Arabidopsis pollen-specific glycerophosphodiester phosphodiesterase-like genes are essential for pollen tube tip growth

In angiosperms,pollen tube growth is critical for double fertilization and seed formation.Many of the factors involved in pollen tube tip growth are unknown.Here,we report the roles of pollenspecific GLYCEROPHOSPHODIESTER PHOSPHO DIESTERASE-LIKE(GDPD-LIKE)genes in pollen tube tip growth.Arabidopsis thaliana GDPD-LIKE6(At GDPDL6)and At GDPDL7 were specifically expressed in mature pollen grains and pollen tubes and green fluorescent protein(GFP)-At GDPDL6 and GFP-At GDPDL7 fusion proteins were enriched at the plasma membrane at the apex of forming pollen tubes.Atgdpdl6 Atgdpdl7 double mutants displayed severe sterility that was rescued by genetic complementation with At GDPDL6 or At GDPDL7.This sterility was associated with defective male gametophytic transmission.Atgdpdl6 Atgdpdl7 pollen tubes burst immediately after initiation of pollen germination in vitro and in vivo,consistent with the thin and fragile walls in their tips.Cellulose deposition was greatly reduced along the mutant pollen tube tip walls,and the localization of pollen-specific CELLULOSE SYNTHASE-LIKE D1(CSLD1)and CSLD4 was impaired to the apex of mutant pollen tubes.A rice pollen-specific GDPD-LIKE protein also contributed to pollen tube tip growth,suggesting that members of this family have conserved functions in angiosperms.Thus,pollen-specific GDPDLIKEs mediate pollen tube tip growth,possibly by modulating cellulose deposition in pollen tube walls.

Targeting and Regulation of Cell Wall Synthesis During Tip Growth in Plants

Root hairs and pollen tubes are formed through tip growth, a process requiring synthesis of new cell wall material and the precise targeting and integration of these components to a selected apical plasma membrane domain in the growing tips of these cells. Presence of a tip-focused calcium gradient, control of actin cytoskeleton dynamics, and formation and targeting of secretory vesicles are essential to tip growth. Similar to cells undergoing diffuse growth, cellulose, hemi-celluloses, and pectins are also deposited in the growing apices of tip-growing cells. However, differences in the manner in which these cell wall components are targeted and inserted in the expanding portion of tip-growing cells is reflected by the identification of elements of the plant cell wall synthesis machinery which have been shown to play unique roles in tip-growing cells. In this review, we summarize our current understanding of the tip growth process, with a particular focus on the subcellular targeting of newly synthesized cell wall components, and their roles in this form of plant cell expansion.

Arabidopsis SYP121 acts as an ROP2 effector in the regulation of root hair tip growth

Tip growth is an extreme form of polarized cell expansion that occurs in all eukaryotic kingdoms to generate highly elongated tubular cells with specialized functions, including fungal hyphae, animal neurons, plant pollen tubes, and root hairs (RHs). RHs are tubular structures that protrude from the root epidermis to facilitate water and nutrient uptake, microbial interactions, and plant anchorage. RH tip growth requires polarized vesicle targeting and active exocytosis at apical growth sites. However, how apical exocytosis is spatially and temporally controlled during tip growth remains elusive. Here, we report that the Qa-Soluble N-ethylmaleimide-sensitive factor attachment protein receptor (SNARE) SYP121 acts as an effector of Rho of Plants 2 (ROP2), mediating the regulation of RH tip growth. We show that active ROP2 promotes SYP121 targeting to the apical plasma membrane. Moreover, ROP2 directly interacts with SYP121 and promotes the interaction between SYP121 and the R-SNARE VAMP722 to form a SNARE complex, probably by facilitating the release of the Sec1/Munc18 protein SEC11, which suppresses the function of SYP121. Thus, the ROP2-SYP121 pathway facilitates exocytic trafficking during RH tip growth. Our study uncovers a direct link between an ROP GTPase and vesicular trafficking and a new mechanism for the control of apical exocytosis, whereby ROP GTPase signaling spatially regulates SNARE complex assembly and the polar distribution of a Q-SNARE.

青贮甘蔗梢替代玉米秸秆对湖羊生长性能、消化代谢及肉品质的影响

[目的]本试验旨在探索青贮甘蔗梢替代青贮玉米秸秆作为肉羊日粮的可行性,并确定最佳的替代比例。[方法]选取3月龄、体重相近[(20.15±2.18)kg]的健康湖羊公羔48只,随机分成4组,每组3个重复,分别用青贮甘蔗梢替代0%(对照组)、50%(A组)、75%(B组)、100%(C组)青贮玉米秸秆饲喂,预试期10 d,正试期为60 d。试验开始和结束时测定湖羊生产性能,并采集血液样品进行血清生化分析;饲喂试验结束后,从每组不同重复各选择1只湖羊屠宰,测定其屠宰性能及肉品质;从每组不同重复再挑选3只湖羊进行消化代谢试验,测定养分消化代谢参数。[结果]B组和C组平均日增重、胴体重和屠宰率显著高于A组和对照组(P<0.05);B组和C组氮沉积量显著高于A组和对照组,A组、B组和C组的表观消化能和能量转化率均显著高于对照组;各组间血液生化指标、肉品质及肉营养成分均无显著差异(P>0.05)。青贮甘蔗梢替代75%和100%青贮玉米秸秆可以显著提高湖羊生长性能和屠宰性能,而且对湖羊血清生化指标、组织器官发育和肉品质无不利影响。[结论]青贮甘蔗梢可替代青贮玉米秸秆饲喂肉羊,且最佳替代比例为75%~100%。

Distribution and role of calmodulin in tip growing hyphae of Saprolegnia ferax

Since direct staining of growing hyphae with trifluoperazine (TFP) could result in the migration of protoplasm in hyphae of water mold Saprolegnia feraX, an improved staining method for fixation of growing hyphae was developed. When hyphae of Saprolegnia ferax were pre-fixed with paraformaldehyde, the TFP fluorescence showed a clear tip-high Ca(2+)-activated calmodulin (CaM) gradient. By indirect immunohistochemical staining, we proved that total CaM also mainly concentrated in the apex of hyphae.It is noticeble that when the hyphal tip growth ceased, the high intensity of TFP fluorescence usually disappeared in non-growing tips and became evident in the newly emerged growing tips, which implied that the concentration of CaM shifted in concord with the transfer of growing point in hyphae. 2×10(-5) mol/L CaM inhibitor TFP could reduce the tip growth rate and the percentage of growing hyphal tips to about 50%, and induce multibranching of hyphal tips. These findings strongly suggest that the high concentration of calmodulin in the hyphal tip may be involved in regulation of hyphal tip growth.

Fractographic analysis of the overload effect on fatigue crack growth in 2024-T3 and 7075-T6 Al alloys

The effect of single overload on the fatigue crack growth in 2024-T3 and 7075-T6 Al alloys was analyzed.Fatigue tests under constantamplitude loading with overload peak were carried out on V-notched specimens.Fractographic analysis was used as a principal approach to explain the crack growth retardation due to the overload.Scanning electron microscopy(SEM)analyses were conducted on the fractured surface of failed specimens to study the retardation effect.The obtained results show that the overload application generates a plastic zone in both aluminum alloys.The generated plastic zone is three times larger in the case of 2024-T3 compared to 7075-T6,and thus,a significant crack retardation was induced for 2024-T3.The retardation effect due to the overload for 2024-T3 and 7075-T6 lasted for about 10 mm and 1 mm,respectively,from the point of overload application.

FATIGUE GROWTH MODELING OF MIXED-MODE CRACK IN PLANE ELASTIC MEDIA

This paper presents an extension of a displacement discontinuity method with cracktip elements （a boundary element method） proposed by the author for fatigue crack growth analysis in plane elastic media under mixed-mode conditions. The boundary element method consists of the non-singular displacement discontinuity elements presented by Crouch and Starfield and the crack-tip displacement discontinuity elements due to the author. In the boundary element implementation the left or right crack-tip element is placed locally at the corresponding left or right crack tip on top of the non-singular displacement discontinuity elements that cover the entire crack surface and the other boundaries. Crack growth is simulated with an incremental crack extension analysis based on the maximum circumferential stress criterion. In the numerical simulation, for each increment of crack extension, remeshing of existing boundaries is not required because of an intrinsic feature of the numerical approach. Crack growth is modeled by adding new boundary elements on the incremental crack extension to the previous crack boundaries. At the same time, the element characteristics of some related elements are adjusted according to the manner in which the boundary element method is implemented. As an example, the fatigue growth process of cracks emanating from a circular hole in a plane elastic plate is simulated using the numerical simulation approach.

Numerical simulation for isothermal dendritic growth of succinonitrile-acetone alloy

Numerical simulation based on phase field method was developed to describe the solidification of two-dimensional isothermal binary alloys. The evolution of the interface morphology was shown and the effects of phase field parameters were formulated for succinonitrile-acetone alloy. The results indicate that an anti-trapping current(ATC) can suppress many trapped molten packets, which is caused by the thickened interface. With increasing the anisotropy value from 0 to 0.05, a small circular seed grows to develope secondary dendritic, dendritic tip velocity increases monotonically, and the solute accumulation of solid/liquid interface is diminished distinctly. Furthermore, with the increase of the coupling parameter value, the interface becomes unstable and the side branches of crystals appear and grow gradually.

Improving Effect of Salicylic Acid on the Multipurpose Tree <i>Ziziphus spina-christi</i>(L.) Willd Tissue Culture

Salicylic acid (SA) is one of numerous phenolic compounds found in plants with numerous important physiological events. Exogenously application of Salicylic acid (SA) is useful for the growth and development of plants. This investigation aimed to study the improving effect of salicylic acid on the tissue culture of Ziziphus spina-christi. To study its improving effect were used shoot-tip explants cultured on Murashige and Skoog (MS) solid medium supplemented with different concentrations and various combinations of auxins, cytokinins and Salicylic acid. Media without growth regulators enhanced the growth and elongation of shoot-tip explants not its proliferation. Lower concentrations of cytokinin were better for shoot-tip proliferation than higher ones. 6-Benzylaminopurine (BAP) was superior to kinetin (KN) in shoot-tip proliferation. The optimum culture conditions for shoot-tip proliferation were achieved on MS medium supplemented with 0.25 mg/l 6-Benzylaminopurine (BAP) and 25 mg/l Salicylic acid (SA). The optimum culture conditions for callus formation were obtained on MS medium supplemented with 3 mg/l 2,4-Dichlorophenoxyacetic acid (2,4-D) and 25 mg/l Salicylic acid (SA), while the optimum culture conditions for somatic callus formation were obtained on MS medium supplemented with 2.0 mg/l 2,4-Dichlorophenoxyacetic acid (2,4-D) and 10 mg/l Salicylic acid (SA). The optimum culture conditions for rooting of shoots were obtained on MS medium supplemented with 0.25 mg/l of Indole-3-butyric acid (IBA) and 10 mg/l Salicylic acid (SA). The highest percentage of survival plants was obtained in the soil mixture supplied with 10 mg/l Salicylic acid (SA). Salicylic acid (SA) showed positive effect and good response on callusing, shooting and rooting of Z. spina-christi. Cultures received small amounts of salicylic acid were better than those lack it.

THE ANALYSES OF THE THREE-DIMENSIONAL STRESS STRUCTURE NEAR THE CRACK TIP OF MODE I CT SPECIMENS IN ELASTICPLASTIC STATE(Ⅰ)—THE ANALYSES OF CONSTRAINT PARAMETERS AND FRACTURE PARAMETERS

In the present paper, three dimensional analyses of some general constraint parameters and fracture parameters near the crack tip of Mode I CT specimens in two different thicknesses are carried out by employing ADINA program. The results reveal that the constraints along the thickness direction are obviously separated into two parts: the keeping similar high constraint field (Z1) and rapid reducing constraints one(Z2). The two fields are experimentally confiremed to correspond to the smooth region and the shear lip on the fracture face respectively. So the three dimensional stress structure of Mode I specimens can be derived through discussing the two fields respectively. The distribution of the Crack Tip Opening Displacement (CTOD) along the thickness direction and the three dimensional distribution of the void growth ratio (Vg) near the crack tip are also obtained. The two fracture parameters are in similar trends along the thickness direction, and both of them can reflect the effect of thickness and that of the loading level to a certain degree.

基于改进YOLO v5s的复杂环境下蔗梢分叉点识别与定位

甘蔗蔗梢分叉点的精确识别与高度定位是实现甘蔗收获机切梢器实时控制的关键技术之一,也是提高甘蔗收获机械化水平和降低甘蔗含杂率的重要途径。针对甘蔗地环境复杂、光照变化大、蔗梢分叉点相互遮挡等问题,首先通过田间调查,并现场测试、分析甘蔗生长点、甘蔗分叉点及相互关系的特征规律,采集图像的甘蔗分叉点的统计分析,并结合现场对甘蔗分叉点高度的测量统计分析,发现其均具有明显的正态统计特征。接着,提出了一种基于改进YOLO v5s的蔗梢分叉点识别方法。该方法采用单目和双目相机在广西大学扶绥农科基地采集甘蔗图像数据,并进行数据预处理和标注,构建了甘蔗蔗梢分叉点数据集。然后,在YOLO v5s中引入BiFPN特征融合结构和CA注意力机制,以增强不同层次特征的交互和表达能力,并使用GSConv卷积和Slim-Neck范式设计,在原始模型主干网络中引入Ghost模块替换原始普通卷积,来降低模型的计算量和参数量,提高模型的运行效率。最后,通过在现场采集的数据集上进行训练和测试,验证了该方法的有效性和优越性。实验结果表明,该方法在甘蔗蔗梢分叉点数据集上平均精确率达到92.3%、召回率89.3%和检测时间19.3 ms,相比原始YOLO v5s网络,平均精确率提高5个百分点,召回率提高4个百分点,参数量降低43%,模型内存占用量减少5.5 MB,检测时间减少0.7 ms。最后,根据甘蔗分叉点具有明显的正态统计特征的规律,利用该特征结合双目视觉的定位算法,可为开展甘蔗收获机切梢的特征识别、切梢器高度定位及实时控制研究奠定理论及技术基础。

电子加速器源射线对小麦根尖染色体及生理特性的影响

为探究电子加速器源射线对小麦的生物学效应,利用10 MeV电子直线加速器辐射处理小麦种子,分析不同辐射剂量对小麦的生长、生理特性和根尖细胞染色体形态的影响。结果表明,与0 Gy相比,200、400 Gy辐射处理下,小麦种子发芽率差异不显著,但随着辐射剂量的增大,发芽时间明显延长、生长速度减慢,生长10 d的小麦幼苗株高分别下降了49.67%和81.32%,根长分别下降了74.79%和89.67%,鲜重分别下降了50.93%和62.01%。同时,两种剂量处理下,两叶一心期小麦叶片过氧化氢酶(CAT)活性分别上升了171.01%和37.69%,过氧化物酶(POD)活性分别上升了89.77%和59.74%,可溶性蛋白含量分别上升了63.20%和102.45%,丙二醛(MDA)含量分别上升了44.85%和75.36%,H_(2)O_(2)含量分别上升了120.64%和175.78%,而超氧化物歧化酶(SOD)活性分别下降了34.91%和45.45%,叶绿素a含量下降了42.55%和54.69%,叶绿素b含量下降了28.03%和54.44%。表明高剂量(400 Gy)辐射影响植物细胞中的正常代谢,进而影响生长。200、400 Gy辐射处理下,小麦根尖细胞有丝分裂指数分别降低了4.37和6.00个百分点,畸变率分别升高了6.80和16.19个百分点,微核率分别升高了6.02和14.22个百分点。表明高剂量辐射导致根尖细胞无法正常完成有丝分裂,并且造成染色体畸变,生长速率被抑制,对小麦正常生长造成不良影响。试验结果可为应用电子加速器源射线辐射小麦诱变育种提供参考依据。

5个品种草莓茎尖组培快繁体系的建立

目的:探索氯化汞不同处理时间对草莓茎尖培养消毒的影响和不同种类、不同浓度植物生长调节剂对不同草莓试管苗增殖、生根的影响,建立不同品种草莓茎尖脱毒组培快繁体系。方法:以草莓品种‘红颜’‘红花’‘天仙醉’‘越丰’‘雪兔’匍匐茎茎尖为材料,设置不同的0.1%氯化汞处理时间,筛选出草莓茎尖消毒效果最佳的氯化汞处理。通过在MS培养基中添加不同种类、不同浓度植物生长调节剂,筛选出5个草莓品种最适的增殖培养基。并通过试管苗的移栽炼苗,比较不同品种草莓的移栽成活率。结果:0.1%氯化汞处理6 min最适合草莓茎尖外植体消毒。‘红颜’品种最适增殖配方为MS+0.4 mg/L 6-BA+0.06 mg/L IBA;‘红花’品种最适增殖配方为MS+0.6 mg/L 6-BA+0.03 mg/L IBA;‘天仙醉’品种最适增殖配方为MS+0.2 mg/L 6-BA+0.06 mg/L IBA;‘越丰’品种增殖最适增殖配方为MS+0.2 mg/L 6-BA+0.03 mg/L IBA;‘雪兔’品种最适增殖配方为MS+0.2 mg/L 6-BA+0.06 mg/L IBA。草莓试管苗比较容易生根,在无激素的培养基上能长出大量根。5个草莓品种的组培苗在MS不添加任何激素的培养基中生根培养30 d,组培苗的根都能长出,且平均根数为4~5条,生根率为100%。结论:不同草莓品种茎尖组培快繁体系得以建立,不同草莓品种试管苗脱毒率存在差异。

基于SBFEM研究T应力对岩石起裂特性的影响

传统断裂判据在分析岩石裂纹尖端起裂特性时忽略了非奇异项参数的影响,从而导致理论结果与试验结果产生较大的偏差。比例边界有限元法(Scaled boundary finite element method-SBFEM)是一种半解析的数值计算方法,可以较精确的计算实数、复数以及幂-对数奇异性问题同时不需要对裂纹尖端进行特殊处理,应力强度因子等裂尖奇异参数都可以根据定义直接进行提取。基于此方法对复合型岩石裂纹尖端奇异参数I、II型应力强度因子和T应力进行了提取,并建立了考虑T应力的断裂准则,对不同裂纹形式下岩石的起裂特性进行研究,并与现有试验结果进行对比。结果表明,T应力为正值时会加剧裂纹扩展,T应力为负值时会抑制裂纹扩展,可见裂纹尖端的非奇异参数即T应力的影响不容忽视。

花粉管细胞结构与生长机制研究进展

花粉管的极性顶端生长是一个复杂的动力学过程,在高等植物有性生殖过程中起着重要的作用。花粉管的生长过程包括许多方面,其中最为重要的是花粉管细胞骨架动态和胞质运动。本文较全面地综述了花粉管的结构、细胞骨架、胞质运动、囊泡转运及循环、线粒体运动以及内质网和高尔基体之间囊泡运动等。

多效唑和乙烯利处理对芒果花期的影响

[目的]调整芒果产期,以稳定芒果市场,增加果农收益。[方法]选用海南2个主要栽培当家种台农1号芒、金煌芒作为参试材料,在2005~2009年对2个品种分7个时段进行多效唑和乙烯利叶面喷施控梢处理,分析其对芒果花期的影响。[结果]芒果提早剪枝,喷施多效唑和乙烯利混合液时间提早、处理时间长、控梢次数多、控梢量足,枝梢老熟快,花芽分化早,抽穗开花（花期）提早,反之,花期推迟;芒果控梢有效方法：前期轻控（不伤害嫩芽、嫩梢）,中期重控（促进枝梢提前老熟,提早花芽分化）,后期轻控、薄控（诱导开花）。采用这种控梢方法7个时段处理的台农1号芒、金煌芒在9~11月催花均能整齐开花。[结论]获得了多效唑和乙烯利叶面控梢处理对诱导芒果提早或推迟开花的规律。

pH影响Ca^(2+)和EGTA对水霉(Saprolegnia ferax)菌丝顶端生长的作用效应

水霉(Saprolegia ferax)菌丝在pH6.0-8.0的OM液体培养基中生长良好,在pH5.0时生长速率有所下降,在pH3.0—4.0时停止生长。短时间(30min)作用研究表明,低浓度的CaCl_2促进pH5.0(1—5mmol/L)和pH6.0(1mmol/L)条件下的菌丝顶端生长,抑制pH7.0—8.0条件下的菌丝生长。1mmol/L以上的EGTA则抑制pH5.0条件下菌丝顶端生长,促进pH6.0—8.0条件下的菌丝顶端生长。但CaCl_2和EGTA都不能使pH3.0—4.0条件下的菌丝恢复生长。长时间(8h)作用跟踪观察表明,2mmol/L EGTA(pH6.8)短时间作用可促进菌丝生长,但随着培养时间延长,则产生抑制作用,并诱导原生质从菌丝最顶端喷出。说明细胞壁Ca^(2+)起着提供胞外Ca^(2+)源和细胞壁修饰成分的双重作用。Ca^(2+)通道阻断剂verapamil对菌丝顶端生长的抑制作用也说明顶端生长所需的Ca^(2+)来自胞外。

T应力对岩石裂纹扩展路径及起裂强度的影响研究

经典断裂判据在分析岩石起裂角度及强度时,往往只选择裂尖应力场展开式中的r^(1/2)奇异应力项,而将高阶的O(r^(1/2))项以及非奇异应力项(T应力)忽略,造成理论预测并不能完全吻合实际的试验结果。在充分考虑非奇异应力项对裂纹扩展影响作用的基础上,利用最大周向应力判据重新研究了岩石类材料脆性破坏的I、II及I-II复合型裂纹扩展。研究结果表明:(1)纯I型裂纹状态下,T应力为负时(压缩),裂纹的扩展是稳定的;而当T应力为正时(拉伸),只有当T2πr1/2<3K_1/8,裂纹才沿着裂纹方向扩展(经典断裂判据所预测的方向),而其他情况下裂纹的扩展将发生偏转;(2)纯II型裂纹时,不仅沿着裂纹方向的T应力影响起裂角度及强度,垂直裂纹面上的N应力也同样具有重要的影响作用;(3)对I-II型裂纹而言,修正后的最大周向应力准则与试验结果吻合良好,且正的T应力增大开裂角,而负的T应力降低开裂角。通过控制T应力的大小,可以对裂纹扩展方向加以控制,从而使得裂纹扩展偏离最危险的方向,最大地限度阻止或延缓结构整体断裂的发生。

钙离子在水霉(Saprolegnia ferax)菌丝顶端细胞壁中呈极性分布

焦锑酸钾处理的水霉(Saprolegnia ferax)菌丝显示:焦锑酸沉淀颗粒仅存在菌丝细胞壁而不是原生质中,并呈顶端到基部的极性分布,即在菌丝最顶端细胞壁中丰富致密、重叠在一起,在约3—10μm的亚顶端则变得稍为稀薄而可分辨,在约10μm以后的成熟区域进一步显得松散而无规律。焦锑酸沉淀颗粒可经EGTA螫合处理去除,并经X-射线微区分析证明在3.6—3.7keV区域可产生Sb和Ca元素混合峰,说明焦锑酸沉淀反映了Ca^(2+)的分布。对冷冻干燥菌丝细胞壁表面进行扫描电镜X-射线微区分析,同样证明菌丝细胞壁含有大量的Ca,菌丝最顶端Ca信号强度高于10μm以后的成熟区。由于Ca^(2+)和H^+可能为一对拮抗因子维持菌丝顶端细胞壁可塑性和刚性间的平衡以保证菌丝顶端生长,我们检验了菌丝生长过程中培养介质的pH变化,证实培养介质pH随培养时间的延长而逐渐下降。上述结果提示细胞壁Ca^(2+)可能在菌丝顶端生长过程中起作用。

摘心对柠檬苗新梢的影响

为探明不同摘心处理对柠檬苗生长的影响,以移栽1年生枳砧嫁接的柠檬苗为研究对象,嫁接3个月后分别进行自然生长(CK),摘心留桩0.0cm,摘心留桩0.5cm,摘心留桩1.0cm处理。试验结果表明:摘心留桩1.0cm时,处理效果最佳,其抽梢数量、苗木基部粗度均优于摘心留桩0.0cm及自然生长(CK),其苗高度也达到了优质苗木出圃移栽的规格。研究结果也显示,与自然生长(CK)相比,不同程度的摘心留桩均增加了侧芽萌发的数量、主干茎粗及侧枝生长的整齐度,但侧枝平均长度有所降低。