Synthesis and antibacterial applications of self-assembled carbon nanocrystals.

Divalent copper is a double-edged sword for plants, excess or shortage of copper ions will cause adverse reactions in plants. Currently, Cu2+ sensor for plants is still underdeveloped and new technology is urgently required for realizing one-step and real-time detection of Cu2+ in plants. Herein, a home-made and low-cost sensing platform is constructed by using carbon dots (CDs) as the optical probe, electronic devices for image acquisition, and a built-in algorithm program for image processing, which allows the dynamic monitoring of Cu2+ distribution in different plant species with high spatial and temporal resolution. We found that the detection limit of R-CDs for Cu2+ in water sample was 0.375 nM, and 11.7 mg/kg or even less Cu2+ in plants can be visually observed and accurately detected by the sensing platform. Moreover, this sensing platform has also been employed for reporting the spatial distribution of Cu2+ in the external environment of plants, demonstrating its applicability for monitoring Cu2+ both in living plants and the surrounding environment. This study provides a smart sensing platform for precise detection in plant internal and external environments, offering a promising strategy for precision agriculture in real-time and remote-control manners.

Optimizing photosynthesis is imperative for providing energy and organics for all life on the earth. Here, carbon dots doped with pyridinic nitrogen (named lev-CDs) are synthesized by the one-pot hydrothermal method, and the structure-function relationship between functional groups on lev-CDs and photosynthesis of Chlorella pyrenoidosa (C. pyrenoidosa) is proposed. Pyridinic nitrogen plays a key role in the positive effect on photosynthesis caused by lev-CDs. In detail, lev-CDs act as electron donors to supply photo-induced electrons to P680+ and QA+ , causing electron transfer from lev-CDs to the photosynthetic electron transport chain in the photosystems. In return, the recombination efficiency of electron-hole pairs on lev-CDs decreases. As a result, the electron transfer rate in the electron transport chain, the activity of photosystem II, and the Calvin cycle are enhanced. Moreover, the electron transfer rate between C. pyrenoidosa and external circumstances enhanced by lev-CDs is about 50%, and electrons exported from C. pyrenoidosa can be used to reduce iron(III). This study is of great significance for engineering nanomaterials to improve photosynthesis.

As the cadmium-free semiconductor quantum dots, ZnO quantum dots (ZnO QDs) have wide potential applications in agriculture. However, the effects of ZnO quantum dots on crop growth and nutritional quality have not been fully studied. In this work, the lettuce was sprayed with different concentrations of ZnO QDs from 50 to 500 mg·L–1 to evaluate their influence on lettuce antioxidant, biomass, and nutritional quality. The results showed that ZnO QDs existed in the lettuce in the form of Zn2+. Lettuce treated with 500 mg·L–1 ZnO QDs would produce a large amount of reactive oxygen species (ROS), which adversely affected the absorption of nutrients, soluble protein content, and chlorophyll content, thus reducing plant biomass. When the concentrations range from 50 to 200 mg·L–1, the antioxidant enzyme systems of lettuce were triggered to counteract the damage caused by excessive ROS. Moreover, ZnO QDs at this level promoted Ca, Mg, Fe, Mn, Zn, and B absorption and accumulation; increased soluble sugar content; and improved the lettuce biomass and nutritional quality.

The regulation of plant growth and developmental processes by carbon dots (CDs) has been frequently reported. However, little is known about how CDs are related to the yield and nutritional quality. In this study, carbon dots, obtained by the hydrothermal method with l-cysteine and glucose, were systematically characterized and applied to lettuces and tomatoes in a hydroponic nutrient solution to comprehensively investigate the mechanism of regulation of plant development by CDs. We found that CDs could accelerate seed germination, promote root and hypocotyl elongation of seedlings by activating the expression of genes encoding aquaporin proteins, and enhance the yield and nutritional qualities of mature plants by promoting the absorption of mineral elements together with the enhancement of photosynthesis. These results provide systematic insights into the mechanisms by which CDs regulate plant development.

Plant growth and development are tightly regulated by phytohormones. However, little is known about the interaction between auxin and gibberellin acid (GA) during flower stalk elongation and how it is directly related to organ formation. Therefore, the effects of indole acetic acid (IAA) and GA3 treatments and their interaction on flower stalk elongation in flowering Chinese cabbage were investigated. The growth of flowering Chinese cabbage is regulated by IAA and GA3, and the opposite results were observed after treatments with uniconazole (GA synthesis inhibitor) and N-1-naphthylphthalamic acid (NPA) (auxin transport inhibitor). Anatomical analysis of the pith region in stalks revealed that IAA promoted expansion via signal transduction and transport pathways. GA3 regulated the elongation of flower stalks by controlling GA synthesis and partially controlling the IAA signaling pathway. GA3 also had a stronger effect on stalk elongation than IAA. The results of qRT-PCR and histological analysis revealed that GA3 and IAA induced the expansion of cell walls by activating the expression of genes encoding cell wall structural proteins such as Expansin (EXP). These findings provide new insights into the mechanism of stalk formation regulated by the combination of IAA and GA3.

Red emissive carbon dots (RCDs) dominated by surface state emission mechanism were prepared by one-step hydrothermal method, the photoluminescence quantum yield (QY) of RCDs reaches to 78.3% in N,N-Dimethylformamide (DMF). RCDs mainly absorb UV and yellowish green light and emit red light in the region from 550 to 800 nm, which perfectly matches the light needed by plant for photosynthesis. Besides, the fluorescence quenching of RCDs is ascribed to oxidation on the surface of RCDs by oxygen. Further evidences about that are obtained from the changes in fluorescence, singlet oxygen (O-1(2)) signal of RCDs and the amount of O elements between the RCDs and quenched RCDs (QCDs). Antioxidant RCDs/PVA film, served as an agricultural sunlight conversion film, consisting of RCDs, polyvinyl alcohol-1799 (PVA-1799) and ascorbic acid, not only converts yellowish green light (500-610 nm) to red light (610-800 nm) from RCDs with tough, environment-friendly, waterproof properties from PVA-1799, but also gain antioxidant ability on account of ascorbic acid preventing the antioxidant RCDs/PVA film from fluorescence quenching. When antioxidant RCDs/PVA film was applied to the practical agricultural planting, the fresh weight, dry weight and the chlorophyll a content of the mung bean sprouts increased by 10.4% and 13.9%, and 7.1%, respectively. The application of the antioxidant RCDs/PVA film improve the utilization rate of solar energy in agricultural field.

Drought stress is widespread worldwide, which severely restricts world food production. The antioxidant property of carbon dots (CDs) is promising for inflammation and disease treatment. However, little is known about the functions of CDs in the abiotic stress of plants, especially in drought-resistant fields. In this study, CDs were synthesized using cysteine and glucose by the hydrothermal method. The in vitro antioxidant capacity of CDs and the reactive oxygen species (ROS) scavenging capacity were evaluated. We speculate on the antioxidant mechanism of CDs by comparing size distribution, fluorescence spectra, elements, and surface functional groups of CDs before and after oxidation. Besides, we evaluated the effects of CDs on seed germination and seedling physiology under drought stress. Also, the responses of antioxidant CDs to long-term drought stress and subsequent recovery metabolism in tomato plants were evaluated. The results show that CDs accelerated the germination rate and the germination drought resistance index by promoting the water absorption of seeds. CDs enhanced the drought resistance of seedlings by improving the activity of peroxidase (POD) and superoxide dismutase (SOD). Moreover, CDs can activate the antioxidant metabolism activity and upregulate the expression of aquaporin (AQP) genes SlPIP2;7, SlPIP2;12, and SlPIP1;7. All of these results render tomato plants distinguished resilience once rewatering after drought stress. These results facilitate us to design and fabricate CDs to meet the challenge of abiotic stress in food production.

白光LED器件作为新一代绿色固态照明光源,已广泛应用于照明、液晶背光等领域,也与智能照明、物联网技术等高新科技产业密切相关。常用的蓝光芯片复合黄光YAG∶Ce 3+ (Y 3 Al 5 O 12 ∶Ce 3+ )荧光粉的白光器件由于缺少红色光谱的成分,导致器件光谱较窄,显色指数较低,色温偏高。因此,红色荧光粉对改善白光LED的光色品质起到了重要作用。本文首先制备了红色碳点（量子效率28%）,通过把红色碳点与纤维素复合,制备了红色荧光粉（量子效率为18%）。该红色荧光粉与黄光YAG∶Ce 3+ 荧光粉混合,封装得到暖白光。结果表明,相较于只有黄光YAG∶Ce 3+ 荧光粉封装的LED,红色荧光粉掺杂之后,在460 nm蓝光芯片的激发下,白光LED的色坐标由（0.30,0.33）变化到（0.33,0.35）,色温从7 396 K下降到5 714 K,显色指数从78.2升高到82.9,实现了由色温高、显示指数低的冷白光向色温低、显色指数高的暖白光的调节。

以"油青33号"菜心为试材,采用温室盆栽方式,设置3个不同水杨酸浓度梯度(0,50、100 μmol ? L-1),从菜心四叶一心期至现蕾初期进行叶面喷施,探究了不同浓度水杨酸对菜心生长发育与营养品质的影响,以期为水杨酸在薹茎类蔬菜上的推广应用提供参考依据.结果表明:与对照相比,叶面喷施50、100 μmol ?L-1水杨酸均显著提高菜心现蕾率和开花率;水杨酸处理还明显增加菜心株高,增幅分别为18.06％、17.42％,但对茎粗有降低趋势;水杨酸处理增加菜心叶绿素含量且有降低Chl a/Chl b趋势,但对类胡萝卜素含量无明显影响;水杨酸处理还增加菜心可溶性糖、维生素C、可溶性蛋白质含量等品质指标,对于可溶性糖含量和维生素C含量,50 μmol ? L-1水杨酸处理高于100 μmol ? L-1处理,但对于可溶性蛋白质含量和游离氨基酸含量,2个处理呈现相反结果.相关性分析表明,水杨酸浓度与菜心株高、现蕾率、可溶性蛋白质含量、游离氨基酸含量呈显著正相关,而与菜心茎粗呈现显著负相关.综上所述,不同水杨酸处理可促进菜心植株生长发育、改善产品品质,以50 μmol ? L-1水杨酸的效果较佳.

Ammonium (NH4+) is generated during many endogenous metabolic processes in the leaves of plants, and there is increasing evidence that ammonium transporters (AMTs) play important roles in NH4+ transmembrane transport and distribution. However, the expression of different AMT genes is tissue-type specific and their functions differ. Information about AMT genes and their expression under different environmental conditions in flowering Chinese cabbage (Brassica campestris L.) is currently limited. Here, we isolated and characterized an AMT gene, BcAMT1;4, in flowering Chinese cabbage. BcAMT1;4 was localized to the plasma membrane and complemented NH4+ transport in NH4+ uptake-deficient yeast. The highest expression levels of BcAMT1;4 were detected in the flowers and leaves of flowering Chinese cabbage. The expression of BcAMT1;4 was induced by nitrogen deficiency and significantly inhibited by the reapplication of NH4+ (NH4Cl or NH4NO3). In contrast, when plants pre-cultured in nitrate were transferred to an NH4+ nutrient solution, BcAMT1;4 expression was significantly enhanced. BcAMT1;4 exhibited a diurnal expression pattern, with higher expression levels during the light period than during the dark period, and a peak expression at the later stage of the light period. Knowledge of AMT genes in flowering Chinese cabbage will lay a foundation for enhancing our understanding of the functional roles of different AMT members in the regulation of its growth by NH4+, as BcAMT1;4 seems to play an important role in leaf NH4+ transport.

转光膜具有转换光质、改善设施环境特征、提高作物产量和品质等优点,因此在设施园艺生产上得到了广泛的关注与应用.该研究综述了转光膜的原理及制备、转光膜的环境效应及转光膜在设施园艺生产中的应用,同时对转光膜的应用前景进行了展望,以期为转光膜研究及其在设施园艺生产中的应用提供参考依据.

以3个黄瓜品种的种子为试材,采用不同浓度(质量分数5％、10％、15％、20％)PEG-6000模拟干旱胁迫试验,测定了各品种的发芽率、相对发芽率、发芽指数、种子萌发抗旱指数、活力指数、种子活力抗旱指数、胚根长度以及幼苗叶绿素、丙二醛、脯氨酸含量.结果表明:各品种的发芽率、种子萌发抗旱指数、胚根长度等与PEG溶液的浓度呈明显的负相关关系;随PEG浓度的增加,3个黄瓜品种幼苗的丙二醛、脯氨酸含量增加,叶绿素含量有所下降;不同品种的抗旱性有所不同,“露地王”在种子萌发及生理指标方面均优于其它品种,表现出了最强的抗旱性.