Changes in leaf gas exchange, chlorophyll a fluorescence and antioxidant metabolism within wheat leaves infected by Bipolaris sorokiniana

Abstract

The photosynthetic performance (leaf gas exchange and chlorophyll a (Chla) fluorescence), activities of antioxidant enzymes [superoxide dismutase (SOD), catalase (CAT), peroxidase (POX), ascorbate peroxidase (APX)] and the concentrations of hydrogen peroxide (H2O2) and malondialdehyde (MDA) in the flag leaves of plants from two wheat cultivars with contrasting levels of resistance to spot blotch was assessed. Spot blotch severity was significantly lower in plants from cv. BR‐18 compared to cv. Guamirim. Net carbon assimilation rate, stomatal conductance and concentrations of Chla, Chlab and carotenoids were significantly decreased from fungal infection. In contrast, internal CO2 concentration was significantly increased from fungal infection in comparison to their non‐inoculated counterparts. Similarly, inoculation significantly reduced photochemical performance in the inoculated flag leaves in comparison to their non‐inoculated counterparts. However, plants from cv. BR‐18 were able to sustain greater functionality of the photosynthetic apparatus during fungal infection process compared to cv. Guamirim. The activities of SOD, POX, APX and CAT increased in inoculated flag leaves from both cultivars compared to non‐inoculated plants, and the highest increases were measured in cv. BR‐18. The greater activities of these enzymes were associated with a reduced H2O2 concentration in the inoculated flag leaves from cv. BR‐18, resulting, therefore, in a lower MDA concentration. Thus, a more efficient antioxidative system in flag leaves from cv. BR‐18 plays a pivotal role in removing the excess reactive oxygen species that were generated during the infection process of Bipolaris sorokiniana, therefore limiting cellular damage and largely preserving the photosynthetic efficiency of the infected flag leaves.

Defence responses in flag leaves and spikes of common wheat Triticum aestivum cultivars with contrasting levels of basal resistance to blast caused by Pyricularia oryzae

“…A total of 300 mg of flag leaves and spikelets was ground with liquid nitrogen in a mortar and pestle to obtain a fine powder, which was used to determine the ascorbate peroxidase (APX, EC 1.11.1.11), catalase (CAT, EC 1.11.1.6), peroxidase (POX, EC 1.11.1.7) and superoxide dismutase (SOD, EC 1.15.1.1) activities, as previously described (Debona et al ., ; Rios et al ., ). Each extraction was read three times.…”

Changes in leaf gas exchange, chlorophyll a fluorescence, and antioxidantsin maize leaves infected by Exserohilum turcicum

“…The homogenate was centrifuged at 12 000 g and 4 °C for 15 min and the supernatant was divided into aliquots, which were used for determinations of activities of APX (EC 1.11.1.11), CAT (EC 1.11.1.6), GPX (EC 1.11.1.9), GR (EC 1.8.1.7), GST (EC 2.5.1.18), POX (EC 1.11.1.7), SOD (EC 1.15.1.1) as previously described (Bermúdez-Cardona et al 2015a, Tatagiba et al 2016, Rios et al 2017. Protein content was measured using the Bradford assay with bovine serum albumin as a standard (Bradford 1976).…”

“…Chlorophyll a fluorescence imaging: The images and fluorescence parameters of Chl a, maximum quantum yield of photosystem (PS) II (Fv/Fm), effective quantum yield of PS II (Fv'/Fm'), quantum yield of regulated energy dissipation (NPQ), and quantum yield of nonregulated energy dissipation Y(NO) were obtained at 5, 10, 15, and 20 dai using an IMAGING-PAM fluorometer (a Maxi version) and the Imaging Win software (Heinz Walz, Effeltrich, Germany). In order to obtain images at a resolution of 640 × 480 pixels, the fourth leaf was used to obtain the images of Chl a fluorescence following the procedures previously described (Debona et al 2014, Silveira et al 2015, Bermúdez-Cardona et al 2015b, Tatagiba et al 2015, Bispo et al 2016, Rios et al 2017, Rios et al 2018.…”

“…Several studies have shown physiological disorders in plants infected by pathogens primarily at the photosynthetic level (Tatagiba et al 2016, Rios et al 2017. The image analysis of chlorophyll (Chl) a fluorescence has been used in studies investigating physiological changes in plants exposed to abiotic and biotic stresses (Lei et al 2017, Yadav et al 2017.…”

Complexity of Brassica Oleracea-Alternaria Brassicicola Susceptible Interaction Reveals Down-regulation of Photosynthesis at Ultrastructural, Transcriptional and Physiological Levels

“…brassicicola [9] and in other plants infected with necrotrophic fungi [84,85]. Also, in wheat plants infected with Bipolaris sorokiniana, a decrease in F v /F m correlated with the loss of chlorophyll has been noted [86].…”