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Two wild populations of Helichrysum (Mill.) located at Elba Island (Tuscan Archipelago, Central Italy) were morphologically and phytochemically analyzed to taxonomically identify H. litoreum (population A) and H. italicum subsp. italicum (population B). Micromorphological and histochemical analyses were performed on the indumentum using Scanning Electron Microscope (SEM) and Light Microscope (LM). Morphometric analyses on vegetative and reproductive traits were also conducted. Finally, a chemotaxonomic analysis was carried out on the terpene profile of flowers, leaves and bark tissues using gas chromatography (GC-MS). Results suggested that morphological discriminant traits were mainly in leaves and cypselae glandular tissues. Phytochemical analysis indicated that a high relative content of α-pinene and β-caryophyllene were the main markers for population A, while a high relative content of neryl-acetate, α-curcumene, isoitalicene and italicene, especially in the terpene profile of bark tissue, were the main compounds for discriminating population B. The analysis suggested that the wild population A could be mainly ascribed to H. litoreum, whilst population B is defined by H. italicum.

This paper describes the antigerminant capacity of water extracts of silver fir needles created by means of hydrodynamic cavitation processes. Fir needles (2 kg fresh weight) collected in the winter were blended and crushed in ice, poured in water only (120 L) and processed in a controlled hydrodynamic cavitation device based on a fixed Venturi-shaped reactor. The A. alba water extract (AWE), comprising an oil-in-water emulsion of silver fir needles’ essential oil (100% AWE), was diluted in distilled water to 75% and 50% AWE, and all aqueous solutions were tested as antigerminant against four weeds and four horticultural species and compared to control (distilled water). This study shows the effective inhibitory effect of pure AWE on germination, which mainly contains limonene (15.99 ng/mL) and α-pinene (11.87 ng/mL). Seeds showed delayed germination and inhibition but also a reduction in radicle elongation in AWE treatments as compared to control. This combined effect was particularly evident in three weeds (C. canadensis, C. album and A. retrofllexus) while horticultural species showed mainly effects on the radicle elongation as found in L. sativa, P. crispum and S. lycospermum, which showed on average 58%, 32% and 28%, respectively, shorter radicles than in the control. P. sativum was not affected by AWE, thus raising the hypothesis that seed characteristics and nutrition reserve might play a role in the resistance to terpenes inhibitory effect.

This study investigated within-plant variability of the main bioactive compounds in rosemary (Rosmarinus officinalis L.). Volatile terpenes, including the enantiomeric distribution of monoterpenes, and phenols were analyzed in young and mature foliar, cortical and xylem tissues. In addition, antimicrobial activity of rosmarinic acid and selected terpenes was evaluated against two rosemary pathogens, Alternaria alternata and Pseudomonas viridiflava. Data showed that total concentration and relative contents of terpenes changed in relation to tissue source and age. Their highest total concentration was observed in the young leaves, followed by mature leaves, cortical and xylem tissues. Rosmarinic acid and carnosic acid contents did not show significant differences between leaf tissues of different ages, while young and mature samples showed variations in the content of four flavonoids. These results are useful for a more targeted harvesting of rosemary plants, in order to produce high-quality essential oils and phenolic extracts. Microbial tests showed that several terpenes and rosmarinic acid significantly inhibited the growth of typical rosemary pathogens. Overall, results on antimicrobial activity suggest the potential application of these natural compounds as biochemical markers in breeding programs aimed to select new chemotypes less susceptible to pathogen attacks, and as eco-friendly chemical alternatives to synthetic pesticides.

Plants produce considerable amounts of volatile organic compounds (VOCs) with several biological functions, including protection against biotic agents such as viruses and their vectors. In citrus species, these metabolites can be related with their different susceptibility/tolerance toward the Tristeza virus (CTV), one of the main biotic constraints for the citrus industry. The objective of this study was to compare the VOCs pattern from the leaves of a CTV-susceptible citrus variety such as Citrus aurantium and from three CTV-tolerant varieties: Citrus volkameriana, Carrizo citrange, and Forner-Alcaide no. 5. The VOCs emitted were analyzed via the headspace SPME method, while plant metabolites sequestered in the leaves were analyzed by heptane extraction followed by GC-MS. The results indicated that the majority of the VOCs emitted and sequestered in the leaves of the varieties tolerant and susceptible to CTV are constituted mainly by volatile terpenes (VTs) that exhibit strong qualitative/quantitative differences among the profiles of the four citrus species. In detail, the VOC emission indicated different patterns between C. aurantium and C. volkameriana and from both of them in comparison with Forner-Alcaide no. 5 and Carrizo citrange that exhibited more similarities, with the last two characterized by a higher presence of sesquiterpenes. The data obtained from the analysis of the VOCs sequestered in leaf tissues of the CTV-tolerant varieties indicated a higher presence of monoterpenes such as limonene, α-pinene, and p-cymene, known to be the main components of several plant extracts showing deterrent properties toward viruses and insect vectors. As VOC evaluation is a fast and noninvasive measure of phenotypic dynamics, allowing the association of plant phenotypes in accordance to plant disease resistance and/or stress tolerance, the possible implications of such differences in terms of tolerance grade to CTV and/or its related vectors are discussed.