Carbohydrate and carbon metabolite accumulation responses in leaves of ozone tolerant and ozone susceptible spinach plants after acute ozone exposure

Abstract

The objective of this study was to determine whether exposure of plants to ozone (O3) increased the foliar levels of glucose, glucose sources, e.g., sucrose and starch, and glucose-6-phosphate (G6P), because in leaf cells, glucose is the precursor of the antioxidant, L-ascorbate, and glucose-6-phosphate is a source of NADPH needed to support antioxidant capacity. A further objective was to establish whether the response of increased levels of glucose, sucrose, starch and G6P in leaves could be correlated with a greater degree of plant tolerance to O3. Four commercially available Spinacia oleracea varieties were screened for tolerance or susceptibility to detrimental effects of O3 employing one 6.5 hour acute exposure to 25O nL O3 L(-1) air during the light. One day after the termination of ozonation (29 d post emergence), leaves of the plants were monitored both for damage and for gas exchange characteristics. Cultivar Winter Bloomsdale (cv Winter) leaves were least damaged on a quantitative grading scale. The leaves of cv Nordic, the most susceptible, were approximately 2.5 times more damaged. Photosynthesis (Pn) rates in the ozonated mature leaves of cv Winter were 48.9% less, and in cv Nordic, 66.2% less than in comparable leaves of their non-ozonated controls. Stomatal conductance of leaves of ozonated plants was found not to be a factor in the lower Pn rates in the ozonated plants. At some time points in the light, leaves of ozonated cv Winter plants had significantly higher levels of glucose, sucrose, starch, G6P, G1P, pyruvate and malate than did leaves of ozonated cv Nordic plants. It was concluded that leaves of cv Winter displayed a higher tolerance to ozone mediated stress than those of cv Nordic, in part because they had higher levels of glucose and G6P that could be mobilized during diminished photosynthesis to generate antioxidants (e.g., ascorbate) and reductants (e.g., NADPH). Elevated levels of both pyruvate and malate in the leaves of ozonated cv Winter suggested an increased availability of respiratory substrates to support higher respiratory capacity needed for repair, growth, and maintenance.

The effect of ozone fumigation and different Brassica rapa lines on the feeding behaviour of Pieris brassicae larvae

“…When plants are exposed to ozone, an accumulation of carbohydrates including starch occurs (Robinson & Rowland, 1996;Einig et al, 1997;Trumble et al, 1987;Grantz & Farrar, 1999;Lux et al, 1997). We have found a similar response in B. rapa since ozone fumigation caused a significant increase in the starch level in the sensitive line and the resistant line.…”

“…Ozone is a gaseous pollutant and acts as a phytotoxin through reactions in the leaves with the subsequent production of highly oxidative intermediates (Robinson & Rowland, 1996). This induction of stress on the plants, along with other types of plant stresses such as drought, nutrient deficiency, and herbivory is the cause of a series of short and long-term biochemical and growth-related alterations (Herold, 1980).…”

“…A known and well-investigated response of the plants to ozone is a decrease in photosynthetic activity and, as a consequence of this, a decrease in shoot biomass. This reduced development and expansion of new leaves causes a decreasing demand for starch and other carbohydrates in these leaves, which leads to an accumulation of carbohydrates in the fully developed leaves (Robinson & Rowland, 1996;Barnes et al, 1999;Herold, 1980). Stressed plants are believed to become more vulnerable to herbivory when biochemical changes lead to increases in the nutritional value or decreases in plant chemical defences (White, 1974(White, , 1984).…”

Inter- and Intra-specific Differences in the Response of Chinese Leafy Vegetables to Ozone

“…Both of the experiments in the present study revealed a decrease in photosynthesis rates ranging from 13% to 27% (interspecific) and 20-31% (intraspecific). Similar results have been found for spinach cultivars which were exposed to 250 ppb O 3 for a 6.5 h acute exposure, with photosynthetic rates of cv Winter reduced by 48.9% and cv Nordic by 66.2% (Robinson and Rowland 1996). Calatayud et al (2002a) also found that the photosynthetic rate of lettuce leaves was reduced by 77% (compared to filtered air) after O 3 exposure (66 ppb, 12 h day −1 for 90 days).…”

Growth and nutrition of Agelastica coerulea (Coleoptera: Chrysomelidae) larvae changed when fed with leaves obtained from an O3-enriched atmosphere

“…Furthermore, an increase in background O 3 levels in regions of the northern hemisphere may occur in the near future (The Royal Society 2008). O 3 is a gaseous pollutant which causes toxicity to plants at macro-and microscopic levels, when its concentrations exceed species-specific thresholds, through reactions in the leaves, with a subsequent production of highly oxidative intermediates (Robinson and Rowland 1996;Oksanen et al 2013;Vaultier and Jolivet 2015). Such exceedances may result in reduction in plant vigor, suppression of yields and productivity, with further implications to ecological processes and trophic cascades (Feng et al 2008;Lindroth 2010;Ainsworth et al 2012;Koike et al 2013;Blande et al 2014; 2016a; Chappelka and Grulke 2016).…”