中国春黄菊族植物叶表皮结构的研究

本文对分布在中国的春黄菊族(Anthemideae)中的25属98种植物叶的表皮结构进行了观察。1.毛状体的类型适于作为本族自然群、属、亚属、组或系的分类特征。2.轴型、半平列型和螺旋型等复合结构的气孔适于作属以下各单位的分类依据。3.表皮细胞的大小、气孔的保卫细胞长度和 T 型-毛的顶端长度等,这些只是数量特征,在本族分类上意义不大。     

COMPARATIVE LEAF STRUCTURE OF SEVERAL SPECIES OF HOMOSPOROUS LEPTOSPORANGIATE FERNS

The structure of the mature leaves of 13 species from 9 families of homosporous leptosporangiate ferns was examined by light and electron microscopy. In 11 species (Adiantum pedatum L., Athyrium angustum Roth., Cyathea dregei Sm., Lygodium palmatum Sw., Mohria caffrorum (L.) Desv., Oleandra distenta Kuntae, Pellaea calomelanos (Sw.) Link, Pityrogramma calomelanos (L.) Link var. austro-americana (Domn.) Farw., Trichomanes melanotrichum Schlechtend., Vittaria guineensis Desv., and Woodwardia orientalis Sw.) the lamina veins are collateral; in two (Phlebodium aureum and Platycerium bifurcatum), bicollateral as well as collateral veins are present. The vascular bundles in the midribs of C. dregei and those in the petioles and midribs of Phlebodium and Platycerium are concentric. All of the vascular bundles in the homosporous leptosporangiate ferns studied are delimited by a tightly arranged cylinder of endodermal cells with Casparian strips. Within the veins without parenchymatic xylem sheaths, some sieve elements commonly abut tracheary elements with hydrolyzed primary walls. The majority of vascular parenchyma cells contact both sieve elements and tracheary elements, although some parenchyma cells are associated with only one type of conducting cell. Transfer cells (parenchyma cells with wall ingrowths) occur in the veins of 6 species examined. Most of the vascular parenchyma cells, however, have no distinctive structural characteristics. The sieve elements of the homosporous leptosporangiate ferns are very similar structurally and each consists of a plasmalemma, a parietal, anastomosing network of smooth endoplasmic reticulum (ER), and variable numbers of refractive spherules, plastids and mitochondria. The sieve elements of L. palmatum also contain plasmalemma tubules. The parenchymatic cells of the leaf (mesophyll, endodermal and vascular parenchyma cells) are united by desmotubule-containing plasmodesmata. The sieve elements are connected to each other by sieve pores and to parenchymatic cells by pore-plasmodesma connections. The sieve-area pores contain variable amounts of membranous material, apparently ER membranes, but do not occlude them. These membranes commonly are found in continuity with the parietal ER of the lumen. Based upon the relative frequencies of cytoplasmic connections between cell types, the photosynthates may move from the mesophyll to the site of phloem loading via somewhat different pathways in different species of homosporous leptosporangiate ferns.     

魔芋葡甘露聚糖化学结构及改性研究进展

本文综述了魔芋葡甘露聚糖的理化性质、化学结构及改性的研究进展     

叶表皮结构在榆属分类中的应用

本文利用扫描电子显微镜对榆属9种1变种的成熟叶表皮结构进行了观察,认为榆属叶表皮结构在扫描电镜下存在着明显的差别,可以作为榆属分种的辅助特征。     

STRUCTURE AND DEVELOPMENT OF SIEVE ELEMENTS IN THE LEAF OF ISOETES MURICATA

Leaf tissue of Isoetes muricata Dur. was fixed in glutaraldehyde and postfixed in osmium tetroxide for electron microscopy. The very young sieve elements can be distinguished from contiguous parenchyma cells by their distinctive plastids and the presence of crystalline and fibrillar proteinaceous material in dilated cisternae of the rough ER. During differentiation, the portions of ER enclosing this proteinaceous substance become smooth surfaced and migrate to the cell wall. Along the way they apparently form multivesicular bodies which then fuse with the plasmalemma, discharging their contents to the outside. At maturity, the sieve element contains an elongate nucleus, which consists of dense chromatin material, and remnants of the nuclear envelope. In addition, the mature sieve element is lined by a plasmalemma and a parietal, anastomosing network of smooth ER. Both plastids and mitochondria are present. P-protein is lacking at all stages of development. Tonoplasts are. not discernible in mature sieve elements. The end walls of mature sieve elements contain either plasmodesmata or sieve pores or both, but only plasmodesmata occur in the lateral walls.     

MOLECULAR ASSOCIATION OF HEMOCYANIN PRODUCED BY X-RAYS AS OBSERVED IN THE ULTRACENTRIFUGE

1. When normal, monodisperse hemocyanin (60.5S) from Limulus Rolyphemus was irradiated in neutral buffer with x-rays, several new, more rapidly sedimenting ultracentrifugal components (86S, 107S, 122S) were produced, with a corresponding loss in the amount of the unaffected protein. The amount of the effect was roughly proportional to the amount of irradiation. 2. The new resolvable components apparently represented an association of the primary particles into aggregates of 2, 3, and 4 primary particles respectively. 3. The proportional amount of hemocyanin affected decreased almost to the vanishing point as the concentration of the protein was raised to high levels. 4. The absolute effect, i.e. the total number of particles affected in a given volume, increased with the concentration of hemocyanin, at least for concentrations below 15 per cent. 5. The presence of 33 per cent horse serum during irradiation inhibited the effect on the hemocyanin almost completely, with hemocyanin concentrations of both 0.8 and 14 per cent. 6. The presence of 2.8 per cent egg albumin during irradiation lowered the effect by about 70 per cent in the case of dilute preparations (0.8 per cent hemocyanin), but by only about 25 per cent in the case of 14 per cent solutions. 7. A lowering of the solution''s oxygen tension during irradiation enhanced the effect, almost doubling it in some cases. 8. The probable theoretical significance of these and other observations are discussed in the text.     

POLAROGRAPHIC MEASUREMENT OF PHOTOSYNTHETIC OXYGEN EVOLUTION BY LEAF DISCS

A simple polarographic device is described which permits the measurement, in the gas-phase, of O₂ evolved by leaf discs during photosynthesis and O₂ consumed in respiration. A method of calibration is described and results are included which illustrate the performance of the apparatus in typical experiments.