摘要:

A shock pressure pulse of 60 pounds per square inch (psi; 4.22 kg/cm2) effectively inhibited root growth of onion bulbs. Morphological changes observed after shock included a reduction in cell number in transverse section, a decrease in cell length, a decrease in cell volume, and an increase in cell cross‐sectional area. Mitotic activity was consistently increased one day after shock, and this may have accounted for the increased cell number per millimeter of root tip segment 8 days after shock. The development of the tissues appeared normal after shock exposure; however, the tissue response to pressures seems to depend on whether they are exposed to prolonged confining pressures or a brief pressure pulse. Responses which were unique to shock treatment include a decrease in cell number in transverse section, reduced cell volume, and increased radial enlargement of the cell. These responses have not been observed under prolonged pressure treatment.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1971.tb09954.x

出版商:Wiley    

年代:1971

数据来源: WILEY

摘要:

Photomicrographs of normal and aberrantPolymnia(Compositae) pollen were made with the scanning electron microscope and with the light microscope. Anomalous pollen forms from F1hybrids ofP. maculataCav. are compared to the parental type and to the closely relatedP. uvedalia(L.) L. Among the variations discussed are differences in size and form, fused aggregates, and reduction in length of spines. The cause of these variations is unknown, although similar anomalies were later found in a singleP. maculataparent, Wells No. 740, which grew under similar standard greenhouse conditions.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1971.tb09955.x

出版商:Wiley    

年代:1971

数据来源: WILEY

摘要:

Shoot apical meristems ofPicea abiesseedlings can be cultured on a relatively simple, defined, basal medium. Dome‐like explants initially about 200 μ tall, without externally obvious primordia, and having dry weights of about 3 μg, usually initiate 5–10 new primordia within a week. They typically show 10‐ to 30‐fold dry weight increases in three weeks. None of the 5,000 meristems cultured has produced any basal callus. Growth is strongly influenced by both the type and concentration of agar used to gel the medium. Dry weight yield increases as agar concentration decreases. This is probably partly due to increased diffusion rates of enzymes or other large molecules through more dilute agar gels but possibly also partly ascribable to unknown agarborne inhibitors. About half of the agar concentration effect can be eliminated by substituting glucose and fructose for sucrose in the medium. This suggests that diffusion of invertase through the agar gel in this medium may be a growth limiting factor. Growth of cultures is also promoted by autoclaving sucrose in the presence of the agar. The basis of this effect is not yet understood.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1971.tb09956.x

出版商:Wiley    

年代:1971

数据来源: WILEY

摘要:

Our ontogenetic analysis of paper birch root systems shows that the fate of a root tip is related to its relative primary xylem diam (PXD). Lateral root tips with an initial PXD less than about 25 % of the parent root PXD are ephemeral. Some tips having a PXD of more than about 25 % of the parent root PXD become the permanent portions of the root system, enlarging over time as they elongate. In seedling root systems, the primary root and first‐formed laterals are initially about the same size, and their PXD's all enlarge with increasing distance from the stem as the tips elongate to form the initial horizontal woody framework. Permanent lateral root branches with a large relative PXD develop after root tip injury, when the root tip is forced to grow in a curve, or from other unaccountable causes. Our observations show the importance of using relative diameters when classifying roots and when applying the concept of heterorhizy to paper birch root systems. Evidence points to the existence of some form of apical dominance in roots.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1971.tb09957.x

出版商:Wiley    

年代:1971

数据来源: WILEY

摘要:

Flowering soybeans were sprayed at the tips with 50 ppm TIBA. Microscopic and macroscopic observations were made of the nodes, internodes, and shoot meristems every week for 4 wks after TIBA treatment. TIBA‐treated plants produced open flowers at the upper nodes 1 week earlier than did control plants. Accompanying this early flower development, the following changes occurred in the upper internodes, as compared to controls: (a) increased activity of the procambium; (b) rapid development of thick‐walled protophloem cells; (c) production of small vessels. Three weeks after treatment middle internodes of treated plants showed less cambial activity than did corresponding internodes of controls. The changes in the middle internodes of treated plants suggest a close correlation with increased flowering. Two weeks after treatment some lateral shoot apices at nodes nearest the main shoot apex exhibited the following changes, in contrast with controls: (a) development of conical apices with stack‐of‐brick‐like peripheral cells; (b) shrinkage of protoplasmic contents in some rib meristem cells and young pith cells; (c) frequent thickening of primary walls in young pith cells. Three weeks after treatment cells of lateral shoot meristems with conical axillary buds showed a denser stain for protein than did cells of corresponding meristems of controls. Floral apices in these meristems also stained more densely for protein than did similar apices in control plants. Together with early flower production in the upper nodes of treated plants, less starch occurred 2–3 weeks after treatment than in corresponding nodes of controls. Two to three weeks after treatment lateral shoot apices of both treated and control plants had numerous, large starch grains in the rib meristem, young pith, leaf and bud primordia, and developing flowers but few starch grains appeared in the tunica, corpus, and procambium.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1971.tb09958.x

出版商:Wiley    

年代:1971

数据来源: WILEY

摘要:

Cambial activity in white spruce stems in Alaska was observed during a 2‐year period in 50–60‐year‐old natural stands. Mitotic index was used as a measure of the rate of periclinal division of fusiform cells in the cambial zone. Anticlinal divisions were relatively rare, averaging only one per 27S periclinal divisions in most stems. Mitotic index, at any given time, appeared uniform throughout the cambial zone of an internode, among internodes of the same tree, and even among trees growing at markedly different rates. Diurnal variation in mitotic index was observed. There were three distinct growing season periods: early, grand, and late. Early period activity was characterized by reactivation of periclinal division, erratic mitotic indices, and an approximate doubling of the number of cambial zone cells per radial file (NCZ). Production of the first new xylem and phloem elements marked the beginning of the grand period. Rate of cell production in the cambial zone remained about equal to derivative production for the next 45–50 days, when about 80 % of annual xylem and phloem increment occurred. There was a drop in NCZ at the beginning of the late period coincident with a decline in mitotic index, and NCZ soon dropped to the dormant level. Complete termination of cambial activity was gradual, extending through late August and perhaps into September.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1971.tb09959.x

出版商:Wiley    

年代:1971

数据来源: WILEY

摘要:

Cells ofStreptanthus tortuosuscallus tissue contain chloroplasts when cultured in a liquid medium in the light. Similar cells grown in the dark contain proplastids that fail to develop prolamellar bodies but do contain a complex of loosely‐associated membranes. When green, light‐grown cultures are cut into small pieces and subcultured to a fresh culture medium, they become bleached even though maintained under the same illumination. The fine structure of the chloroplasts and the chlorophyll content of the cells indicate a dedifferentiation of the chloroplasts to a proplastid state during the early culture period. The changes in the ultrastructure of the plastids are paralleled by a dedifferentiation of the vacuolate cells to a less differentiated, meristematic state. Subsequent growth in the light results in a re‐formation of chloroplasts and an increase in the chlorophyll content of the cells. The period of chloroplast redevelopment is associated with the re‐formation of large central vacuoles in the cultured cells. Invaginations of the inner membrane of the plastid envelope occur at all stages of plastid development and are not lost during the period of grana degeneration. The proplastids formed from the dedifferentiation of the chloroplasts contain a large number of these invaginations and the redevelopment of grana is associated with a change in the electron density of the invaginating membranes. The degradation of the chlorophyll‐containing membranes of the grana occurs during a period of rapid cytoplasmic synthesis induced by the fresh supply of nutrients in the culture medium. These results suggest that the high levels of nutrients may act directly on the chloroplasts and cause their dedifferentiation or that the rapid cell growth induced by the nutrients may cause a degradation of the membrane proteins in the grana of the chloroplasts and an incorporation of the released amino acids into non‐plastid components of the cytoplasm.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1971.tb09960.x

出版商:Wiley    

年代:1971

数据来源: WILEY

摘要:

The chemical composition of perinuclear crystals ofLychnis chalcedonicaand intranuclear crystals ofDianthus barbatusin leaf tissue embedded in glycol methacrylate was tested by differential enzyme digestion of ultra‐thin sections. TheLychniscrystals were digested readily by pepsin but with great difficulty and never to completion by trypsin. TheDianthuscrystals were rapidly and completely digested by pronase; inconsistently and with difficulty by pepsin; and were unaffected by trypsin. Pre‐incubation with water increased the effectiveness of pepsin digestion. Neither RNase nor DNase had any effect, either alone, or when preceded or followed by the proteinases. It was concluded that theLychniscrystals are composed of protein that is probably high in aromatic amino acid content, and possibly low in the basic amino acids arginine and lysine. TheDianthuscrystals also seem to be protein, but because of their amino acid composition or conformation, and possibly because of complex reactions with the fixative, these crystals are not readily hydrolyzed by pepsin and trypsin.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1971.tb09961.x

出版商:Wiley    

年代:1971

数据来源: WILEY

摘要:

Ten kinds of interspecific hybrids were obtained involving the following species:H. surattensisL. (2x, genome constitution BB),H. sudanensisHochr. (2x, GG), andH. rostellatusGuill. and Perr. (4x, GGHH) from Africa;H. furcatusRoxb. non Willd. (8x) from India and Ceylon;H. furcellatusLam. andH. bifurcatusCav. (both 4x, PPQQ) from South America; andH. heterophyllusVent. (6x) from Australia. Chromosome pairing in pollen mother cells (PMC's) at metaphase I in the 4x hybridsH. bifurcatus‐rostellatusandH. furcellatus‐rostellatusindicated that the parents have one genome in common (Q = G or H).Hibiscus furcatuswas shown earlier to have a B genome; hybrids ofH. surattensis‐sudanensisF1Xfurcatuswere hexaploid, having received an unreduced gamete from their hybrid parent, and had approximately 36 II, 36 I in PMC's. The genome formula ofH. furcatusmay therefore be designated BBGGWWZZ. The hybridH. rostellatus‐furcatus(BGGHWZ) confirmed thatH. furcatushas a G genome in common withH. rostellatus; pairing of the other three genomes was inconsistent, as was that inH. rostellatus‐heterophyllus. Some samples of the latter approached 36 II, 36 I, expected ifH. heterophylluswere GGHHJJ; other samples had less pairing.Hibiscus furcatus‐heterophyllushybrids apparently arose from unreduced gametes ofH. heterophyllusand originated as decaploids rather than heptaploids; chromosome number was unstable in PMC's. Nevertheless, multivalents, especially trivalents, were frequent enough to suggest thatH. furcatusandH. heterophyllusshare G genomes. On the other hand, an 8xH. bifurcatus‐furcatushybrid, which apparently arose from an unreduced gamete ofH. bifurcatus, had a low multivalent frequency. Hybrids were obtained ofH. heterophyllusXsudanensisandH. surattensis‐sudanensisXheterophyllus, but the plants were weak and were not analyzed cytologically. We suggest that the New World, African, Indian, and Australian genomes which retain a considerable degree of homology (G or H or both) were distributed by land prior to separation of the southern continents by continental drift.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1971.tb09962.x

出版商:Wiley    

年代:1971

数据来源: WILEY

摘要:

Young excised floral buds ofAquilegiawere grown on a chemically defined medium containing various concentrations of single amino acids or mixtures of amino acids. γ‐Amino butyric acid significantly promoted floral development through the initiation and differentiation of carpels. These floral organs were generally absent on the basal medium. Alanine, glutamic acid, and aspartic acid had no effect upon floral development. All other amino acids were either ineffective at lower concentrations and inhibitory at higher concentrations or were inhibitory at all concentrations. Casein hydrolysate and a mixture of amino acids found in coconut milk were ineffective. The addition of both γ‐amino butyric acid and alanine to the basal medium promoted development approaching that achieved on the coconut‐milk medium. However, further growth factors appear to be required before development on coconut‐milk medium is equalled or exceeded.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1971.tb09963.x

出版商:Wiley    

年代:1971

数据来源: WILEY