Effects of Growth Hormone Application on the Secondary Growth of Roots and Stems in Picea sitchensis (Bong.) Carr

Indol-3-ylacetic acid (IAA), gibberellin A3 (GA) and 6 benzylaminopurine(BAP) were applied factorially each at 3x10^–2 M in lanolinto the roots and stems of Sitka spruce seedlings and the activityof the two secondary meristems, the vascular cambium and phellogen,and of the parenchymatous tissues between them, was examined.All the treatments, with the exception of GA produced a localizedstimulation of radial growth at the point of application andthere was a similarity in the response of the various tissuesin both the root and stem. Radial growth of the xylem was notsignificantly affected in the roots whereas in the stems BAPand IAA stimulated growth. In the phloem BAP produced significantstimulation in both roots and stems and IAA stimulated growthin the roots. Growth of the parenchyma and periderm externalto the phloem was also strongly stimulated by both BAP, andIAA in roots and stems. In roots and stems the application of BAP altered the derivativesproduced by the vascular cambium, resulting in the productionof large multiseriate rays in the xylem, and giving rise toan overall increase in the proportion of ray tissue. Picea sitchensis (Bong.) Carr, Sitka spruce, secondary growth, xylem, phloem, periderm, wood rays, Indol-3-ylacetic acid, gibberellin A3, 6 benzylaminopurine, growth hormones     

木立芦荟叶的发育解剖学研究

应用植物解剖学方法研究了木立芦荟（Aloe arborescens Mill.)叶的发育过程。研究结果表明,叶原基在发育早期其形态是不对称的,内部为同形细胞组成,但很快分化成原表皮,原形成层束和基本分生组织。以后,原表皮发育成表皮,位于原表皮下的2－5层基本分生组织细胞发民同化薄壁组织,而位于中央的基本分生组织细胞则发育成储水薄壁组织,原形成层束发育成维管束。维管束由维管束鞘、木质部、韧皮部和大型薄壁细胞组成。大型薄壁细胞起源于原形成层束,位于韧皮部内,其发育迟于筛管、伴胞,为芦荟属植物叶的结构特征。     

芦荟维管束的结构与芦荟素积累的相关性

应用半薄切片、组织化学、荧光显微镜观察和薄层层析 (TLC)相结合的方法研究了中华芦荟 (Aloeve-ra L.var.chinensis)、木立芦荟 (Aloe arborescens)叶和茎内维管束的结构及其与芦荟素积累的关系。结果表明 ,木立芦荟叶内维管束和中华芦荟叶内外轮的维管束中有大型韧皮薄壁细胞 ,而木立芦荟茎和中华芦荟叶中内轮维管束无大型韧皮薄壁细胞。组织化学结果表明 ,用醋酸铅处理过的上述材料 ,大型韧皮薄壁细胞内出现沉淀物 ;在荧光显微镜下经蓝光激发 ,大型韧皮薄壁细胞发出桔黄色荧光 ,都显示出芦荟素反应。薄层层析(TLC)结果证明 ,木立芦荟和中华芦荟叶含有大型韧皮薄壁细胞的维管束都含芦荟素 ,而木立芦荟茎及中华芦荟叶中内轮维管束都不含芦荟素。为此 ,维管束中的大型韧皮薄壁细胞与芦荟素的积累密切相关 ,维管束中是否有大型韧皮薄壁细胞可作为判断是否含有芦荟素的解剖学指标。     

Changes in Soybean Raceme and Petiole Anatomy Induced by 6-Benzylaminopurine

An enlargement of the peduncle and rachis of the terminal racemeand the petiole of the uppermost mainstem leaf was observedin soybean plants [Glycine max (L.) Merr.] treated with thecytokinin, 6-benzylaminopurine (BAP). Histological studies wereperformed to determine the timing and extent of anatomical changesaccompanying BAP treatment. Swelling of treated ‘Tracy-M’peduncles, rachises, and petioles was observed within 4–6d after treatment initiation. A significant increase in totalcross-sectional tissue area was observed at lower and intermediateinternodes of treated rachises after 11 d. Rachis enlargementwas due to increases in both cell size and cell number, particularlyof the vascular tissue. In treated petioles of IX93-100, procambialcells of vascular bundles were the first to respond to the BAPtreatment. These cells differentiated into a vascular cambiumwhich formed secondary xylem and phloem. Soybean, Glycine max (L.) Merr., anatomy, rachis, BAP.     

OsYSL16 plays a role in the allocation of iron

Graminaceous plants acquire iron by secreting mugineic acid family phytosiderophores into the rhizosphere and taking up complexes of iron and phytosiderophores through YSL (yellow stripe 1-like) transporters. Rice OsYSL15 is a transporter of the iron(III)-2'-deoxymugineic acid complex. OsYSL16 has 85?% similarity to both OsYSL15 and the iron(II)-nicotianamine transporter OsYSL2. In the present study, we show that OsYSL16 functionally complemented a yeast mutant defective in iron uptake when grown on medium containing iron(III)-deoxymugineic acid, but not when grown on medium containing iron(II)-nicotianamine. OsYSL16-knockdown seedlings were smaller than wild-type seedlings when only iron(III)chloride was supplied as an iron source. The iron concentration in shoots of OsYSL16-knockdown plants was similar to that of the wild type; however, they showed more severe chlorosis than wild-type plants under iron-deficient conditions. Furthermore, OsYSL16-knockdown plants accumulated more iron in the vascular bundles of the leaves. Expression of the OsYSL16 promoter fused to the β-glucuronidase gene showed that OsYSL16 is expressed in the root epidermis and vascular bundles of whole plants. The expression was typically observed around the xylem. In the vascular bundles of unelongated nodes, it was detected in the xylem of old leaves and the phloem of new leaves. Graminaceous plants translocate iron from the roots to old leaves mainly via the xylem and to new leaves mainly via the phloem. Our results suggest that OsYSL16 plays a role in the allocation of iron(III)-deoxymugineic acid via the vascular bundles.     

THE PRODUCTION AND DIFFERENTIATION OF SECONDARY XYLEM IN XANTHIUM PENSYLVANICUM

The removal of leaves and buds from the shoot of Xanthium seedlings caused the cessation of xylem fiber differentiation in all internodes while allowing the production of cambial derivatives to continue toward both the xylem and the phloem. The potential xylem fibers developed into parenchymatous cells with thin cell walls. The vessels developed normally except for their small size. Cambial derivatives and vessels were produced linearly with time in intact plants (6.1 cells per file/day and 9.7 vessels per vascular bundle/day) and in decapitated plants (2.2 cells per file/day and 5.5 vessels per vascular bundle/day). Fiber production was linear with time in intact plants (163 fibers per vascular bundle/day) and did not occur in decapitated plants. When a single leaf was allowed to develop from a lateral bud of a decapitated plant, xylem fiber differentiation was restored for a period of time corresponding to the period of rapid expansion of the leaf blade. When the leaf passed the phase of rapid expansion, it no longer had an inductive effect on xylem fiber differentiation.     

Stem anatomy of Dolichos lablab Linn (Fabaceae): Origin of cambium and reverse orientation of vascular bundles

Secondary growth in the stem of Dolichos lablab is achieved by the formation of eccentric successive rings of vascular bundles. The stem is composed of parenchymatous ground tissue and xylem and phloem confined to portions of small cambial segments. However, development of new cambial segments can be observed from the obliterating ray parenchyma, the outermost phloem parenchyma and the secondary cortical parenchyma. Initially cambium develops as small segments, which latter become joined to form a complete cylinder of vascular cambium. Each cambial ring is functionally divided into two distinct regions. The one segment of cambium produces thick-walled lignified xylem derivatives in centripetal direction and phloem elements centrifugally. The other segment produces only thin-walled parenchyma on both xylem and phloem side. In mature stems, some of the axial parenchyma embedded deep inside the xylem acquires meristematic activity and leads to the formation of thick-walled xylem derivatives centrifugally and phloem elements centripetally. The secondary xylem comprises vessel elements, tracheids, fibres and axial parenchyma. Rays are uni-multiseriate in the region of cambium that produces xylem and phloem derivatives, while in some of the regions of cambium large multiseriate, compound, aggregate and polycentric rays can be noticed.     

STUDIES OF NECROTIC LESIONS IN CORN STALKS

Littlefield , Larry J., and Roy D. Wilcoxson . (U. Minnesota, St. Paul.) Studies of necrotic lesions in corn stalks . Amer. Jour. Bot. 49(10): 1072–1078. Illus. 1962.—In 3-day-old necrotic lesions in corn stalks caused by Fusarium graminearum, ground parenchyma cells were discolored and small amounts of a dark substance were present in the cells. The walls of phloem cells were also slightly discolored and a small amount of dark substance was present in the xylem cells. In older lesions the discoloration of parenchyma and phloem cells was more intense; many of the cells contained occluding substances; many phloem protoplasts collapsed, and xylem cells were partially to completely occluded. The occluding substance filling the cells appeared to be translocated from the lesion into the vessel elements extending beyond the lesion so that the bundles appeared as long, dark streaks in the stalk. The occluding substance in xylem, but not in phloem or parenchyma, stained with ruthenium red, a result indicating presence of pectin. Pectinase, however, did not remove the occluding substance. The pectinase dissolved the parenchyma cells in healthy tissues but not in the necrotic lesions. Necrosis in naturally infected plants began as small lesions, but the parenchyma cells quickly dissolved leaving the vascular bundles free of ground parenchyma. No occlusions were found in the central vascular system; a few xylem cells in the peripheral vascular system were occluded with the same substance observed in artificially inoculated plants. Phloem was entirely destroyed by the pathogen. The necrosis prevented upward movement of dye solution in the stalk, but did not measurably affect transpiration, probably because the lesions were not large. Yield was reduced in plants when lesions involved more than 50% of the tissue in inoculated internodes. Smaller lesions had no effect on yield.     

9种芦荟属植物叶的结构和芦荟素含量的比较研究

9种芦荟属植物叶的比较解剖研究结果表明,它们都具有明显的旱生叶的结构特征,其维管束的韧皮部内都有大型薄壁细胞,但其表皮角质膜的厚度,表面纹饰,气孔上,下腔的形状和大小,同化组织 导 ,细胞分化情况,维管束的大小,分布密度和其大型薄壁细胞占维管束的比例,中央贮水组织占叶横切面的比例等特征,在各种间存在差异,且性状稳定,可以作为该属内种间分类的解剖学指标,植物化学分析结果表明,9种植物叶内蒽醌类物质的主要种类和含量不同,其含量高,低与叶内维管束密度,大型薄壁细胞占维管束的比例以及同化组织的厚度密度切相关,从而为芦荟属植物选育商业用良种提供了植物解剖学依据。     

Comparative vegetative anatomy of Stanhopeinae (Orchidaceae)

Stanhopeinae are a group of tropical American orchids characterized by euglossine bee pollination and lateral inflorescences stemming from the bases of pseudobulbs. Leaves are hypostomatal, and all stomatal configurations are tetracytic. Chlorenchyma is homogeneous and characterized by fibre bundles in adaxial/abaxial or adaxial/median/abaxial positions. Collateral vascular bundles occur in a single row and feature phloic and xylic sclerenchymatous caps and thin-walled bundle sheath cells. Fibre bundles and vascular sclerenchyma are accompanied by stegmata containing conical silica bodies. Pseudobulbs have thick-walled turbinate epidermal cells and ground tissue of smaller, living assimilatory cells and larger, dead water-storage cells. Fibre bundles are usually absent but occur in several genera. Collateral vascular bundles show phloic sclerenchyma, but xylic sclerenchyma occurs only in die larger vascular bundles. Phloic and xylic sclerenchyma are associated with stegmata containing conical silica bodies. Roots are velamentous. Velamen cell walls have fine, spiral thickenings. Exodermal cells are thin-walled. The cortex features scattered thick-walled cells and in some cases branched bars of secondary cell wall material. Endodermis is either u-or O-thickened, but pericycle is always O-thickened opposite the phloem. Vascular tissue consists of alternating strands of xylem and phloem surrounded by a matrix of thick-walled cells. Pith cells may be parenchymatous or sclerenchymatous.     

Vascular Continuity in the Primary and Secondary Stem Tissues of Bougainvillea (Nyctaginaceae)

An investigation of stem structure of Bougainvillea by serialsections and cine-photography shows that the medullary systemof the inner area of young stems is the sole vascular systemdirectly continuous into the lateral appendages (leaves, axillarybuds and axillary thorns) via complex nodal anastomoses. Thevascular system at the periphery of the primary bundles is notdirectly continuous into these appendages. In secondary growth,there is direct continuity between vascular bundles within asingle ring, in a tangential direction via either xylem aloneor both xylem and phloem, and between rings in a radial directionalways via xylem and phloem, even though the rings are derivativesof successive cambia. Bougainvillea, vascular system, phloem, xylem, anomalous secondary thickening     

The unusual vascular structure of the corm of Eriophorum vaginatum: implications for efficient retranslocation of nutrients

Eriophorum spp. are abundant perennial graminoids in the Arctic tundra and boreal peatlands. Because ecological studies indicated that some plants are unusually productive on infertile and cold sites, the anatomy of the overwintering corms of Eriophorum vaginatum (L.) and Eriophorum scheuchzeri (Hoppe) were examined to determine their involvement in nutrient uptake and storage. Components of the long-distance transport pathways were identified within the plants by using histochemical techniques and transport of apoplastic and symplastic dyes. E. scheuchzeri produced a rhizome that consisted mainly of storage parenchyma cells within which collateral vascular bundles were centrally located and arranged in a circle. By contrast, E. vaginatum developed a ring of horizontally arranged xylem and phloem, in addition to axial amphivasal vascular bundles leading to the leaves, all of which were bordered by transfer cells. As shown by the transport of fluorescein in the phloem and Safranine O in the xylem, each axial bundle and adventitious root contacted the horizontal ring of vascular tissues so that solutes from one vascular bundle were translocated into the vascular ring and circulated to another vascular bundle and/or to the roots. In addition, special groups of sclereids that functioned in both phloem and xylem transport were found at the base of the leaf traces and within junctions of senescing roots. These sclereids were named 'vascular sclerenchyma' and it was hypothesized that they provide a moving end for the vascular system because the corm dies progressively from the distal end as it grows upward from the apical meristem. It was concluded that this unusual vascular system of E. vaginatum is efficient in recycling nutrients internally, which may account for its competitive advantage in infertile and cold sites.     

Nucleotide pyrophosphatase activity in dry and germinated seeds of Triticum,and its relationship to general acid phosphatase activity

A cytochemical investigation has been made of nucleotide pyrophosphatase activity in dry and germinated seeds of Triticum, and its distribution compared to that of general acid phosphatase reactions seen with naphthol AS-BI phosphate and p-nitrophenylphosphate as substrates. Acid phosphatase activity was present in the cytoplasm and in channels through the walls of the aleurone cells in both dry and germinated seeds. The cytoplasmic activity was even more marked with nucleotide pyrophosphatase which was almost entirely absent from the cell walls. Nucleotide pyrophosphatase was active in all endosperm cells but particularly in some cells adjacent to the aleurone layer. In addition, all cells of the scutellum and embryo were positive for nucleotide pyrophosphatase activity, especially the developing fibres and xylem elements of leaves and coleoptiles, mature leaf xylem and phloem elements, scutellar provascular and vascular tissues and the epidermis of dark grown coleoptiles.Abbreviation GA₃ gibberellic acid     

Sites of accumulation in excised Phloem and vascular tissues

Excised pieces of vascular bundle and phloem tissue were allowed to accumulate radioactive phosphate and sulfate, and were then sectioned and autoradiographed so as to detect the sites of accumulation. Special methods were needed to prevent any diffusion of the radioisotope. Some autoradiographs obtained are presented. In excised celery vascular bundles, the most radioactive area and hence the most actively accumulating tissue was the young secondary phloem at the sides of the bundle. In intact plants, the same tissue was the most active in translocating. In excised apple phloem there was some variation in behavior, but again the young secondary phloem was generally the most actively accumulating tissue. Accumulation activities of individual cells in the phloem and vascular tissue were compared. It appeared that all cell types, ray, phloem and xylem parenchyma, cambial cells and sieve tubes, accumulated at least 5 times more actively than did the cortical parenchyma cells. The sieve tubes were among the most actively accumulating cells present, accumulating 20 times more actively than the cortical parenchyma cells. It is concluded that accumulation processes have a primary role to play in the mechanism of phloem transport.     

Anatomical Studies on Hypocotyl of Circaeaster

The stem of Circaeaster agrestis Maxim. is very short but the length of hypocotyl is comparatively long, almost occupying the whole length of the plant. This tender hypocotyl is mainly supported by the thickening of cuticle on the outer wall of the epidermal cell and the primary xylem in the center. Between primary xylem and primary phloem there are 2–3 layers of parenchymatous cells, regularly or irregularly arranged, but no cambial zone can be recognized. The transition region where root and stem meet showed no evidence of twisting, splitting or inversion of the strands in the primary vascular tissues which are common in most of the dicots. The extending cotyledon traces differentiate directly from the parenchymatous cells which locate on the outside of the poles of primary xylem. The first and the second leaf traces are organized in the middle of the primary phloem.     

EFFECT OF ISOLATION OF BARK ON CAMBIAL ACTIVITY AND DEVELOPMENT OF XYLEM AND PHLOEM IN TREMBLING ASPEN

Circular patches of bark were surgically isolated on the sides of trembling aspen (Populus tremuloides Michx.) trees at breast height at various times during the dormant and growing seasons. Subsequently, samples of wood and attached bark were taken from isolated and control sites to determine the effects of isolation of the bark on cambial activity and xylem and phloem development. In control trees cambial activity and xylem and phloem development occurred normally. Isolation of bark during the dormant season (in November, February, or March) did not prevent initiation of cambial activity and of phloem differentiation in spring but continued normal cambial activity and phloem developmented were prevent. Xylem differentiation was essentially prevented by isolation of tissues during the dormant season. The ultimate effect of isolation of the bark on the cambium, either during the dormant season or during the growing season, was subdivision of all fusiform cambial cells into strands of parenchymatous elements; the ultimate effect on the newly formed phloem was early death of the sieve elements. The most conspicuous effect of isolation of the bark after xylem differentiation had begun was the curtailment of secondary wall formation. Shortening of cells of the cambial region was reflected in the length of the vessel members which differentiated from such cells. These results indicate that normal cambial activity and xylem and phloem development require a supply of currently translocated regulatory substances from the shoots.     

STRUCTURALLY PRESERVED FOSSIL PLANTS FROM ANTARCTICA. I. ANTARCTICYCAS,GEN. NOV., A TRIASSIC CYCAD STEM FROM THE BEARDMORE GLACIER AREA

Silicified stems with typical cycadalean anatomy are described from specimens collected from the Fremouw Formation (Triassic) in the Transantarctic Mountains of Antarctica. Axes are slender with a large parenchymatous pith and cortex separated by a narrow ring of vascular tissue. Mucilage canals are present in both pith and cortex. Vascular tissue consists of endarch primary xylem, a narrow band of secondary xylem tracheids, cambial zone, and region of secondary phloem. Vascular bundles contain uni- to triseriate rays with larger rays up to 2 mm wide separating the individual bundles. Pitting on primary xylem elements ranges from helical to scalariform; secondary xylem tracheids exhibit alternate circular bordered pits. Traces, often accompanied by a mucilage canal, extend out through the large rays into the cortex where some assume a girdling configuration. A zone of periderm is present at the periphery of the stem. Large and small roots are attached to the stem and are conspicuous in the surrounding matrix. The anatomy of the Antarctic cycad is compared with that of other fossil and extant cycadalean stems.     

无距虾脊兰营养器官解剖结构及其生态适应性

采用石蜡切片法对无距虾脊兰(Calanthe tsoongiana T.TangetF.T.Wang)营养器官解剖结构进行研究。结果显示,无距虾脊兰叶为等面叶,与一般植物相比,表皮毛和气孔器较少,均分布在下表皮,气孔器稍外凸,叶片维管束分化程度不一,木质部厚度远大于韧皮部。假鳞茎由表皮、基本组织和维管束组成,基本组织发达,含有丰富的内含物。维管束散生于基本组织中;根主要由根被、皮层和中柱组成,根被通常可见4层,皮层由8~10层薄壁细胞组成,菌丝体通过破坏根被细胞侵入皮层。除正对木质部脊的中柱鞘细胞外,其余中柱鞘通道细胞全面增厚,维管束类型为辐射维管束,中柱中央为薄壁细胞组成的髓。无距虾脊兰营养器官的解剖特征表现出阴生植物的特点,引种栽培过程中应注意适当遮荫和通风。     

无距虾脊兰营养器官解剖结构及其生态适应性

采用石蜡切片法对无距虾脊兰（Calanthe tsoongiana T.Tang et F.T.Wang）营养器官解剖结构进行研究。结果显示,无距虾脊兰叶为等面叶,与一般植物相比,表皮毛和气孔器较少,均分布在下表皮,气孔器稍外凸,叶片维管束分化程度不一,木质部厚度远大于韧皮部。假鳞茎由表皮、基本组织和维管束组成,基本组织发达,含有丰富的内含物。维管束散生于基本组织中;根主要由根被、皮层和中柱组成,根被通常可见4层,皮层由8~10层薄壁细胞组成,菌丝体通过破坏根被细胞侵入皮层。除正对木质部脊的中柱鞘细胞外,其余中柱鞘通道细胞全面增厚,维管束类型为辐射维管束,中柱中央为薄壁细胞组成的髓。无距虾脊兰营养器官的解剖特征表现出阴生植物的特点,引种栽培过程中应注意适当遮荫和通风。     

Rice sucrose transporter1 (OsSUT1) up‐regulation in xylem parenchyma is caused by aphid feeding on rice leaf blade vascular bundles

The role of the sucrose transporter OsSUT1 in assimilate retrieval via the xylem, as a result of damage to and leakage from punctured phloem was examined after rusty plum aphid (Hysteroneura setariae, Thomas) infestation on leaves from 3‐week‐old rice (Oryza sativa L. cv Nipponbare) plants. Leaves were examined over a 1‐ to 10‐day infestation time course, using a combination of gene expression and β‐glucuronidase (GUS) reporter gene analyses. qPCR and Western blot analyses revealed differential expression of OsSUT1 during aphid infestation. Wide‐field fluorescence microscopy was used to confirm the expression of OsSUT1‐promoter::GUS reporter gene in vascular parenchyma associated with xylem elements, as well as in companion cells associated with phloem sieve tubes of large, intermediate and small vascular bundles within the leaf blade, in regions where the aphids had settled and were feeding. Of great interest was up‐regulation of OsSUT1 expression associated with the xylem parenchyma cells, abutting the metaxylem vessels, which confirmed that OsSUT1 was not only involved in loading of sugars into the phloem under normal physiological conditions, but was apparently involved in the retrieval of sucrose leaked into the xylem conduits, which occurred as a direct result of aphid feeding, probing and puncturing of vascular bundles. The up‐regulation of OsSUT1 in xylem vascular parenchyma thus provides evidence in support of the location within the xylem parenchyma cells of an efficient mechanism to ensure sucrose recovery after loss to the apoplast (xylem) after aphid‐related feeding damage and its transfer back to the symplast (phloem) in O. sativa leaves.