Response of photosynthesis and chlorophyll fluorescence to acute ozone stress in tomato (Solanum lycopersicum Mill.)

A A Thwe,G Vercambre,H Gautier,F Gay,P Kasemsap,J Phattaralerphong

doi:10.1007/s11099-014-0012-2

Abstract

The crop sensitivity to ozone (O3) is affected by the timing of the O3 exposure, by the O3 concentration, and by the crop age. To determine the physiological response to the acute ozone stress, tomato plants were exposed to O3 at two growth stages. In Experiment I (Exp. I), O3 (500 μg m−3) was applied to 30-d-old plants (PL30). In Experiment II (Exp. II), three O3 concentrations (200, 350, and 500 μg m−3) were applied to 51-d-old plants (PL51). The time of the treatment was 4 h (7:30–11:30 h). Photosynthesis and chlorophyll fluorescence measurements were done 4 times (before the exposure; 20 min, 20 h, and 2–3 weeks after the end of the treatment) using a LI-COR 6400 photosynthesis meter. The stomatal pore area and stomatal conductance were reduced as the O3 concentration increased. Ozone induced the decrease in the photosynthetic parameters of tomato regardless of the plant age. Both the photosystem (PS) II operating efficiency and the maximum quantum efficiency of PSII photochemistry declined under the ozone stress suggesting that the PSII activity was inhibited by O3. The impaired PSII contributed to the reduced photosynthetic rate. The greater decline of photosynthetic parameters was found in the PL30 compared with the PL51. It proved the age-dependent ozone sensitivity of tomato, where the younger plants were more vulnerable. Ozone caused the degradation of photosynthetic apparatus, which affected the photosynthesis of tomato plants depending on the growth stage and the O3 concentration.

Highlights

Ozone is regarded as one of the most widespread air pollutants around the world and it is recognized as a global problem (UNECE 2010)
Twenty minutes after the end of the treatment, gs was reduced by 85%, from 1.19 to 0.21 mol(H2O) m–2 s–1, in the PL30 and by 32%, from 0.46 to 0.28 mol(H2O) m–2 s–1, in the PL51 at O500
The relative value of the stomata pore area decreased from 99% to 71% as the O3 concentration increased from O200 to O500 (Fig. 1A)

Summary

Introduction

Ozone is regarded as one of the most widespread air pollutants around the world and it is recognized as a global problem (UNECE 2010). Ground-level O3 is formed from the pollutants emitted from vehicle exhausts, industrial production, and photochemical reactions with the O3 precursors. The elevated O3 concentration is a growing concern for rapidly developing nations with rising emissions of the O3 precursors from expanding transportation networks (Bell et al 2006). Ozone modifies different physiological processes in plants: photosynthesis (Nighat et al 2000, Calatayud et al 2011), stomata function (Robinson et al 1998, Singh et al.2009), plant growth and development (Saitanis and Karandinos 2002, Kharel and Amgain 2010, Mina et al 2010), and crop productivity (Chen et al 2008). Ozone enters a leaf through the stomata by a diffusion process and it is quickly destroyed in the cellular wall and plasmalemma (Laisk et al 1989). Contran and Paoletti (2007)

Methods

Results

Discussion

Conclusion