Effects of Silver Fir (Abies alba Mill.) Needle Extract Produced via Hydrodynamic Cavitation on Seed Germination.

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.

Assessing the influence of topsoil and technosol characteristics on plant growth for the green regeneration of urban built sites.

Achieving urban regeneration through the creation of new green areas is a widely promoted strategy to improve the quality of life in densely built neighborhoods. "De-sealing" actions can compensate for the creation of new built-up areas, as demonstrated by the EU-funded Life + project 'Save our Soils for LIFE' (SOS4LIFE, LIFE15ENV/IT/000225), in which guidelines for de-sealing have been published. For the generation of new urban greening, it is important to know the characteristics of the soils used in order to better define the most appropriate landscaping decisions and management practices. In this study the physical and chemical characteristics of topsoils and technosols (soils enclosed under sealed surfaces) were assessed in relation to growth and leaf gas exchanges in two ornamental species (V. tinus and E. x ebbingei), in two partner municipalities of the project, Carpi and San Lazzaro di Savena (north-east Italy), during a three-year trial. Results of the study confirmed the dependence of plant growth on the chemical evolution of the soils, and identified the optimal soil moisture range based on soil texture and soil-plant water relationships. In addition, the technosols were found to actually be beneficial for plant growth, due to their high drainage capacity and nutrient content.

Temperature effects on recovery time of bacterial growth after rewetting dry soil.

The effect of temperature on the recovery of bacterial growth after rewetting dry soil was measured in a soil that responded with bacterial growth increasing immediately upon rewetting in a linear fashion (type (i) response sensu Meisner et al. (Soil Biol Biochem 66: 188-192, 2013)). The soil was air-dried for 4 days and then rewetted at different temperatures. Bacterial growth over time was then estimated using the leucine incorporation method. At 25 °C, the recovery of bacterial growth to levels of a wet control soil was rapid, within 6 h, while at 15 °C, recovery time increased to around 60 h, becoming more than a week at 5 °C. The temperature dependency of the recovery time was well modeled by a square root function. Thus, temperature will not only directly affect growth rates but also affect length of transition periods, like resuscitation after a drying event. The temperature during the rewetting event thus has to be taken into consideration when analyzing the microbial response dynamics.