Rosemary plants were analysed using HPLC and eight different compounds (vanillic acid, caffeic acid, rosmarinic acid, naringin, hispidulin, cirsimaritin, carnosol and carnosic acid) were identified and quantified. The analysis of the DPPH (1,1-diphenyl-2-picrylhydrazyl) radical scavenging activity revealed that rosmarinic and carnosic acids were the best rosemary scavengers with IC sun(50) values of 27 and 32 micro M, respectively. Environmental influences on rosmarinic and carnosic acids content in rosemary plants were studied over a period of one year under southern UK conditions. Carnosic acid reached the maximum concentrations in December, decreasing by 50% during the summer months, while rosmarinic acid showed a constant concentration during the year. The significance of these results has been discussed later in this paper.

Water scarcity is one of the main challenges faced by modern agriculture, leading to a substantial drop in crop productivity and a threat to food security. Thus, novel agricultural approaches are necessary and urgent to face this problem. Some natural compounds such as amino acids have been shown to increase yield and mitigate the effects of drought stress. In this study, we demonstrate that the application of pyroglutamic acid (PG) is capable of increasing lettuce yield, under field conditions with 30% less than optimal irrigation. PG treatment showed a clearly protective effect in stressed plants, enhancing their fresh weight by 37% and yield by 31%, in comparison to untreated plants. PG appears to promote drought tolerance effects in deficit irrigated lettuce plants, with several advantages. It acts by enhancing photosynthesis rate and antioxidant defences, while maintaining osmotic and water balance, without toxicity to soil microorganisms. This illustrates the potential use of PG to combat productivity losses due to water scarcity.

SummaryMenadione sodium bisulphite (MSB) is a water-soluble derivative of vitamin K3, or menadione, and has been previously demonstrated to function as a plant defence activator against several pathogens in several plant species. However, there are no reports of the role of this vitamin in the induction of resistance in the plant model Arabidopsis thaliana. In the current study, we demonstrate that MSB induces resistance by priming in Arabidopsis against the virulent strain Pseudomonas syringae pv.tomato DC3000 (Pto) without inducing necrosis or visible damage. Changes in gene expression in response to 0.2 mM MSB were analysed in Arabidopsis at 3, 6 and 24 h post-treatment using microarray technology. In general, the treatment with MSB does not correlate with other publicly available data, thus MSB produces a unique molecular footprint. We observed 158 differentially regulated genes among all the possible trends. More up-regulated genes are included in categories such as 'response to stress' than the background, and the behaviour of these genes in different treatments confirms their role in response to biotic and abiotic stress. In addition, there is an over-representation of the G-box in their promoters. Some interesting functions are represented among the individual up-regulated genes, such as glutathione S-transferases, transcription factors (including putative regulators of the G-box) and cytochrome P450s. This work provides a wide insight into the molecular cues underlying the effect of MSB as a plant resistance inducer.

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