Combined application of organic fertilizer and chemical fertilizer alleviates the kernel position effect in summer maize by promoting post-silking nitrogen uptake and dry matter accumulation

Adjusting agronomic measures to alleviate the kernel position effect in maize is important for ensuring high yields.In order to clarify whether the combined application of organic fertilizer and chemical fertilizer(CAOFCF)can alleviate the kernel position effect of summer maize,field experiments were conducted during the 2019 and 2020 growing seasons,and five treatments were assessed:CF,100%chemical fertilizer;OFCF1,15%organic fertilizer+85%chemical fertilizer;OFCF2,30%organic fertilizer+70%chemical fertilizer;OFCF3,45%organic fertilizer+55%chemical fertilizer;and OFCF4,60%organic fertilizer+40%chemical fertilizer.Compared with the CF treatment,the OFCF1 and OFCF2 treatments significantly alleviated the kernel position effect by increasing the weight ratio of inferior kernels to superior kernels and reducing the weight gap between the superior and inferior kernels.These effects were largely due to the improved filling and starch accumulation of inferior kernels.However,there were no obvious differences in the kernel position effect among plants treated with CF,OFCF3,or OFCF4 in most cases.Leaf area indexes,post-silking photosynthetic rates,and net assimilation rates were higher in plants treated with OFCF1 or OFCF2 than in those treated with CF,reflecting an enhanced photosynthetic capacity and improved postsilking dry matter accumulation(DMA)in the plants treated with OFCF1 or OFCF2.Compared with the CF treatment,the OFCF1 and OFCF2 treatments increased post-silking N uptake by 66.3 and 75.5%,respectively,which was the major factor driving post-silking photosynthetic capacity and DMA.Moreover,the increases in root DMA and zeatin riboside content observed following the OFCF1 and OFCF2 treatments resulted in reduced root senescence,which is associated with an increased post-silking N uptake.Analyses showed that post-silking N uptake,DMA,and grain yield in summer maize were negatively correlated with the kernel position effect.In conclusion,the combined application of 15-30%organic fertilizer and 70-85%chemical fertilizer alleviated the kernel position effect in summer maize by improving post-silking N uptake and DMA.These results provide new insights into how CAOFCF can be used to improve maize productivity.

Effects of drought on non-structural carbohydrates and C,N,and P stoichiometric characteristics of Pinus yunnanensis seedlings

To study non-structural carbohydrate character-istics and nutrient utilization strategies of Pinus yunnanen-sis under continuous drought conditions,2-year-old seed-lings were planted in pots with appropriate water,light and moderate and severe drought treatments[(80±5),(65±5),(50±5),and(35±5)%of field water-holding capacity].Non-structural carbohydrates,carbon(C),nitrogen(N),and phosphorus(P)concentrations were measured in each plant component.The results show that:(1)With increasing drought,non-structural carbohydrates gradually increased in leaves,stems,and coarse roots,while gradually decreased in fine roots;(2)C concentrations of all were relatively stable under different stress levels.Phosphorous utilization of each component increased under light and moderate drought conditions,while N and P utilization efficiency of each plant component decreased under severe drought.Growth was mainly restricted by N,first decreasing and then increasing with increased drought;(3)There was a correlation between the levels of non-structural carbohydrates and C,N,and P in each component.Changes in N concentration affected the interconversion between soluble sugar and starch,which play a regulatory role in the fluctuation of the concentration of non-structural carbohydrates;and,(4)Plasticity analysis showed that P.yunnanensis seedlings responded to drought mainly by altering starch concentration,the ratio of soluble sugar to starch in leaves and stems,and further by alter-ing N and P utilization efficiencies.Overall,these results suggest that the physiological activities of all organs of P.yunnanensis seedlings are restricted under drought and that trade-offs exist between different physiological indicators and organs.Our findings are helpful in understanding non-structural carbohydrate and nutrient adaptation mechanisms under drought in P.yunnanensis seedlings.

Novel miR-490-3p/hnRNPA1-b/PKM2 axis mediates the Warburg effect and proliferation of colon cancer cells via the PI3K/AKT pathway

BACKGROUND Heterogeneous ribonucleoprotein A1(hnRNPA1)has been reported to enhance the Warburg effect and promote colon cancer(CC)cell proliferation,but the role and mechanism of the miR-490-3p/hnRNPA1-b/PKM2 axis in CC have not yet been elucidated.AIM To investigate the role and mechanism of a novel miR-490-3p/hnRNPA1-b/PKM2 axis in enhancing the Warburg effect and promoting CC cell proliferation through the PI3K/AKT pathway.METHODS Paraffin-embedded pathological sections from 220 CC patients were collected and subjected to immunohistochemical analysis to determine the expression of hnRNPA1-b.The relationship between the expression values and the clinicopathological features of the patients was investigated.Differences in mRNA expression were analyzed using quantitative real-time polymerase chain reaction,while differences in protein expression were analyzed using western blot.Cell proliferation was evaluated using the cell counting kit-8 and 5-ethynyl-2’-deoxyuridine assays,and cell cycle and apoptosis were detected using flow cytometric assays.The targeted binding of miR-490-3p to hnRNPA1-b was validated using a dual luciferase reporter assay.The Warburg effect was evaluated by glucose uptake and lactic acid production assays.RESULTS The expression of hnRNPA1-b was significantly increased in CC tissues and cells compared to normal controls(P<0.05).Immunohistochemical results demonstrated significant variations in the expression of the hnRNPA1-b antigen in different stages of CC,including stage I,II-III,and IV.Furthermore,the clinicopathologic characterization revealed a significant correlation between hnRNPA1-b expression and clinical stage as well as T classification.HnRNPA1-b was found to enhance the Warburg effect through the PI3K/AKT pathway,thereby promoting proliferation of HCT116 and SW620 cells.However,the proliferation of HCT116 and SW620 cells was inhibited when miR-490-3p targeted and bound to hnRNPA1-b,effectively blocking the Warburg effect.CONCLUSION These findings suggest that the novel miR-490-3p/hnRNPA1-b/PKM2 axis could provide a new strategy for the diagnosis and treatment of CC.

Effects of tree size and organ age on variations in carbon,nitrogen,and phosphorus stoichiometry in Pinus koraiensis

Carbon(C),nitrogen(N),and phosphorus(P)are of fundamental importance for growth and nutrient dynamics within plant organs and deserve more attention at regional to global scales.However,our knowledge of how these nutrients vary with tree size,organ age,or root order at the individual level remains limited.We determined C,N,and P contents and their stoichiometric ratios(i.e.,nutrient traits)in needles,branches,and fine roots at different organ ages(0-3-year-old needles and branches)and root orders(1st-4th order roots)from 64 Pinus koraiensis of varying size(Diameter at breast height ranged from 0.3 to 100 cm)in northeast China.Soil factors were also measured.The results show that nutrient traits were regulated by tree size,organ age,or root order rather than soil factors.At a whole-plant level,nutrient traits decreased in needles and fine roots but increased in branches with tree size.At the organ level,age or root order had a negative effect on C,N,and P and a positive effect on stoichiometric ratios.Our results demonstrate that nutrient variations are closely related to organ-specific functions and ecophysiological processes at an individual level.It is suggested that the nutrient acquisition strategy by younger trees and organ fractions with higher nutrient content is for survival.Conversely,nutrient storage strategy in older trees and organ fractions are mainly for steady growth.Our results clarified the nutrient utilization strategies during tree and organ ontogeny and suggest that tree size and organ age or root order should be simultaneously considered to understand the complexities of nutrient variations.

Numerical Analysis on the Effect of n-Si on Cu(In, Ga)Se2 Based Thin-Films for High-Performance Solar Cells by 1D-SCAPS

We report the performances of a chalcopyrite Cu(In, Ga)Se2 CIGS-based thin-film solar cell with a newly employed high conductive n-Si layer. The data analysis was performed with the help of the 1D-Solar Cell Capacitance Simulator (1D-SCAPS) software program. The new device structure is based on the CIGS layer as the absorber layer, n-Si as the high conductive layer, i-In2S3, and i-ZnO as the buffer and window layers, respectively. The optimum CIGS bandgap was determined first and used to simulate and analyze the cell performance throughout the experiment. This analysis revealed that the absorber layer’s optimum bandgap value has to be 1.4 eV to achieve maximum efficiency of 22.57%. Subsequently, output solar cell parameters were analyzed as a function of CIGS layer thickness, defect density, and the operating temperature with an optimized n-Si layer. The newly modeled device has a p-CIGS/n-Si/In2S3/Al-ZnO structure. The main objective was to improve the overall cell performance while optimizing the thickness of absorber layers, defect density, bandgap, and operating temperature with the newly employed optimized n-Si layer. The increase of absorber layer thickness from 0.2 - 2 µm showed an upward trend in the cell’s performance, while the increase of defect density and operating temperature showed a downward trend in solar cell performance. This study illustrates that the proposed cell structure shows higher cell performances and can be fabricated on the lab-scale and industrial levels.

通过成结模拟器研究n^(+)-n^(-)-p碲镉汞高温探测器

第三代红外探测器发展的一个重要方向是高工作温度探测器。对于碲镉汞n-on-p探测器而言,n^(+)-n^(-)-p结构以及良好的钝化工艺能够有效的抑制暗电流的产生,从而在高工作温度条件下获得较好的探测器性能。基于自行开发的成结模拟器,对n^(+)-n^(-)-p结构地高温器件进行了工艺仿真和器件仿真,获得成结过程的制备参数,并结合抑制表面漏电的组分梯度钝化工艺,将高工作温度下的暗电流抑制至理论极限,研制出可以在更高温度工作下的碲镉汞n-on-p红外焦平面探测器。经测试,中波n-on-p红外焦平面器件在不同工作温度下性能优异,在80 K工作温度下噪声等效温差(NETD)达到了6.1 mK,有效像元率为99.96%;而在150 K工作温度下噪声等效温差(NETD)为11.0 mK,有效像元率为99.50%,达到了同类器件的理论极限。

高压管汇材料疲劳性能测试及P-S-N模型曲线的拟合

高压管汇作为压裂设备中的主要易损件之一,其失效危害较大。它的失效原因主要是疲劳、冲蚀、腐蚀或者材料缺陷引起的刺漏和爆裂,其中尤以疲劳失效最不可预估。目前,对于高压管汇材料的疲劳性能研究不够深入,为解决高压管汇材料疲劳寿命的准确描述问题,以某国产高压管汇材料为例,进行了一系列疲劳试验,并基于试验数据,采用多种分布模型和不同S-N模型进行拟合分析,得出综合评价拟合能力最强的P-S-N模型。结果表明,该材料在中长疲劳寿命区,Weibull三参数模型在7级应力水平下综合评价能力最好;在存活率分别为50%、90%、99%、99.9%时,指数S-N模型的拟合系数均大于0.98,拟合能力最好。得出的P-S-N模型曲线可以为高压管汇的疲劳寿命以及安全设计提供依据。

云南松苗木N、P、K元素含量间异速生长关系对N、P添加的响应

为了解云南松苗木不同器官N、P、K的分布特征,分析云南松不同器官N、P、K含量间的分配差异,进一步探讨各器官N、P、K元素间的异速生长关系。采用N、P二因素三水平的方法开展不同施肥试验,并对苗木采样测定,研究云南松苗木N、P、K元素含量间异速生长关系对N、P添加的响应。结果表明,云南松苗木对N、P、K在不同器官间具有不同的分配策略,总体K变动较小,N、P波动较大且相似,在各器官中N、K分配表现为萌条>叶>茎>根;P表现为萌条>茎>叶>根。与对照相比,单施N、P和N、P配施均对云南松苗木生长的影响产生一定差异,总体来看N、P配施更能促进苗木的养分合理分配,有效缓解单施N、P对植株的限制作用,使养分处于一个平衡状态,进而促进苗木的生长。随施肥时间的推移,各器官营养元素间的异速生长关系也随之发生变化,且各器官表现为N、P的积累速度相接近,总体表现为K的积累速度低于N、P。总体而言,随施肥时间的改变,云南松苗木各器官之间元素的异速生长轨迹发生了显著变化,形成不同的营养元素分配模式。

木质基N,P共掺杂氧化石墨烯改性泡沫炭制备及电容去离子性能研究

以落叶松木屑为原料,磷酸二氢铵(NH_(4)H_(2)PO_(4))为掺杂剂,氧化石墨烯(GOs)为改性剂,经过液化、树脂化、发泡、炭化以及CO_(2)活化制备出木质基N、P共掺杂氧化石墨烯改性泡沫炭(N,P-GCF)。采用SEM、XRD、Raman、XPS、接触角测量仪分别对N,P-GCF的表面形态、晶体结构、化学性质、亲水性能进行分析,通过改变NH_(4)H_(2)PO_(4)的添加量探究其对泡沫炭孔结构、电化学性能及电容去离子性能(CDI)的影响。结果表明:经GOs改性与NH_(4)H_(2)PO_(4)掺杂后,孔泡尺寸下降,无序性提高。N,P-GCF具有分级孔结构。当NH_(4)H_(2)PO_(4)掺杂量为2 g时,具有最高的比表面积(2684.11 m^(2)·g^(-1))、总孔容(1.42 cm^(3)·g^(-1))和介孔率(49.45%),N、P质量分数分别为2.48%和3.46%。N元素主要以N-5、N-6、N-X形式存在,P元素主要为P-C、P-N。相比于CF,N,P-GCF2.0具有优异的润湿性及力学性能。在1 mol·L^(-1)NaCl电解液的三电极体系中,1 A·g^(-1)的电流密度时N,P-GCF2.0的比电容为256.48 F·g^(-1),当电流密度增加至15 A·g^(-1)时,比电容保持率达72.51%。在500 mg·L^(-1)的初始NaCl溶液、1.2 V的工作电压下,N,P-GCF2.0具有最佳脱盐能力(29.97 mg·g^(-1))及盐吸附速率(1.84 mg·g^(-1)·min^(-1)),10次循环后脱盐能力保留率为90.12%,具有较好的循环稳定性。

贺兰山东、西坡群落植物叶N、P化学计量沿海拔梯度的格局及群落构建机制

为了研究贺兰山不同气候类型群落植物叶N、P化学计量沿海拔梯度的格局及群落构建机制,以贺兰山东、西坡沿不同海拔梯度的群落植物为研究对象,分析群落植物叶片N、P质量分数的加权平均值与海拔的关系,并通过构建零模型,探究沿海拔梯度贺兰山东、西坡植物群落构建机制。结果表明:贺兰山东坡植物叶片N质量分数和N、P质量分数比的群落加权平均值随着海拔的升高,呈现先增加后降低的趋势,并在海拔1600~2000 m处最高;东、西坡叶片P质量分数均随海拔升高逐渐增加。贺兰山东坡群落叶片N质量分数在中海拔(2000 m左右)处发散,在中高海拔(2600 m左右)处收敛;叶片P质量分数在中高海拔(2600 m左右)处最收敛,叶片N、P质量分数比在中低海拔(1700 m左右)处最发散。而贺兰山西坡植物叶片N质量分数在中高海拔(2600 m左右)处最发散,叶片P质量分数在中高海拔(2700 m左右)处最发散。环境因子不是贺兰山东坡群落构建的主要驱动因素,而是贺兰山西坡群落构建的主要驱动因素,其中,土壤N、P质量分数显著影响叶片N、P化学性状的群落加权方差。

铁电效应调控的高性能p-NiO/i-BaTiO_(3)/n-ITO自供能紫外光电探测器

近年来,自供能的紫外光电探测器由于无需任何外部偏压即可工作而成为军事和民用领域的研究热点。其中,钛酸钡(BTO)作为一种宽禁带铁电材料,拥有良好的铁电、压电和热电性能,可以产生本征自发极化场来分离光生载流子,从而实现自供能紫外光电探测。到目前为止,基于BTO的自供能光电探测器已经取得了巨大进展,然而,除了使用高质量的单晶材料外,所报道的器件往往表现出低响应度(10^(-8)~10^(-7) A·W^(-1))。本文利用低成本的射频溅射技术,制造了一种高性能的NiO/BTO/ITO p-i-n异质结构自供能紫外光电探测器。通过将BTO的铁电去极化场和p-i-n结的内建电场耦合,能有效提高光生载流子的分离和迁移。因此,该器件在正极化态下255 nm波长紫外光照射下的响应度可以达到3.4×10^(-5) A·W^(-1),远远高于其他已报道的基于非晶态和陶瓷BTO制备的紫外光电探测器。此外,该器件具有0.3 s/0.4 s的快速响应时间。本工作为提高BTO光电探测器的性能提供了一种新的策略。

基于VLPE技术的碲镉汞p-on-n双层异质结材料与器件研究进展

本文对比分析了碲镉汞p-on-n器件四种制备方式的优劣,其中,VLPE(Vertical Liquid Phase Epitaxy)技术具有原位As掺杂与高激活率的技术优势,是制备高性能p-on-n双层异质结器件的重要方式。针对该技术,从材料生长、器件工艺和器件性能方面回顾了国内外研究进展,讨论了国内外差距,明确了制约该技术发展的关键问题和技术难点,并提出了解决思路。最后,展望了VLPE技术pon-n异质结器件的发展趋势。

干旱胁迫对白枪杆幼苗生长生物量及C、N、P化学计量特征的影响

【目的】研究不同干旱胁迫程度对白枪杆幼苗生长、生物量积累与分配,以及不同器官C、N、P积累与分配,探究白枪杆对不同干旱环境的适应性。【方法】以1 a生白枪杆幼苗实生苗为试验材料,研究干旱胁迫处理分别是对照(CK)、轻度干旱胁迫(LS)、中度干旱胁迫(MS)和重度干旱胁迫(SS)对白枪杆幼苗生长、生物量的积累量与分配、根冠比、各器官C、N、P含量及化学计量特征的分析和各器官C、N、P的积累和分配规律等指标测定。【结果】随干旱胁迫程度的上升,白枪杆幼苗的苗高和地径的增长量显著降低(P<0.05)。叶片、茎和根的生物量及总生物量、叶片生物量占比降低,茎和根生物量占比和根冠比降低。白枪杆幼苗C、N和P的积累量随干旱胁迫程度的上升呈下降趋势;与适宜的水分处理相比,白枪杆幼苗各器官的C∶N均呈先下降后上升的趋势,叶片和根的C∶P呈先下降后上升的趋势;白枪杆幼苗各器官N∶P低于14,表明生长主要受N限制。【结论】白枪杆幼苗生长及生物量和C、N、P含量及化学计量特征对不同干旱胁迫程度的响应有差异,主要表现在随干旱胁迫程度的上升,白枪杆幼苗的苗高、地径增长量呈下降趋势,生物量的分配也倾向于地下部分,干旱胁迫处理下不利于白枪杆幼苗的生长,生物量的积累减少,C、N和P的积累量降低。

用P204+N235联合萃取分离氯化镍溶液中的镍钴

研究了以二(2-乙基己基)膦酸(P204)和三异辛胺(N235)为萃取剂联合萃取氯化镍溶液中的镍、钴,考察了有机相P204体积分数、相比、料液pH、皂化率、N235体积分数、Cl-质量浓度、反应温度对氯化镍溶液净化除杂的影响。结果表明:用P204萃取除杂后再用N235从P204萃余液中萃取分离钴钼,在P204体积分数20%、相比V_(O)/V_(A)=1.5/1、料液pH=3.5、皂化率50%、反应温度40~50℃,以及N235体积分数16%、相比V_(O)/V_(A)=1.2/1、反应温度40~50℃、P204萃余液pH=3.0、Cl^(-)质量浓度≥280g/L及盐酸酸化浓度3mol/L条件下,萃余液中Ni^(2+)质量浓度为218.10g/L,Cu^(2+)、Fe^(3+)、Co^(2+)和Zn^(2+)质量浓度分别为1.1、1.2、1.0和0.1mg/L,能满足生产高品质电积镍的阴极液要求。

Grain yield and N uptake of maize in response to increased plant density under reduced water and nitrogen supply conditions

The development of modern agriculture requires the reduction of water and chemical N fertilizer inputs.Increasing the planting density can maintain higher yields,but also consumes more of these restrictive resources.However,whether an increased maize density can compensate for the negative effects of reduced water and N supply on grain yield and N uptake in the arid irrigated areas remains unknown.This study is part of a long-term positioning trial that started in 2016.A split-split plot field experiment of maize was implemented in the arid irrigated area of northwestern China in 2020 to 2021.The treatments included two irrigation levels:local conventional irrigation reduced by 20%(W1,3,240 m^(3)ha^(-1))and local conventional irrigation(W2,4,050 m^(3)ha^(-1));two N application rates:local conventional N reduced by 25%(N1,270 kg ha^(-1))and local conventional N(360 kg ha^(-1));and three planting densities:local conventional density(D1,75,000 plants ha^(-1)),density increased by 30%(D2,97,500 plants ha-1),and density increased by 60%(D3,120,000 plants ha^(-1)).Our results showed that the grain yield and aboveground N accumulation of maize were lower under the reduced water and N inputs,but increasing the maize density by 30% can compensate for the reductions of grain yield and aboveground N accumulation caused by the reduced water and N supply.When water was reduced while the N application rate remained unchanged,increasing the planting density by 30% enhanced grain yield by 13.9% and aboveground N accumulation by 15.3%.Under reduced water and N inputs,increasing the maize density by 30% enhanced N uptake efficiency and N partial factor productivity,and it also compensated for the N harvest index and N metabolic related enzyme activities.Compared with W2N2D1,the N uptake efficiency and N partial factor productivity increased by 28.6 and 17.6%under W1N1D2.W1N2D2 had 8.4% higher N uptake efficiency and 13.9% higher N partial factor productivity than W2N2D1.W1N2D2 improved urease activity and nitrate reductase activity by 5.4% at the R2(blister)stage and 19.6% at the V6(6th leaf)stage,and increased net income and the benefit:cost ratio by 22.1 and 16.7%,respectively.W1N1D2 and W1N2D2 reduced the nitrate nitrogen and ammoniacal nitrogen contents at the R6 stage in the 40-100 cm soil layer,compared with W2N2D1.In summary,increasing the planting density by 30% can compensate for the loss of grain yield and aboveground N accumulation under reduced water and N inputs.Meanwhile,increasing the maize density by 30% improved grain yield and aboveground N accumulation when water was reduced by 20% while the N application rate remained constant in arid irrigation areas.

多孔n-GaN/p-Zn_(x)Cu_(1-x)S异质结的制备及紫外探测性能研究

本文首先采用紫外光辅助电化学刻蚀(UV-EC)方法制备出了孔隙密度为1.51×10^(10)cm^(-2)、平均孔径为38 nm的多孔n-GaN薄膜;随后在其上通过水浴法沉积了一系列Zn_(x)Cu_(1-x)S复合薄膜,x为0.0、0.2、0.4、0.6、0.8、1.0,形成的多孔n-GaN/p-Zn_(x)Cu_(1-x)S异质结带隙在2.34~3.51 eV调控;最后基于这些异质结构建出p-n结型紫外探测器。I-V曲线结果表明这些探测器均具有良好的整流特性,特别是n-GaN/p-Zn_(0.4)Cu_(0.6)S探测器性能最优。在暗态下,I_(+3 V)/I_(-3 V)约为1.78×10~5;在偏压为-3 V、光功率密度为432μW/cm^(2)(365 nm)的条件下,光暗电流比超过10~3,上升/下降时间为0.09/39.8 ms,响应度(R)为0.352 A/W,外量子效率(EQE)为119.6%,探测率(D^(*))为3.21×10^(12)Jones。I-t曲线结果表明,多孔n-GaN/p-Zn_(x)Cu_(1-x)S异质结紫外探测器在连续开-关光循环过程中拥有稳定的光电流响应。该研究为制备异质结紫外探测器提供了一定的理论指导和实验数据。

天坑森林植物叶-凋落物-土壤C、N、P生态化学计量特征

为探究广西乐业大石围天坑森林群落的C、N、P养分循环特征,比较了天坑内外森林群落的植物叶片-凋落物-土壤C、N、P含量及其化学计量比,采用相关性分析和冗余分析等统计方法研究其内在联系和相互影响。结果表明,与天坑外部森林相比,天坑内部森林植物叶片和凋落物呈现出C低N、P高,土壤为C、N低P高的格局。植物叶片C:N、C:P与凋落物C、N:P显著正相关,植物叶片C与土壤P显著负相关;天坑外部森林的植物叶片N、N:P与土壤N:P显著负相关,植物叶片C:N与土壤C、C:N显著正相关,说明天坑森林内部凋落物的C、P养分可能主要来源于植物叶片,而天坑外部森林的植物叶片C、N主要来自土壤。土壤C:N:P对植物叶、凋落物的C:N:P变化的解释率分别为90.7%和50.6%,其中土壤P对植物叶和凋落物的C:N:P计量特征变化的解释度最高,坑内生境植物对P含量变化更为敏感、坑外植物对于N含量变化更为敏感,表明天坑内部森林可能是P素受限位点、天坑外部森林是N素受限位点。喀斯特天坑内部森林和外部森林植物叶-凋落物-土壤的C:N:P的差异和联系,体现了天坑内外森林群落的养分循环特征和植物群落的适应性。

基于转录组学探究Lactobacillus plantarum 6A促进二乙基亚硝胺形成的机制

乳酸菌是食品工业和人体肠道常见微生物,可促进强致癌物亚硝胺的合成,而其促进机制尚待揭示,严重制约了发酵食品安全的提升和益生菌产品的推广。该文考察植物乳杆菌(Lactobacillus plantarum)6A对二乙基亚硝胺(N-nitrosodiethylamnie,NDEA)促进作用在不同环境中的变化趋势,以转录组技术进一步探究促进作用的关键基因和形成途径,构建其机制网络。结果表明,NDEA胁迫L.plantarum 6A通过上调嘌呤核苷酸合成/代谢(关键基因purL、purK、purC、purB、purA)、核黄素合成/代谢(ribBA、ribH、ribE)、双组分系统途径(dltD、dltB、dltA)的基因表达,产生NDEA前体物,如富含氮元素的嘌呤、核黄素及丙氨酸,从而促进NDEA形成;还可能通过核黄素合成/代谢以及双组分系统途径间接催化亚硝化反应,加速NDEA的形成。

CuO/CeO_(2) p−n异质结光催化降解亚甲基蓝的性能及机理

采用简单微波回流法和均相沉淀技术合成CuO/CeO_(2) p−n异质结复合材料,并对其光催化降解亚甲基蓝溶液的性能进行研究。CuO/CeO_(2)异质结复合材料的降解效率明显强于CeO_(2)。结果表明,以Cu/Ce摩尔比为1/3制备的复合材料(1/3 Cu/Ce)的光催化活性最高,在180 min内降解效率达到96.2%。CuO和CeO_(2)之间形成的p−n异质结促进了光生载流子的分离和传输,从而提高了其光催化活性。计算了CuO/CeO_(2)异质结的能带位置偏移,其价带偏移(∆EVBO)为1.58 eV,导带偏移(∆ECBO)为−0.48 eV。计算结果进一步证明CuO与CeO_(2)之间形成了p−n异质结。

水曲柳叶片功能性状及C、N、P化学计量对海拔的响应

【目的】水曲柳是小陇山主要珍贵的用材树种,探讨其叶片性状对小生境变化的适应性,可为深入研究影响该树种的主要环境因子提供理论基础。【方法】以黑河保护区天然水曲柳为研究对象,分析4个海拔梯度(1268,1529,1741,1926 m)间14种叶片功能性状和叶片营养元素含量的差异显著性及其相关性。【结果】(1)随海拔升高,叶片厚度、干物质含量和叶绿素含量逐渐增大,并分别在海拔1741 m、1926 m、1741 m处达到最大,比叶面积、最大净光合速率、蒸腾速率、叶C和N含量则逐渐减少,除叶C含量外均在海拔1268 m达到最大。叶面积、气孔导度和叶C∶N随着海拔升高呈先增后降的趋势,胞间CO_(2)浓度、C∶P和N∶P呈先降后升的趋势。(2)海拔平均每上升200 m,叶片功能性状和C∶N平均增加1.13%~30.72%,比叶面积、最大净光合速率和C、N含量减小2.22%~15.75%。(3)各海拔叶N∶P为4.36~6.89,与最大净光合速率呈极显著正相关。最大净光合速率与比叶面积、C和N含量、C∶P和N∶P呈极显著正相关,与叶片厚度、干物质含量和叶绿素含量呈极显著负相关,比叶面积与干物质含量呈极显著负相关,与C和N含量和C∶P呈极显著正相关。【结论】海拔显著影响水曲柳叶片功能性状及元素含量,海拔1700 m以下有利于叶的发育和养分的积累。