AbstractsBiology & Animal Science

The impact of elevated carbon dioxide on the stress tolerance of selected vegetable crops

by Razifah Mohd Razali




Institution: University of Otago
Department:
Year: 0
Keywords: Plant stress; RCNMV; Antioxidant; Stress; tolerance; leafy; vegetables
Record ID: 1298367
Full text PDF: http://hdl.handle.net/10523/5277


Abstract

Plant responses to different stresses are highly complex and involve changes at both the cellular and physiological levels. The physiological interaction between carbon dioxide (CO2) enrichment, biotic and abiotic stressor was studied in crop plants. Metabolic acclimation through the accumulation of protective metabolites is regarded as a basic strategy for protection and survival of plants in stress environments. The aim of this study was to investigate the relations between CO2 enrichment and stress-inducing microcystins or Red clover necrotic mosaic virus (RCNMV) replication on plant growth and physiology. A preliminary study was carried out to investigate the growth and developmental response of selected leafy vegetable crops that were exposed to elevated carbon dioxide (CO2). Lettuce cvs. Great Lake and Red Fire, spinach, Swiss chard and cabbage were grown under ambient (380 ppm) and elevated (760 ppm) CO2 concentrations. Elevated CO2 was positively correlated with increased plant height, number of leaves and total leaf area except in cabbage. However, the photosynthetic pigments for lettuce, Swiss chard and cabbage decreased under elevated CO2, while the photochemical efficiency of PS II (fv/fm) remained unchanged under elevated CO2 except in cabbage and Swiss chard. Microcystin contamination of soil is a widespread environmental problem. A large-scale experiment was conducted to study the mechanisms involved in plant adaptation to microcystin stress under increasing atmospheric CO2 levels. Selected leafy vegetable species were grown under ambient (380 ppm) and elevated (760 ppm) CO2 concentrations. Microcystins caused oxidative damage, with increased levels of protein carbonyls and lipid hydroperoxides in microcystin-treated plants. Subsequently a significant increase in antioxidant enzymes (i.e. superoxide dismutase, catalase, glutathione reductase, glutathione peroxidase and ascorbate peroxidase) was observed. A significant increased of total ascorbate was recorded in microcystin-treated plants under elevated CO2 levels, but the percentage of oxidized ascorbate increased in microcystin-treated plants at both CO2 levels. The level of total glutathione increased rapidly in microcystin-treated plants under elevated CO2 levels and the oxidation process increased in microcystin-treated plants. Microcystin treatments drastically influenced the accumulation of polyamine compounds especially in the plants grown at ambient CO2 levels. It has been suggested that an increased ability to accumulate polyamines represents a plant defence mechanism. Results from this study provide evidence that microcystins cause oxidative stress and that exposure to microcystins through the irrigation route poses a threat to the yield and quality of leafy vegetables. The effect of RCNMV on Top Crop beans was also investigated in this study. Following RCNMV inoculation, plants were grown at ambient (380 ppm) and elevated CO2 (760 ppm) levels. Findings suggest that, CO2 enrichment could help infected plants to survive under biotic stress…