麻花秦艽根内中柱裂分的发育解剖研究

通过发育解剖学研究表明,麻花秦艽根的初生结构正常,初生木质部四原型。次生生长的早期阶段也是正常的。在以后的次生生长过程中,由于木质部柱局部区域外的维管形成层向内衍生的细胞分化成木薄壁组织细胞的数量多于导管,从而在木质部内形成薄壁组织细胞区域,并且由于此区域内细胞的增殖,将木质部分成两部分。以后韧皮部也随之分开,从而中柱被分成两个独立的裂分中柱。以后,每个裂分中柱又产生各自的周皮,进而使主根分裂成两个支根。每个支根也可以同样方式分裂产生许多支根。     

六盘山鸡爪大黄葸醌类化合物积累特征的研究

采用多种组织化学方法研究了六盘山鸡爪大黄营养器官中蒽醌类化合物的积累特征。结果显示：蒽醌类化合物在根中分布于周皮的木栓层和栓内层、次生维管组织的维管射线和根中央的部分木薄壁细胞内,且维管射线是根中贮藏和积累蒽醌类化合物的主要组织;在根茎中分布于周皮的木栓层和栓内层、次生维管组织的形成层和维管射线,以及髓的异常维管束射线中,且维管射线是根茎中贮藏和积累蒽醌类化合物的主要组织;在茎中主要分布于表皮、近表皮皮层和维管束的维管束鞘及其薄壁细胞,大型和小型维管束之间和周围的部分薄壁细胞,以及髓射线中有不同程度的分布;在叶中主要积累在叶柄的表皮、叶柄和大叶脉的部分基本组织、维管束的部分薄壁细胞等部位。结果表明,六盘山鸡爪大黄的根和根茎是蒽醌类化合物贮藏和积累的主要器官,维管射线是其贮藏和积累的主要组织,而且各营养器官中蒽醌类化合物积累的数量与植物各相关器官组织的发育程度、细胞中含淀粉粒的多少存在着一定的相关性。     

六盘山鸡爪大黄蒽醌类化合物积累特征的研究

采用多种组织化学方法研究了六盘山鸡爪大黄营养器官中蒽醌类化合物的积累特征.结果显示:蒽醌类化合物在根中分布于周皮的木栓层和栓内层、次生维管组织的维管射线和根中央的部分木薄壁细胞内,且维管射线是根中贮藏和积累蒽醌类化合物的主要组织;在根茎中分布于周皮的木栓层和栓内层、次生维管组织的形成层和维管射线,以及髓的异常维管束射线中,且维管射线是根茎中贮藏和积累蒽醌类化合物的主要组织;在茎中主要分布于表皮、近表皮皮层和维管束的维管束鞘及其薄壁细胞,大型和小型维管束之间和周围的部分薄壁细胞,以及髓射线中有不同程度的分布;在叶中主要积累在叶柄的表皮、叶柄和大叶脉的部分基本组织、维管束的部分薄壁细胞等部位.结果表明,六盘山鸡爪大黄的根和根茎是蒽醌类化合物贮藏和积累的主要器官,维管射线是其贮藏和积累的主要组织,而且各营养器官中蒽醌类化合物积累的数量与植物各相关器官组织的发育程度、细胞中含淀粉粒的多少存在着一定的相关性.     

掌叶大黄根多糖的积累分布特征

采用组织化学方法和苯酚硫酸比色法研究了掌叶大黄（Rheum palmatum）根中大黄多糖的贮藏分布特征和含量变化规律。结果表明：大黄多糖在根内的贮藏是多位点的,在根周皮的栓内层、次生维管组织的薄壁细胞内不同程度地贮藏和积累了一定数量的大黄多糖,次生木质部的木薄壁细胞和次生韧皮部的韧皮薄壁细胞是主要贮藏和积累的部位;不同发育时期根中大黄多糖含量的变化规律为,随着植物的不断成熟,根及其各组织中大黄多糖的总含量表现为逐渐增高的趋势,但在发育的后期略有下降;韧皮薄壁细胞与木薄壁细胞相比,贮藏大黄多糖的含量相对较多,大黄多糖的贮藏积累方式为逐渐累积的方式。     

欧美杂种山杨微扦插不定根发生过程的解剖学研究

采用石蜡切片技术,以欧美杂种山杨插穗基部茎段为实验材料,连续解剖观察插穗不定根发生发育过程,分析根原基发生部位与扦插生根的关系。结果显示:欧美杂种山杨插穗不定根的发生过程分为4个时期,为根原基诱导期,不定根起始期、表达期和伸长生长期。根原基诱导期维管形成层产生具有分生组织特点的薄壁细胞;不定根起始期,维管形成层及附近的薄壁细胞脱分化,形成不定根原基发端细胞;不定根表达期,根原基发端细胞不断分裂成具有方向性的根原基,根原基穿过韧皮射线和皮层,向皮孔方向发展;不定根伸长生长期,根原基从皮孔伸出,其内部的维管系统开始发育,形成不定根。研究认为,欧美杂种山杨为皮部诱导生根类型,不定根原基起源于维管形成层区,起源部位单一,扦插难生根。     

中药秦艽根内中柱裂分的发育解剖学研究

通过发育解剖学研究表明,秦艽根的初生结构正常,初生木质部四原型。次生生长早期阶段也是正常的,但天以后的次生生长过程中,由于木质部内部分薄壁细胞的分裂,且迅速 化成异常形成层细胞,并与原维管形成层相连,从而形成多个新的形成层环,将木质部柱分为几个子木质部。     

远志根的形态发生及组织化学研究

应用植物解剖学方法对远志(Potygda tenuiflia Willd.)根的发生和发育过程,以及1 a生与2 a生根的结构进行了比较观察,还应用组织化学方法对远志根储藏物质及主要药用成分积累部位进行了研究.结果表明:远志的药用部位为其主根,发育过程包括原分生组织、初生分生组织、初生结构和次生结构4个发育阶段.原分生组织来源于胚根,由3群原始细胞组成,具有典型分生组织的细胞学特征;初生分生组织包括根冠原、表皮原、皮层原和中柱原;初生结构由表皮、皮层和维管柱组成,初生木质部为二原型;次生生长主要是依靠维管形成层和木栓形成层的活动来完成.木栓形成层由中柱鞘细胞恢复分裂能力而形成,并且产生多层栓内层薄壁细胞.2 a生远志根的基本结构与1 a生的基本相同,只是栓内层增加至10层以上.远志根的储藏物质主要是脂类物质及少量的多糖.远志皂苷积累在远志根的薄壁细胞中,而山酮类化合物主要分布在根的木栓形成层、栓内层薄壁细胞和次生韧皮部中.     

单瘤酸模根—茎转换区初生维管组织的解剖学研究

作者在对单瘤酸模（Ｒｕｍｅｘ ｃｒｉｓｐｕｓ ｖａｒ．ｕｎｉｃａｌｌｏｓｕｓ）幼苗维管组织做连续切片的解剖观察时看到,该植物维管组织从根到茎的变化过程中出现４个不同的中柱类型即（１）根－下胚轴的三元型星状中柱;（２）子叶节区下部的单体型原生中柱;（３）子叶节区上部的管状中柱和（４）上胚轴－苗端的真中柱。作者对此进行了讨论,认为子叶节区既然具有原始的单一管状类型的中柱,说明这一部位应为与古老 性顺官     

杂种鹅掌楸插穗不定根发生与发育的解剖学观察

从解剖学角度着手,对杂种鹅掌楸〔Liriodendronchinense(Hemsl.)Sarg.×L.tulipiferaL.〕扦插过程中不定根的发生发育进行了研究。结果表明:杂种鹅掌楸插穗内未发现潜伏根原基。扦插后,不定根原基起源于维管形成层区,属于诱导生根类型。维管形成层恢复活动后,在不定根发生的部位附近形成1个明显的多薄壁细胞区域,在此区域不定根较容易发生。愈伤组织内没有发现根原基,愈伤组织在发育的过程中,内部细胞部分分化,并形成不规则的输导组织。大量的愈伤组织对不定根的发生有较强的抑制作用。杂种鹅掌楸插穗上不定根的发生可分为4个阶段:(1)维管形成层恢复活动,分裂出多层薄壁细胞;(2)维管形成层及附近的薄壁细胞脱分化,形成不定根原基发端细胞;(3)根原基发端细胞不断分裂成具有方向性的根原基,根原基穿过韧皮射线和皮层,向皮孔或下切口方向发展;(4)不定根从皮孔或下切口伸出,其内部的维管系统开始发育。     

六盘山鸡爪大黄根多糖贮藏和分布特征的研究

采用组织化学方法对六盘山鸡爪大黄根不同生长发育时期大黄多糖贮藏和分布进行定位观察分析,以明确大黄多糖在其根中的分布与累积特征.结果显示:六盘山鸡爪大黄根内大黄多糖的分布是多位点的,其中在根周皮的栓内层内不同程度地贮藏和积累有一定的数量,而在次生维管组织的薄壁细胞中大量积累,是其根内大黄多糖贮藏与分布的主要部位;韧皮薄壁细胞与木薄壁细胞相比,前者贮藏大黄多糖的时间较早,含量也较多,且大黄多糖的贮藏积累随根的生长发育进程呈逐渐累积的方式.结果表明,六盘山鸡爪大黄根的次生维管组织薄壁细胞是其大黄多糖贮藏和分布的主要组织,而且大黄多糖累积数量与其根的发育程度存在着一定的相关性.     

紫菀根的结构与主要药用成分积累研究

为揭示紫菀根的结构、主要药用成分积累部位和含量,用石蜡切片法研究不同发育阶段根的结构、组织化学法定位三萜皂苷和黄酮类成分的积累部位、HPLC法测定根中紫菀酮、槲皮素和山奈酚的含量。结果表明,紫菀根的初生结构包括表皮、皮层和维管柱。次生结构包括外皮层、皮层和维管组织,其中分泌道位于皮层内侧,数量与韧皮部束一致,随着根的增粗,中央分化出髓部。三萜皂苷成分在韧皮部和皮层内侧积累较多;黄酮类成分积累于皮层和髓部。紫菀根下部的紫菀酮含量高于上部,槲皮素和山萘酚仅为上部的1/3。因此,建议加工时保留下部细根,实现资源综合利用。     

Anatomical patterns of condensed tannin in fine roots of tree species from a cool-temperate forest

Background and AimsCondensed tannin (CT) is an important compound in plant biological structural defence and for tolerance of herbivory and environmental stress. However, little is known of the role and location of CT within the fine roots of woody plants. To understand the role of CT in fine roots across diverse species of woody dicot, we evaluated the localization of CT that accumulated in root tissue, and examined its relationships with the stele and cortex tissue in cross-sections of roots in 20 tree species forming different microbial symbiotic groups (ectomycorrhiza and arbuscular mycorrhiza).MethodsIn a cool-temperate forest in Japan, cross-sections of sampled roots in different branching order classes, namely, first order, second to third order, fourth order, and higher than fourth order (higher order), were measured in terms of the length-based ratios of stele diameter and cortex thickness to root diameter. All root samples were then stained with ρ-dimethylaminocinnamaldehyde solution and we determined the ratio of localized CT accumulation area to the root cross-section area (CT ratio).Key ResultsStele ratio tended to increase with increasing root order, whereas cortex ratio either remained unchanged or decreased with increasing order in all species. The CT ratio was significantly positively correlated to the stele ratio and negatively correlated to the cortex ratio in second- to fourth-order roots across species during the shift from primary to secondary root growth. Ectomycorrhiza-associated species mostly had a higher stele ratio and lower cortex ratio than arbuscular mycorrhiza-associated species across root orders. Compared with arbuscular mycorrhiza species, there was greater accumulation of CT in response to changes in the root order of ectomycorrhiza species.ConclusionsDifferent development patterns of the stele, cortex and CT accumulation along the transition from root tip to secondary roots could be distinguished between different mycorrhizal associations. The CT in tissues in different mycorrhizal associations could help with root protection in specific branching orders during shifts in stele and cortex development before and during cork layer formation.     

Exogenous zeatin accumulation in wheat-root cells and its role in regulation of cytokinin transport

It was shown that the cytokinin content in the xylem sap of a wheat plant treated with exogenous zeatin was about ten times lower than in the nutrient solution in 24 h. Cytokinins were accumulated in roots rather shoots of treated plants. These data demonstrate the existence of a barrier in the cytokinin pathway from the nutrient solution to plant shoots. The deposition of lignin and suberin in stele detected with Sudan @III is enlarged with an increase in the distance from the tip of the root. The augmented content of suberin and lignin coincided with reduced cytokinin immunolabeling in root cells revealed by monoclonal antibodies to cytokinin and secondary gold-labeled antibodies. The accumulation of exogenous cytokinin in root stele cells shows that Casparian bands are not the only barrier on the cytokinin pathway to plant shoots. Intensive cytokinin immunolabeling in parenchyma cells surrounding stele vessels indicates the accumulation of cytokinin by these cells and suggests that there are mechanisms that limit the hormone loading in xylem vessels during transport to the shoot. The role of cytokinin transporters in this process is discussed.     

Tissue specificity of assimilation and transport of nitrogen in the root ofZea mays L. seedlings. I. Transformations of14C- sucrose and the nitrogen metabolism enzymes in cortex and stele

An investigation has been carried out to find out in what compounds carbon is radially transported from stele to the cortex and to study sucrose metabolism in the root. These tissues were fed with¹⁴C-sucrose either directly or through the mesocotyle. In the latter case, the bulk of radioactivity, both in the stele and cortex, was concentrated in sucrose rather than in mono saccharides. This corresponds to the radial transport of carbon from stele to cortex predominantly in the form of sucrose. In the case of a direct exposure of stele and cortex,¹⁴C-sucrose was utilized for respiration, amino acid biosynthesis, and accumulation of carbon in the form of glucose. The hydrolysis of sucrose to the monosaccharides and subsequent utilization of the latter in respiration was more intensive in the stele. In the cortex, the sucrose carbon was more actively used for amino acid synthesis, owing to a high concentration of nitrate reductase, glutamate dehydrogenase and glutamine synthetase. It was concluded that the cortex is the main issue zone providing nitrogen assimilation in the root.     

Histochemical Localization and Nematoxicity of Terpenoid Aldehydes in Cotton

In healthy cotton, except for random occasional occurrence in cortical cells, terpenoid aldehydes (TA) are localized in the epidermis and, even there, are absent from the tip 2-4 cm of the root. Since constitutive TA do not occur in the endodermis and stele of the root, they cannot be effective agents against the development of the sedentary stage of the root-knot nematode, Meloidogyne incognita. Within 4 days after inoculation with the root-knot nematode, infection-induced TA accumulated in the endodermis and outer stele. These induced TA were thus localized where they could be effective against the sedentary stage of the nematode. Infection-induced TA accumulation was more rapid and occurred in more stele cells in a resistant cotton cultivar than in two susceptible cultivars.TA extracts from cotton were inhibitory to nematode movement. All second-stage larvae exposed to 1,000 ppm TA for 3 h became rigid, made no movement, and appeared dead. Washing these larvae to remove the TA and incubating them for an additional 24 h did not change their appearance. Shorter exposure times or lower TA concentrations allowed some larvae to recover. Exposing larvae to 10 ppm of TA for 24 h had little effect on them. TA extracted from G. arboreum, a cotton that does not methylate TA, were slightly less inhibitory to the root-knot nematode than TA extracted front G. hirsutum which partially methylates TA.     

Exogenous zeatin accumulation in wheat root cells shows its role in regulation of cytokinin transport

Here we have shown that 24 hours after addition of zeatin to the nutrient solution the cytokinin content in xylem sap of wheat plants appears to be about 10 times lower that in the nutrient solution. Cytokinins accumulated mostly in roots and not in shoots of treated plants. These data demonstrate the existence of some barrier on cytokinin pathway from the nutrient solution to the plant shoot. With the help of Sudan III an increase in lignin and suberin deposition in the endodermis could be detected, being stronger with the increase in the distance from the root tip. The increase in deposition of suberin and lignin coincided with the decrease in cytokinin immunolabeling in root cells revealed with the help of monoclonal cytokinin antibodies and the second gold-labelled antibodies. Simultaneously exogenous cytokinins accumulated in root stele cells showing that the Casparian band was not only barrier on cytokinin pathway to plant shoot. It is concluded that high cytokinin immunolabe ling in the stele parenchyma cells around the stele vessels demonstrated accumulation of cytokinins by these cells, which could be important in regulation of cytokinin loading to the xylem vessels during there transport to the shoot. The role of cytokinin transporters is discussed.     

Radial transport of ions in roots

Measurements were made of the relative amounts of ⁸⁶Rb, ³⁶Cl, and ³²P accumulated in the cortex and stele of intact roots of corn (Zea mays), either detached or attached to their shoots. Both 4- and 7-day-old roots accumulated as much or more ⁸⁶Rb in the stele as in the cortex. In experiments with ³⁶Cl, cortex and stele accumulated the same amount, except for 4-day-old and 7-day-old attached roots, in which the cortex contained more ³⁶Cl than the stele after 23 hr. An additional study of ³²P uptake showed greater accumulation in the cortex than the stele for a short period of time, but as much in the stele as in the cortex after 8 to 24 hr. Transport of ⁸⁶Rb, ³⁶Cl, and ³²P into the xylem exudate increased with increasing accumulation of these ions in stele and cortex of the root. These experiments show no consistent difference between cortex and stele of intact corn roots with respect to their ability to accumulate several kinds of ions.     

应用电子探针对植物根际和根内营养元素微区分布的探讨

用电子探针可检测出玉米、大豆根际和根内含有Na,Mg,Al,Si,P,S,Cl,K,Ca,Ti,Fe,Cu和Zn 13种元素。这些元素在根际土壤、粘液层和根组织内的含量分布有一定的规律性。除Si,Al,Ca,Fe在根际土壤中峰值较高外,Ti仅在土壤中达到可检测量;S,Fe和Zn富集在粘液层,Mg,P,Cl只在根组织内才有较明显的峰。这些规律可作为区分根—土界面的参考指标。K含量在根内明显高于根际土壤,并由表皮层到中柱径向增加;Ca则与K不同,且受植物种类的影响。     

Water-Transporting System in Higher Plants and Its Elements: 6. Relationship between Root Pressure and Transpiration in an Intact Plant

Novel experimental data were adapted to a previously devised concept of water relations in plant roots. The improved concept explains the formation in the root stele of a high water potential that exceeds the water potential of the root environment. The physical basis of this phenomenon relies on active metabolism of the peripheral root zone (cortex) and, more importantly, on the unloading of assimilates from the root central cylinder (stele) to the outer cylinder (cortex). The unloading not only raises the water potential of the root stele but also increases the hydraulic resistance; these two factors account for the elevation of root pressure. The process of unloading assimilates from the root stele to the cortex is apparently promoted by the transit of the ascending water flow through the cortex. This flow, enriched with the dissolved oxygen of the root environment, stimulates the unloading and metabolic conversion of assimilates in the root symplast.     

Cell-type action specificity of auxin on Arabidopsis root growth

The plant hormone auxin plays a critical role in root growth and development; however, the contributions or specific roles of cell-type auxin signals in root growth and development are not well understood. Here, we mapped tissue and cell types that are important for auxin-mediated root growth and development by manipulating the local response and synthesis of auxin. Repressing auxin signaling in the epidermis, cortex, endodermis, pericycle or stele strongly inhibited root growth, with the largest effect observed in the endodermis. Enhancing auxin signaling in the epidermis, cortex, endodermis, pericycle or stele also caused reduced root growth, albeit to a lesser extent. Moreover, we established that root growth was inhibited by enhancement of auxin synthesis in specific cell types of the epidermis, cortex and endodermis, whereas increased auxin synthesis in the pericycle and stele had only minor effects on root growth. Our study thus establishes an association between cellular identity and cell type-specific auxin signaling that guides root growth and development.