RESUMO
Two-dimensional (2D) transition-metal carbon/nitrogen/carbon nitride (MXene) has extremely high conductivity and easily modifiable surface functional groups. Compared with graphene, another 2D layered material, MXene is easily dispersed in water owing to its hydrophilic groups. Its unique characteristics make MXene a valuable material. Nanocomposites can be endowed with functionality when MXene is compounded with an elastomer. Particularly in electromagnetic interference shielding and sensing, MXene exhibits extraordinary properties. We review various preparation methods, properties, and applications of MXene and MXene/elastomer nanocomposites and present a summary of the prospects for MXene/elastomer nanocomposites, which are in their initial stage of development and providing promising results.
RESUMO
Drought stress is considered the main obstacle restricting Camellia vietnamensis Huang (C. vietnamensis) yield. Hainan is the southernmost distribution region of C. vietnamensis in China and experiences a drought period annually. To study the drought-stress-response mechanism of C. vietnamensis, we treated seedlings of drought-tolerant (HD1) and drought-sensitive (WH1) cultivars with PEG-6000 (PEG) to simulate drought stress and compared the physiology and transcriptome of their leaves at 0 d, 3 d and 6 d posttreatment. Under drought stress, the growth of C. vietnamensis was inhibited, the relative water content (RWC) of leaves decreased and the contents of malondialdehyde (MDA), antioxidant enzyme activities, osmotic regulatory substances and secondary metabolites increased. Compared with those of WH1, the leaf RWC, osmotic-regulation substance content (proline, soluble protein and soluble sugar) and antioxidant enzyme activity (superoxide dismutase, peroxidase and catalase) of HD1 were significantly increased, while the relative electrical conductivity and MDA content were significantly decreased. Compared with WH1, 2812, 2070 and 919, differentially expressed genes (DEGs) were detected in HD1 0 d, 3 d and 6 d posttreatment, respectively, and the number of DEGs increased with increasing treatment time. The detected DEGs are involved in the drought stress response of C. vietnamensis mainly through plant-hormone signal transduction and lignin and flavonoid biosynthesis pathways. Drought stress significantly activated the expression of several lignin and flavonoid biosynthesis genes in HD1. Moreover, total flavonoid and total polyphenol contents in HD1 were significantly increased, suggesting that the accumulation of flavonoids may be a key factor in the drought stress response of C. vietnamensis. Additionally, 191 DEGs were associated with coding transcription factors (TFs). This study provides insight into the molecular mechanism of the drought stress response of C. vietnamensis and provides a theoretical basis for the development and cultivation of new drought-resistant cultivars.
