 concentrations was streamed through the chambers. 1 10,000 ppm, 2 38 ppm, while 3 and 4 had normal CO2 concentration (380 ppm). b Mean leaf temperature (red line; n = 16) and photosynthetically active photon flux density (PPFD; black line) for the whole duration of the exposure. c Typical CPs in leaf mesophyll of R. glacialis immediately after the 2.5 h exposure at 38 ppm CO2 and at natural solar irradiation. The DIC microscopy image clearly shows CPs as broad and beak-like, stroma-filled extensions of the chloroplast envelope. d Schematic drawing of c; light blue areas indicate CPs. Horizontal bars 2 μm
© Copyright Policy - OpenAccess
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC4628086&req=5

Fig1: Experimental set-up for determining the effect of different CO2 concentrations on the formation of chloroplast protrusions (CPs) in leaves of R. glacialis. On 15 August 2013, a potted plants (n = 5) were placed inside cylindrical exposure chambers made of highly transparent Plexiglas and exposed to natural solar irradiation with the exception of (3) which was kept in darkness. During the 2.5 h exposure, air with different CO2 concentrations was streamed through the chambers. 1 10,000 ppm, 2 38 ppm, while 3 and 4 had normal CO2 concentration (380 ppm). b Mean leaf temperature (red line; n = 16) and photosynthetically active photon flux density (PPFD; black line) for the whole duration of the exposure. c Typical CPs in leaf mesophyll of R. glacialis immediately after the 2.5 h exposure at 38 ppm CO2 and at natural solar irradiation. The DIC microscopy image clearly shows CPs as broad and beak-like, stroma-filled extensions of the chloroplast envelope. d Schematic drawing of c; light blue areas indicate CPs. Horizontal bars 2 μm
Mentions: To determine the impact of different CO2 concentrations on CP formation under natural solar irradiation or darkness, four experimental conditions (ECs) were applied for 2.5 h. The CO2 concentrations in EC1 and EC2 were controlled to stimulate and prevent photorespiration, respectively. EC1 and EC2 comprised CO2 concentrations of 38 and 10,000 ppm, respectively, under natural solar irradiation. EC3 and EC4 comprised atmospheric CO2 concentrations (380 ppm) either kept in the dark using metal cylinders or under natural solar irradiation, respectively (Fig. 1a). Environmental conditions were maintained using highly transparent Plexiglas cylinders (200 × 350 mm, XT 29070, Röhm, Darmstadt, Germany; spectral transmittance: see Suppl. 1). Each cylinder contained five individuals of R. glacialis that were provided with variable CO2 concentrations (Airliquide, Schwechat, Austria) at a constant flow rate of 4000 ml min−1. Leaf temperatures of four individual leaves in EC1, EC2 and EC4 were monitored every 5 s by software-controlled heat tolerance testing system (HTTS; Buchner et al. 2013) to enable regulating EC3 to the same temperature of EC1, EC2 and EC4.Fig. 1

Bottom Line: We investigated in the alpine plant Ranunculus glacialis L. treated under various CO2 concentrations if CP formation is related to photorespiration, specifically focusing on hydrogen peroxide (H2O2) metabolism.The same relationship was found for CAT activity, which decreased from 34.7 nkat mg(-1) DW under low CO2 to 18.4 nkat mg(-1) DW under high CO2, while APX activity did not change significantly.In summary, CP formation and CAT activity are significantly increased under conditions that favour photorespiration, while in darkness or at high CO2 concentration under light, CP formation is significantly lower, providing evidence for an association between CPs and photorespiration.

View Article: PubMed Central - PubMed

Affiliation: Institute of Botany, Functional Plant Biology, University of Innsbruck, Sternwartestrasse 15, 6020, Innsbruck, Austria. Othmar.Buchner@uibk.ac.at.

ABSTRACT
Chloroplast protrusions (CPs) have frequently been observed in plants, but their significance to plant metabolism remains largely unknown. We investigated in the alpine plant Ranunculus glacialis L. treated under various CO2 concentrations if CP formation is related to photorespiration, specifically focusing on hydrogen peroxide (H2O2) metabolism. Immediately after exposure to different CO2 concentrations, the formation of CPs in leaf mesophyll cells was assessed and correlated to catalase (CAT) and ascorbate peroxidase (APX) activities. Under natural irradiation, the relative proportion of chloroplasts with protrusions (rCP) was highest (58.7 %) after exposure to low CO2 (38 ppm) and was lowest (3.0 %) at high CO2 (10,000 ppm). The same relationship was found for CAT activity, which decreased from 34.7 nkat mg(-1) DW under low CO2 to 18.4 nkat mg(-1) DW under high CO2, while APX activity did not change significantly. When exposed to natural CO2 concentration (380 ppm) in darkness, CP formation was significantly lower (18.2 %) compared to natural solar irradiation (41.3 %). In summary, CP formation and CAT activity are significantly increased under conditions that favour photorespiration, while in darkness or at high CO2 concentration under light, CP formation is significantly lower, providing evidence for an association between CPs and photorespiration.

No MeSH data available.


Related in: MedlinePlus