Analysis of the Current Structure and Response Strategies of Intensive Vegetable Seedling Cultivation in Hebei Province

In the last few years, vegetable industry developed rapidly in Hebei province, intensive raising seedling as its main component, also entered a period of rapid development. The background and characteristics, the current situation and existed questions of intensive seedling cultivation were analyzed. A series of developmental ideas and response strategies for developing more quickly in Hebei Province were put forward.

Effects of light intensity on leaf microstructure and growth of rape seedlings cultivated under a combination of red and blue LEDs

The aim of this study was to evaluate the growth of rape （Brassica napus L.） seedlings under different light intensities to select appropriate conditions for cultivation in an indoor system. Seedlings were grown under different light intensities of red and blue light provided by light-emitting diodes （LEDs） and their self-adjustment ability and changes in leaf microstructure were evaluated. Light was supplied by red LEDs with peak wavelengths of 630 （R1） and 660 nm （R2） and by blue LEDs （B） with a peak wavelength of 445 nm （the light intensity ratio of R1：R2：B was 3：3：2）, at intensities of 400 （R1R2B400）, 300 （R1R2B300）, and 200 μmol m-2 s-1 （R1R2B200）. Natural solar light served as the control （C）. Plant height, stem diameter, root length, leaf area, and dry weight of rape seedlings gradually increased with increasing light intensity. The seedlings in the R1R2B400 treatment grew more vigorously, while those in the R1R2B200 treatment were weaker. The photosynthetic pigment contents did not differ significantly between the R1R2B400 treatment and C, but were significantly lower in the R1R2B300 and R1R2B200 treatments. The highest intercellular CO2concentration, stomatal conductance, and transpiration rate were in the R1R2B300 treatment. The highest photosynthetic rate was in the R1R2B400 treatment, and was related to more compact leaves, thicker and tidier palisade and spongy tissues, and well-developed chloroplasts. In contrast, the seedlings in the R1R2B200 treatment had disordered mesophyll cells, round chloroplasts, and fractured and fuzzy grana lamellae, all of which inhibited plant growth. In conclusion, the seedlings in the R1R2B400 treatment had well-developed leaves, which favored photosynthesis. Compared with the light intensities below 300 μmol m-2 s-1, the light intensity of 400 μmol m-2 s-1 provided by a cembination of red and blue LEDs was beneficial for cultivating strong and healthy rape seedlings in an artificial system.

Effects of soil moisture and light intensity on ecophysiological characteristics of Amorpha fruticosa seedlings

We investigated the combined effects of soil moisture and light intensity on the growth, development and ecophysiological characteristics of one-year old Amorpha fruticosa seedlings. Soil moisture and light intensity influenced the ecophysiological characteristics of Amorpha fruticosa seedlings. Soil moisture resulted in the decreases of growth rate, individual size, net photosynthetic rate, transpiration rate, leaf water loss rate （WLR）, and biomass accumulation of plant parts, and led to increased leaf water saturation deficit （WSD）. Under water stress, more photosynthetic products were allocated to root growth. With decreasing light intensity, net photosynthetic rate, transpiration rate, chla/b, water saturation deficit, water use efficiency, water loss rate and biomass accumulation declined, while Chla, Chlb, Chla＋b and carotenoids （Car） increased and more photosynthetic products were allocated to stem and leaf growth. Maximum growth vigor, net photosynthetic rate and total biomass accumulation in Amorpha fruticosa seedlings was recorded at 75 80% soil water-holding capacity and 100% light density in greenhouse environments.

Research on Testing System for Three-dimensional Distribution of Luminous Intensity of LED

In terms of asymmetrical three-dimensional distribution(ID) of luminous intensity(LI) of light-emitting-diode(LED),a testing system was conducted in this study. Design and principle of the testing system were introduced. 31 photometers were placed on a concentric circle,and all of them were used to gather LI data of LED at the same time. The data acquisition card(DAC) was used to gather multichannel data and controlled motor. Experimental results indicated that the testing system had achieved the goal of testing three-dimensional distribution of LI. And each parameter could meet the requirements of industrial production and measurement.

CONVOLUTION OF THE IMPACT THREE-DIMENSIONAL ELASTO-DYNAMICS AND DYNAMIC STRESS INTENSITY FACTOR FOR AN ELLIPTIC CRACK

This paper presents a formulation for three-dimensional elasto-dynamics with an elliptic crack based on the Laplace and Fourier transforms and the convolution theorem. The dynamic stress intensity factor for the crack is determined by solving a Fredholm integral equation of the first kind. The results of this paper are very close to those given by the two-dimensional dual integral equation method.

Controlling Three-Dimensional Electron-Electron Correlation via Elliptically Polarized Intense Laser Field

The three-dimensional electron-electron correlation in an elliptically polarized laser field is investigated based on a semiclassical model. Asymmetry parameter α of the correlated electron momentum distribution is used to quantitatively describe the electron-electron correlation. The dependence of α on elliptieity e is totally different in three directions. For the z direction （maJor polarization direction）, α first increases and reaches a maximum at ε = 0.275, then it decreases quickly. For the y direction in which the laser field is always absent, the ellipticity has a minor effect, and the asymmetry parameter fluctuates around α = -0.15. However, for the x direction （minor polarization direction）, α increases monotonously with ellipticity though starts from the same value as in the y direction when ε = 0. The behavior of α in the x direction actually indicates a transformation from the Coulomb interaction dominated correlation to the laser field dominated correlation. Therefore, our work provides an efficient way to control the three-dimensional electron electron correlation via an elliptically polarized intense laser field.

THREE-DIMENSIONAL ELLIPTIC CRACK UNDER IMPACT LOADING

The dynamic stress intensity factor of a three-dimensionalelliptic crack under impact loading is determined with the finiteelement method. The computation results can take into account theinfluence of time and the ratio of the wave speeds on the stressintensity factor. The present method is suitable not only forthree-dimensional dynamic crack, but also for three-dimensionaldynamic contact.

Analysis of Three-dimensional Crack Propagation by Using Displacement Discontinuity Method

A technique for modelling of three-dimensional(3D)quasi-statically propagating cracks in elastic bodies by the displacement discontinuity method(DDM)was described.When the crack is closed,the Mohr-coulomb rule on the two contacted surfaces of the crack must be satisfied.A simple iterative method was adopted in order to consider three different states of cracks.Under the assumption that the advance of the point on the crack front would occur only in the normal plane which is through this edge point,the maximum energy release rate criterion is modified to be used as the criterion for the crack growth.With discretization,the process of crack propagation can be seen as the advance of the vertices of the crack front.The program MCP3D was developed based on these theories to simulate the 3D quasi-static crack propagation.A numerical example of a penny-shaped crack subject to tension and compression in an infinite elastic media was analyzed with MCP3D,and the results in comparison with others' show that the present method for 3D crack propagation is effective.

INTERFACIAL CRACK ANALYSIS IN THREE-DIMENSIONAL TRANSVERSELY ISOTROPIC BI-MATERIALS BY BOUNDARY INTEGRAL EQUATION METHOD

The integral-differential equations for three-dimensional planar interfacial cracks of arbitrary shape in transversely isotropic bimaterials were derived by virtue of the Somigliana identity and the fundamental solutions, in which the displacement discontinuities across the crack faces are the unknowns to be determined. The interface is parallel to both the planes of isotropy. The singular behaviors of displacement and stress near the crack border were analyzed and the stress singularity indexes were obtained by integral equation method. The stress intensity factors were expressed in terms of the displacement discontinuities. In the non-oscillatory case, the hyper-singular boundary integral-differential equations were reduced to hyper-singular boundary integral equations similar to those of homogeneously isotropic materials.

设施西瓜集约化育苗技术

随着北京地区集约化育苗技术的广泛应用,小型西瓜秧苗壮苗率及定植成活率达到95%以上。文中从设施类型、品种选择、田间管理、应用现状4个方面总结了北京地区小型西瓜集约化育苗技术的要点,以期为该技术的进一步推广应用奠定基础。

光质和光强变化对油松幼苗生长及非结构性碳水化合物的影响

为研究不同光质和光强对油松幼苗生长的影响,以培育5个月的油松容器苗为材料,设置红蓝绿混合光源(red∶blue∶green=6.5∶1.2∶2.3)、红蓝混光光源(red∶blue=5∶1)和全光谱植物生长灯作对照处理,分别在RGB和RB光源条件下50 cm处设置光子通量为90、150、210μmol·m^(-2)·s^(-1)的3个不同光照强度对油松幼苗继续补光4个月,揭示不同光质和光强对油松幼苗生长及非结构性碳水化合物的影响规律。结果表明:1)RB和RGB光质处理下除W1处理外,油松幼苗苗高和地径均高于CK,达到油松1年生播种苗的一级苗木标准。RGB处理下光照强度为210μmol·m^(-2)·s^(-1)时油松幼苗的苗高与地径最大,分别是CK处理的149.44%和152.00%。2)RB和RGB光质处理下整株干重、根冠比、根分配率及壮苗指数均在光照强度为210μmol·m^(-2)·s^(-1)时最高。3)RB光质处理下光照强度为150μmol·m^(-2)·s^(-1)时油松幼苗的淀粉含量变化明显,RGB光质处理下光照强度为210μmol·m^(-2)·s^(-1)时油松幼苗的可溶性糖含量最多,且可溶性糖与淀粉含量之间的转化相对稳定。4)RB和RGB光质处理下油松幼苗整株生物量、地径和苗高与淀粉含量存在正相关,与可溶性糖含量存在负相关(P<0.01)。

光照强度对不同苗龄水曲柳裸根苗和容器苗生长的影响

分析不同苗龄水曲柳裸根苗和容器苗在不同光照强度下的适应能力,可为水曲柳苗木精准造林提供科学依据。以水曲柳1年生裸根苗、1年生容器苗、2年生裸根苗和2年生容器苗为试验材料,观察大田遮阴设置的100%、75%、50%和25%光照强度下水曲柳各类型苗木生长情况。结果显示,容器苗的苗高增长量和地径增长量分别比裸根苗显著高出58.74%、60.27%,4种苗木的地径增长量和根生物量积累量均在25%光照强度下为最低。在50%光照强度下,1年生容器苗的苗高增长量、地径增长量、叶面积和细根数量分别比1年生裸根苗高出39.51%、28.80%、35.27%、28.73%,2年生容器苗的苗高增长量、地径增长量、叶面积和细根数量分别比2年生裸根苗高出96.03%、94.06%、28.45%、40.69%,1年生裸根苗的苗高增长量和地径增长量分别比2年生裸根苗高出59.56%、85.57%。研究表明,4种水曲柳苗木在25%光照条件下生长均较差,1年生裸根苗比2年生裸根苗在弱光(50%)条件下生长更优,容器苗比裸根苗具有更强的弱光(50%)适应性。

不同光强下琼岛杨幼苗生长和光合特性

[目的]本文旨在探究不同光照强度对琼岛杨(Populus qiongdaoensis)幼苗生长和光合特性的影响。[方法]以1.5年生琼岛杨幼苗为试验材料,设置全光100%(CK)、全光70%(RI70%)、全光40%(RI40%)和全光10%(RI10%),处理12个月后,分析不同光强对琼岛杨幼苗生长和光合特性的影响。[结果]成活率、地径增长量、叶片数、叶长、叶宽、叶面积和单叶质量均随着光强的减弱而降低,株高增长量和叶片数增长量呈先增后减趋势,RI70%和RI40%处理的琼岛杨幼苗的成活率、株高、地径和叶片数均显著高于RI10%处理;RI70%处理的根生物量、根生物量比和根冠比显著高于RI40%和RI10%处理,而RI70%和RI40%处理的根、茎、叶生物量和总生物量均显著高于RI10%;随着光照强度的降低,叶片叶绿素a、叶绿素b和总叶绿素含量逐渐增大,类胡萝卜素含量随之减小;净光合速率(Pn)随光照强度的减小而显著下降,在RI70%光强下琼岛杨幼苗叶片的Pn最大,分别是RI40%和RI10%的1.72倍和2.16倍;叶片数增长量与株高增长量、地径增长量呈显著正相关关系,净光合速率与类胡萝卜素含量(Car)和蒸腾速率(Tr)呈显著正相关,气孔限制值(Ls)与胞间CO_(2)浓度(Ci)和气孔导度(GS)呈显著负相关。[结论]琼岛杨幼苗能忍耐一定程度遮阴,适度遮阴可促进幼苗地上和地下部分的生长并提高其气体交换能力,但在弱光胁迫下幼苗难以成活和生长,相对光强70%下琼岛杨幼苗的适应性最强。

干旱胁迫下3种籽粒苋幼苗的抗旱性评价

[目的]研究不同干旱胁迫强度对籽粒苋幼苗生长及生理特性的影响,比较不同品种籽粒苋幼苗的抗旱性。[方法]选取3个品种籽粒苋(千穗谷、美国籽粒苋、籽粒苋N053)为试验材料,采用室内盆栽和人工控水试验,以土壤最大含水量的80%为对照组(CK),设置轻度、中度、重度3个干旱胁迫处理强度,土壤含水量分别为最大含水量的60%、40%、20%;测定并比较不同品种籽粒苋幼苗在不同干旱胁迫强度下的生长指标和生理指标;通过主成分分析筛选评价指标,利用隶属函数综合评价法对3个品种籽粒苋幼苗的抗旱性进行评价。[结果]3个品种籽粒苋幼苗的生长指标(株高、叶片数、茎宽)均随干旱胁迫强度的增加呈逐渐下降趋势;在中度和重度干旱胁迫下,3个品种籽粒苋幼苗的株高、叶片数、茎宽均显著(P<0.05)低于CK和轻度干旱。在受到不同强度的干旱胁迫处理后,3个品种籽粒苋幼苗普遍表现出SPAD值降低、丙二醛(malondialdehyde,MDA)含量升高、脯氨酸(proline,PRO)含量升高、可溶性糖(soluble sugar,SS)含量先升高后降低的变化特点,而可溶性蛋白(soluble protein,SP)含量变化不明显。随干旱胁迫强度的增加,美国籽粒苋幼苗叶片的相对电导率(relative conductivity,RC)逐渐下降,千穗谷幼苗叶片的RC逐渐上升,籽粒苋N053的RC呈先升高后降低的变化趋势。3个品种籽粒苋幼苗的超氧化物歧化酶(superoxide dismutase,SOD)、过氧化氢酶(catalase,CAT)、过氧化物酶(peroxidase,POD)活力总体呈先升高后降低的趋势;在重度干旱胁迫下,美国籽粒苋幼苗的SOD和POD活力显著(P<0.05)高于千穗谷和籽粒苋N053,CAT活力也高于千穗谷和籽粒苋N053。主成分分析显示,前4个主成分的贡献率分别为35.456%、20.030%、12.507%、8.371%,累计贡献率为76.364%;前4个主成分中特征向量绝对值较大的指标包括株高、叶片数、茎宽、MDA含量、CAT活力、POD活力、SOD活力、SS含量,以这些指标作为抗旱性综合评价的指标来源。隶属函数综合评价显示,美国籽粒苋、千穗谷、籽粒苋N053幼苗抗旱性指标的平均隶属函数值分别为0.72、0.53、0.29。[结论]通过对籽粒苋幼苗生长指标和生理指标进行主成分分析和隶属函数综合评价,3个品种籽粒苋幼苗的抗旱性由强到弱依次为美国籽粒苋>千穗谷>籽粒苋N053。

光照强度对云南松幼苗生长的影响

为探寻云南松幼苗生长适宜的光照强度,为当地云南松栽植产业提供参考及借鉴,以云南松2年生播种苗为试验材料,设置了4个不同的光照强度处理,比较了不同光照强度对云南松幼苗生长的影响。结果表明:光照强度对云南松幼苗生长存在显著影响,光照强度过高或过低均会在一定程度上影响云南松幼苗的生长。综合考虑云南松幼苗生长、生物量积累、抗氧化生理指标及叶绿素含量,认为最适宜的光照强度为75%。因而,建议在云南松幼苗培育中给予适当的遮阴以利于苗木生长。

天津市集约化育苗增温技术及装备——以天津兴有农业科技有限公司应用为例

天津市集约化育苗过程中存在技术水平与设备不够成熟完善的问题,其中冬季低温是培育壮苗最大的阻力因素,过低的温度会导致僵苗或者死苗情况的发生。介绍了4种可应用于集约化育苗的增温技术及装备,并在天津兴有农业科技有限公司设施园区内进行试验,从能耗、温度、增温效果、使用成本等方面进行分析对比。结果表明,智能温控电采暖设备增温效果最好,地能水空调设备使用成本最低。用户需根据实际情况因地制宜选择合适的增温设备。

基于育秧机插新技术创制的中国双季稻区“稻-稻-油”三熟制模式优化研究

本研究围绕提高中国双季稻区“稻-稻-油”三熟制的发展现状及可持续性展开,以江西省为研究对象,深入分析了该模式当前面临的主要挑战。研究发现,由于茬口紧张和较低的比较效益,农民对该模式的采纳率不高。通过解决水稻、油菜机播育苗移栽环节的瓶颈问题,本研究提出了培育长秧龄带蘖壮秧的新技术目标。利用钵体毯盘技术实现了精量稀播匀播,成功培育了早稻35 d的长秧龄壮秧以及中、晚稻30 d的长秧龄带蘖壮秧,有效缓解了“稻-稻-油”三熟制的茬口紧张问题。本研究的成果不仅提高了“稻-稻-油”模式的实际可操作性,还为促进农业机械化和提升作物生产效率提供了新的思路。

灌水强度对毛乌素沙地樟子松苗木生长的影响

为探讨不同灌水强度对樟子松人工林动态生长及生产力的影响,通过田间灌水试验对樟子松苗高、地径进行了模拟。结果表明:(1)对生长模型中理论生长上限、生长增速点、生长减速点、速生点和速生期等5个具有生物学意义的指标进行不同灌水处理间的多重比较,灌水强度主导的参数差异性使樟子松苗高和地径生长模型具备了多形性。(2)灌水强度为自然降水量3倍时苗高年生长量最大。

THE 3-D STRESS INTENSITY FACTOR FOR A HALF PLANE CRACK IN A TRANSVERSELY ISOTROPIC SOLID DUE TO THE MOTION OF LOADS ON THE CRACK FACES

Three-dimensional analysis of a half plane crack in a transversely isotropic solid is performed. The crack is subjected to a pair of normal point loads moving in a direction perpendicular to the crack edge on its faces. Transform methods are used to reduce the boundary value problem to a single integral equation that can be solved by the Wiener-Hopf technique. The Cagniard-de Hoop method is employed to invert the transforms. An exact expression is derived for the mode I stress intensity factor as a function of time and position along the crack edge. Some features of the solution are discussed through numerical results.

Closed form solution of stress intensity factors for cracks emanating from surface semi-spherical cavity in finite body with energy release rate method

In this paper, a new semi-analytical and semi-engineering method of the closed form solution of stress intensity factors （SIFs） of cracks emanating from a surface semi-spherical cavity in a finite body is derived using the energy release rate theory. A mode of crack opening displacements of a normal slice is established, and the normal slice relevant functions are introduced. The proposed method is both effective and accurate for the problem of three-dimensional cracks emanating from a surface cavity. A series of useful results of SIFs are obtained.