Comparative physiological and root transcriptome analysis of two annual ryegrass cultivars under drought stress.

Annual ryegrass is a widely cultivated forage grass with rapid growth and high productivity. However, drought is one of the abiotic stresses affecting ryegrass growth and quality. In this study, we compared the physiological and transcriptome responses of Chuansi No.1 (drought-tolerant, DT) and Double Barrel (drought-sensitive, DS) under drought stress simulated by PEG-6000 for 7 days. The results showed that Chuansi No. 1 had stronger physiological and biochemical parameters such as root properties, water content, osmotic adjustment ability and antioxidant ability. In addition, RNA-seq was used to elucidate the molecular mechanism of root drought resistance. We identified 8588 differentially expressed genes related to drought tolerance in root, which were mainly enriched in oxidation-reduction process, carbohydrate metabolic process, apoplast, arginine and proline metabolism, and phenylpropanoid biosynthesis pathways. The expression levels of DEGs were consistent with physiological changes of ryegrass under drought stress. We found that genes related to sucrose and starch synthesis, root development, osmotic adjustment, ABA signal regulation and specifically up-regulated transcription factors such as WRKY41, WRKY51, ERF7, ERF109, ERF110, NAC43, NAC68, bHLH162 and bHLH148 in Chuansi No. 1 may be the reason for its higher drought tolerance. This study revealed the underlying physiological and molecular mechanisms of root response to drought stress in ryegrass and provided some new candidate genes for breeding rye drought tolerant varieties.

Carbon-ZnO alternating quantum dot chains: electrostatic adsorption assembly and white light-emitting device application.

Aggregation-induced quenching (ACQ) in carbon nanodots (CNDs) impede their applications in solid devices. Herein, the concept of alternating quantum dot (QD) chains was proposed to overcome the common issue of fluorescence quenching in CNDs; in this study, CNDs and ZnO QDs were interlinked to form carbon-ZnO alternating quantum dot chains (CZA-QDCs), which overcame the ACQ of CNDs and hence ensured efficient full-spectrum fluorescence for white light-emitting devices (WLEDs) without excessive blue emission. Under the excitation of 365 nm lines, white emission resulting from the combination of blue emission from the CNDs and yellow emission from the ZnO QDs has been achieved from these powders. The quantum efficiency of the CZA-QDC powders can reach 49% and remain stable for two months. By coating the powders onto an ultraviolet chip as phosphors, WLEDs with a luminous efficiency of 20.1 lm W-1, color coordinate of (0.30, 0.35), correlated color temperature of 5205 K, and a color rendering index of 84 have been fabricated. Due to the relatively high abundance and eco-friendly characteristics of both carbon and ZnO, the results reported herein may provide a promising alternative to fluorescent phosphors that are widely used in WLEDs.