盐生车前根液泡膜ATPase对盐胁迫的响应

用蔗糖密度梯度离心法从对照和盐处理的盐生车前根中分离出液泡膜,并对其ＡＴＰａｓｅ某些特性进行了比较研究,蔗糖连续密度梯度离心后ＮＯ＾－３敏感的ＡＴＰａｓｅ活性主要分布在２２％－３５％蔗糖浓度之间,用不连续密度梯度离心法从２２％－３５％界面收集到的膜主要源于液泡膜。因为,这种膜ＡＴＰａｓｅ活性受到Ｃｌ＾－的促进和ＮＯ＾－３的强抑制,而叠氮化钠和正钡酸钠只抑制酶活性的１０％左右,最适ｐＨ８．０。     

Molecular Markers for Ion Compartmentation in Cells of Higher Plants: II. LIPID COMPOSITION OF THE TONOPLAST OF THE HALOPHYTE SUAEDA MARITIMA (L.) DUM.

Vacuoles of high purity were isolated from the leaves of thehalophyte Suaeda maritima (L.) Dum. The relative compositionsof phospholipids, phytosterols, and fatty acids in the tonoplastmembrane were determined and membrane fluidity was assessedby electron spin resonance. The characteristics of the tonoplastwere consistent with minimizing passive permeability to NaCI.The phospholipid: protein ratio (1.1: 1.0) was higher than thatrecorded in other membrane preparations, including vacuolesfrom beetroot storage material, commensurate with the low density(1.05 g cm^–3) of the S. maritima tonoplast. The tonoplastfatty acids were highly saturated and dominated by n-hexadecanoicacid and n-octadecanoic acid. Phytosterols identified by gaschromatography were cholesterol, campesterol, stigmasterol,and ß-sitosterol. Cholesterol was a trace percentagein protoplasts, but comprised 30% of the tonoplast sterols.Semi-quantitative analysis by chromatography on silica gel revealedan enrichment in the tonoplast of glycolipid which was not accountedfor as chloroplast contamination. The fluidity of the tonoplast,determined by electron spin resonance, was lower than the protoplasts,consistent with the high degree of saturation of the fatty acidchains. The relevance of the lipid composition of the tonoplastto its central role in ion compartmentation within the halophytecell is discussed. Key words: Ion compartmentation, membrane lipids, salinity, vacuole     

Salt tolerance in the halophyte Suaeda maritima (L.) Dum. The influence of the salinity of the culture solution on leaf starch and phosphate content

Abstract. The starch concentration in mature leaves of the halophyte Suaeda maritima increased from 4.7 to 7.3 mg mg⁻¹ chlorophyll when sodium chloride (680 mol M⁻³) was added to the solution in which the plants were grown. This effect of salinity on the starch: chlorophyll ratio was greater in young than in old leaves. Electron micrographs showed the starch to be in the chloroplasts and this was confirmed by measurements on isolated chloroplasts. Total phosphorus concentration (mg mg⁻¹ chlorophyll) in leaves of all ages from plants of S. maritima decreased on salinization of the growth medium suggesting an inverse relationship between phosphorus and starch concentrations. However, although leaf starch concentration varied with leaf age, phosphorus concentration did not. The cause of starch accumulation in chloroplasts at salinities which are optimal for growth (340 mol m⁻³) remains unclear.     

ENTOSIPHON SULCATUM (EUGLENOPHYCEAE): FLAGELLAR ROOTS OF THE BASAL BODY COMPLEX AND RESERVOIR REGION1,2

The flagellar root system of Entosiphon sulcatum (Dujardin) Stein (Euglenophyceae) is described and compared with kinetoplastid and other euglenoid systems. An asymmetric pattern of three microtubular roots, one between the two flagellar basal bodies and one on either side (here called the intermediate, dorsal, and ventral roots), is consistent within the euglenoid flagellates studied thus far. The dorsal root is associated with the basal body of the anterior flagellum (F₁) and lies on the left dorsal side of the basal body complex. Originating between the two flagellar basal bodies, and associated with the basal body of the trailing flagellum (F₂), the intermediate root is morphologically distinguished by fibrils interconnecting the individual microtubules to one another and to the over lying reservoir membrane. The intermediate root is often borne on a ridge projecting into the reservoir. The ventral root originates near the F₂ basal body and lies on the right ventral side of the cell. Fibrillar connections link the membrane of F₂ with the reservoir membrane at the reservoircanal transition level. A large cross-banded fiber joins the two flagellar basal bodies, and a series of smaller striated fibers links the anterior accessory and flagellar basal bodies. Large nonstriated fibers extend from the basal body complex posteriorly into the cytoplasm.     

ENTOSIPHON SULCATUM (EUGLENOPHYCEAE): FLAGELLAR ROOTS OF THE BASAL BODY COMPLEX AND RESERVOIR REGION1,2

The flagellar root system of Entosiphon sulcatum (Dujardin) Stein (Euglenophyceae) is described and compared with kinetoplastid and other euglenoid systems. An asymmetric pattern of three microtubular roots, one between the two flagellar basal bodies and one on either side (here called the intermediate, dorsal, and ventral roots), is consistent within the euglenoid flagellates studied thus far. The dorsal root is associated with the basal body of the anterior flagellum (F₁) and lies on the left dorsal side of the basal body complex. Originating between the two flagellar basal bodies, and associated with the basal body of the trailing flagellum (F₂), the intermediate root is morphologically distinguished by fibrils interconnecting the individual microtubules to one another and to the overlying reservoir membrane. The intermediate root is often borne on a ridge projecting into the reservoir. The ventral root originates near the F₂ basal body and lies on the right ventral side of the cell. Fibrillar connections link the membrane of F₂ with the reservoir membrane at the reservoir-canal transition level. A large cross-banded fiber joins the two flagellar basal bodies, and a series of smaller striated fibers links the anterior accessory and flagellar basal bodies. Large nonstriated fibers extend from the basal body complex posteriorly into the cytoplasm.     

STUDIES ON THE BIOCHEMISTRY AND FINE STRUCTURE OF SILICA SHELL FORMATION IN DIATOMS. II. THE STRUCTURE OF THE CELL WALL OF NAVICULA PELLICULOSA (BRÉB.) HILSE

The cell wall of the freshwater diatom Navicula pelliculosa (Bréb.) Hilse is composed of the silica shell and an organic skin which surrounds it. Isolated skins can be prepared by first removing the contents of the cell by mechanical shaking, followed by a posttreatment of these isolated cell walls with HF vapor to remove the silica shell. T h e skins can also be seen in sections, particularly well after the silica shell has been removed B y H. F; vapor. The origin and morphological composition of the shin in N. pelliculosa are not yet completely ascertaincd. As parts of the cell wn11, both the silica shell and the skin are extracellularly located. The growth of the silica shell, however, occurs intracellularly inside a vesicle delimited by a triple-layered membrane, the silicalemma. This membrane or secondary excreted organic material or both in various proportions may compose the skin.     

FURTHER OBSERVATIONS AND SOME COMMENTS ON THE FINE STRUCTURE OF THE CENTRIC DIATOM AULACOSEIRA ISLANDICA (BACILLARIOPHYCEAE)1

Using light and electron microscopy, the diatom species Aulacoseira islandica (O. Müll.) Sim. was examined with special emphasis on the following characteristics: structure of the valve areolae, heterovalvy, and distribution of the rimoportulae. The mantle and valve face areolae were pores containing volate occlusions. However, observations only using transmission electron microscopy may result in an incomplete interpretation because of the fragility of the dissected system of volae. Relief valves with a stepped mantle and intaglio valves with a plain mantle occurred. Another form of heterovalvy resulted from the formation of separation valves. Linking valves had spatulate spines while separation valves bore tapering spines. In Aulacoseira, the rimoportulae usually occurred near the “Ringleiste.” The presence of several rimoportulae on the mantle was one of the most striking features in Aulacoseira islandica.     

STUDIES IN THE QUIESCENT ROOT MERISTEM OF THE BULB OF ALLIUM CEPA L.: FINE STRUCTURE AND DNA SYNTHESIS *

Study of the quiescent root meristem of Allium cepa L. bulbs has revealed that its histological organization does not differ significantly from the growing meristem, except for the fact that the cells are all arrested in interphase. Ultrastructure of the quiescent tissue is, however, different in the organization of the nucleolus and in the absence of prominent endoplasmic reticulum, microtubules and golgi complexes. A variety of lomasome-like structures, plasma membrane modifications and vacuoles have been recorded. Most of the cells except for the ones in the root cap and quiescent center are highly vacuolated; vacuolation is maximum in the cortical zone of the meristem. The pattern of ³H thymidine incorporation during early stages of sprouting indicates that asynchrony of the mitotic cycle, which is the characteristic of the growing meristem, is maintained during quiescence by the arrest of nuclei at different subphases of interphase.