Glutathione Levels in Tomato Plants Subjected to Airjection Irrigation.

Oxidative stress is one of the most important abiotic stress factors that can adversely affect plant yield and quality. Oxidative stress caused by activated oxygen species like superoxide radical (0₂- ) hydrogen peroxide (H₂0₂), and the hydroxyl radical (OH ) formed as intermediates in plant metabolism react with cellular enzymes and cell wall resulting in  the formation of lipid peroxides and other destructive species causing severe damage to the plants. Glutathione (GLU), an important plant antioxidant is considered to play a key role in the control of oxidative stress.  The two forms of GLU, reduced GLU (GSH) and the oxidized form (GSSG) play the crucial role in the breakdown of these harmful reactivated oxygen species (ROS). The ratio of GSH:GSSG is a key marker of oxidative stress in a plant. Lower ratio indicates a lower level of oxidative stress and vice versa. The use of advanced irrigation technology has the potential for improving plants defense to changing environmental conditions. Airjection^® irrigation is one such advancement which has already been established as a method of improving plant yields. The primary objective of this study was to compare the levels of GSH, GSSH and total GLU in leaf samples collected from plants subjected to Airjection^® irrigation with those irrigated with water only. The three different forms of GLU were quantified using a Biovision™ assay kit. Overall, GLU concentrations were 50% more in plants subjected to Airjection irrigation compared to plants receiving water only. While there was no significant difference in plant biomass and the GSH concentrations (p= 0.94) for plants irrigated with either method, the GSSG concentrations were significantly different (p= 0.03) with 47% more GSSG detected in plants subjected to Airjection irrigation compared to plants receiving water only. The leaves in the Airjection irrigated plants also had relatively 24% lower GSH:GSSG ratios than the leaves sampled in water only beds.  In summary, this study was successful in quantifying the levels of different forms of GLU and these preliminary findings seem to imply that Airjection^® irrigation has the potential to reduce oxidative stress in tomato plants. To the best of our knowledge, this is the first study to measure the indicators of oxidative stress in plants subjected to Airjection irrigation system. For future work, we intend to test leaves, root and fruit samples to analyze the effect of Airjection^® irrigation to minimize oxidative stress in tomatoes in saline soils.