Plant Growth and Root Morphology Are Affected by Earthworm-Driven (Eisenia sp.) Changes in Soil Chemico-Physical Properties: a Mesocosm Experiment with Broccoli and Faba Bean

Earthworms are "ecosystem engineers" that improve soil water and nutrient content, soil macroporosity, and aeration, and provide suitable habitats for microbial populations. This study aimed at defining if the presence of epigeic earthworms (Eisenia sp.) affected the growth and development of two plant species (Brassica oleracea and Vicia faba) via the modifications of soil chemico-physical properties. A mesocosm experiment, in which plants were grown outdoors for 4 months with or without earthworms, was performed. The two plant species were selected based on their different habitus and root architecture and morphology. Soil macroporosity (M-soil) and water holding capacity (WHCsoil) were determined. Earthworm-driven bioturbation (B-soil) was measured by filling mesh bags with artificial soil. Earthworm abundance and biomass, together with plant morphometric parameters (root and leaf morphology by imaging and microscope techniques), were measured at the end of the trial. The presence of earthworms increased M-soil (on average +16%) and WHCsoil (on average +9%) and this was accompanied by a remarkable degree of B-soil. In most of the cases, earthworms enhanced plant growth in the two plant species studied, with a significant positive influence on the majority of the shoot and root traits. A significant increase of stomatal density (on average +24%) occurred in the leaves of both the plant species in the presence of earthworms. Our results confirmed the hypothesis that bioturbation by Eisenia sp. had a significant positive effect on plant growth, independently from the plant species cultivated, and that these growth-promoting effects were mediated by changes in soil chemico-physical parameters. By taking into account the essential role of earthworms in maintaining healthy soils and the vegetation they support, soils can become more resilient against environmental perturbations and climate change

The assessment and the within-plant variation of the morpho-physiological traits and VOCs profile in endemic and rare Salvia ceratophylloides Ard. (Lamiaceae)

Salvia ceratophylloides (Ard.) is an endemic and rare plant species recently rediscovered as very few individuals at two different Southern Italy sites. The study of within-plant variation is fundamental to understand the plant adaptation to the local conditions, especially in rare species, and consequently to preserve plant biodiversity. Here, we reported the variation of the morpho-ecophysiological and metabolic traits between the sessile and petiolate leaf of S. ceratophylloides plants at two different sites for understanding the adaptation strategies for surviving in these habitats. The S. ceratophylloides individuals exhibited different net photosynthetic rate, maximum quantum yield, light intensity for the saturation of the photosynthetic machinery, stomatal conductance, transpiration rate, leaf area, fractal dimension, and some volatile organic compounds (VOCs) between the different leaf types. This within-plant morpho-physiological and metabolic variation was dependent on the site. These results provide empirical evidence of sharply within-plant variation of the morpho-physiological traits and VOCs profiles in S. ceratophylloides, explaining the adaptation to the local conditions

Spatial distribution of coarse root biomass and carbon in a high-density olive orchard: effects of mechanical harvesting methods

The in situ 3D root architecture of Olea europea was described by a semi-automatic 3D digitizing approach, which permitted the estimation of the biomass and carbon content of coarse roots in the soil environment.Coarse roots, the skeleton of the root system, are of primary importance for soil exploration and plant anchorage and only recently have been recognized as playing a major role in "long-term" carbon sequestration. Despite this role, the 3D architecture of coarse roots represents a gap in knowledge on the biomass and carbon allocation within the root system and, consequently, below-ground carbon sequestration capacity. Using a semi-automatic 3D digitizing approach (3 Space Fastrak plus Long Ranger), the 3D distribution in the soil environment of coarse root biomass and C content and how these parameters were affected by manual and mechanical (trunk shaker) harvesting methods were quantified in a high-density olive orchard. The below-ground C content at stand level was estimated to be 11.93 Mg C ha(-1) and distributed at deeper soil layers (45-60 cm) in the form of first- and second-order branching roots. The present study also revealed that the mechanical harvesting method significantly increased both the angle of growth (0A degrees = vertically downwards) of first-order lateral roots and the stump biomass, but neither the biomass allocation nor the C content was increased within the first three branching orders

Coumarin inhibits the growth of carrot (Daucus carota L. cv. Saint Valery) cells in suspension culture

We used a carrot (Daucus carota L. cv. Saint Valery) cell suspension culture as a simplified model system to study the effects of the allelochemical compound coumarin (1,2 benzopyrone) on cell growth and utilisation of exogenous nitrate, ammonium and carbohydrates. Exposure to micromolar levels of coumarin caused severe inhibition of cell growth starting from the second day of culture onwards. At the same time, the presence of 50μmol/L coumarin caused accumulation of free amino acids and of ammonium in the cultured cells, and stimulated their glutamine synthetase, glutamate dehydrogenase, glucose-6-phosphate dehydrogenase and phosphoenolpyruvate carboxylase activities. Malate dehydrogenase, on the other hand, was inhibited under the same conditions. These effects were interpreted in terms of the stimulation of protein catabolism and/or interference with protein biosynthesis induced by coumarin. This could have led to a series of compensatory changes in the activities of enzymes linking nitrogen and carbon metabolism. Because coumarin seemed to abolish the exponential phase and to accelerate the onset of the stationary phase of cell growth, we hypothesise that such allelochemical compounds may act in nature as an inhibitor of the cell cycle and/or as a senescence-promoting substance

Root architectural traits of rooted cuttings of two fig cultivars: Treatments with arbuscular mycorrhizal fungi formulation

Many fruit tree species develop symbioses relationships with mycorrhizal fungi by which they improve their efficiency in water and nutrient uptake and, in turn, increase their vegetative growth and productivity, particularly under stressful environments. These benefits origin from the effects that mycorrhizal determined on the root architecture, morphology and physiology. Usually, few attentions has been devoted to the tree root structure and function, especially, in fig plants during their growth phase in the nursery. Recently, several root traits or phenes have been reported as fundamental for the root functions such as the root length ratio (plant's potential for the exploitation of soil resources); root mass ratio (allocation traits); the root fineness and tissue density (structural traits); the root very fine, fine and coarse (functional traits). Aim of the study was to test the effects of an arbuscular mycorrhizal fungi (AMF) on the root architecture traits of self-rooted cuttings of two fig (Ficus carica L.) cultivars: Dottato and Natalese. The root architecture traits were evaluated by image analysis system (WinRHIZO). Single root traits and rooting architecture models were statistically tested by univariate and multivariate analysis, respectively. This study confirmed that also the Ficus carica was positively responsiveness to the mycorrhizal inoculation but with cultivar-dependent patterns. Further, the fig with coarse root architecture is more responsive to the fungi inoculation and the AMF induced different root architecture models in Natalese and Dottato suggesting diverse root strategies for exploiting the soil resources

Root morphology

Root system defined as the Hidden Half of plant, has not attracted a great deal of attention for a long time from plant biologists. In recent years, through the new innovative techniques, root system has been deeply studied allowing all to reveal its structure, function, but also its genetic potential, which could be manipulated to improve crop yield and plant survival in stressful environments. Plant root system has three major functions: site of water and nutrients acquisition from the soil, essential support for plant anchoring and sensor of abiotic and biotic stresses. It also points out secondary functions such as photoassimilates storage, phytohormones synthesis and clonal propagation