Salicylic acid (SA) is a stimulant as well as a suppressant when applied exogenously to plants. Several published studies suggest its effects are mainly beneficial in helping plants adapt more effectively to environmental stresses. As a consequence of climate change, extreme weather events to include increased heatwave frequencies and changes in precipitation patterns are predicted to disrupt many plant species. Depending on the rate of such changes and the plants capacity to adapt, there is cause for concern. Using a range of concentrations, the effects of SA applications have been investigated in plant species from two unrelated genera, namely tomato (Solanum lycopersicum) and the economically important forestry tree species Picea sitchensis and Pseudotsuga menziesii. Through use of seed priming (SP) and exogenous spray (ES) methods, experiments have explored the effects of SA on germination and responses to different application types. Results have indicated that SA and temperature significantly influenced radicle emergence rates in four cultivars tested and strong interaction effects were observed (p<0.01). The method of application had a significant effect on increasing plant biomass, particularly root mass. Under unchallenged environments, an exogenous application of SA shows highly variable differences on overall performance depending on plant age. An ES application of SA delivered when the plant is older, significantly increases total biomass when compared to SP (p<0.01). Finally, the effects of SA under the stress of flash drought and waterlogging have been determined. A significantly higher (p<0.01) chlorophyll content was observed in plants which had been treated with an SA concentration of 0.25 mM and a marked increase in chlorophyll content was apparent in plants exposed to drought. Similar patterns have been observed in plants exposed to waterlogging for a period of 28 days and differentiation in carbon and nitrogen partitioning have too been evaluated. By predetermination of optimum SA dose responses at seed level, the results have shown that positive outcomes can be achieved in mitigating the damaging responses to hypoxic conditions. Some of the major findings conclude that SA is not only species specific, but is cultivar specific. Results also reveal the identification of a non-monotonic dose response.
“Eustress Elixir”: Investigating salicylic acid as a hormetin to produce climate-smart plants
Morris-Hay, A. (Author). 2024
Student thesis: Doctoral Thesis › Doctor of Philosophy