Determination of optimal NH4+/K + concentration and corresponding ratio critical for growth of tobacco seedlings in a hydroponic system

Inherently, ammonium (NH4+) is critical for plant growth; however, its toxicity suppresses potassium (K+) uptake and vice-versa. Hence, attaining a nutritional balance between these two ions (NH4+ and K+) becomes imperative for the growth of tobacco seedlings. Therefore, we conducted a 15-day experimental study on tobacco seedlings exposed to different concentrations (47 treatments) of NH4+/K+ at different corresponding 12 ratios simultaneously in a hydroponic system. Our study aimed at establishing the optimal NH4+-K+ concentration and the corresponding ratio required for optimal growth of different tobacco plant organs during the seedling stage. The controls were the baseline for comparison in this study. Plants with low or excessive NH4+-K+ concentration had leaf chlorosis or dark greenish colouration, stunted whole plant part biomass, and thin roots. We found that adequate K+ supply is a pragmatic way to mitigate NH4+-induced toxicity in tobacco plants. The optimal growth for tobacco leaf and root was attained at NH4+-K+ concentrations 2-2 mM (ratio 1:1), whereas stem growth was optimal at NH4+-K+ 1-2 mM (1:2). The study provided an insight into the right combination of NH4+/K+ that could mitigate or prevent NH4+ or K+ stress in the tobacco seedlings

Interfacial microstructure evolution and bonding mechanism transformation of CoCrFeMnNi high-entropy alloy joints fabricated by vacuum hot-compression bonding

Vacuum hot-compression bonding (VHCB) is a promising solid-phase bonding technology, but its feasibility and applicability in high entropy alloy (HEA) are still unclear. Herein, the VHCB process of CoCrFeMnNi HEA was investigated, and the interfacial bonding quality was comprehensively evaluated via microstructure characterization and tensile test. Results exhibit that the VHCB enables to obtain the high-quality CoCrFeMnNi HEA joints, and the excellent bonding performance is attributed to the dissolution of interfacial oxide particles (IOPs) (MnCr2O4) and the migration of interfacial grain boundaries (IGBs). The bonding quality results suggest that the sluggish diffusion of the dissolved elements resulted in partial nanoscale IOPs remaining at the original bonding interface, and the mechanical properties of the joints were not compromised when the IOPs were smaller than 35 nm in size and less than 15/100 μm in amount. Crystallographic analysis indicates that the migration behavior of IGBs is closely associated with the evolution of recrystallized grains and twin boundaries in the interfacial region, and the migration mechanism transformed with the rising bonding temperature. Furthermore, a new interfacial bonding mechanism, i.e., twin-induced interfacial boundary migration, was revealed and its beneficial effect on interfacial bonding quality was demonstrated

Achieving polycrystalline transformation and microstructural segregation reduction of nickel-based single crystal super-alloys by ultrasonic pulse arc welding

The sub-grains coarsening and low melting point eutectic are the internal causes of cracking of single crystal super-alloys in welding. Aiming to overcome two internal causes, in this paper, the effect of ultrasonic pulse arc welding on the grains, sub-grains and the precipitations of single crystal super-alloys (IN738) has been comprehensively studied, and the microstructure evolution of IN738 in ultrasonic pulse arc welding has been systematically revealed. The results show that (1) the combined effect of ultrasonic vibration and electromagnetic oscillation not only realizes the synchronous refinement of grains and sub-grains in WMZ (weld metal zone), and the polycrystalline transformation of single crystal super-alloys. A novel 3D schematic model of sub-grains is established to evaluate the size and orientation of sub-grains in 3D direction. (2) The ultrasonic vibration and electromagnetic field induced by ultrasonic pulse current can effectively reduce the microstructural segregation of welds. With the increase of ultrasonic pulse frequency, the size and volume fraction of harmful precipitations (η + δ eutectic, mixed eutectic and MC carbides) decrease greatly, especially the morphology and distribution characteristics of γ′ in HAZ (heat affected zone). Thanks to the above outstanding advantages, ultrasonic pulse arc welding has great application value in single crystal super-alloys

Adjusting cotton planting density under the climatic conditions of Henan Province, China.

The growth and development of cotton are closely related to climatic variables such as temperature and solar radiation. Adjusting planting density is one of the most effective measures for maximizing cotton yield under certain climatic conditions. The objectives of this study were (1) to determine the optimum planting density and the corresponding leaf area index (LAI) and yield under the climatic conditions of Henan Province, China, and (2) to learn how climatic conditions influence cotton growth, yield, and yield components. A three-year (2013-2015) field experiment was conducted in Anyang, Henan Province, using cultivar SCRC28 across six planting density treatments: 15,000, 33,000, 51,000, 69,000, 87,000, and 105,000 plants ha-1. The data showed that the yield attributes, including seed cotton yield, lint yield, dry matter accumulation, and the LAI, increased as planting density increased. Consequently, the treatment of the maximum density with 105,000 plants ha-1 was the highest-yielding over three years, with the LAIs averaged across the three years being 0.37 at the bud stage, 2.36 at the flower and boll-forming stage, and 1.37 at the boll-opening stage. Furthermore, the correlation between the cotton yield attributes and meteorological conditions indicated that light interception (LI) and the diurnal temperature range were the climatic factors that most strongly influenced cotton seed yield. Moreover, the influence of the number of growing degree days (GDD) on cotton was different at different growth stages. These observations will be useful for determining best management practices for cotton production under the climatic conditions of Henan Province, China

Differential Effects of Ammonium (NH₄⁺) and Potassium (K⁺) Nutrition on Photoassimilate Partitioning and Growth of Tobacco Seedlings

Plants utilize carbohydrates as the main energy source, but much focus has been on the impact of N and K on plant growth. Less is known about the combined impact of NH4+ and K+ nutrition on photoassimilate distribution among plant organs, and the resultant effect of such distribution on growth of tobacco seedlings, hence this study. Here, we investigated the synergetic effect of NH4+ and K+ nutrition on photoassimilate distribution, and their resultant effect on growth of tobacco seedlings. Soluble sugar and starch content peaks under moderate NH4+ and moderate K+ (2-2 mM), leading to improved plant growth, as evidenced by the increase in tobacco weight and root activity. Whereas, a drastic reduction in the above indicators was observed in plants under high NH4+ and low K+ (20-0.2 mM), due to low carbohydrate synthesis and poor photoassimilate distribution. A strong positive linear relationship also exists between carbohydrate (soluble sugar and starch) and the activities of these enzymes but not for invertase. Our findings demonstrated that NH4+ and K+-induced ion imbalance influences plant growth and is critical for photoassimilate distribution among organs of tobacco seedlings

Effects of thermal history of in-situ thermal management on as-built property heterogeneity of plasma arc additively manufactured Inconel 625

In-situ thermal management (ISTM) is one of the most prospective approaches to alleviating heat accumulation and achieving progressive forming for arc-based additive manufacturing. The aim of this study was to investigate the influences of thermal history, i.e., the cooling rate and the intrinsic heat treatment (IHT), of ISTM on as-built property heterogeneity of plasma arc additively manufactured Inconel 625 thin-wall deposit. The thermal history is obtained from numerical simulation. Results show that the variation of the thermal history of ISTM results in the bottom-up varied cooling rate and IHT, which together lead to the location-heterogeneous primary dendrite arm spacing, interdendritic phases and grain size. IHT of each layer is quantified by temperature-time integration (TTI), and Gaussian distributed TTI (above 600 °C) indicates the middle region of the deposit with ISTM is subjected to the most intense IHT. Compared with the counterpart of the conventional interlayer cooling strategy, the intensified high-temperature IHT of ISTM contributes to significant mitigation of micro-segregation, i.e., the brittle-hard interdendritic phases reduce 61.9%. Furthermore, a weighted value of cooling rate and TTI is innovatively introduced to depict the heterogeneity of mechanical property, which presents an exponential growth of ultimate tensile strength with the weighted value. Moreover, the layer-by-layer decreased heat input and the high-temperature preheating between layers of ISTM contribute to a certain residual stress release effect along the building direction