Exposure of spring wheat (Triticum aestivum) to ozone in open‐top chambers. Effects on acyl lipid composition and chlorophyll content of flag leaves

Abstract

SUMMARYSpring wheat {Triticum aestivum L, cv, Drabant) was exposed to different concentrations of ozone in open-top chambers in a Held of commercially grown wheat. The following treatments were used: charcoal-Hltered air (CF), non-filtered air (iNF) and non-filtered air supplemented with 25 nl 1"^ ozone (NF-f) and 35 nl 1"' ozone {NF-f-+) for 7hd"'. Flag leaves were analysed for chlorophyll content, total fatty acid composition and fatty acid compositions and contents of monogalactosyldiacylglycerol (MGDG), digalactosyldiacylglycerol (DGDG), phosphatidylcholine (PC) and phosphatidylethanolamine (PE), I'he chlorophyll content decreased significantly with time and ozone concentration. After 4 wk of exposure, the content of MGDG was significantly lower in flag leaves from the NF+ + treatments than in those from the other treatments. The contents of DGDG and PC also decreased while that of PE increased, although these changes were not statistically significant. In the total lipid extract the proportion of 18:3 decreased with time and ozone concentration. Similar changes occurred in MGDG 18:3 at a later stage. Using the concept of accumulated exposure over threshold (AOT), it was evident that the parameters studied differed in ozone sensitivity. After 4 wk of exposure, the best linear dose-response relationships between accumulated exposure and chlorophyll as weli as MGDG contents were obtained with a threshold ozone concentration of 30 n! 1"V For total lipid 18:3 and MGDG 18:3 the corresponding thresholds were 40 and 50 nl 1"\ respectively. Furthermore, the sensitivity to ozone, expressed as loss of chlorophyll, increased with increasing fiag leaf age. In leaves exposed for 7, 13 and 20 d, the best linear fits were obtained with AOT50, AOT40 and AOT30, respectively. In conclusion, ozone sensitivity increased with Hag leaf age and different membrane constituents were differently sensitive to ozone. The results support previous suggestions that ozone causes premature senescence m wheat Bag leaves.

Physiological changes on agricultural crops induced by different ambient ozone exposure regimes

“…short term ozone episodes have to be considered more carefully for establishing threshold values. One approach for this is to describe dose-effect relationships by cumulative doses (Lefohn, Laurence & Kohut, 1988;Fuhrer, 1995;Legge et al, 1995;Pleijel et al, 1995) but giving different weighting to concentrations (Krupa, Nosal & Legge, 1994;Sanders et al, 1995) for setting of thresholds. Further investigations have to be done to elucidate the infiuence of environmental (Grijnhage & Jager, 1996;Fuhrer, 1995) and plant specific conditions Vandermeiren, de Temmerman & Hookham, 1995).…”

“…Were experienced m 1994 and 199s with monthly mean concentrations of c. 130/(gm ' can aff'ect photosynthesis and storage (sink) organs of plants (Cooley & Manning, 1987;Reiling & Davison, 1994;Pleijel et al, 1995), Photosynthesis is disturbed by ozone, and (stress) factors which influence stomatal conductivity clearly affect uptake of ozone and consequently its impact (Fuhrer, 1995;Griinhage & Jager, 1996), Since Laisk, Kull & Moldau (1989) showed that the chloroplast in the mesophyll cell is not directly damaged by ozone, it is widely accepted that the first target within at cellular level within the leaf must be the plasma membrane (Willenbrink & Schatten, 1993;Mortensen & Engvild, 1995;Sandelius et al, 1995), This view is strengthened by measurements of antioxidants in the apoplast which are part of the plant defence system against oxygen radicals (Luwe & Heber, 1995;Polle & Rennenberg, 1994), and by investigations which show premature senescence of wheat leaves as a result of ozone exposure, as suggested by Lehnherr et al (1987) and Soja & Soja (1995), However, if sucrose accumulates in leaf cells, it might cause down-regulation of photosynthesis (Jang & Sheen, 1996;Pollock & Farrar, 1996) which could occur as a consequence of disturbance of the overall phloem loading process by previous damage to the mesophyll plasma membrane, and not only by reducing sink strength (Heath, 1987), Down-regulation of photosynthesis might result in photoinhibition, particularly if the defence systems again oxygen radicals within the mesophyll are diverted towards the apoplast. In order to get information on early physiological response of crop plants to ozone regimes which were monitored in North-Rhine Westphalia during the last years, spring wheat grown in a charcoal-filtered glasshouse was fumigated in specially designed exposure chambers for 14 d, during the main developmental stages.…”

Ozone effects on wheat grain quality – A summary

“…Feng and Kobayashi, 2009;Mills et al, 2007;Tai et al, 2014) as well as effects on photosynthesis and other physiological aspects/processes such as senescence (e.g. Feng et al, 2008;Mulholland et al, 1997;Sandelius et al, 1995) which are important for the mechanistic understanding of growth effects and for modelling. Although some studies have included quality aspects (e.g.…”

Air pollution tolerance index of selected plants in industrial and urban areas of Vellore district

“…Chlorophyll pigments exist in highly organized state, and under stress, they may undergo several photochemical reactions, such as oxidation, reduction and reversible bleaching (Puckett et al,1973).The total chlorophyll contents of the selected plants at College farm recorded high values when compared to Arcot and Ranipet samples (Table 1,2 &3). The air pollution can directly affects the plants via leaves and the photosynthetic pigments are the most likely to be damaged (Steubing et al,1989;Singh et al,1990 andSandelius et al .,1995).The ascorbic acid, a stress reducing factor, associated with particular environmental conditions was also analyzed from the selected plants and the plants from College farm recorded low ascorbic acid content when compared to Arcot and Ranipet. The present investigation revealed a great deal of variation in the levels of Ascorbic acid content among the three different study areas.…”