Untersuchungen zur funktionellen Anatomie des Leitgewebesystems im Blatt von Pelargonium zonale

Summary The petiole of Pelargonium zonale is traversed by 17 bundles, whose arrangement and form are typical for this plant. The bundles of the petiole are connected with the conducting system of the axis and with the main nerves by a system of phloem anastomoses in the leaf base and in the junction between the petiole and the leaf blade (Fig. 2). The anatomical findings were confirmed and extended by a study of the translocation of K-fluorescein and ¹⁴C. It could be shown that the metaphloem of the central petiole bundle is composed of phloem subunits, each of which is connected with the phloem of one certain main nerve only (Fig. 4). Accordingly, if fluorescein or ¹⁴CO₂ is applied to one main nerve, the dye or ¹⁴C-material is translocated exclusively in a small phloem area of the central bundle. Autoradiograms of the petioles indicate that the ¹⁴C-labelled assimilates (sucrose, glucose, fructose and amino acids) are translocated exclusively in the phloem. A lateral movement of the labelled material within the petiole was not observed. The metaphloem of the central petiole bundle of Pelargonium zonale revealed a functional organization of phloem subunits.

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Teil einer Dissertation unter der wissenschaftlichen Leitung von Prof. Dr. J. Willenbrink.     

Virus-like particles in phloem tissue of chervil (Anthriscus cerefolium) infected with anthriscus yellows virus

Clusters of isometric virus-like particles c. 22 nm in diameter, embedded in amorphous electron-dense material, were found in the phloem tissue of Anthriscus cerefolium (chervil) plants infected with the semi-persistent aphid-borne virus, anthriscus yellows (AYV). The particles resembled those seen previously in thin sections of AYV-transmitting aphids (Cavariella aegopodii). The particles were found only in the central vascular bundle of the petiole and its continuation in the leaf midrib. They were also found in extracts made by grinding petiole and midrib tissue in 10 % sucrose using Carborundum. These results confirm earlier studies which suggest that AYV is confined to deeper-lying tissues.     

THE ANATOMIC RESPONSES OF DAUCUS CAROTA TO THE ASTER YELLOWS VIRUS

Struckmeyer, B. Esther. (U. Wisconsin, Madison.) The anatomic responses of Daucus carota to the aster yellows virus. Amer. Jour. Bot. 50(9): 959–963. Ilus. 1963.—The leaves, petioles, and roots of carrots (Daucus carota) displaying aster yellows virus in the field and those infected with the aster yellows virus inoculated by the 6-spotted leafhopper were examined anatomically. Compared to the uninoculated, the young infected leaves displayed fewer layers of palisade cells and larger spongy parenchyma cells with a more compact arrangement. Mature leaves of infected plants sometimes were undulated and had few chloroplasts, many of which appeared fragmented. Hypertrophy and hyperplasia in the phloem tissue were associated with some necrosis and obliteration of cells. Long, needle-shaped crystalline inclusion bodies were present in the phloem in the leaves and roots. Most of the vascular bundles of the petiole were abnormal. Malformations included proliferating phloem cells, which in some instances almost encircled the bundle, hyperplasia of the phloem, hypertrophy of the parenchyma, and considerable necrosis and obliteration of these cells. Other responses included the division into 3 or 4 rows of the large outer phloem parenchyma by parallel walls so that a cambium-like layer was simulated. The tissue enclosed by this layer divided and underwent considerable necrosis and gummosis. Lacunae were found between the phloem bundle cap and the older phloem. Some of the cells in the phloem tissue differentiated into bundles with xylem. Numerous, short, lateral roots were conspicuous on the main root. The most noticeable response of the root tissue to this malady was hyperplasia and hypertrophy of the phloem followed by cellular disorganization, necrosis, and obliteration of cells. Some sieve tubes, companion cells, and parenchyma contained a gumlike deposit.     

国产杜鹃花叶解剖与分类群

报道了分别隶属于杜鹃花属 ( Rhododendron)中 8个亚属的国产 33个种叶片的解剖特征。根据中脉维管束结构特点 :木质部与韧皮部的位置 ,木质部的形状 ,木射线排列的方式 ,可分为 5个类型 :( 1)圆形周韧维管束 ;( 2 )羽线肾形周韧维管束 ;( 3)扇线肾形周韧维管束 ;( 4 )近周韧维管束 ;( 5)下韧维管束。讨论了中脉维管束类型可能的演化趋势 :周韧维管束→近周韧维管束→下韧维管束。还讨论了 8个亚属中脉维管束所处的演化阶段     

芦荟叶内芦荟素细胞的发育和蒽醌类物质的积累

应用石蜡切片、半薄切片、组织化学和荧光显微镜观察相结合的方法研究了木立芦荟叶内芦荟素细胞的发生、发育以及其蒽醌类物质的积累过程。结果表明,在叶内原形成层束分化成维管束初期,原形成层束外侧的一层细胞发育成维管束鞘。原生韧皮部筛管产生时,其外方尚保留1—2层原形成层细胞,当后生韧皮部和木质部开始分化时,此层细胞分裂。在后生韧皮部和木质部发育成熟过程中,这些细胞体积逐渐增大,并液泡化,发育成为大型薄壁细胞(芦荟素细胞),位于筛管外侧。据此,芦荟叶维管束内的大型薄壁细胞的来源与韧皮部相同,属于特化的韧皮部薄壁组织细胞。用醋酸铅处理过的上述材料的切片观察表明,芦荟素细胞在细胞体积增大,并液泡化时,在液泡内出现蒽醌类物质沉淀物,在成熟细胞的大液泡中充满沉淀物,此时,在荧光显微镜下芦荟素细胞发出桔黄色荧光。可见,此种芦荟素细胞是芦荟叶内蒽醌类物质的主要储存场所。     

芦荟叶内芦荟素细胞的发育和蒽醌类物质的积累

应用石蜡切片、半薄切片、组织化学和荧光显微镜观察相结合的方法研究了木立芦荟叶内芦荟素细胞的发生、发育以及其蒽醌类物质的积累过程。结果表明,在叶内原形成层束分化成维管束初期,原形成层束外侧的一层细胞发育成维管束鞘。原生韧皮部筛管产生时,其外方尚保留1-2层原形成层细胞,当后生韧皮部和木质部开始分化时,此层细胞分裂。在后生韧皮部和木质部发育成熟过程中,这些细胞体积逐渐增大,并液泡化,发育成为大型薄壁细胞(芦荟素细胞),位于筛管外侧。据此,芦荟叶维管束内的大型薄壁细胞的来源与韧皮部相同,属于特化的韧皮部薄壁组织细胞。用醋酸铅处理过的上述材料的切片观察表明,芦荟素细胞在细胞体积增大,并液泡化时,在液泡内出现蒽醌类物质沉淀物,在成熟细胞的大液泡中充满沉淀物,此时,在荧光显微镜下芦荟素细胞发出桔黄色荧光。可见,此种芦荟素细胞是芦荟叶内蒽醌类物质的主要储存场所。     

Expression of the phloem lectin is developmentally linked to vascular differentiation in cucurbits

The conducting elements of phloem in angiosperms are a complex of two cell types, sieve elements and companion cells, that form a single developmental and functional unit. During ontogeny of the sieve element/companion cell complex, specific proteins accumulate forming unique structures within sieve elements. Synthesis of these proteins coincides with vascular development and was studied in Cucurbita seedlings by following accumulation of the phloem lectin (PP2) and its mRNA by RNA blot analysis, enzyme-linked immunosorbent assay, immunocytochemistry and in␣situ hybridization. Genes encoding PP2 were developmentally regulated during vascular differentiation in hypocotyls of Cucurbita maxima Duch. Accumulation of PP2 mRNA and protein paralleled one another during hypocotyl elongation, after which mRNA levels decreased, while the protein appeared to be stable. Both PP2 and its mRNA were initially detected during metaphloem differentiation. However, PP2 mRNA was detected in companion cells of both bundle and extrafascicular phloem, but never in differentiating sieve elements. At later stages of development, PP2 mRNA was most often observed in extrafascicular phloem. In developing stems of Cucurbita moschata L., PP2 was immunolocalized in companion cells but not to filamentous phloem protein (P-protein) bodies that characterize immature sieve elements of bundle phloem. In contrast, PP2 was immunolocalized to persistent ␣ P-protein bodies in sieve elements of the extrafascicular phloem. Immunolocalization of PP2 in mature wound sieve elements was similar to that in bundle phloem. It appears that PP2 is synthesized in companion cells, then transported into differentiated sieve elements where it is a component of P-protein filaments in bundle phloem and persistent P-protein bodies in extrafascicular phloem. This differential accumulation in bundle and extrafascicular elements may result from different functional roles of the two types of phloem. Received: 31 July 1996 / Accepted: 27 August 1996     

Value of phloem necrosis in the diagnosis of potato leaf-roll

In plants infected with leaf-roll virus a type of phloem obliteration and necrosis occurs which is distinct from any abnormality produced by other pathogens or arising from physiological causes. The necrosis occurs in the primary phloem only of the bicollateral bundles. The affected tissue reacts with phloro-glucinol in HCI. It was present in all of 179 plants of 33 varieties showing secondary leaf-roll which were examined and was not found in any of 83 healthy plants of 20 varieties. The amount of necrosis varies in different plants. If the disease is severe, necrosis may extend to almost all parts of the plant except the stolon, tubers and roots. If the infection is mild it may be confined to a very few strands in two or three nodes near the base of the main stem. Phloem necrosis can always be found before leaf rolling is apparent.
In primary leaf-roll, slight necrosis can be found in the stem near the bases of the lowest rolled leaves and sometimes in the petioles.
A technique is suggested for the use of this symptom in diagnosis.     

Frequencies of plasmodesmata in Allium cepa L. roots: implications for solute transport pathways.

Plasmodesmatal frequencies (PFs) were analysed in Allium cepa L. roots with a mature exodermis (100 mm from the tip). For all interfaces within the root, the numbers of plasmodesmata (PD) microm(-2) wall surface (Fw) were calculated from measurements of 60 walls on ultrathin sections. For tissues ranging from the epidermis up to the stelar parenchyma, the frequencies were also expressed as total PD numbers mm(-1) root length (Fn), which is most instructive for considering the radial transport of ions and photosynthates (because the tissues were arranged in concentric cylinders). The Fn values were constantly high at the interfaces of exodermis-central cortex, central cortex-endodermis and endodermis-pericycle (4.05x10(5), 5.13x10(5), and 5.64x10(5), respectively). If the plasmodesmata are functional, a considerable symplastic transport pathway exists between the exodermis and pericycle. Two interfaces had especially low PFs: epidermis-exodermis (Fn=8.96x10(4)) and pericycle-stelar parenchyma (Fn=6.44x10(4)). This suggests that there is significant membrane transport across the interface of epidermis-exodermis (through short cells) and direct transfer of ions from pericycle to protoxylem vessels. In the phloem, the highest PF was detected at the metaphloem sieve element-companion cell interface (Fw=0.42), and all other interfaces had much lower PFs (around 0.10). In the pericycle, the radial walls had a high PF (Fw=0.75), a feature that could permit lateral circulation of solutes, thus facilitating ion (inward) and photosynthate (outward) delivery.     

STUDIES ON THE ROOT OF HORDEUM VULGARE L.– ULTRASTRUCTURE OF THE SEMINAL ROOT WITH SPECIAL REFERENCE TO THE PHLOEM

Seminal root tissue of Hordeum vulgare L. var. Barsoy was fixed in glutaraldehyde and osmium tetroxide and studied with the light and electron microscopes. The roots consist of an epidermis, 6–7 layers of cortical cells, a uniseriate endodermis and a central vascular cylinder. Cytologically, the cortical and endodermal cells are similar except for the presence of tubular-like invaginations of the plasmalemma, especially near the plasmodesmata, in the former. The vascular cylinder consists of a uniseriate pericycle surrounding 6–9 phloem strands occurring on alternating radii with an equal number of xylem bundles. The center of the root contains a single, late maturing metaxylem vessel element. Each phloem strand consists of one protophloem sieve element, two companion cells and 1–3 metaphloem sieve elements. The protophloem element and companion cells are contiguous with the pericycle. Metaphloem sieve elements are contiguous with companion cells and are separated from tracheary elements by xylem parenchyma cells. The protoplasts of contiguous cells of the root are joined by various numbers of cytoplasmic connections. With the exception of the pore-plasmodesmata connections between sieve-tube members and parenchymatic elements, the plasmodesmata between various cell types are similar in structure. The distribution of plasmodesmata supports a symplastic pathway for organic solute unloading and transport from the phloem to the cortex. Based on the arrangement of cell types and plasmodesmatal frequencies between various cell types of the root, the major symplastic pathway from sieve elements to cortex appears to be via the companion and xylem parenchyma cells.     

甘遂乳汁管的解剖学及营养器官中二萜类化合物分布的研究

利用石蜡切片、半薄切片及组织化学的方法对甘遂各器官中乳汁管的类型、分布和大小进行了研究。结果表明,甘遂乳汁管为无节分枝型,在各器官中主要分布在维管束韧皮部的外侧或周围,此外,在根的中柱鞘薄壁细胞、叶片的叶肉组织、果实的中果皮及胚乳细胞内也有少量乳汁管的分布。甘遂乳汁管的大小在各器官中略有不同,其中茎中直径最大为39.79μm,块根中直径居中为36.90μm,叶肉组织中直径最小,仅有8.94μm;乳汁管的密度在其营养器官中差异较大,依次为叶>茎>根>块根。组织化学实验结果显示二萜类化合物在甘遂的营养器官中分布广泛。根中柱鞘和韧皮部的薄壁组织细胞,茎皮层、维管形成层和韧皮部的薄壁组织细胞,叶的叶肉细胞以及叶脉中的厚角组织和薄壁组织细胞的腔中都显示不同程度的红色,而乳汁管中乳汁的显色较深。     

Morphology ofCoptis japonica and its meaning in phylogeny

In the genusCoptis, some interesting features are found which are considered important phylogenetically. The median bundles of petiole and petiolule, and the midrib of lamina are double. They seem to represent a transitional situation between a dichotomy and a single median bundle found in usual angiospermous venation. The double bundle is either derived from 2 independent leaf trace bundles or formed by dichotomy of a leaf trace bundle, and it does not seem so important whether the number of trace bundles is even or odd. The nodal structure is trilacunar or pentalacunar with 3, 4, 6 or 8 trace bundles. The upper part of the carpel does not produce ovules and is open from the initiation of the carpel. It is suggested that the carpel becomes open secondarily concomitant with the reduction of ovules. This shows that the closure of the carpel is not perfectly established.     

DEVELOPMENT OF THE EPIPHYLLOUS INFLORESCENCE OF HELWINGIA JAPONICA (HELWINGIACEAE)

The inflorescence of Helwingia japonica (Thunb.) Dietr. is initiated adjacent to the leaf axil on the adaxial side of the base of a leaf primordium during its second plastochron. The inflorescence which develops from the resulting primordium comes to be situated on the midrib of the mature fertile leaf, through the action of a basal, intercalary meristem. In fertile leaves this meristem develops beneath, as well as above, the insertion of the inflorescence primordium on the leaf primordium. The same meristem is present in sterile leaves as well. A separate, adaxial vascular bundle departs from the leaf trace in the base of the petiole and leads to the inflorescence, in the mature fertile leaf. This adaxial vascular bundle is absent in sterile leaves. It is argued that the vascular anatomy does not conclusively confirm the hypothesis that the epiphyllous inflorescence is the congenital fusion product of a leaf and an axillary inflorescence. Instead, it is suggested that the interplay of changes in the position of primordium initiation, and intercalary growth, offers an ontogenetic explanation of the situation, which in turn may be related to the phylogeny of the species in question. It appears to be misguided and futile to look for homologies (i.e., 1:1 correspondences) between fertile and sterile leaves, since 1:1 correspondences do not exist in this case.     

ONTOGENY AND CORRELATIVE RELATIONSHIPS OF THE PRIMARY THICKENING MERISTEM IN FOUR-O'CLOCK PLANTS (NYCTAGINACEAE) MAINTAINED UNDER LONG AND SHORT PHOTOPERIODS

The developmental anatomy of Mirabilis jalapa was investigated during the first 90 days of growth. The primary thickening meristem (PTM) initially differentiates in the pericycle at the top of the cotyledonary node 18 days after germination, then basipetally in the pericycle through the hypocotyl. The PTM differentiates acropetally into the stem and in the pericycle of the primaiy root, commencing 22 days after germination. Endodermis is easily identifiable in hypocotyls as well as in primary roots because of Casparian thickenings in its cells. It has not been definitely identified in stems. There are three rings of primary vascular bundles in the stem. The PTM differentiates as segments of cambium in a layer of cells (probably in the pericycle) on an arc between vascular bundles of the outer bundle ring. Later, arcs of PTM differentiate externally to the phloem of each bundle. Each arc forms a connection between original segments of PTM lying on either side of each vascular bundle. Thus, the PTM becomes a continuous cylinder. The PTM differentiates in the pericycle outside vascular tissue in the hypocotyl and root. Differentiation of the PTM and the mode of secondary thickening is similar in plants exposed to short (8-hr) and to long (18-hr) photoperiods, but some differences were observed. The PTM differentiates closer to the stem apex in all plants over 18 clays of age growing vegetatively under long photoperiods. That is, the diffuse lateral meristem, in whose cells the PTM differentiates in young intemodes, is shorter in nearly all investigated plants growing in long photoperiods. The hypocotyl and base of the primary root of 40-day-old plants in short photoperiods were more enlarged than those of the same age plants in long photoperiods; but, at the end of 64 days, the hypocotyl and primaiy root base were larger in plants growing under short photoperiods. Thirty-four days after seed germination, flower initiation occurs in plants exposed to short photoperiods. One hundred fifty days after seed germination, flowers differentiate on plants exposed to long photoperiods.     

STUDIES ON THE LEAF OF POPULUS DELTOIDES (SALICACEAE): MORPHOLOGY AND ANATOMY

Mature field- and growth-chamber-grown leaves of Populus deltoides Bartr. ex Marsh. were examined with light and scanning electron microscopes to determine their vasculature and the spatial relationships of the various orders of vascular bundles to the mesophyll. Three leaf traces, one median and two lateral, enter the petiole at the node. Progressing acropetally in the petiole these bundles are rearranged and gradually form as many as 13 tiers of vascular tissue in the petiole at the base of the lamina. (Most leaves contained seven vertically stacked tiers.) During their course through the midrib the tiers “unstack” and portions diverge outward and continue as secondary veins toward the margin on either side of the lamina. As the midvein approaches the leaf tip it is represented by a single vascular bundle which is a continuation of the original median bundle. Tertiary veins arise from the secondary veins or the midvein, and minor veins commonly arise from all orders of veins. All major veins–primaries, secondaries, intersecondaries, and tertiaries–are associated with rib tissue, while minor veins are completely surrounded by a parenchymatous bundle sheath. The bundle sheaths of tertiary, quaternary, and portions of quinternary veins are associated with bundle-sheath extensions. Minor veins are closely associated spatially with both ad- and abaxial palisade parenchyma of the isolateral leaf and also with one or two layers of paraveinal mesophyll that extend horizontally between the veins. The leaves of growth-chamber-grown plants had thinner blades, a higher proportion of air space, and greater interveinal distances than those of field-grown plants.     

Complexity untwined: The structure and function of cucumber (Cucumis sativus L.) shoot phloem

Cucurbit phloem is complex, with large sieve tubes on both sides of the xylem (bicollateral phloem), and extrafascicular elements that form an intricate web linking the rest of the vasculature. Little is known of the physical interconnections between these networks or their functional specialization, largely because the extrafascicular phloem strands branch and turn at irregular angles. Here, export in the phloem from specific regions of the lamina of cucumber (Cucumis sativus L.) was mapped using carboxyfluorescein and ¹⁴C as mobile tracers. We also mapped vascular architecture by conventional microscopy and X-ray computed tomography using optimized whole-tissue staining procedures. Differential gene expression in the internal (IP) and external phloem (EP) was analyzed by laser-capture microdissection followed by RNA-sequencing. The vascular bundles of the lamina form a nexus at the petiole junction, emerging in a predictable pattern, each bundle conducting photoassimilate from a specific region of the blade. The vascular bundles of the stem interconnect at the node, facilitating lateral transport around the stem. Elements of the extrafascicular phloem traverse the stem and petiole obliquely, joining the IP and EP of adjacent bundles. Using pairwise comparisons and weighted gene coexpression network analysis, we found differences in gene expression patterns between the petiole and stem and between IP and EP, and we identified hub genes of tissue-specific modules. Genes related to transport were expressed primarily in the EP while those involved in cell differentiation and development as well as amino acid transport and metabolism were expressed mainly in the IP.     

牛膝根的结构发育与三萜皂苷积累的关系

应用植物解剖学、组织化学定位及植物化学技术,研究了不同发育时期牛膝根的结构特征与三帖皂苷积累的关系。结果表明:牛膝根的初生结构和次生结构类似于一般双子叶植物,其根的加粗主要是由于三生结构的发生和分化。第一圈额外形成层产生于次生韧皮部外侧的薄壁组织细胞和射线细胞,以后的每一圈由前一圈向外衍生的薄壁组织细胞产生。额外形成层无纺锤状原始细胞和射线原始细胞之分,在切向纵切面上呈叠生排列。三生维管束以离心方式排成整齐的同心环状,由薄壁结合组织将其彼此分开,其圈数与额外形成层的圈数是一致的,随着根的个体发育而不断增加。在根的初生结构中,三萜皂苷主要分布于中柱鞘、初生韧皮部及初生韧皮部和初生木质部之间的薄壁组织细胞内;在根的次生结构中,主要分布于次生韧皮部及栓内层的薄壁组织细胞内。当三生结构形成后,除次生韧皮部及栓内层细胞外,在额外形成层和三生维管束韧皮部细胞内均有皂苷类物质积累。三生结构在牛膝根中占主要地位,是三萜皂苷积累与分布的主要场所。在牛膝根的生长发育过程中,三萜皂苷元齐墩果酸的百分含量呈“S”型曲线增长,其根的增长、加粗、三生维管束圈数、三萜皂苷总量及根中干重的积累量都在出苗后约120天达到高峰,此时应为牛膝根的最佳采收期。