摘要:

Callus and plantlets derived from callus cultures ofNicotiana tabacumvar. Wisc. #38 were grown on medium containing serial combinations of gibberellic acid (GA3) and the cytokinin 6‐(3‐methyl‐2‐butenylamino)purine (2iP). Increasing levels of both growth substances resulted in the production of greater amounts of both callus and shoot tissue. More buds were induced when the cytokinin level was increased, and this effect was counteracted by raising the GA3/2iP ratio. Furthermore, the size and form of the shoots depended on the GA3/2iP ratio. High ratios resulted in tall, spindly plants with narrow leaves while low ratios resulted in short shoots with rounded leaves.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1973.tb05949.x

出版商:Wiley    

年代:1973

数据来源: WILEY

摘要:

Analyses of3H‐uridine,3H‐thymidine, and3H‐lysine incorporation in the root epidermis ofPanicum virgatumwere undertaken. Highly significant differences between the mean incorporation of3H‐uridine and3H‐lysine in epidermal and adjacent cortical cells were observed. While the cortex exhibited a steady decrease of precursor incorporation with distance from the apex, the epidermal cells exhibited differential incorporation. These results were regarded as further evidence for the hypothesis that cells of two maturation potentials exist in the epidermis of this panicoid grass. Treatment with 20.0 μg/ml of actinomycin D resulted in a differential inhibition in the epidermal‐cortical incorporation of3H‐uridine. The possibility of endopolyploidy in the epidermis was suggested by the observation that root hairs, hair initials, and some epidermal cells incorporated two to four times more3H‐thymidine than meristematic cells. Neither puromycin nor actinomycin D treatment affected the protein‐positive particles present in the cytoplasm of epidermal cells in this grass. Similarly, RNase did not affect their structural integrity. Attempts to clarify the significance of these inclusions and their possible role, if any, in the differentiation of the epidermis are now in progress.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1973.tb05950.x

出版商:Wiley    

年代:1973

数据来源: WILEY

摘要:

The Kranz syndrome, as indicated by relatively high13C/12C ratios is characteristic of 16 ½ tribes and about ½ of the species of the Gramineae. Data are given for 198 species from 129 genera and 47 tribes, and from at least 6 subfamilies of grasses. This information is correlated with data from the literature on anatomical and physiological characters of both Kranz and non‐Kranz grasses. All subfamilies, tribes, and genera seem to be uniformly all Kranz or non‐Kranz except the subfamily Panicoideae and the genusPanicumwhich have both Kranz and non‐Kranz species represented.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1973.tb05951.x

出版商:Wiley    

年代:1973

数据来源: WILEY

摘要:

The single gene recessive mutant stamenless‐2 (sl2/sl2) differs phenotypically from the normal (+/+) only in the stamen structure. Stamens of the mutant plants were laterally free, twisted, shorter, paler in color, possessed abnormal pollen, and bore naked external ovules (E.O.) on the adaxial surface near the junction of anther and filament. Mutant plants grown in the field during summer produced flowers in which a number of carpel‐like organs (‘carpelloid stamens‘) with few or no E.O. replaced the stamens. On the other hand, plants grown in the greenhouse during winter possessed flowers with greater number of yellow and pubescent stamens and many E.O. Study of stamen ontogeny revealed that at initiation (up to 100 μ in length) stamen primordia of normal and mutant plants resembled each other. Thereafter the development of stamens in the two genotypes could be distinguished.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1973.tb05952.x

出版商:Wiley    

年代:1973

数据来源: WILEY

摘要:

Three distinct types of glandular hairs of increasing morphological complexity which occur on flowering tops ofCannabis sativaL. (marihuana) are described from scanning electron microscopy. These gland types—termed bulbous, capitate‐sessile, and capitate‐stalked, described from pistillate plants—occur in greatest abundance on the outer surface of bracts ensheathing the ovary. Bulbous and capitate‐sessile glands, which arise at an early stage in bract development, are scattered over the bract surface. Mature bulbous glands have a small swollen head on a short stalk, whereas capitate‐sessile glands have a large globular head attached directly to the bract surface. Because of their numbers and large size, capitate‐sessile glands are the most conspicuous gland type during the early phase of bract development. Capitate‐stalked glands, which have a large globular head on a tall, multicellular stalk, differentiate during subsequent bract development. These stalked glands arise first along the bracteal veins and then over the entire bract surface. A voluminous, fluid secretory product accumulates in the glandular head of all three types. These glands are believed to be a primary site of localization of the marihuana hallucinogen, tetrahydrocannabinol.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1973.tb05953.x

出版商:Wiley    

年代:1973

数据来源: WILEY

摘要:

3H‐thymidine was incorporated into leaf tissue ofXanthium pennsylvanicumduring the stage of active cell division, during cellular differentiation, and into mature cells. Incorporation into nuclear DNA was high in the early stages of development. No nuclear incorporation was found after cessation of cell division. However, significant incorporation could be demonstrated in cytoplasm of differentiating and mature cells. Depending upon the time of growth in the radioisotope and the time of growth after treatment,3H‐thymidine, or its metabolized fraction, was incorporated into the secondary wall depositions of epidermal cells, mesophyll parenchyma cells, xylem cells, and chloroplasts. Autoradiographic technique and liquid scintillation spectrometry were used in these studies. The significance of3H‐thymidine incorporation into various organelles is discussed in relation to cell metabolism and its regulation during leaf development.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1973.tb05954.x

出版商:Wiley    

年代:1973

数据来源: WILEY

摘要:

Meiosis in homosporous ferns allows chromosomes to pair within homoeologous sets rather than restricting pairing to homologs; this allows homozygous spore mother cells to give rise to genetically heterogeneous meiospores. It is envisioned that such a meiotic system has evolved in homosporous ferns in response to a life cycle which allows the attainment of total homozygosity in one generation of selfing.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1973.tb05955.x

出版商:Wiley    

年代:1973

数据来源: WILEY

摘要:

Evidence is presented that a geographically peripheral population of the annualStephanomcria exiguassp.coronaria(Compositae), a widespread and ecologically diverse species, has recently given rise by a process of sympatric speciation to a diploid species presently designated “Malheurensis.” The new species comprises less than 250 individuals and is found only at a single locality in eastern Oregon where it grows interspersed with its parental population.Stephanomeria exiguassp.coronariais an obligate outcrosser and “Malheurensis” is highly self‐pollinating. Reproductive isolation is maintained by differences in breeding system, a crossability barrier that reduces seed set following cross‐pollination between them, and reduction in hybrid fertility caused by chromosomal structural differences. They are very similar morphologically. Electrophoretic analyses of seven enzyme systems demonstrate that all the alleles but one at the controlling 13 gene loci in “Malheurensis” are identical to alleles in ssp.coronaria. The new species displays certain maladapted features including loss of the specific requirements for seed germination characteristic of the progenitor population of ssp.coronaria. The origin of “Malheurensis” appears to be an exception to the theory of geographical speciation because spatial isolation is not necessary at any time for the origin or establishment of its reproductive isolating barriers. The nature of these barriers plus the genetic homogeneity of the species are compatible with the hypothesis that it derives from a single progenitor individual. Very little genetic change is involved initially in this mode of speciation.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1973.tb05956.x

出版商:Wiley    

年代:1973

数据来源: WILEY

摘要:

Near‐ultraviolet and visible radiations increased the duration of the mitotic cycle in excised pea root meristems primarily by lengthening the duration of the pre‐DNA synthetic period (G1). All radiations tested shortened the duration of the post‐DNA synthetic period (G2). The most pronounced effects were exhibited by green radiation, which lengthened the duration of the cell cycle, G1, DNA synthesis (S), and mitosis (M), and shortened the duration of G2. Progression of cells arrested by starvation in G1and G2into DNA synthesis and mitosis was also affected by light treatments. Green radiation appeared to arrest a group of cells in DNA synthesis as well as in G1and G2. Meristems receiving green and near‐ultraviolet radiations exhibited the most rapid progression of G1cells through S and G2.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1973.tb05957.x

出版商:Wiley    

年代:1973

数据来源: WILEY

摘要:

Description of the new cone is based on a single specimen from the Lower Permian Leonard Series of west Texas. The cone is 2.0 cm in diam. It has numerous fertile dwarf shoots subtended by ovate nonbifurcate bracts arranged in a compact spiral around the axis. The dwarf shoots are free from their subtending bracts and equal them in length. Each dwarf shoot is dorsiventrally flattened and bears about 30 sterile scales each of which is ovate and has a single vascular strand. These sterile scales are in spiral sequence but are lacking on the medial adaxial side of the dwarf shoot. A single flattened erect ovule is attached at the base on the adaxial side of the dwarf shoot and equals it in length. Tracheids and elongate parenchyma cells enclosed by the megaspore wall of one seed give evidence of the oldest embryos on record. Their occurrence in seeds that remain in the cone indicates that the kind of development in most modern plants, in which embryo growth precedes seed dispersal, had evolved by Lower Permian time.Moyliostrobus texanumgen. et sp. n. combines features typical of theLebachiaandErnestiodendrontypes of cones.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1973.tb05958.x

出版商:Wiley    

年代:1973

数据来源: WILEY