Abstract
Plant priming is an induced physiological state where plants are protected from biotic and abiotic stresses. Whether seaweed extracts promote priming is largely unknown as is the mechanism by which priming may occur. In this study, we examined the effect of a seaweed extract (SWE) on two distinct stages of plant priming (priming phase and post-challenge primed state) by characterising (i) plant gene expression responses using qRT-PCR and (ii) signal transduction responses by evaluating reactive oxygen species (ROS) production. The SWE is made from the brown algae Ascophyllum nodosum and Durvillaea potatorum. The priming phase was examined using both Arabidopsis thaliana and Solanum lycopersicum. At this stage, the SWE up-regulated key priming-related genes, such as those related to systemic acquired resistance (SAR) and activated the production of ROS. These responses were found to be temporal (lasting 3 days). The post-challenge primed state was examined using A. thaliana challenged with a root pathogen. Similarly, defence response-related genes, such as PR1 and NPR1, were up-regulated and ROS production was activated (lasting 5 days). This study found that SWE induces plant priming-like responses by (i) up-regulating genes associated with plant defence responses and (ii) increasing production of ROS associated with signalling responses.
Highlights
Agricultural biostimulants made from seaweed extracts have received considerable attention in recent years due to their use in conventional, sustainable, and regenerative agriculture
All four defence priming-related genes were up-regulated at the time of inoculation in those plants harvested at 3 days after SWE application, which indicates an enhanced priming response following two applications of SWE in comparison with that of a single application. These results suggest that the variation in timing of expression for major priming-related genes is based upon the duration of the primed state following seaweed extract application
Treatment of plants with the SWE derived from two brown algal species induced a typical priming response that included reactive oxygen species (ROS) activation and major priming-related gene expression
Summary
Agricultural biostimulants made from seaweed extracts have received considerable attention in recent years due to their use in conventional, sustainable, and regenerative agriculture. Seaweed extracts have been demonstrated to increase crop productivity, increase nutrient use, and enhance plant tolerance to biotic and abiotic stress [1]. Extracts from a single macroalgae, such as Ascophyllum nodosum, can stimulate an increase in plant growth, and increase crop productivity [2,3,4]. Other extracts derived from two brown algal species, A. nodosum and Durvillaea potatorum, stimulated tomato plant growth and productivity and improved soil health [5]. Ghaderiardakani et al [8] found that extracts from Ulva species contained a range of hormones that had both inhibitory and stimulatory effects on plant growth and development
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