摘要:

A systematic survey of the leaf anatomy of 51 taxa in the palm genusSyagruswas made. Cross sections of the middle pinnae of each taxon were embedded, cut, stained, and mounted on slides. Criteria used to distinguish species were based mainly on differences in the laminar surface and hypodermis: frequency and location of various sized veins; frequency, shape, and location of nonvascular fibers; size and shape of midrib and main vascular bundle; and size and shape of expansion cell tissue. The included key to the species employs mostly these characteristics. Each taxon is listed under subgenera and sections in the order presented in a previous article, where gross morphology was used as the basis of classification. Relationships between species of each subgenus and section are discussed in terms of the original arrangement of each group and needed changes. It is significant that certain evolutionary sequences have become unfolded which were not apparent by use of morphological characters alone. Although all relationships have not been completely worked out, this survey has resulted in a revision of my original classification of the genusSyagrusand at the same time has also corroborated certain alignments of species previously based on gross morphology.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1972.tb10152.x

出版商:Wiley    

年代:1972

数据来源: WILEY

摘要:

All hybrid plants from interspecific crosses among the three species,Sonchus asper(L.) Hill,S. oleraceusL., andS. arvensisL., were male‐sterile, but the progeny of the crossS. arvensisXS. oleraceusand reciprocal cross produced seed after backcrossing to the male parent. Hybrid plants from crosses betweenS. oleraceusandS. asperlacked vigor. Cytological data indicated thatS. arvensishas one genome in common withS. asperand thatS. oleraceusis an autotetraploid (2n = 36) with no genomes in common withS. arvensisorS. asper.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1972.tb10153.x

出版商:Wiley    

年代:1972

数据来源: WILEY

摘要:

The redifferentiation of tobacco pith cells was examined in two experimental systems: wounds recovering from an incision that severed vascular tissue of the stem, and induced differentiation of excised pith responding to indoleacetic acid supplied locally via pipets inserted into the tissue. In both systems there was an initial period during which cell division was resumed and the pith cells were cleaved into numerous small cells. This was followed by redifferentiation of some of the divided cells as tracheary elements and, especially in the stem, by the formation of a cambial meristem that produced further xylem and phloem. In the stem the size of the wound meristem decreased as the wound was made further from the shoot apex, and in the cultured pith tissue it was demonstrated that the size of the dividing zone increased with the concentration of auxin supplied. Auxin was, therefore, demonstrated to be limiting in the division phase of redifferentiation. The sequence of redifferentiation in the two experimental systems resembled the normal ontogeny of vascular tissues in the intact plant sufficiently that these systems could be used to investigate the relationship between cell differentiation and auxin transport.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1972.tb10154.x

出版商:Wiley    

年代:1972

数据来源: WILEY

摘要:

Structurally similar proplastids occur in the shoot, scutellum, and root of the oat embryo at the start of germination. These proplastids follow several pathways of differentiation, depending on their location within an organ and on previous exposure to light. During the first 24 hr of germination morphologically similar amyloplasts are formed from the preexisting proplastids in most of the cells of the seedling. After about 24 hr in the light, unique chloroplasts begin to develop in a subepidermal ring of small cortical parenchyma cells in the coleoptile and give the organ a pale green color. At 48 and 72 hr the coleoptile chloroplasts and etioplasts are conspicuously different from the corresponding leaf plastids in morphology and ontogeny but contain typical photosynthetic grana and prolamellar bodies. Study of the ontogeny of plastids in the epidermal and nongreening parenchymal regions of dark grown coleoptiles shows that these plastids undergo significant losses in starch content, and some increase of membranes within the plastid, related to the age of the cell. Light has little effect on the structure of these plastids. It is suggested that the ontogeny of all the plastid types of the oat seedling begins with a common precursor—a relatively simple proplastid that is present at the time of germination. Starch grains showing two distinct types of erosion, apparently enzymatic, were observed in oat coleoptile plastids. In one type (grooved appearance) the starch grains are consistently associated with plastid membranes, while in the other type (irregular, spiny appearance) the starch grains are associated with the plastid stroma only. We suggest that there are two enzyme systems for metabolizing starch in oat plastids—one membrane‐bound and the other free in the stroma.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1972.tb10155.x

出版商:Wiley    

年代:1972

数据来源: WILEY

摘要:

The secondary phloem inEphedrais atypical of the gymnosperms in general and exhibits several angiosperm‐like characteristics. The ray system of the conducting phloem consists of parenchymatous, multiseriate rays. The axial system contains parenchyma cells, sieve cells, and unusual albuminous cells reminiscent of the specialized parenchyma cells found in some angiosperms. These cell types may intergrade with each other. P‐protein in the developing sieve element appears early in the form of a single, ovoid slime body. Later, smaller slime bodies appear and quickly disperse. In the mature sieve element the single, ovoid slime body is lost, and P‐protein is then evident in the form of a parietal cylinder, thread‐like strands, amorphose globules, or a slime plug. Necrotic‐appearing nuclei are commonly found in mature sieve cells.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1972.tb10156.x

出版商:Wiley    

年代:1972

数据来源: WILEY

摘要:

Genetic and cytochemical investigations of the origin, development, nuclear activity, and ploidy level of Plasmodia obtained from selfed clones S‐2 and B1P‐33 of the heterothallic myxomycete,Didymium iridis, are presented. To demonstrate that selfing did not result from contamination of the clones, or mutations at the mating‐type locus, crosses were made between F1clones and clones of known mating types. The data were inconsistent with these two possibilities. DNA was quantified by Feulgen‐DNA microspectrophotometry. All cellular phases studied (logarithmic amoebae, swarmers, and encysted amoebae) appear to be haploid, with the nuclear DNA being in the replicated (2C) state. The plasmodia are in all cases diploid; however, the data indicate that the selfed Plasmodia are in an extended G1condition. The nuclear DNA content of these is therefore 2C, whereas that of the cross Plasmodium is 4C. Sporangial nuclei exhibit DNA in diploid replicated (4C) category.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1972.tb10157.x

出版商:Wiley    

年代:1972

数据来源: WILEY

摘要:

Colchicine‐induced amphiploids, 2n = 42, of diploidAgropyron libanoticumHack., 2n = 14, X tetraploidA. caninum(L.) Beauv., 2n = 28, were morphologically and cytologically similar toA. leptourum(Nevski) Grossh., 2n = 42. BothA. leptourumand the induced amphiploids were self‐fertilizing. The induced amphiploids crossed readily withA. leptourumand gave rise to partially fertile hexaploid hybrids. Chromosome pairing in the hybrids averaged 0.60I, 18.29II, 0.36III, 0.58,v, 0.02v, and 0.22VIin 90 diakinesis or metaphase‐I cells. The genomes of the induced amphiploids are essentially homologous with those ofA. leptourumexcept for two or more reciprocal translocations. The morphological, cytological, fertility, and crossing data provide conclusive evidence thatA. libanoticumandA. caninum, or their close relatives, are the parents ofA. leptourum. The genome formulas ofA. libanoticum, A. caninum, andA. leptourummay be written as SS, SxSxHxHx, and SSSxSxHxHx, respectively, where S is the basicA. libanoticumgenome and H is a genome derived fromHordeum.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1972.tb10158.x

出版商:Wiley    

年代:1972

数据来源: WILEY

摘要:

Six species ofEuphorbiaendemic to the Hawaiian Islands have disjunct veins as a normal component of their foliar anatomy. An ontogenic study of the foliar venation of one of these species,E. forbesii, showed a normal development of the foliar procambium as determined by previous studies of dicotyledonous leaves. The disjunct veinlets are isolated early in the histogenesis of the intersecondary veins when certain procambial cells fail to differentiate into vascular tissue. It appears that these cells develop into normal parenchymatous cells of the ground tissue. It is suggested that these cells are physiologically distinct from the rest of the procambial cells. In no instance was a tracheary element seen which appeared to have arisen independently of the normal procambial reticulum.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1972.tb10159.x

出版商:Wiley    

年代:1972

数据来源: WILEY

摘要:

Certain embryological and biochemical effects of the cytokinin (SD 8339) in converting flower sex from male to hermaphrodite were studied in a clone ofVitis viniferaL.(sylvestris). The cytokinin accelerated the meiotic division of the megaspore mother cell, mitotic divisions of the megaspore and cells of pistillate tissue, and increased the rate of protein synthesis in flower buds. Two working hypotheses for the possible mode of action of the cytokinin in sex conversion are presented.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1972.tb10160.x

出版商:Wiley    

年代:1972

数据来源: WILEY

摘要:

In cap cells of intact plant roots exposed to 1mM uranyl for 30 min or less, uranyl crystals were found only in cell walls and in secretory products which had been extruded from the protoplast. In roots exposed for 10–20 hr to 0.1mmuranyl, packets of uranyl crystals bound to secretory products were found within the protoplasts of those exterior cells which contained accumulations of secretory products between the cell wall and protoplast. Although the evidence indicated that these packets of crystals entered the protoplast pinocytotically, results with these specialized exterior cells did not apply to the vast majority of root cap cells in which, after prolonged exposure to 0.1mmuranyl, crystals were concentrated in vacuoles. In roots exposed to 1 or 5mmuranyl for 1 hr, the plasmalemma of interior cap cells was much thicker (13.1 nm) than normal (8.2 nm), and many invaginations and vesicular structures were found near the protoplast surface. Crystals were confined to cell walls except for a few found in vesicles with thickened membranes. Serial sections indicated that most vesicular structures with thickened membranes were in contact with the cell wall, but a few, including some which contained uranyl crystals, were within the protoplast. These results provide evidence of pinocytotic activity in intact plant cells exposed to a toxic heavy metal.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1972.tb10161.x

出版商:Wiley    

年代:1972

数据来源: WILEY