Maria Giordano

Impact of the invasive tree black locust on soil properties of Mediterranean stone pine-holm oak forests

Background and aimsInvasion by N2-fixing species may alter biogeochemical processes. We hypothesized that the grade of invasion by the N2-fixer black locust (Robinia pseudoacacia L.) could be related to the distribution and pools of carbon (C) and nitrogen (N) along the profile of two Mediterranean mixed forests of stone pine (Pinus pinea L.) and holm oak (Quercus ilex L.).MethodsA low-invaded (LIN) and a high-invaded (HIN) mixed forest were studied. We assessed: N concentration in green and in senescent leaves; C and N pools along the soil profile; seasonal changes of soluble C and N fractions, and microbial activity.ResultsCompared to coexisting holm oak and stone pine, black locust had higher N content in green and in senescent leaves. In the mineral soil: N stocks were similar in LIN and HIN; water soluble C and microbial activity, were lower in HIN compared to LIN; water soluble N showed seasonal changes consistent with tree growth activity in both HIN and LIN. In the organic layer of HIN, C and N stocks were about twofold larger than expected on the basis of stand density.ConclusionBlack locust increased C and N stocks in the upper organic layers that are more vulnerable to disturbance. However, it did not increase N stocks in the mineral soil.

Changes in Leaf Anatomical Traits Enhanced Photosynthetic Activity of Soybean Grown in Hydroponics with Plant Growth-Promoting Microorganisms

The use of hydroponic systems for cultivation in controlled climatic conditions and the selection of suitable genotypes for the specific environment help improving crop growth and yield. We hypothesized that plant performance in hydroponics could be further maximized by exploiting the action of plant growth-promoting organisms (PGPMs). However, the effects of PGPMs on plant physiology have been scarcely investigated in hydroponics. Within a series of experiments aimed to identify the best protocol for hydroponic cultivation of soybean [Glycine max (L.) Merr.], we evaluated the effects of a PGPMs mix, containing bacteria, yeasts, mycorrhiza and trichoderma beneficial species on leaf anatomy, photosynthetic activity and plant growth of soybean cv. ‘Pr91m10’ in closed nutrient film technique (NFT). Plants were grown in a growth chamber under semi-aseptic conditions and inoculated at seed, seedling and plant stages, and compared to non-inoculated (control) plants. Light and epi-fluorescence microscopy analyses showed that leaves of inoculated plants had higher density of smaller stomata (297 vs. 247 n/mm2), thicker palisade parenchyma (95.0 vs. 85.8 μm), and larger intercellular spaces in the mesophyll (57.5% vs. 52.2%), compared to non-inoculated plants. The modifications in leaf functional anatomical traits affected gas exchanges; in fact starting from the reproductive phase, the rate of leaf net photosynthesis (NP) was higher in inoculated compared to control plants (8.69 vs. 6.13 μmol CO2 m-2 s-1 at the beginning of flowering). These data are consistent with the better maximal PSII photochemical efficiency observed in inoculated plants (0.807 vs. 0.784 in control); conversely no difference in leaf chlorophyll content was found. The PGPM-induced changes in leaf structure and photosynthesis lead to an improvement of plant growth (+29.9% in plant leaf area) and seed yield (+36.9%) compared to control. Our results confirm that PGPMs may confer benefits in photosynthetic traits of soybean plants even in hydroponics (i.e., NFT), with positive effects on growth and seed production, prefiguring potential application of beneficial microorganisms in plant cultivation in hydroponics.

Functional quality in novel food sources: genotypic variation in the nutritive and phytochemical composition of thirteen microgreens species

Compositional variation was examined across 13 microgreens species/subspecies representing Brassicaceae, Chenopodiaceae, Lamiaceae, Malvaceae and Apiaceae, grown in controlled environment. Macro-mineral concentrations were determined by ion chromatography, chlorophyll and ascorbate concentrations, and hydrophilic/lipophilic antioxidant potentials by spectrophotometry, and major carotenoids by HPLC-DAD. Nitrate hyper-accumulators and wide genotypic differences in Na, K and S concentrations were identified. Antioxidant capacity was highest in brassicaceous microgreens and significant genotypic variation was demonstrated in chlorophyll and carotenoid concentrations. High phenolic content was confirmed in Lamiaceae microgreens, with significant varietal differences, and alternative phenolics-rich microgreens from the Apiaceae were identified. Twenty-eight phenolic compounds were variably detected and quantitated through Orbitrap LC-MS/MS with flavonol glycosides, flavones and flavone glycosides, and hydroxycinnamic acids representing 67.6, 24.8 and 7.6% of the mean total phenolic content across species, respectively. The obtained information is critical for selecting new species/varieties of microgreens that may satisfy demand for both taste and health.