Comparative Characterization of Eastern Carrot Accessions for Some Main Agricultural Traits

Background: Unevaluated open-pollinated germplasm represents a promising source of variability to face the problems of worldwide food production under a changing environment. In carrots, this is particularly true for black carrot accessions, which are the most relevant among Eastern carrot germplasm due to their high anthocyanin content and, concomitantly, antioxidant capacity. Methods: In the present work, a comparative characterization was conducted for the first time on 11 Eastern carrot landraces and Night Bird ‘F1’ as the reference cultivar, grown under glasshouse conditions at temperatures up to 33 °C. Results: Some landraces showed their potential for ulterior evaluation in terms of plant and taproot size, plant compactness, specific leaf area and leaf area ratio, among other traits. The highest anthocyanin and flavonoid contents were found in the reference cultivar, whereas remarkable differences in these variables were observed for the rest of accessions, which in turn may correlate with very distinct coloration patterns. Premature bolting and taproot shape abnormalities were also recorded. Mineral composition analysis showed the nutritional potential of Eastern carrot leaves, which displayed higher concentration than taproot tissue for several macro- and micronutrients. Moreover, several accessions had higher nutrient concentrations than the reference cultivar, which also highlights their profitability. Conclusions: This work contributes to the knowledge on Eastern black carrot germplasm by characterizing some of its main agricultural traits, and opens up the prospect for complementary evaluation on high-yield accessions.

Sample fabrication and metrological characterization of single-photon emitters based on nitrogen vacancy centers in nanodiamonds

Quantum metrology requires a stable single-photon emission and a high single-photon purity. Since nitrogen-vacancy (NV-) centers provide both features at room temperature, they are promising candidates for the application in this field [1, 2]. The knowledge about a suitable sample preparation technique is crucial, because the quality of the single-photon emission strongly depends on the sample purity and on the spatial resolvability of the emitters. This work presents the comparison and optimization of various sample fabrication techniques of nitrogen vacancy center doped nanodiamonds on standard cover glasses. The preparation is followed by a comparative characterization of the centers of the various samples. The sample fabrication includes the removal of contaminants on the cover glass surface. This was carried out by using peroxymonosulfuric acid (piranha solution, H2SO5) in comparison to the commercially available lye Hellmanex III (by Hellma Analytics). After cleaning the cover glasses, volumes of various nanodiamond dilutions were applied via spin coating. In subsequent steps, the nanodiamonds themselves were cleaned with peroxymonosulfuric acid, too, to remove contaminants resulting from the manufacturing process, e.g. graphite. The samples were analyzed by using a confocal laser scanning microscope with an oil immersion objective. Single-photon purity was determined by measuring the second order correlation function with a Hanbury Brown and Twiss setup. Spectral analysis revealed the presence of NV-- and NV0-centers. It was shown that a suitable cleansing method has an immense impact on single-photon emission, as was proven by a comparative characterization of differently manufactured nanodiamonds.