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2D half‐metallic multiferroic materials have attracted great interest due to their rich novel performances and wide application prospect in nanoelectronics and nanodevices. Three intrinsic half‐metallic multiferroic monolayers AV2S4 (A = Na, K, and Rb) are predicted based on the first‐principles calculations. From the calculations, their ground states are all ferromagnetic and are completely spin‐polarized at the Fermi level. Their total magnetic moments are always 3.00 μB per primitive cell, which origin mainly from V‐ions. The two‐center electronic structure t2g6↑t2g4↓eg1↑ of V‐ions is proposed from the perspective of the crystal field theory to explain successfully the calculated magnetic moments. Interestingly, the alkali‐metal ions are non‐magnetic, but they may cause important influence on the magnetic coupling between transition ions, and then the half‐metallicity of these monolayers. Their electric and magnetic properties may be tuned by their charge states and strains. Especially, their half‐metallic stability may be evidently improved by the tensile strains. The half‐metallic gaps of these monolayers may be increased by about 67.4%, 50.8%, and 32.4% for NaV2S4, KV2S4, and RbV2S4 by the tensile strain 2.0%, respectively. [ABSTRACT FROM AUTHOR]

Sweetpotato is a heliophile crop. However, it is usually shaded in the lower position in the interplanting cultivation mode. During the middle and late field growing period, it often faces rainy weather with little illumination, which affects the dry matter accumulation in tuberous roots. Thus, analyzing the metabolic response pathways of sweetpotato under shade stress will provide the theoretical basis for the varieties' genetic improvement of shade tolerance. In this study, the sweetpotato variety Zhenghong 23 was exposed to shade stress with 50% light transmittance for 15 days. Results showed that chlorophyll b and the total chlorophyll contents of Zhenghong 23 under shade stress were significantly increased compared with those under natural light. The maximum photochemical efficiency (Fv/Fm), the potential activity (Fv/Fo), and the comprehensive index of photosynthetic performance (PIABS) of the chlorophyll photosystem PSII decreased significantly under shade stress. The net photosynthetic rate and water use efficiency decreased significantly, while SOD and POD enzyme activities increased significantly. In addition, shade stress increased significantly the vine length and specific leaf area of Zhenghong 23, but reduced significantly the fresh weight of roots. Transcriptome and metabolome analysis of leaf tissues under shade stress and natural light conditions showed that the DEGs and DMs were mainly enriched in phenylpropanoid biosynthesis, sugar metabolism, sphinolipid metabolism, and arginine biosynthesis pathways. Most of the up-regulated DEGs enriched in the phenylpropanoid biosynthesis pathway were POD enzyme family genes, indicating that the shade stress triggered the ROS scavenging system in sweetpotato. Meanwhile, shade stress reduced sugar metabolism level of sweetpotato, decreased the soluble sugar content of leaves, inhibited both the synthesis and degradation of starch, and blocked the expansion of tuberous roots. In addition, the sphinolipid and arginine metabolism pathways may better adapt sweetptoato plants to shade stress through improving the stability of biomembranes and increase the synthetic substrates of polyamine anti-stress factors. These results provide new theoretical basis for understanding the metabolic response pathways of sweetpotato under shade stress. [ABSTRACT FROM AUTHOR]