Compensatory effects of elevated CO₂ concentration on the inhibitory effects of high temperature and irradiance on photosynthetic gas exchange in carrots

Abstract

We determined the interactive effects of irradiance, elevated CO 2 concentration (EC), and temperature in carrot (Daucus carota var. sativus). Plants of the cv. Red Core Chantenay (RCC) were grown in a controlled environmental plant growth room and exposed to 3 levels of photosynthetically active radiation (PAR) (400, 800, 1 200 μmol m -2 s -1 ), 3 leaf chamber temperatures (15, 20, 30 °C), and 2 external CO 2 concentrations (C a ), AC and EC (350 and 750 μmol mol -1 , respectively). Rates of net photosynthesis (P N ) and transpiration (E) and stomatal conductance (g s ) were measured, along with water use efficiency (WUE) and ratio of internal and external CO 2 concentrations (C i /C a ). P N revealed an interactive effect between PAR and C a . As PAR increased so did P N under both C a regimes. The g s showed no interactive effects between the three parameters but had singular effects of temperature and PAR. E was strongly influenced by the combination of PAR and temperature. WUE was interactively affected by all three parameters. Maximum WUE occurred at 15 o C and 1 200 µmol m -2 s -1 PAR under EC. The C i /C a was influenced independently by temperature and C a . Hence photosynthetic responses are interactively affected by changes in irradiance, external CO 2 concentration, and temperature. EC significantly compensates the inhibitory effects of high temperature and irradiance on P N and WUE.

The Alleviating Effect of Elevated CO2 on Heat Stress Susceptibility of Two Wheat (Triticum aestivum L.) Cultivars

“…Wheat plants grown in elevated CO 2 have been shown to have a higher temperature optimum for photosynthesis which may be related to modifications in the temperature dependency of Rubisco activity (Alonso et al 2008) and a higher thermo-tolerance of PSII (Taub et al 2000). However, in the present study, the increased ITE seen in plants grown in elevated CO 2 was probably more attributed to an increased competitiveness of CO 2 against O 2 for the active site on the Rubisco protein, which was also suggested as the main effect of elevated CO 2 on photosynthesis in carrot (Thiagarajan et al 2007).…”

“…However, in the present study, the increased ITE seen in plants grown in elevated CO 2 was probably more attributed to an increased competitiveness of CO 2 against O 2 for the active site on the Rubisco protein, which was also suggested as the main effect of elevated CO 2 on photosynthesis in carrot (Thiagarajan et al. ).…”

Ecophysiological characteristics of two carrot (Daucus carota L.) cultivars in response to agroecological factors and nitrogen application

“…1). The trends observed in this study were comparable to those observed during our previous studies (Thiagarajan et al 2007).…”

“…The two major environmental parameters that change with planting and harvesting time are ambient air temperature and photosynthetic photon flux density (PPFD). The relationship between PPFD (Kyei-Boahen et al 2003), temperature (Thiagarajan et al 2007) and P N has been investigated in carrots (Daucus carota L.), nevertheless, under noncompetitive and/or controlled environments. High plant densities arising from high seeding rates under field conditions enforce resource limitations particularly, in terms of water, nutrients, and light (Rajasekaran et al 2006).…”

Selection of Sunflower Genotypes With Tolerance to Salinity

“…In general, photosynthesis can be negatively affected by salt stress due to the decrease of CO2 availability for Rubisco IV INOVAGRI International Meeting, 2017 activity (Hura et al, 2007); as well as decreases in the efficiency of biochemical processes, such as the low electron transport through the electron transport chain of the chloroplast and the inhibition of the activity of several enzymes related to CO2 assimilation (Wise et al, 2004;Thiagarajan et al, 2007). Herein, saline stress significantly reduced the photosynthetic rate of Catissol, BRS 323, BRS 324, H360 and H25 plants, with the most strongly effects in Catissol genotype, whereas no significant changes were registered in the BRS 321 genotype (Figure 2).…”