Large Starch Grains Research Articles

Electron microscope observations on protocorm cells of Cypripedium reginae with special reference to differentiation of plastids

Differentiation was followed at subcellular level in Cypripedium reginae Walt , by studying aseptically cultivated protocorms and leaves of a more developed seeedling. In the young protocorm, the main features of the fine structure were about the same in the different parts. The most characteristic structures were compound amyloplasts and smooth ER. The cells were not highly vacuolated and lipid and protein stores were rarely seen. In the evolute leaf of an older seedling, the chloroplasts contained several large starch grains and plastoglobuli. The accumulation of large amounts of starch seemed to be an indication of retardation of the further development of the seedling.

Ultrastructure of the mesophyll in scots pine and Norway spruce: Seasonal variation and molarity of the fixative buffer

Resolution of the ultrastructure of the needles of both Scots pine (Pinus silvestris L.) and Norway spruce [Picea abies (L.) Karst.] is strongly influenced by the molarity of the buffer used in fixation. When 0.2 M or 0.1 M buffer is used in fixation during the summer, the constituents of the cytoplasm are precipitated, resulting in poor resolution of the membranes and lamellae and often in negative staining. The tannin in the central vacuole appears as a thick ribbon. By using correct molarities of buffer during each season (0.1 M for autumn and winter and ca. 0.05 M for the growing season), the best possible resolution will be achieved. With good resolution the tannin in the central vacuole appears in granular form throughout the year, and the cytoplasm and its organelles are clearly distinguishable during every season. During the growing season, the chloroplasts in the needles of Scots pine are spread to the cell walls and have large starch grains; the stroma and grana lamellae are well developed; the stroma and cytoplasm are rich in polysomes. Mitochondria and microbodies can be clearly resolved. During hardening and afterwords throughout the winter, the chloroplasts, which at this time contain no starch, and other cytoplasmic organelles aggregate in the corners of the cells. The chloroplast envelopes and the stroma and grana lamellae stay intact. The cytoplasm is netlike and rich in ribosomes, mitochondria and microbodies, all of which are intact and clearly distinguishable. During spring activation the structure returns to that described for the growing season.

DEVELOPMENTAL ANATOMY AND ULTRASTRUCTURE OF THE ANT‐FOOD BODIES (BECCARIIAN BODIES) OF MACARANGA TRILOBA AND M. HYPOLEUCA (EUPHORBIACEAE)

Macaranga is a common secondary growth tree of S.E. Asia. Nine species possess hollow stems which harbor an ant colony, and also produce food bodies which are eaten by the ants. In return, the ants protect the plant from herbivore damage. The multicellular food bodies of M. triloba (Bl.) Muell. Arg. are developed on the underside of down‐turned clasping stipules, while in M. hypoleuca (Reichb. f. and Zoll.) Muell. Arg. they are produced on the abaxial surface of young leaves. Food body cells of both species are very rich in lipid, contain large starch grains, and possess an electron‐dense hyaloplasm. It is proposed to name the Macaranga ant‐food bodies Beccariian bodies in honor of the Italian botanist Odoardo Beccari who explored S.E. Asia in the late 1800s.

THE OCCURRENCE AND PHYLOGENETIC SIGNIFICANCE OF A MULTILAYERED STRUCTURE IN COLEOCHAETE SPERMATOZOIDS

Spermatozoid‐forming cells of Coleochaete scutata were found in packets of four arranged in concentric internal bands. Spermatozoids, which occur singly in antheridial cells, are spherical to ovoid, approximately 7 μm long by about 3.9 μm wide. As compared to relatively unspecialized zoospores, male gametes undergo a number of specialized cellular changes during development. The spherical nuclei and cytoplasm of mature spermatozoids are increased in density. Posterior plastids are reduced and contain large starch grains. Many small mitochondria are clustered near the cell anterior. The plasmalemma is covered with a layer of flattened, diamond‐shaped scales, while body scales of zoospores are pyramidal. The two flagella of both zoospores and spermatozoids are covered with flattened, diamond‐shaped scales and hairs. The spermatozoids contain an anterior multilayered structure (MLS) structurally similar to, though smaller than, the MLS observed in zoospores. An asymmetrical cytoskeleton consisting of a band of 30–45 microtubules extends from the MLS down one side of the spermatozoid close to the plasmalemma. An immature MLS was observed in an early stage of spermatozoid development. The finding of an MLS and asymmetrical cytoskeleton in specialized male gametes as well as relatively unspecialized zoospores of Coleochaete strengthens assumptions of homology between MLSs of green algal reproductive cells and those found in flagellated spermatozoids of archegoniate plants. The structure of the spermatozoid of Coleochaete supports the hypothesis that this alga may be relatively close to the phylogenetic line which led directly to archegoniates.

Abscisic-acid and gibberellin action in developing kernels of triticale (cv. 6A190)

Abscisic-acid (ABA) levels were determined in triticale 6A190 kernels at various stages of development from anthesis to maturity. ABA reached a maximum at ca. 22 d post-anthesis and declined rapidly 12 d later. Associated with drying of the kernel at maturity there was a rapid increase in the endogenous level of α-amylase, apparently based upon de-novo synthesis. Simultaneously there were visible signs of degradation of the large starch grains in the starchy endosperm. Regulation of α-amylase production in the kernel by exogenous gibberellic acid (GA3) was only evident in the almost mature kernel (30-40 d after anthesis) and then only if these kernels were first dried artificially. Furthermore, little α-amylase mRNA could be detected prior to kernel maturity and water loss. Thus, the high levels of gibberellin (GA) that have been found early in kernel development in cereals do not appear to control the later production of α-amylase and onset of kernel germination in the ear of triticale. However, the presence of high levels of ABA until maturity could prevent early germination and premature production of α-amylase. Kernels of triticale 6A190 are characteristically shrivelled and non-dormant at maturity. The relevance of changes in the capacity of kernels to respond to and produce GA and ABA is discussed in relation to problems of harvest dormancy in cereals.

The Growth Responses of Soybean Plant to Photoperiod and Temperature : III. The effects of photoperiod and temperature on the development and anatomy of photosynthetic organ

Developmental and anatomical features of soybean leaves grown under different photoperiod and temperature were compared in consideration for their relations to growth parameters. 1. Leaf number increased with increase of temperature and daylength. The leaflet size of the 5th leaf was greater under long day than under short day, and greatest at 25°C or 30°C day temperature. Thus, relative growth rate of leaf area per plant increased with increase of temperature and under long day condition. The thicknesses of leaf blade, mesophyll and pallisade layer, and specific leaf weight increased with decrease of temperature, whereas leaf area ratio decreased with decrease of temperature. 2. The volume of each pallisade cell increased while air-space percentage decreased with decrease of temperature. Pallisade tissue consisted of two layers of cells, being about twice as thick as spongy tissue and this situation was little affected by the treat-ments. 3. The mean area of epidermal cell was greatest at the intermediate temperatures, becoming smaller as temperature increased or decreased. It was greater under long day than under short day. Stomatal density was high at abaxial surfacc and low at adaxial surface, and the density of the latter increased with increase of temperature although that of the former changed a little. The mean length of guard cell parallelled the mean epidermal cell size. The total guard cell length of both leaf surfaces per unit leaf area increased with increase of temperature. 4. TAC concentration, TAC content per unit leaf area increased with decrease of temperature, and were greater under long day. Crude protein concentration, on the contrary, decreased with decrease of temperature and was smaller under long day, although its content increased with decrease of temperature and was greater under short day. 5. The diameter of petiole was greater under long day and greatest at 30/25°C. The number of large and intermediate vascular bundles of petiole changed little by the treatment, but that of small bundles increased with increase of temperature. The petiole diameter and mean area of large vascular bundles were intimately related to leaf area. 6. The starch deposit in the chloroplasts increased with decrease of temperature, especially abundant in the spongy tissue. Under low temperatures, large peculiar compound starch grains were stored in the parenchymatous cells of petiole and stem. 7. Anatomical features affected by temperature and photoperiod did not show significant correlations to NAR, although SLW, leaf thickness, nitrogen content and Sol-N/Total-N ratio had negative correlations with NAR. 8. SLW had positive correlations with both leaf thickness and TAC concentration, a negative correlation with air-space percentage. 9. The growth parameters such as RGR, RLGR, LAR and NAR were all positively correlated with the mean ambient diurnal temperatures, and the correlation coefficients were higher for RGR, RLGR and lower for NAR.

Guard cell ontogeny in leaf stomata of the fern Ophioglossum petiolatum

Guard cells in Ophioglossum petiolatum leaves are initiated by a single division of a stomatal initial with no subsidiary cells being formed. The stomatal initials have few vacuoles, plastids with little starch, and a large nucleus with much heterochromatin and prominent nucleoli. Young guard cells are similar cytologically to stomatal initials; their common cell walls are thin and traversed by plasmodesmata. Plasmodesmata are also present within guard cell and adjacent epidermal cell walls. With increasing age, guard cells develop a lenticular thickening in the median portion of the common cell walls, larger vacuoles, and plastids with several starch grains. Numerous microtubules are present near the thickening wall which also has an electron-translucent region between the cell wall and the plasmalemma. Many dictyosomes and mitochondria are present in the cytoplasm. Older guard cells become more vacuolated, with some of the vacuoles containing fibrillar or dense deposits. Plastids become very large as a result of storing several large starch grains. In the thickened portion of the cell walls, the middle lamella and some of the adjacent cell wall appear to be degraded during stomatal pore formation. Mature guard cells are highly vacuolated and have very thick electron-dense cell walls without plasmodesmata. Fluorescence microscopy following aniline blue staining shows that aniline blue positive materials are present around and within the thickened portion of the cell walls, at the junction of guard cells with epidermal cells, and as distinct spots in guard cell and epidermal cell walls during the early stages of ontogeny. Mature guard cells, however, lack the distinct fluorescent spots, which are interpreted as plasmodesmata, in their walls.

Structure of a stem-derived callus of Ruta graveolens: meristems, leaves, and secretory structures

Differentiation in a stem-derived callus of Ruta graveolens was studied by correlated light and electron microscopy. Shoot apical meristems, some of which initiated leaves, differentiated randomly at the surface of the callus. Some of the apical meristems had a tunica–corpus organization. Cells of the tunica and corpus had large nuclei with prominent nucleoli, small vacuoles, mitochondria, endoplasmic reticulum cisternae, and leucoplasts. The leaves were radial and had well developed stomata and chloroplasts of two types, one storing large starch grains and the other with no starch but with well developed grana. Lysigenous and schizolysigenous secretory glands were initiated in the leaves and towards the periphery of the callus. Central cells in the lysigenous glands underwent lysis forming a gland lumen into which lipid-like material from the degenerating cells was released. During early stages of cell lysis, breakdown of the middle lamella occurred, followed by the degeneration of cell walls. The lipid-like deposits are thought to be the essential oils known to be produced by these callus cultures. Schizolysigenous glands are formed by the separation of gland cells along the middle lamella and the subsequent development of an epithelial layer or layers surrounding a gland lumen. The cytology of epithelial cells was characterized by numerous ribosomes and the presence of plastids with lipid-like deposits, rough endoplasmic reticulum which occurred either as sheets of cisternae or tubular profiles, and osmiophilic deposits in the cytoplasm. Changes in the epithelial cell walls bordering on the gland lumen indicated that these cells were probably undergoing lysis in older stages of gland development.

Seasonal changes in mesophyll ultrastructure of needles of Norway spruce (Picea abies)

Seasonal changes in the ultrastructure of the mesophyll of needles of Norway spruce are described. During the growing season, the tannin is in the form of a ribbon along the margin of the vacuole or in the form of small, more or less scattered particles. The cytoplasm is dark and its organelles are along the cell wall; only the chloroplasts with large starch grains and the nucleus can be clearly resolved. During and after September, the cytoplasm is very netlike, all of the cytoplasmic organelles clump together, the amount of lipid droplets increases, and ribosomes are clearly visible. The tannin is in the form of rather large granules and it increases over its growing-season amount. The shape of chloroplasts changes. Chloroplasts lose their starch and the stroma becomes sparsely granular and rich in ribosomes. This structure is maintained throughout the winter. During spring activation, the cell structure is reorganized and reassumes the condition typical of the growing season. At this time, the needles have some collapsed cells and cells in which some chloroplasts are not quite intact. The injuries were probably caused by weather conditions (a warm period in March followed by a frost).

Ultrastructural changes in chloroplasts of lettuce infected with beet western yellows virus

An electron microscope examination of lettuce plants infected with beet western yellows virus (BWYV) showed that the interveinal leaf-yellowing disease symptoms were associated with the degeneration of the chloroplasts. The disappearance of grana stacks, stroma lamellae and the appearance of abnormally large starch grains in chloroplasts was ultimately followed by an abnormal increase in the number and size of osmiophilic granules. In infected lettuce plants treated with carbendazim (methyl benzimidazole-2-yl carbamate), chloroplasts were normal and disease symptoms were largely prevented. Degeneration of chloroplasts of BWYV-infected Claytonia perfoliata leaves followed a similar pattern to that observed in lettuce, and disease symptoms were evident when leaves changed from green to an orange-red discoloration. Chloroplast breakdown and symptoms in infected C. perfoliata plants were not prevented by the application of carbendazim. BWYV-induced chloroplast degeneration is discussed in relation to chloroplast degeneration during the natural senescence of leaves of other plant species in which senescence is probably controlled by endogenous hormones.

Young plastids in shoot apical cells of a genetic albino strain of Nicotiana (Solanaceae)

The ultrastructure of young plastids in shoot apices of a genetic albino strain of Nicotiana was examined by transmission electron microscopy. Typical young plastids were variable in shape and contained prolamellar bodies in various stages of organization. Thylakoids were few in number, some originating from the prolamellar body while others appeared free in the densely ribosomal stroma. Peripheral areas of the young plastids contained electron-transparent vesicles and tubules which were either in proximity or connected to the inner plastid envelope. Osmiophilic globules occasionally occurred in association with prolamellar bodies. Relatively large starch grains were common; cytoplasmic invaginations into the plastids were less common. Young plastids in the genetic green shoot apex closely resembled those of the genetic albino. These results indicate that organization of large-type grana in plastids of mature phenotypically green, genetic albino leaves occurs beyond the apex stage of germinated seedlings of this strain of Nicotiana.

Ultrastructural changes in trifoliate leaves of bean ( Phaseolus vulgaris) following inoculation of monofoliate leaves with Pseudomonas phaseolicola

Monofoliate leaves of French bean cv. Canadian Wonder were inoculated by injection with suspensions of Pseudomonas phaseolicola ( c. 3·0 × 10 8 cells/ml). Trifoliate leaf tissue was examined by light and electron microscopy 3, 10 and 14 days later. A darkly staining inclusion which occurs in three forms appeared in cell vacuoles after 10 days and increased in concentration 4 days later. Large starch grains occurred in chloroplasts and despite chlorophyll levels being about half those of controls, chloroplast integrity appeared normal. Other organelles also appeared normal, though there were increases in endoplasmic reticulum and numbers of ribosomes.

Changes in Chloroplast Ultrastructure during the Senescence of Leaves in Rice Plants

The flag leaves were sampled from rice plants of the paddy field at intervals of 10 days after the full expansion, and ultrastructure of the chloroplasts was observed by electron microscope. When the leaves had just fully expanded, the large starch grains accumulated in the chloroplasts, but afterwards the starch grains gradually decreased and after 30 days they almost disappeared (Figs. 1, 5, 6 and 7). The number of thylakoids per granum continued to increase for 10 days after leaf expansion (Fig. 3). The separation of thylakoid membranes, which is the first sign of destruction, was observed in some chloroplasts at 20 days after leaf expansion (Fig. 6). The size of chloroplasts and the number of grana continued to increase for 30 days after leaf expansion (Figs. 1 and 2), but they were followed by the breakdown of inner membrane system and by the decrease in amount of stroma (Figs. 7 and 8). As the inner membranes breakdown, the leaf colour changed to yellow-green and the plastoglobuli increased in size and number (Fig. 4). At the ripening stage of rice plants, ultrastructure was compared among chloroplasts in the upper five leaves (Table 1). Structural differences were not so marked among chloroplasts in the upper three leaves. However, the chloroplasts in the fourth leaf counted downwards from the flag leaf, showed a disappearance of the starch grains, a decrease in number of the grana, and a spectacular accumulation of the plastoglobuli. In the yellow area of the fifth leaf, the chloroplasts shrank because of the disappearance of grana and stroma (Fig. 9), and finally the chloroplasts envelope disappeared (Fig. 10). The similar pattern of destruction as mentioned above was observed in the chloroplasts from seedling leaves, but the destruction was more rapid than those at the ripening stage.

Ultrastructural Development of Mesophyll Cells in Rice Seedlings

Ultrastructural observations were made on the mesophyll cells in leaves at different stages of development. In the ground meristem of the leaf primordium, the plastids and mitochondria, both are approximately the same in dimention, locate around the large nucleus (Fig. 1). The plastids contain several lamellae and small starch grains (Fig. 4). The plastids in the intercalary meristem have more developed lamellae and larger starch grains than those in the leaf primordium. The protuberance formation of the arm-palisade cell progresses in parallel with the cell enlargement, and has completed just before emerging from sheath (Fig. 18). At the stage of cell enlargement, the number of lamellae, the size of starch grains and the rudimentary grana increase in the plastids (Fig. 6, 10). The dividing plastids are frequently observed (Fig. 6). The plasma membrane of the vacuolated cells is observed to possess numerous invaginations (Fig. 7). These invaginations continue to increase in size and project into the large central vacuole (Fig. 8, 9). These structures are bounded by two membranes, an outer tonoplast and inner invaginated plasma membranes. Some invaginations may separate from the peripheral cytoplasm and subsequently attach to the plastids (Fig. 10, 11, 12). The inner membranes of the invagination attached to the plastid, are connected with the plastid envelope. It is assumed that the invaginations may possibly be related to the formation of plastid envelope. In the leaf portion emerged out from sheath, all of the plastids take up a peripheral position in the cell and increase in size (Fig. 14). Another prominent features of the plastids are the increase in both the number of grana and thylakoids per granum (Fig. 16). The microbodies of 0.5-1.0 μm in diameter, are found in the mesophyll cells of expanded leaves (Fig. 17), but they are not found at the stage of cell division and cell enlargement.

Characterization of cytoplasmic and nuclear genomes in the colorless alga Polytoma. I. Ultrastructural analysis of organelles.

Electron microscope studies have been made on the fine structure of the colorless biflagellate, Polytoma obtusum, with main emphasis on the structural organization of the mitochondria and the leucoplast. Both organelles have been demonstrated to contain DNA aggregates as well as ribosomal particles within their matrix material. Reconstructions from serial showed that (a) the mitochondria were highly convoluted and irregular in shape and size, and (b) the leucoplast was a single cup-shaped entity, with large starch grains, localized at the posterior end, and multiple sites of DNA aggregates. The starch-containing compartments appeared to be interconnected by narrow tubular or sheetlike bridges. Cytoplasmic invaginations into the plastid, often containing mitochondria, were of frequent occurrence, and membranes of mitochondria and the leucoplast appeared to be closely apposed. Membranes elements, both sheetlike and vesicular, were also present in the matrix. The Polytoma leucoplast was, in certain respects, morphologically similar to the plastids of various photosynthetic mutants of Chlamydomonas, most of which show Menedelian segregation. It is suggested that Polytoma arose from a Chlamydomonas-like ancestor, possibly through combined mutational processess of both chloroplast and nuclear genomes. Since Polytoma leucoplasts contain both DNA and ribosomal particles, it is probable that these organelles still possess semiautonomy and limited ability for protein synthesis.

Ontogeny of the protophloem fibers and secondary xylem fibers within the stem of Coleus. II. An electron microscope study

Ultrastructural changes within the protophloem fibers and secondary xylem fibers accompany their ontogeny in the Colens stem. The plasmalemma of both fibers portrays a gently undulating pattern against the wall before secondary wall formation. Commonly a narrow, hyaline region separates the primary wall and the plasmalemma. Fibrillar material arising from the plasmalemma is condensed in the wall. With the onset of secondary wall formation, undulation of the plasmalemma increases. Many microtubules traverse the membrane and are modified into extracytoplasmic microtubules. Vesicles produced by the dictyosomes and endoplasmic reticulum (ER) pass through or fuse with the plasmalemma. These processes abate after the initiation of the secondary wall. Cisternal, vesicular, and tubular forms of ER, the latter a rare form in wood fibers, fluctuate in amount during ontogeny. Mitochondria increase in number by fission and change in size and cristae volume. Microbodies are common in the youngest phloem fibers but are absent from the xylem initials. Microbodies arising as swellings of ER cisternae are numerous after secondary wall formation is underway in both fibers. Microfilaments are rare in wood fibers but are common in young phloem fibers. Spherosomes, which originate from ER cisternae, disappear during the initiation of the secondary wall. Phloem fiber plastids increase in number by either constriction or concentralization until shortly after the start of secondary wall formation. The plastids of the xylem fibers differ from those of the phloem fibers since the organelles contain phytoferritin and large starch grains initially, divide only by constriction, and do not form membrane-bound bodies.

Amyloplast Size and Number in Gravity-compensated Oat Seedlings

Gravity compensation by the horizontal clinostat increases the diameter of amyloplast starch grains of oat (Avena sativa cv. Victory) coleoptile parenchyma cells, as compared to vertically rotated and stationary controls. In dark-grown coleoptile tip parenchyma cells, measured starch grain sizes exhibit a wide distribution of diameters, from approximately 1.5 to approximately 8.0 mum, but fall into three prominent diameter classes. The compensated tissues from both the tip and the subapical region have more starch grains in the larger, and fewer in the smaller size classes, compared to controls. The total number of starch grains per cell, the total plastid number per cell, and cell volume are unaffected by gravity compensation. Amyloplasts with large starch grains are denser, as well as larger in diameter, than those with smaller starch grains. The amyloplast is considered as a geosensor with an active metabolic role in the geotropic transduction mechanism.

Ultrastructure of Chloroplasts of some Chlamidospermae (Ephedra Twediana, Gnetum Montana, Welwitschia Mirabilis)

SUMMARYSeedlings from dark grown seeds of Ephedra twediana are green and their chloroplasts show a normally developed photosynthetic apparatus, while seedlings from dark grown seeds of Gnetum montana and Welwitschia mirabilis do not contain chlorophyll and their plastids show prolamellar bodies, electron dense thickenings and, particularly in Gnetum, also large starch grains. Only after light exposure the seedlings turn green and the plastids show a differentiated photosynthetic apparatus.

Ultrastructure of the hypersensitive reaction in roots of tomato, Lycopersicon esculentum L., to infection by the root-knot nematode, Meloidogyne incognita

The hypersensitive reaction in roots of Lycopersion esculentum L., cv. Nematex, infected by Meloidogyne incognita was studied by light and electron microscopy. An increase in cytoplasmic density characterized by increased numbers of ribosomes, proliferation of endoplasmic reticulum and increased stainability of the cytoplasmic ground substance was the first symptom of the resistance response to the nematode larvae. Concomitant with this change was a disappearance of dense osmiophilic inclusions from the vacuoles of hypersensitive cells. There followed a general loss in distinctness of the cell membranes resulting in the disappearance of mitochondria and Golgi bodies. The fibrillar structure of the nucleoplasm disappeared and numerous electron-dense inclusions appeared in the nucleoplasm. Organized arrays of ribosomes appeared on the outer membrane of the nuclear envelope. The plastid stroma lost its granular texture although large starch grains persisted. Changes in cell structure were restricted to cells close to the nematode, but the products of cell breakdown moved away from this region through intercellular spaces. Giant cell production was generally suppressed by the hypersensitive reaction. Heat-treatment of Nematex roots inhibited the hypersensitive reaction and thus enabled giant cell formation. Treatment of roots with the growth substance kinetin did not inhibit the hypersensitive reaction although it appeared to enhance giant cell formation.

The Fine Structure of the Wheat Scutellum During Germination

The cytological changes that take place in the scutellar epithelium and parenchyma during the first 5 days of germination are described by light and electron microscopy. Within 6 hr small starch grains appear in the plastids of both cell types and the size and number of starch grains increase gradually as germination proceeds. Later in germination starch disappears again from the plastids in the epithelial cells, but large starch grains still remain in the parenchyma cells. The reserves of the protein bodies are hydrolysed and the residual vacuoles undergo extensive coales-cence. Modifications in the appearance of the wall material of the epithelial cells as these cells elongate are illustrated and possible functional bases for these changes are suggested. The cells of the scutellar epithelium show no cytological evidence for their known functions of diastase secretion and nutrient absorption.