Water stress is one of the most important factors limiting sustainable crop production. Therefore, the effects of the plant growth regulators (PGRs) fulvic acid (FA), brassinolide (BR), and uniconazole (Uni) on seedling growth and physiology of two maize (Zea mays L.) varieties were evaluated under???0.7 MPa water stress induced by polyethylene glycol-6000. Under drought stress, the PGRs promoted seedling growth, altered the root-to-shoot ratio, and significantly increased root biomass, length, surface area, diameter, and volume. In addition, depending on the PGR, net photosynthesis rate, SPAD value (indicating chlorophyll content), and water use efficiency increased significantly, under drought stress, whereas transpiration rate decreased. The PGRs also significantly increased antioxidant enzyme activities and significantly decreased malondialdehyde accumulation in leaves and roots under drought stress. Zhengdan958 showed greater variation in physiological responses and stronger drought resistance than Xundan20. In alleviating drought stress in maize seedlings, FA had the greatest effects on shoot growth and leaf physiology; Uni exerted its effects by regulating root structure, and BR effects were intermediate. Under drought stress, the three PGRs increased maize seedling growth, which reduced drought stress-induced damage and improved plant ability to resist the adversity. Based on a comprehensive analysis of physiological indices of drought resistance, Uni is recommended as the best PGR to improve maize seedlings resistance to drought.
Rational design of high-efficiency N-heterocyclic carbene (NHC) palladium catalyst is of great importance to modern organic synthesis, especially in chemical and pharmaceutical industries. Herein, we fabricate a polymer network containing N-heterocyclic carbene palladium (PNNHC-Pd) catalytic active sites via an immobilization process. The N-heterocyclic carbene palladium can serve as a promising linkage of polymer network as well as an effective catalytic active site owing to its structural preference and strong σ-donating ability with palladium species. The results display that N-heterocyclic carbene palladium disperses homogeneously in polymer network, thus rendering PNNHC-Pd excellent catalytic activity, high stability and superior reusability in palladium-catalyzed Suzuki–Miyaura coupling reaction in aqueous medium. This work provides a new insight into the development of heterogenization of homogeneous catalysts based on polymer network. 相似文献
In recent years, black ginseng, a new type of processed ginseng product, has attracted the attention of scholars globally. Ginsenoside and ginseng polysaccharide, the main active substances of black ginseng, have been shown to carry curative effects for many diseases. This article focuses on the mechanism of their action in anti-inflammatory response, which is mainly divided into three aspects: activation of immune cells to exert immune regulatory response; participation in inflammatory response-related pathways and regulation of the expression level of inflammatory factors; effect on the metabolic activity of intestinal flora. This study identifies active anti-inflammatory components and an action mechanism of black ginseng showing multi-component, multi-target, and multi-channel characteristics, providing ideas and a basis for a follow-up in-depth study of its specific mechanism. 相似文献
The ithomiine butterflies (Nymphalidae: Danainae) represent the largest known radiation of Müllerian mimetic butterflies. They dominate by number the mimetic butterfly communities, which include species such as the iconic neotropical Heliconius genus. Recent studies on the ecology and genetics of speciation in Ithomiini have suggested that sexual pheromones, colour pattern and perhaps hostplant could drive reproductive isolation. However, no reference genome was available for Ithomiini, which has hindered further exploration on the genetic architecture of these candidate traits, and more generally on the genomic patterns of divergence. Here, we generated high-quality, chromosome-scale genome assemblies for two Melinaea species, M. marsaeus and M. menophilus, and a draft genome of the species Ithomia salapia. We obtained genomes with a size ranging from 396 to 503 Mb across the three species and scaffold N50 of 40.5 and 23.2 Mb for the two chromosome-scale assemblies. Using collinearity analyses we identified massive rearrangements between the two closely related Melinaea species. An annotation of transposable elements and gene content was performed, as well as a specialist annotation to target chemosensory genes, which is crucial for host plant detection and mate recognition in mimetic species. A comparative genomic approach revealed independent gene expansions in ithomiines and particularly in gustatory receptor genes. These first three genomes of ithomiine mimetic butterflies constitute a valuable addition and a welcome comparison to existing biological models such as Heliconius, and will enable further understanding of the mechanisms of adaptation in butterflies. 相似文献
The relationship between head pteridine fluorescence (HPF) levels and age in adult females and males of a common necrophagous fly, Chrysomya megacephala, and effects of temperature and fly sex on the relationship were studied by pteridine fluorescence spectrophotometry. Factors affecting HPF levels in flies were found to include fly age, temperature and fly sex, among which the fly age was the most dominant one. There were significant linear relationships between HPF levels and age both for female and male adult flies at five constant temperatures, i. e. 16°C, 20°C, 24°C, 28°C and 32°C. The relationship between mean rate of pteridine accumulation (FV or MV) and temperature (t) could be well described by a modified exponential equation of FV=0.01288 e(0.2241t‐3.127)+0.3649 (r2= 0.9987) for females and a linear regression equation of MV= 0.0574 t ‐ 0.3637 (r2= 0.9557) for males. Using the information from the experiments at five constant temperatures, three calculated methods as the candidates were developed for accurately determining the age of the fly by HPF levels at ambient temperature. The results revealed that these three methods were suitable for estimating the age only for male flies, but not for female flies. The smallest average error of the predicated age was 2.55 days for males. In addition, how to employ which of these three developed methods for determining ages of male flies in practical was also discussed. 相似文献
In previous studies with tropical plant species, low root zone temperature (RZT) induced boron (B) deficiency, but it is not known if the same response to RZT will be expressed in temperate species, like oilseed rape, that are more tolerant of low temperature. The present experiments investigated the effect of RZT (10 and 20°C) on oilseed rape ( Brassica napus L. cv. Hyola 42) response to B in solution culture, in summer and winter. Regardless of canopy growth conditions, low RZT (10°C) promoted the partitioning of shoot B to the actively growing leaves, especially when B supply was low. However, low RZT did not significantly alter net B uptake rates or plant biomass. Low RZT decreased the shoot-to-root ratio, countering the effects of low B which increased it, leading to a decreased demand for B in the shoot at low RZT. At low B supply, B-deficiency symptoms appeared later at 10 than at 20°C, corresponding with higher B concentrations in the youngest fully opened leaves (YOLs) at 10°C RZT. Thus 10°C RZT increased the tolerance to low B supply. As a result, it is concluded that the effect of decreasing RZT on the responses of the temperate species, oilseed rape, to low B supply depends on whether the low RZT is above or below the optimal root temperature for growth. 相似文献
Responses in stomatal conductance (gst) and leaf xylem pressure potential (
leaf) to elevated CO2 (2x ambient) were compared among 12 tallgrass prairie species that differed in growth form and growth rate. Open-top chambers (OTCs, 4.5 m diameter, 4.0 m in height) were used to expose plants to ambient and elevated CO2 concentrations from April through November in undisturbed tallgrass prairie in NE Kansas (USA). In June and August,
leafwas usually higher in all species at elevated CO2 and was lowest in adjacent field plots (without OTCs). During June, when water availability was high, elevated CO2 resulted in decreased gstin 10 of the 12 species measured. Greatest decreases in gst(ca. 50%) occurred in growth forms with the highest potential growth rates (C3 and C4 grasses, and C3 ruderals). In contrast, no significant decrease in gstwas measured in the two C3 shrubs. During a dry period in September, reductions in gstat elevated CO2 were measured in only two species (a C3 ruderal and a C4 grass) whereas increased gstat elevated CO2 was measured in the shrubs and a C3 forb. These increases in gstwere attributed to enhanced
leafin the elevated CO2 plants resulting from increased soil water availability and/or greater root biomass. During a wet period in September, only reductions in gstwere measured in response to elevated CO2. Thus, there was significant interspecific variability in stomatal responses to CO2 that may be related to growth form or growth rate and plant water relations. The effect of growth in the OTCs, relative to field plants, was usually positive for gstand was greatest (>30%) when water availability was low, but only 6–12% when
leafwas high.The results of this study confirm the importance of considering interactions between indirect effects of high CO2 of plant water relations and direct effects of elevated CO2 on gst, particularly in ecosystems such as grasslands where water availability often limits productivity. A product of this interaction is that the potential exists for either positive or negative responses in gstto be measured at elevated levels of CO2. 相似文献
This paper reports studies on the growth and biosynthesis of monoterpenes by transformed shoot cultures of Mentha citrata and Mentha piperita, originally developed 5 years ago and since maintained by regular subculturing. Throughout this time, the M. citrata culture has stably maintained production of an oil closely resembling that of the parent plant in which linalool and linalyl acetate are the predominant components. However, M. piperita, which initially showed a divergence from the parent plant in producing significant amounts of menthofuran in addition to the characteristic oil components menthol and menthone, has now been found to produce pulegone and menthofuran as the major components. The cultures were subjected to different environmental conditions of varying periods of light and temperature in an attempt to restore menthol and menthone production. Increased illumination reduced the yields of pulegone and menthofuran but did not stimulate the production of either menthol or menthone, which remained only at trace levels (below 0.2 g/g fresh weight). Cultures of M. citrata were, however, stimulated by increased illumination, and produced more linalool and linalyl acetate. Shoot cultures of M. citrata and M. piperita were grown in 14–1 fermenters for up to 60 dys during which the biomass increased from approximately 100 g to 2.5 kg and 3.5 kg respectively. Both cultures rapidly consumed sucrose with a concomitant release of glucose, and the uptake of inorganic ions was similar except that M. citrata consumed far less Na+ during the fermentation. The total yields of monoterpenes from the fermentations were 1.16 g (M. piperita) and 0.18 g (M. citrata). *** DIRECT SUPPORT *** AG903062 00005 相似文献