Peeling Affects the Nutritional Properties of Carrot Genotypes

Peeling may result in changes in carrot’s nutritional properties; therefore, the present study focused on its effect on the retention of principal nutrients (minerals, sugars, organic acids) and antioxidants (carotenoids and phenols) in the peeled roots of two landraces (‘Carota a punta lunga’—CPL and ‘Carota a punta tonda’—CPT) and a hybrid cultivar (‘Presto’) grown in the area of the “Salterns of Margherita di Savoia” area (Puglia region). The peel had a higher concentration of cations (+92%), organic acids (+103%), carotenoids (+42%), and phenolic acids (seven times) than root flesh. For each chemical class, the most abundant components were K, malic acid, ß-carotene, and chlorogenic acid, respectively. The two landraces stand out for the accumulation of the phenolic acids and ß-carotene, whereas the peel of ‘Presto’ was distinguished by the concentration of Ca and ascorbic and pyruvic acids. The root flesh had a greater accumulation of simple sugars, nitrate (mainly in CPL), oxalic acid, and in particular in the flesh of ‘Presto’, of Na and Cl. For local varieties, peel removal seems to impact the nutritional and antioxidative properties of carrots more consistently compared to the advanced cultivar, since it represents on average 21% and 59% of the total carotenoids and phenols, respectively, of the intact roots.

Root xylem in three woody angiosperm species is not more vulnerable to embolism than stem xylem

AimsSince plants are compartmentalised organisms, failure of their hydraulic transport system could differ between organs. We test here whether xylem tissue of stems and roots differ in their drought-induced embolism resistance, and whether intact roots are equally resistant to embolism than root segments.MethodsEmbolism resistance of stem and root xylem was measured based on the pneumatic technique for Acer campestre, A. pseudoplatanus and Corylus avellana, comparing also intact roots and root segments of C. avellana. Moreover, we compared anatomical features such as interconduit pit membrane between roots and stems.ResultsWe found a higher embolism resistance for roots than stems, although a significant difference was only found for A. pseudoplatanus. Interconduit pit membrane thickness was similar for both organs of the two Acer species, but pit membranes were thicker in roots than stems of C. avellana. Also, embolism resistance of an intact root network was similar to thick root segments for C. avellana.ConclusionOur observations show that root xylem is not more vulnerable to embolism than stem xylem, although more species need to be studied to test if this finding can be generalised. We also demonstrated that the pneumatic method can be applied to non-terminal plant samples.

Mycolactone-independent pathogenicity of Mycobacterium ulcerans: an experimental study in plants

ABSTRACTMycobacterium ulcerans, the etiologic agent of Buruli ulcer in humans and animals, secretes macrolide exotoxins mycolactones which damage tissues after a cascade of cellular effects. M. ulcerans, an environmental organism with still elusive reservoirs and sources has been detected in soil and water in endemic areas where it could be in contact with plants. Symptom observations, microscopy and molecular biology were used to investigate M. ulcerans contact with plants in an experimental model mimicking the known pathology of Buruli ulcer in humans. Solanum lycopereum (tomato) plants with scarified or intact roots were transplanted into pots containing contaminated soil with M. ulcerans or a mixture of mycolactones A/B and C in the presence of negative control groups. Whereas plants with intact roots remained asymptomatic, M. ulcerans-infected plants with scarified roots had significantly more diseased leaves than controls (p = 0.004). Optic microscopy examination showed significantly more mycobacteria in the secondary and main roots than in controls (p=0.0008). Real-time PCRs detected M. ulcerans DNA in 7/12 (58%) of infected root samples versus none in the control plants (p = 0.04). Further study of plants with mycolactones A/B and C yielded no significant difference with negative controls. These results suggest that in this model, M. ulcerans exhibits a mycolactone-independent pathogenicity whose mechanism remains to be elucidated.

Formation of root silica aggregates in sorghum is an active process of the endodermis

Silica deposition in plants is a common phenomenon that correlates with plant tolerance to various stresses. Deposition occurs mostly in cell walls, but its mechanism is unclear. Here we show that metabolic processes control the formation of silica aggregates in roots of sorghum (Sorghum bicolor L.), a model plant for silicification. Silica formation was followed in intact roots and root segments of seedlings. Root segments were treated to enhance or suppress cell wall biosynthesis. The composition of endodermal cell walls was analysed by Raman microspectroscopy, scanning electron microscopy and energy-dispersive X-ray analysis. Our results were compared with in vitro reactions simulating lignin and silica polymerization. Silica aggregates formed only in live endodermal cells that were metabolically active. Silicic acid was deposited in vitro as silica onto freshly polymerized coniferyl alcohol, simulating G-lignin, but not onto coniferyl alcohol or ferulic acid monomers. Our results show that root silica aggregates form under tight regulation by endodermal cells, independently of the transpiration stream. We raise the hypothesis that the location and extent of silicification are primed by the chemistry and structure of polymerizing lignin as it cross-links to the wall.

Measuring Root Hydraulic Parameters of Container-grown Herbaceous and Woody Plants Using the Hydraulic Conductance Flow Meter

Root hydraulic conductance and conductivity are physiological traits describing the ease with which water can move through the belowground vascular system of a plant, and are used as indicators of plant performance and adaptability to a given environment. The ability to measure hydraulic conductance of container-grown herbaceous and semiwoody plants with soft conductive tissue was tested using a hydraulic conductance flow meter (HCFM). Although the HCFM is a hydraulic apparatus that has been used on woody plants to measure hydraulic conductance of intact roots, it has never been reportedly used on container-grown horticultural plants. Two herbaceous species, Chrysanthemum L. and Solenstemon scutellarioides Thonn., were grown in containers and hydraulic parameters were measured, including root conductance and root conductivity, as well as physical traits such as stem diameter and dry root mass. The HCFM was easily connected to intact roots even on herbaceous stems and was used to determine hydraulic conductance and conductivity directly on container-grown plants with minimal disturbance on the root system. Chrysanthemums, Buddleja davidii Franch., and Hibiscus moscheutos L. were grown in three different substrates, and both root mass and root hydraulic parameters were determined. Chrysanthemums showed a positive response with increasing root hydraulic conductance with increasing root mass. The substrates used in these studies only had an effect on root biomass of chrysanthemums, but substrates had no differential effect on root hydraulic conductivity.

Temporal dynamics of nitrogen rhizodeposition in field pea as determined by 15N labeling

Arcand, M. M., Knight, J. D. and Farrell, R. E. 2013. Temporal dynamics of nitrogen rhizodeposition in field pea as determined by 15 N labeling. Can. J. Plant Sci. 93: 941–950. Assessing the contribution of symbiotically fixed N2 to soil from pulse crops necessitates a full accounting of the total crop residue N remaining in the field after seed harvest. Below-ground N, including root and rhizodeposit N, comprises an important component of this total plant N balance – without it the N input to soil is underestimated. Under controlled conditions in a greenhouse, N in intact roots and N rhizodeposition were quantified in field pea (Pisum sativum L.) using the cotton-wick 15N labeling technique. Plants were supplied with 15N on a continuous basis and harvested at the vegetative stage (nine leaves unfolded), flowering, and maturity. As the plants aged, the 15N enrichment in the rhizosphere soil decreased, whereas that in the bulk soil increased, suggesting that N released as root exudates comprised a more important proportion of N rhizodeposition in plants at the early vegetative stage compared with mature plants. In mature plants, N rhizodeposition was comprised predominantly of N associated with root turnover. The contribution of N rhizodeposition recovered in soil to the total plant N balance decreased from 17.8% at the vegetative stage harvest, to 12.3% at flowering, and finally to 7.5% at maturity. However, the total amount of root-derived N released to soil by pea increased with plant development. Below-ground N, including N rhizodeposition and N in intact roots contributed 11.3% to the total plant N balance of mature pea.

Abstract 036: The Role Of Spinal Modulation On The Ventricular Electrophysiology In A Porcine Model

Background: Enhanced cardiac sympathetic tone has been associated with ventricular arrhythmias and sudden cardiac death. The spinal cord is an important integrative region of afferent and efferent pathways that participate in cardiovascular regulation. The purpose of this study is to investigate the role of spinal processing of cardiac afferent information on ventricular electrophysiology during cardiac sympathoexcitation. Methods: Female Yorkshire pigs (n=5) underwent surgical exposure of the heart and left stellate ganglion (LSG) through thoractomy as well as the dorsal and ventral roots of the spinal cord through laminectomy. A 56-electrode sock was placed over the ventricles to record epicardial electrograms. Animals underwent LSG stimulation in intact, after dorsal root transaction (DRTx), and followed by ventral root transaction (DVRTx). Activation recovery intervals (ARIs) were measured at each electrode before and during LSG stimulation. Results: With intact roots LSG stimulation resulted in significant global ARI shortening by 12.9% (p<0.05). After DRTx, mean global ARI shortened by 7.2%. LSG stimulation after DRTx and DVRTx resulted in greater ARI shortening compared to LSG stimulation with intact roots (21.5 and 18.4 vs 12.9%, p<0.05, see figure 1 below). ARI shortened more during LSG stimulation after DRTx than that after DVRTx (21.5 vs. 18.4%, p<0.05). Conclusion: Spinal afferent pathways play an inhibitory role in sympathoexcitation of ventricle induced by LSG stimulation. This finding provides insight into the mechanism underlying the beneficial effects of thoracic epidural anesthesia in reducing ventricular arrhythmias.

Regeneration of Canada Thistle (Cirsium arvense) from Intact Roots and Root Fragments at Different Soil Depths

In the present field study, the capability of Canada thistle to develop shoots from intact roots and root fragments at different soil depths was studied. The experiments were performed on four sites with high-density Canada thistle, with three or four replications per treatment. At each site, the soil in the plots was removed layer by layer (to 30 or 40 cm, depending on the site), within a 1 by 1-m quadrat, and spread out on a plastic sheet. All roots and other plant parts were removed, and the soil was either replaced without any root material (two sites), or the roots of the thistles were cut into 10-cm-long fragments and replaced into the source holes (two sites). The measured variables were shoot number and biomass. The number of shoots of Canada thistle decreased with increasing depth (P < 0.001) and increased with time. Additionally, the two factors interacted (P < 0.001) such that shoot development was slower from greater depths. Roots from ≤ 20 cm depth produced higher biomasses than did roots from below 20 cm depth. Replacement of root fragments did not affect the amount of biomass produced. It was concluded that the intact root system contributed considerably more to the total biomass produced by Canada thistle than did the root fragments in the upper soil layers.