The Impact of Ozone on Juvenile Maize (Zea mays L.) Plant Photosynthesis: Effects on Vegetative Biomass, Pigmentation, and Carboxylases (PEPc and Rubisco)

Abstract

The impact of ozone on crops was more studied in C (3) than in C (4) species. In C (3) plants, ozone is known to induce a photosynthesis impairment that can result in significant depressions in biomass and crop yields. To investigate the impact of O (3) on C (4) plant species, maize seedlings ( ZEA MAYS L. cv. Chambord) were exposed to 5 atmospheres in open-top chambers: non-filtered air (NF, 48 nL L (-1) O (3)) and NF supplied with 20 (+ 20), 40 (+ 40), 60 (+ 60), and 80 (+ 80) nL L (-1) ozone. An unchambered plot was also available. Leaf area, vegetative biomass, and leaf dry mass per unit leaf area (LMA) were evaluated 33 days after seedling emergence in OTCs. At the same time, photosynthetic pigments as well as carboxylase (PEPc and Rubisco) activities and amounts were also examined in the 5th leaf. Ozone enhanced visible symptoms characterizing foliar senescence. Across NF, + 20, + 40, and + 60 atmospheres, both chlorophylls and carotenoids were found to be linearly decreased against increasing AOT40 ( CA. - 50 % in + 60). No supplementary decrease was observed between + 60 and + 80. Total above-ground biomass was reduced by 26 % in + 80 atmosphere; leaf dry matter being more depressed by ozone than leaf area. In some cases, LMA index was consistent to reflect low negative effects caused by a moderate increase in ozone concentration. PEPc and Rubisco were less sensitive to ozone than pigments: only the two highest external ozone doses reduced their activities by about 20 - 30 %. These changes might be connected to losses in PEPc and Rubisco proteins that were decreased by about one-third. The underlying mechanisms for these results were discussed with special reference to C (3) species. To conclude, we showed that both light and dark reactions of C (4) photosynthesis can be impaired by realistic ozone doses.

Sensitivity of Gas Exchange Parameters to Ozone in Diverse C4 Sugarcane Hybrids

“…The greater sensitivity of PEPCase than rubisco may reflect the less protected localization of PEPCase in the mesophyll cytoplasm compared with the location of rubisco in the bundle sheath chloroplast. The location effect appears to dominate intrinsic differences in antioxidant capacity (Kingston‐Smith and Foyer, 2000), as this was greater in mesophyll cells.…”

Plant Volatile Organic Compounds (VOCs) in Ozone (O3) Polluted Atmospheres: The Ecological Effects

“…O 3 can damage or inhibit almost every step of photosynthesis from light capture in photosystem II to starch accumulation in chloroplasts and phloem loading (Long and Naidu 2002 and references therein). Chronic exposure to O 3 leads to a reduction in photosynthetic pigments (chlorophyll a, b and carotenoids) (Leitao et al 2007). It also negatively affects the levels and activity of Rubisco (ribulose-1,5-biphosphate carboxylase/oxygenase), the enzyme that catalyses the first step of net photosynthetic CO 2 assimilation (Long and Naidu 2002 for a review), as well as increasing the activity and quantity of PEPc (phosphoenolpyruvate carboxylase) (Dizengremel et al 2008), the enzyme that catalyses the carboxylation of phosphoenolpyruvate to form oxaloacetate (Kai et al 2003 for a review).…”

Ozone exposure and flux-based response functions for photosynthetic traits in wheat, maize and poplar

“…Published relationships are based either on CO 2 assimilation rate (Bagard et al, 2008;L€ ow et al, 2007;Dumont et al, 2013) or leaf injury (Marzuoli et al, 2009). While maize worldwide production is the largest among food crops, the literature on the impact of ozone on this C4 grass is relatively poor, with reports of adverse effects of the pollutant on grain yield (Rudorff et al, 1996;Van Dingenen et al, 2009), biomass production (Leitao et al, 2007a) and leaf biochemical parameters (Leitao et al, 2007b;Ahmad et al, 2012). Despite the agroeconomical value of maize, no ozone flux-response relationship is available in the literature.…”