Effects of the interaction between ozone and carbon dioxide on gas exchange, ascorbic acid content, and visible leaf symptoms in rice leaves

Abstract

Tropospheric ozone (O 3 ) decreases photosynthesis, growth, and yield of crop plants, while elevated carbon dioxide (CO 2 ) has the opposite effect. The net photosynthetic rate (P N ), dark respiration rate (R D ), and ascorbic acid content of rice leaves were examined under combinations of O 3 (0, 0.1, or 0.3 cm 3 m -3 , expressed as O 0 , O 0.1 , O 0.3 , respectively) and CO 2 (400 or 800 cm 3 m -3 , expressed as C 400 or C 800 , respectively). The P N declined immediately after O 3 fumigation, and was larger under O 0.3 than under O 0.1 . When C 800 was combined with the O 3 , P N was unaffected by O 0.1 and there was an approximately 20 % decrease when the rice leaves were exposed to O 0.3 for 3 h. The depression of stomatal conductance (g s ) observed under O 0.1 was accelerated by C 800 , and that under O 0.3 did not change because the decline under O 0.3 was too large. . Excluding the stomatal effect, the mesophyll P N was suppressed only by O 0.3 , but was substantially ameliorated when C 800 was combined. Ozone fumigation boosted the R D value, whereas C 800 suppressed it. An appreciable reduction of ascorbic acid occurred when the leaves were fumigated with O 0.3 , but the reduction was partially ameliorated by C 800 . The degree of visible leaf symptoms coincided with the effect of the interaction between O 3 and CO 2 on P N . The amelioration of O 3 injury by elevated CO 2 was largely attributed to the restriction of O 3 intake by the leaves with stomatal closure, and partly to the maintenance of the scavenge system for reactive oxygen species that entered the leaf mesophyll, as well as the promotion of the P N .

Effect of chitosan on physiology, photosynthesis and biomass of rice (Oryza sativa L.) under elevated ozone

“…Similarly, the combination of Chi+EO 3 70 helped to reduce the effect of elevated ozone, whilst they were significantly higher than the sample under EO 3 70. Imai and Kobori (2008) found that shoot, root and total biomass yields of rice were decreased by elevated ozone that suppressed photosynthesis. Rice was considered as another sensitive crop, similar to wheat, which showed reduction of biomass even when exposed to mild ozone concentration at 40 ppb (Feng et al, 2008).…”

Inclination Angle Affects Ozone Injury in the Flag Leaf of Rice

“…The RDS of ascorbic acid in the flag leaf was slightly higher than that in other positioned leaves (not significant at P ≤ 0.05, but significant at P ≤ 0.10). Imai and Kobori (2008) reported that the inhibition of P N in rice leaves by short exposure to O 3 was explained considerably by decreased g s , and at a high O 3 ) of total, reduced form (AA) and oxidized form (DHA) of ascorbic acid and its redox state (RDS) in the 16th (flag leaf) − 13th leaves. In each column, means (n = 4) followed by the same letter are not significantly different at P ≤ 0.05 level as inferred from results of one-way ANOVA.…”

“…Therefore, the effects of exposure to O 3 on physiological processes of rice need to be studied as a basis of dry matter production and yield formation. When exposed to O 3 , rice plants suffer damage such as the inhibition of net photosynthetic rate (P N ), stomatal conductance to CO 2 transfer (g s ), photosystem II (PSII) (Imai and Kobori, 2008;Kobayakawa and Imai, 2011a), decreased ribulose 1,5-bisphosphate carboxylase / oxygenase (Ishioh and Imai, 2005), chlorophyll and carotenoid Rai and Agrawal, 2008) contents and nitrite reductase activity (Kobayakawa and Imai, 2011b), in addition to breakdown of the cellular ultrastructure (Toyama et al, 1989) and visible leaf-related symptoms (Imai and Kobori, 2008). Furthermore, O 3 suppresses the growth rate (Imai and Ookoshi, 2011), alters photoassimilate partitioning (Nouchi et al, 1995) and ultimately decreases the grain yield (Reid and Fiscus, 2008;Yamaguchi et al, 2008;Pang et al, 2009;Rai et al, 2010;Imai and Ookoshi, 2011).…”

Relation between O3-Inhibition of Photosynthesis and Ethylene in Paddy Rice Grown under Different CO2Concentrations

“…Of photochemical oxidant components, 90% or more are O 3 (Cabrera et al, 1988;Nouchi, 2001). When exposed to O 3 , rice plants suffer damage: inhibition of net photosynthetic rate (P N ), stomatal conductance (g s ) and PSII (Imai and Kobori, 2008;Imai, 2011a, 2012a), decreased ribulose 1,5-bisphosphate carboxylase/oxygenase (Ishioh and Imai, 2005), chlorophyll and carotenoid (Rai and Agrawal, 2008) contents and nitrite reductase activity (Kobayakawa and Imai, 2011b), in addition to visible leafrelated symptoms (Imai and Kobori, 2008) and breakdown of the cellular ultrastructure (Toyama et al, 1989). By using a passive light microscope, the 3-D chlorophyll fluorescence imaging suggested that O 3 injury began just under the epidermal cells (Endo and Omasa, 2007).…”

“…Under elevated CO 2 , the g s of plants generally decreases. Consequently, O 3 -inhibition decreases because of the limited inflow of O 3 through stomata (Booker and Fiscus, 2005;Imai and Kobori, 2008). In rice plants, O 3 -inhibition of photosynthesis is ameliorated by elevated CO 2 (Imai and Kobori, 2008;Imai, 2011a, 2012a).…”