bluuebunny/crossref_metadata_2025 huggingface dataset:
MUTATIONS AFFECTING HETEROKARYOSIS IN SCHIZOPHYLLUM COMMUNE
Authors: Raper Carlene A. , Raper John R.
Published: January 2018

Mutations that affect the basic characteristics of heterokaryons of S. commune occur spontaneously and are preferentially selected in the common‐A heterokaryon and in its homokaryotic mimics, strains carrying a mutated B factor or strains disomic for heteroallelic B factors. Nine independent mutations were compared: all segregate independently of A and B incompatibility factors, and at least 3 distinct loci, of which 2 are linked, are involved. None of the mutations is phenotypically expressed in the homokaryon or in the common‐AB heterokaryon. All 9 mutations increase vegetative vigor of the common‐A the effects of all the mutations are additive in both heteroallelic and homoallelic combinations. At least 1 type‐II mutation also affects nuclear distribution in common‐B heterokaryons. Type‐II mutations appear to reduce common‐A, common‐B, and compatible heterokaryons to a single type unlike any of the normal heterokaryons. Pseudoclamping often persists for extended periods in modified homokaryons isolated from modified heterokaryons. Several cases of somatic recombination have been observed among components of modified heterokaryons.
THE PECTIC LAYER OF THE CELL WALL OF SCENEDESMUS QUADRICAUDA
Authors: Bisalputra T. , Weier T. E. , Risley E. B. , Engelbrecht A. H. P.
Published: January 2018

Further evidence from shadow casting techniques of the empty cells of Scenedesmus quadricauda confirms the structure of the pectic layer presented in an earlier work which was based entirely on reconstruction from thin sections. The structure of the net and props and their relationship are clearly seen and the inner boundary of the pectic layer is demonstrated by staining techniques.
COMPARATIVE BIOCHEMICAL STUDY OF TWO ALLELIC FORMS OF A GENE AFFECTING LEAF‐SHAPE IN THE TOMATO
Authors: Mathan David S. , Cole R. David
Published: January 2018

Through successive selfing of lanceolate, a leaf‐shape mutant in the tomato, the 3 leaf‐shape forms, namely, normal (La+/La+), lanceolate (La+/La), and homozygous lanceolate (La/La), were obtained in a uniform genetic background. The mutant allele lanceolate causes the increase in activities of the following oxidative enzymes: tyrosinase, laccase, peroxidase and catalase. The lanceolate gene exhibits a dosage effect with respect to these enzymes; the homozygous lanceolate shows the highest activity, heterozygous lanceolate is intermediate, and normal shows the lowest activity. The relative differences in activity of these enzymes between the 3 genotypes persist at all stages of development and in all organs examined.
AUTOINHIBITOR PRODUCTION BY CHLORELLA VULGARIS
Authors: Scutt J. E.
Published: January 2018

Filtrates from certain liquid cultures of Chlorella vulgaris (Columbian strain) developed sufficient peroxide content, after a few days’ storage, to inhibit further growth of Chlorella when they were used to prepare fresh culture media. Similar inhibition was observed when Chlorella was cultured in media containing various added organic peroxides. Growth of Chlorella was not limited by autoinhibitor production under the conditions employed, and no peroxide or other inhibitor was detected in solvent extracts of the cells or fresh filtrates.
PHYTOKININS AND SENESCENCE IN BROCCOLI
Authors: MacLean David C. , Dedolph Richard R.
Published: January 2018

The respiratory pattern of broccoli bud clusters treated with N6‐benzyladenine at harvest or at daily intervals thereafter was similar to that of at‐harvest‐treated broccoli. The treatment effect did not diminish with time but was conditioned by the degree of physiological degeneration of the tissue prior to treatment. Respiration quotients indicated that the rate of oxidative decarboxylation and phosphorylation was reduced in tissues treated with N6‐benzyladenine. Higher organic phosphorus content was observed in treated tissue, and 2,4‐dinitrophenol overcame the N6‐benzyladenine‐induced respiration inhibition. It is suggested that the mode of action of phytokinins on respiration and senescence inhibition was due to a conservation of adenosine triphosphate in treated tissue.
CENTRIOLES IN THE FUNGUS ALBUGO CANDIDA
Authors: Berlin Jerry D. , Bowen C. C.
Published: January 2018

Electron micrographs reveal perinuclear, paired centrioles in vegetative hyphae, sporangiophores, and developing sporangia of Albugo candida infecting radish. Centrioles elongate to form basal bodies which give rise to flagella as zoospores differentiate. The organization of flagella, basal bodies and accessory structures in this Phycomycete is strikingly similar to that in protozoa.
MORPHOGENESIS IN VERTICILLIUM: A SELF‐INDUCED, NON‐HEREDITARY VARIATION IN COLONY FORM
Authors: Brandt W. H.
Published: January 2018

Some homokaryotic isolates of Verticillium albo‐atrum (microsclerotial form) vary radically in colony appearance even when temperature, lighting, humidity and medium content are held constant. This variation is so great that it may easily be mistaken for hereditary variation. The environmental factors which control the variation are differences in shape of medium on which the colonies grow and presence or absence of other Verticillium colonies. The cause of the variation appears to be a diffusible substance which Verticillium itself produces.
ELECTRON‐MICROSCOPIC STUDIES ON CHLOROPLASTS FROM PHOSPHORUS‐DEFICIENT PLANTS
Authors: Thomson William W. , Weier T. E. , Drever H.
Published: January 2018

The deficiency of phosphorus results in a series of degradative changes in the chloroplasts. These changes can be divided into 4 overlapping phases and each phase or step reflects the severity of the deficiency. The general degenerative pattern involves first the alteration of the grana‐fretwork organization of the chloroplast membranes and the formation of a highly ordered, but more simplified, lamellar system. Subsequently, as the deficiency becomes more severe, the newly formed lamellar system breaks down. Concomitant with the membrane disorganization of the plastids, large osmiophilic globuli develop. These globuli probably form as a result of the gradual breakdown of the lipoprotein membranes with the lipid material accumulating in the globuli.
DIFFUSION RESISTANCE IN LEAVES AS RELATED TO THEIR STOMATAL ANATOMY AND MICRO‐STRUCTURE
Authors: Lee Richard , Gates David M.
Published: January 2018

Transpiration from a plant leaf depends upon the water vapor pressure gradient between the substomatal cavity and the free air beyond the leaf. Transpiration also depends inversely on the resistance of the diffusion pathway through the substomatal cavity, stomate, and surface boundary layer. The value of the diffusion resistance is derived mathematically for Zebrina pendula, Medicago sativa, and Pinus resinosa. The vapor pressure gradient depends on the leaf temperature and therefore is related to the energy budget of the leaf. The exact solution of the diffusion equation is described and limiting examples discussed. The so‐called “diameter law” is a special case which is distinctly limited in its application.
THE TERMINAL IDIOBLASTS IN MAGNOLIACEOUS LEAVES
Authors: Tucker Shirley C.
Published: January 2018

The idioblasts terminating the foliar veinlets were studied in 152 species of the following magnoliaccous genera: Alcimandra, Aromadendron, Elmerrillia, Kmeria, Liriodendron, Magnolia, Manglietia, Michelia, Paramichelia, and Talauma. In all genera, except Liriodendron, some of the veinlets in mature leaves terminate in enlarged, nonliving cells called tracheoidal elements. Only one wall‐facet (rarely 2) in such elements is differentially thickened; this wall lies adjacent to a conventional tracheary element. Ultimate cells of other veinlets in the Magnoliaceae differentiate as thick‐walled sclereids, conventional tracheids, clavate tracheids, reticulate‐walled dilated tracheids, or secretory cells. The terminal elements differentiate relatively late during leaf enlargement. In the Magnoliaceae, foliar structure is frequently characteristic at the generic level, and in some cases at the species level.
CULTURE AND DEVELOPMENT OF HILDENBRANDIA RIVULARIS FROM DENMARK AND NORTH AMERICA
Authors: Nichols H. Wayne
Published: January 2018

Hildenbrandia rivularis was collected in Denmark and the United States. The life history of this encrusting red alga is described on the basis of unialgal cultures maintained for more than 2 years. Significant changes in cellular and colonial morphology are reported. Events of the life history (i.e., reproduction by stolons, fragmentation, or gemmae; and manner of branching) which were previously in question or unknown are clarified. Mechanism(s) of certain morphogenetic phenomena remain obscure (cell wall and plastid ontogeny). These and related problems are now under investigation. Hildenbrandia should be added to the freshwater algal flora of the United States.
GENETICS OF PHYTOPATHOGENIC FUNGI. XI. A GENETIC STUDY OF AVIRULENCE DUE TO AUXOTROPHY IN PENICILLIUM EXPANSUM BY MEANS OF THE PARASEXUAL CYCLE
Authors: Beraha L. , Garber E. D.
Published: January 2018

Nine color and 35 auxotrophic mutants were tested for their virulence, using the ‘Jonathan’ variety of apple; only mutants requiring methionine were avirulent. One tested arginine‐requiring and the methionine‐requiring mutants were avirulent for the ‘Red Delicious’ variety. In vitro and in vivo, supplementation studies indicated that the avirulence was probably related to the relatively low concentration of the required amino acids at the site of inoculation. One heterocaryon and the corresponding diploid, involving 2 avirulent methionine‐requiring mutants, were virulent. Six mutant loci in 3 diploid strains could be assigned to 2 linkage groups by means of the parasexual cycle.
ON THE CHROMOSOMAL BASIS FOR CELLULAR DIFFERENTIATION
Authors: Partanen Carl R.
Published: January 2018

The relationship of somatic polyploidy to cellular differentiation is discussed. Evidences for the occurrence of endopolyploidy on the basis of auxin‐induced divisions are questioned and considered valid in the light of radioisotope studies of DNA synthesis. The non‐universality of endopolyploidy is shown by known exceptions. The occurrence of endopolyploidy in varying degrees in gametophytes of the same species of fern which are of different basic chromosome numbers shows its variability within a given morphogenetic pattern. From these evidences, and from an analysis of the separate component processes of cell multiplication, it can be concluded that polyploidy is not a necessary precursor or concomitant of cell differentiation, but rather is a type of differentiation in itself. As such, it may be one of a cumulative set of steps to yet other differentiation, but this may be incidental to the intrinsic nature and role of the nucleus.
THE SEPTAL PORES OF COPFINUS LAGOPUS IN RELATION TO NUCLEAR MIGRATION
Authors: Giesy R. M. , Day P. R.
Published: January 2018

The septal pores of homokaryotic and dikaryotic mycelia of Coprinus lagopus have the complex structure characteristic of certain Basidiomycetes. The edge of the pore is thickened and covered on either side by a dome‐shaped, perforated, membranous cap. However, in heterokaryotic mycelia in which nuclear migration was believed to be taking place, in addition to the complex pores, simple pores were also observed as well as various intermediate stages interpreted as steps in the breakdown of complex to simple pores. The simple pores may facilitate nuclear migration.
THE DEPENDENCE OF CELL DIVISION IN CHLORELLA ON TEMPERATURE AND LIGHT INTENSITY
Authors: Sorokin Constantine , Krauss Robert W.
Published: January 2018

The effects of temperature and light on cell division were studied in synchronized suspensions of the high‐temperature strain Chlorella 7–11–05. It was found that the time for incipient cell division, the progress in the process after it started, and the number of cells produced are influenced by temperature and light intensity. Within limits, cell division is generally favored by the increase in temperature. The increase in light intensity first favors cell division then, after the optimal light intensity is attained, a further increase in light intensity inhibits cell division. Observations are discussed in connection with the findings of other investigators. The limitations of cell division by temperature and light intensity are considered to be separate from the effects of these factors on growth.
COMPARATIVE MORPHOLOGY OF THE CARPEL IN THE ROSACEAE. V. POMOIDEAE: AMELANCHIER, ARONIA, MALACOMELES, MALUS, PERAPHYLLUM, PYRUS, SORBUS
Authors: Sterling Clarence
Published: January 2018

The carpels of 2 groups of pomoid genera, Amelanchier, Malacomeles, Peraphyllum and Aronia, Malus, Pyrus, and Sorbus, were analyzed morphologically. Open sutures are associated with a lesser extent of tegumentary fusion and ovular bundle–wing bundle fusion than are closed sutures. However, in the genera as a whole (and particularly in Aronia and Sorbus), the extent of sutural closure is inversely related with the amount of intercarpellary adhesion and with the fusion of carpels to the floral cup. In the Amelanchier group and in Malus and Pyrus, ovular‐ and wing‐bundle fusion is directly related with intercarpellary adhesion. Malus and Pyrus have closer structural resemblances with one another than they have with Aronia and Sorbus.
A COMPARATIVE STUDY OF THE CHEMOTAXIS OF THE MOTILE PHASES OF ALLOMYCES
Authors: Carlile M. J. , Machlis Leonard
Published: January 2018

The response of the various motile phases of Allomyces to sirenin and to casein hydrolysate was examined. Male gametes respond chemotactically to sirenin but not to casein hydrolysate. Female gametes do not respond to either of the reagents. Zygotes, mitospores and meiospores respond to casein hydrolysate but not to sirenin. The zygotes were shown to respond to the individual amino acids cysteine, proline and serine but not to the other amino acids tested. Chemotropism of germ‐tubes to casein hydrolysate was also demonstrated. The high activity of sirenin and the specificity of its action is in marked contrast to the low activity and lack of specificity of the amino acids in producing chemotactic and chemotropic responses.
MORPHOGENETIC BEHAVIOR OF TOBACCO TISSUE CULTURES AND IMPLICATION OF PLANT SENESCENCE
Authors: Murashige Toshio , Nakano Richard
Published: January 2018

Decreases in the growth and organ‐forming capacities characterized continuously cultured tobacco (Nicotiana tabacum ‘Wisconsin 38‘) callus. The root‐initiation ability was completely lost in 1 1/2‐year‐old cultures. The rate of shoot formation decreased to a low plateau in cultures that reached 1 1/2‐3 years of age since the explanting. An inverse relationship between callus growth and in vitro clonal age was also observed. Studies with callus clones started from individually isolated pith cells showed that the growth and organ‐forming potentials of somatic cells varied, signifying that cell alterations had occurred in vivo. Both totipotent and non‐totipotent cell lines were obtained. Subculturing the single‐cell lines through several passages disclosed that the morphogenetically depressed state was irreversible and instability was characteristic of the totipotent lines. In the latter, a change toward the morphogenetically repressed level was observed. These findings are discussed in relation to the phenomenon of senescence. It is suggested that an accumulation of somatic mutations, i.e., genetic alterations resulting in reductions in the morphogenetic potential of cells, is a basis underlying senescence.
TRANSLOCATION OF APPLIED GIBBERELLIN IN BEAN SEEDLINGS
Authors: Chin Ting Yun , Lockhart James A.
Published: January 2018

The direction and extent of GA transport in Pinto beans has been studied. The increase in growth rate was used as a measure of the amount of GA which reached the stem apex. The evidence showed that a similar increase in stem growth occurred whether GA was applied to the first trifoliolate leaf or to the apex of the shoot, but considerably less elongation resulted when GA was applied to primary leaves. When leaves were treated with GA after remaining in darkness for extended times, no increase in stem elongation was observed; however, growth was promoted when the plants were returned to light. The time required for a sufficient amount of GA to be translocated from the leaf to increase stem growth is less than 1 hour. The maximum growth response was found when the treated leaf was left on the plant for 3 or more hours. A study of GA movement in two‐branched plants was made. The untreated branch showed no growth response when GA was applied to the apex of the other branch, even if the dose of GA was 20 × greater than a saturating dose. Similar results were observed when GA was applied to the first trifoliolate leaf. Considerable GA moved from a mature leaf to the opposite shoot if this untreated branch had been defoliated. The pattern of GA movement to the opposite shoot was dependent on the position of the treated leaf on the shoot. It is concluded that the movement of applied GA is related to carbohydrate transport within the plant.
CHROMOSOME NUMBERS OF SOME EAST AFRICAN GRASSES
Authors: Tateoka Tuguo
Published: January 2018

Chromosome numbers of 133 collections of grasses belonging to 51 genera and 105 species are reported here for material from East Africa. These include first counts for 5 genera and 51 species. The basic chromsome number of x = 6 has been found in Sporobolus; x = 10 in Loudetia and x = 13 in Pentaschistis have been confirmed. It is pointed out that chromosomes of Eragrostis vary considerably in size. The genera Harpachne, Commelinidium, Acritochaete, Pseudechinolaena and Exotheca, which are cytologically examined for the first time, have chromosomes with the socalled “panicoid” features, viz., chromosomes with small size and x = 9 or 10.
HISTOLOGICAL STUDIES ON THE COLEOPTILE. I. TISSUE AND CELL TYPES IN THE COLEOPTILE TIP
Authors: O'Brien Terence P. , Thimann Kenneth V.
Published: January 2018

The uppermost 1‐4 mm of 25‐mm coleoptiles of oats and wheat have been studied at the optical microscope level, using newer histological methods and sections 1‐4 μ thick. The outer epidermal wall, which shows very fine wrinkling, is continuous with the thinner wall of the inner epidermis through the pore. The cells of both epidermal layers have acidophilic cytoplasm with long transvacuolar strands. Both inner and outer epidermis have stomata, those of the outer epidermis having kidney‐shaped guard cells like those of dicotyledons. The guard‐cell walls are lignified in their inner layers only and are thinly cuticularized. In the vascular bundles the sieve tubes terminate apically about 250 μ below the end of the xylem; the xylem in turn terminates about 400 μ below the extreme apex. A number of clearly undifferentiated cells, with highly basophilic cytoplasm and many mitochondria, separate the xylem elements from the inner epidermis. Towards the outer epidermis there are a few sieve elements, each of which is associated with a special cell having an elongated nucleus supported on fine cytoplasmic strands. The parenchyma of both the tip and the shaft of the coleoptile are generally interpenetrated by air‐spaces, but where they are adjacent to the inner epidermis there is heavy interposition of readily stained intercellular material, especially in Triticum. Plastids are widely distributed throughout the tissue, but their greening in light takes place preferentially towards the phloem side of the vascular bundles. The observations are discussed in reference to earlier literature and with regard to the function of the coleoptile as a protecting and guiding organ for the shoot system of the seedling.
A CYTOGENETIC STUDY OF A THREE‐PAIRED RACE OF HAPLOPAPPUS GRACILIS
Authors: Jackson R. C.
Published: January 2018

Haplopappus gracilis (Nutt.) Gray is an aneuploid species of Compositae of wide distribution in the southwestern U.S.A. and northern Mexico. Except for 2 types of supernumeraries, cytological samples from throughout its range have regularly shown 2 pairs of chromosomes. However, recent collections from a small area in south‐central Arizona had 2n = 4, 2n = 5, and 2n = 6 in the same population. The 2n = 5 plants were hybrids between the 2n = 4 and 2n = 6 types. Both natural and artificial F1 hybrids show preferential disjunction from a trivalent and produce genetically balanced gametes with n = 2 and n = 3. In backcrosses of the F1 to n = 2 plants, a 1:1 ratio of 2n = 4 and 2n = 5 plants was obtained. The possible mechanisms for the evolution of n = 2 from n = 3 and vice versa are discussed.
INDUCTION OF APOGAMY IN MEGAGAMETOPHYTES OF ZAMIA INTEGRIFOLIA
Authors: Norstog Knut
Published: January 2018

Ovules of Zamia integrifolia Ait. were dissected and megagametophytes and embryos excised and cultured. Induction of apogamous, haploid roots and leaves by auxin and kinetin, in combination with glutamine, asparagine and alanine, was observed. The organs resembled their normal diploid counterparts. 2,4‐D at 1 ppm was more effective than 1 ppm IAA, but less effective than 5 ppm IAA. The highest percentage of apogamy was 59% after 5 months of culture. In several cultures embryoids were formed both by diploid excised embryos and by haploid megagametophtyes.
A HISTOCHEMICAL AND ULTRASTRUCTURAL STUDY OF YUCCA SEED PROTEINS
Authors: Horner Harry T. , Arnott Howard J.
Published: January 2018

Embryos and nutritive tissues in ungerminated Yucca seeds of 4 species contain many spherical bodies which stain positively for proteins. Two distinct morphological types were observed at both the light and electron microscope levels. A meshwork‐type consists of electron‐dense and electron‐transparent regions in which are embedded slightly birefringent inclusions. The second type, named the core‐type, consists of a core surrounded by a matrix in which the inclusions are embedded. A single unit membrane surrounds each protein body. Both types are present in the embryo while only the core‐type protein body appears in the surrounding nutritive tissue (perisperm). All regions in each of the two protein body types, except the inclusions, stain histochemically for proteins. Seeds were planted at 2‐day intervals and allowed to germinate through 14 days. As germination commences (day 0) protein bodies in the embryo begin to break down. By day 4 the bodies are depleted in embryos of 3 of the 4 species. About day 4, protein bodies in perisperm surrounding the embryo begin to break down and this process continues outward to the seed coat until day 14 when all seed proteins have disappeared. During germination the protein bodies in the embryo and perisperm of 3 species coalesce and then undergo breakdown. In a fourth species, there is no appreciable increase in size of the bodies, but an erosion of the periphery and possibly internally as well takes place, followed by ultimate dissolution.
A CHEMOTAXONOMIC STUDY OF LEMNACEAE
Authors: McClure Jerry W. , Alston Ralph E.
Published: January 2018

One hundred eighty‐six clones of Lemnaceae, representing world‐wide collections of 22 taxa, were grown in axenic cultures reproduced by clonal subcultures. Following morphological examinations under a range of culture conditions, a “key” clone was selected to represent each taxon. These key clones were completely representative of the qualitative flavonoid chemistry of the taxa as determined from a number of clones. With the exceptions of Spirodela polyrhiza and S. biperforala which produce identical flavonoids, the flavonoid associations of each species of Lemnaceae were unique in the family. Through paper chromatographic comparisons of purified compounds, plus visible and ultraviolet absorption spectroscopy of isolated individual flavonoids, a total of 47 different compounds was described. These substances included: glycosides of anthocyanidins (cyanidin and petunidin); glycosides of flavonols (kaempferol and quercetin); glycosides of flavones (apigenin and luteolin); and several glycoflavones (C‐glycosyl‐flavones). When grown under equivalent controlled conditions of culture, infraspecific variation in the qualitative production of these 47 flavonoids was detected in only one flavone glycoside of the species Lemna perpusilla. The reliability of the flavonoid patterns under various conditions of culture was investigated. Under 62 different regimes S. oligorhiza and S. polyrhiza showed only minor variations in their flavonoid glycosides. Studies of other taxa supported this generalization. Under controlled conditions, morphological intergradation obscured identification of many collections. Each could be conclusively identified by its flavonoid chemistry.
VARIATIONS OF MORPHOGENETIC BEHAVIOR IN PLANT TISSUE CULTURES II. PETROSELINUM HORTENSE
Authors: Vasil I. K. , Hildebrandt A. C.
Published: January 2018

Callus tissue derived several years ago from leaf petiole of parsley (Petroselinum hortense Hoffm., Umbelliferae) was grown on synthetic media. The callus is highly friable and easily dissociates into single cells and cell groups. In several nutrient media many nodular structures with negatively geotropic roots were formed. IAA inhibited root formation. In Murashige and Skoog's synthetic nutrient medium with 15–20 mg/liter adenine sulphate, embryoids were formed that simulated stages in the development of a zygotic embryo and its germination, and finally they developed into normal plantlets with shoots and roots. These embryoids arose after 10–12 weeks’ incubation from the meristematic middle cortex of roots already differentiated in the medium. Freshly isolated callus and coconut milk‐containing nutrient media were not necessary to have embryoid and plantlet formation in tissue cultures.
ECOTYPIC DIFFERENTIATION WITHIN FOUR NORTH AMERICAN PRAIRIE GRASSES. III. CHROMATOGRAPHIC VARIATION
Authors: Bragg Louis H. , McMillan Calvin
Published: January 2018

Four widespread grasses, Andropogon scoparius Michx., A. gerardi Vitman, Sorghastrum nutans (Nash) Hitchc. and Panicum virgatum L., have been studied behaviorally and morphologically. In the present comparison characteristic flavonoid patterns were shown whereby the four grass taxa can be separated at the generic and specific level. The greatest similarity was shown by the two Andropogon species. Panicum was most dissimilar. Although intrapopulational and interpopulational variation was demonstrated within each of the four taxa, both in transplanted material and in native plants of the original transplant site, there was no decisive correlation of biochemical variation with geographic origin, vegetative characteristics or maturity pattern. Early‐flowering clones with short flowering culms and glabrous leaves, originating in northern and western areas, were essentially similar biochemically to later‐flowering clones with tall flowering culms and extremely pubescent leaves, originating in southeastern areas. Blade samples collected in late fall, 1963, and in early spring, 1964, from the same transplanted clones were similar in flavonoid pattern. In P. virgatum. individual clonal patterns were characteristic of ramets grown under various day‐length‐thermoperiod conditions. Although biochemical markers for ecotypes would be useful êological tools, partially replacing their cultivation in transplant gardens, geographically correlated patterns were not revealed in this study. However, this study supports the present systematic position of the various morphologically and behaviorally diverse populations within the four taxa.
ARTIFICIAL INTERSPECIFIC HYBRIDIZATION IN RUELLIA (ACANTHACEAE)
Authors: Long Robert W.
Published: January 2018

Observations were made on the morphology, seed fertility, pollen viability and meiotic configurations of 22 different interspecific hybrids of 12 North American taxa representative of 3 sections of Ruellia. The hybrids were classified as (1) fully vigorous and fertile; (2) vigorous but with reduced fertility; (3) reduced vigor and fertility; (4) weak and sterile. Hybrids showed meiotic irregularities in microsporogenesis: univalents, chains, precocious separation of bivalents, nondisjunction, and micronuclei were commonly observed. Interspecific pollinations within sect. Dipteracanthus resulted in fertile or partially sterile F1 hybrids. Intersectional crosses produced partially or completely sterile hybrids or failed. Assuming that crossability is correlated with degree of evolutionary relationship, the parental species are interpreted in genecological terms to be grouped in polytypic ecospecies. Hybridization experiments doubtless would be of value in clarifying relationships in tropical and subtropical species of Ruellia.
ARTEMISIA PATTERSONII: A 14‐CHROMOSOME SPECIES OF ALPINE SAGE
Authors: Wiens Delbert , Richter Judith A.
Published: January 2018

Artemisia pattersonii and A. scopulorum are closely related species of alpine sages endemic to the Rocky Mountains. The species are compared morphologically, ecologically and especially karyologically. Artemisia pattersonii has a chromosome number of n = 7, 2n = 14, which is presently unique in the genus. The karyotype of A. pattersonii is contrasted to its nearest putative relative, A. scopulorum (n = 9, 2n = 18), in order to determine if A. pattersonii might be derived from A. scopulorum through aneuploid reduction; however, the cytological evidence is inconclusive. Possibly these two species are not as closely related as believed previous'y and the nearest relatives of each might occur in north‐central Asia.
SPORE DEVELOPMENT IN THE LIVERWORT RICCARDIA PINGUIS
Authors: Horner Harry T. , Lersten Nels R. , Bowen C. C.
Published: January 2018

The ontogeny of spores of the liverwort Riccardia pinguis was studied at the light and electron microscope levels. Three stages of development were arbitrarily defined: spore mother cell (SMC); early tetrad with nonpigmented and unsculptured walls; and mature tetrad with pigmented and sculptured spore walls. The SMC is quadrilobed with a two‐layered SMC wall, containing a central nucleus, many chloroplasts, spherosomes, and other organelles. During and following meiosis cell plates form from coalescing Golgi vesicles. These plates by continued coalescence eventually form a septum, completing the tetrad. This septum comprises middle lamella and primexine; within the latter the exine forms. By continued addition of vesicle contents to the septum and dorsal surfaces of the tetrad, the exine (sexine and nexine) and intine layers of the spore wall are laid down. The contents of the vesicles change successively during wall formation, corresponding to the different wall layers being formed. It is concluded that wall formation is under the exclusive control of the spore protoplast, and that the pattern of the mature exine is determined by the primexine. Rearrangement of organelles and other cellular components during sporogenesis is described.
THE DIFFERENTIATION OF PIGMENTATION IN FLOWER PARTS. II. CHANGES IN PIGMENTS DURING DEVELOPMENT OF BUDS IN IMPATIENS BALSAMINA GENOTYPE IIHHPrPr
Authors: Hagen Charles W.
Published: January 2018

Developing buds of the red‐flowered genotype, IIHHPrPr, of Impatiens balsamina exhibit a progressive elaboration of the anthocyanin pigments. Four developmental stages can be recognized; the first lacks anthocyanins although other flavonoid compounds are present; in the second, pelargonidin‐3‐monoglucoside is dominant; the third is marked by multiple intermediates which may represent alternative pathways to the final products; the fourth stage is characterized by reduction in variety of flavonoid compounds and establishment of an acylated pelargonidin‐3,5‐diglucoside as the principal anthocyanin. The operating biosynthetic sequence remains obscure because possible intermediate compounds appear which are not required in single, direct pathways. The relation between observed changes and the developmental regulation of biosynthetic pathways is considered.
THE TENDRIL OF PARTHENOCISSUS INSERTA: DETERMINATION AND DEVELOPMENT
Authors: Millington W. F.
Published: January 2018

Tendrils on long shoots of Parthenocissus inserta occur in a regular pattern opposite the alternate distichous leaves at two successive nodes of each three nodes. Ontogenetic study shows that the tendril is initiated at the flank of the shoot apex during the second plastochron in an essentially axillary position. It is carried upward with growth of the internode above the axillant leaf and ultimately is situated opposite the next younger leaf. In a rhythmic pattern a different group of appendages is produced by the shoot apex at each node in the sequence of three. In acropetal order these are: at the tendrilless node the leaf subtends an axillary bud complex which in turn subtends a tendril; the leaf at the lower tendril‐bearing node directly subtends a tendril, and the leaf at the upper tendril‐bearing node subtends an axillary bud. Tendril primordia were not induced to develop as foliaceous shoots when cultured in vitro or in decapitation experiments, indicating that the meristem which becomes a tendril is determined early in its inception. Although built on a shoot pattern, the tendril is regarded as an organ sui generis with a possible relationship to the inflorescence. The morphological nature of the tendril is discussed in the light of theories postulated in the literature.
STUDIES ON STRIGA SENEGALENSIS II. TRANSLOCATION OF C14‐LABELLED PHOTOSYNTHATE, UREA‐C14 AND SULPHUR‐35 BETWEEN HOST AND PARASITE
Authors: Okonkwo S. N. C.
Published: January 2018

Using a tracer technique, the nutritional relationship between Striga senegalensis and its host (Sorghum vulgare) has been studied. Preliminary trials with aqueous eosin dye indicated that a mechanism exists for the passage of watery solutions from host to parasite but not vice versa. Use of tracers like C14O2, urea‐C14 and sulphur‐35 confirmed that minerals as well as organic compounds are translocated from host to parasite. However, when these tracers were applied to the parasites, translocation of labelled products into the host was insignificant. When C14O2 was used to label the photosynthate in Sorghum, the bulk of activity appeared in sucrose, glucose and fructose, part of which was presumably obtained by the parasite. The photosynthetic ability of the green tissues of Striga was confirmed. Thus the damaging effect of Striga on the host appears to be due to removal of considerable quantities of water, minerals and organic compounds from the latter. The pattern of translocation of photosynthates and minerals from host to parasite suggests a possible application of selective, systemic weed‐killers by aerial spray on the host leaves for control of the parasite.
EFFECTS OF GROWTH SUBSTANCES ON EXCISED FLORAL BUDS OF AQUILEGIA
Authors: Tepfer Sanford S. , Karpoff Arnold J. , Greyson Richard I.
Published: January 2018

Buds at various stages of development were grown for 3 weeks on solid media containing coconut milk, minerals, vitamins, sucrose, and varying quantities of gibberellic acid, indoleacetic acid, and kinetin. The best average growth was obtained on media containing GA at 2.0 mg/liter, IAA at 1.0 mg/liter, and kinetin at 0.05 mg/liter. When results were compared for buds explanted at very young stages and at older stages, however, young buds attained better average growth on media with 0.5 mg/liter of IAA. Evidence is presented for interaction between IAA and kinetin. With buds explanted at young stages, as the kinetin concentration was increased, optimum growth occurred on media with increasing concentrations of IAA. With older buds, on the other hand, as the kinetin concentration was increased, optimum growth occurred on decreasing concentrations of IAA. Bud growth was compared on media with growth substances sterilized by autoclaving with growth on similar media with these substances filter‐sterilized. Better growth occurred generally on the media with filter‐sterilized ingredients. A long‐range objective of this research is the development of a system that would make possible quantitative measurements of floral development in vitro.
BIOSYSTEMATIC STUDIES IN THE BOUTELOUA CURTIPENDULA COMPLEX. V. MEGASPOROGENESIS AND EMBRYO SAC DEVELOPMENT
Authors: Mohamed Aly H. , Gould Frank W.
Published: January 2018

Megasporogenesis and embryo sac development in the sexually reproducing taxa Bouteloua warnockii (2n = 22), B. media (2n = 20), B. uniflora Vasey var. uniflora (2n = 20), B. uniflora var. coahuilensis Gould and Kapadia (2n = 20), and B. curtipendula var. curlipendula (2n = 40) all were found to be of the Adoxa type, in which all 4 megaspores persist and divide once to form an 8‐nucleate embryo sac. On the other hand, evidence indicated that plants of B. curtipendula var. caespitosa with high ancuploid chromosome numbers reproduce by pseudogamous fertilization of an aposporous embryo sac. In this taxon the megaspore mother cell did not go beyond the first anaphase of meiosis and the functional embryo sac developed from a nucellar cell. Although the 8‐nucleate embryo sac was typical, a 3‐nucleate embryo sac was observed to develop in some cases.
NUCLEAR DIVISION IN THE DEVELOPING PYCNOSPORES OF MACROPHOMINA PHASEOLI
Authors: Knox‐Davies P. S.
Published: January 2018

Nuclear behavior was studied in Giemsa‐stained pycnidial material of Macrophomina phaseoli. The young pycnospore was at first uninucleate but repeated nuclear division occurred as it enlarged, and the mature spore was always multinucleate. The developing spore, therefore, provided a favorable site for observing mitosis. Noteworthy features were: (1) a metaphase characterized by a loss in stainability of the nucleolus and by the appearance of centrioles, spindle fibers and countable chromosomes; (2) a short early anaphase; (3) a long late anaphase with a broad band of interzonal fibers separating the daughter nuclei; (4) the occurrence of irregularities such as aneuploidy, chromosome bridge formation and chromosome lagging. The basic chromosome number was six. Following a study of Giemsa‐stained cellophane cultures of the fungus it was concluded that the method of nuclear division in the vegetative hyphae is similar to that observed in the developing spores. Some comparisons are made with observations on nuclear division in the vegetative hyphae of other fungi.
INHIBITION OF MITOSIS IN PISUM ROOT MERISTEMS BY CONTINUOUS GAMMA RADIATION: THE INFLUENCE OF TEMPERATURE ON THE SYNTHESIS OF DNA, RNA AND PROTEIN DURING INHIBITION
Authors: Hof Jack Van't
Published: January 2018

Tritiated precursors of DNA, RNA and protein were used to measure synthesis at 10 and 20C in root meristem cells of Pisum after they were mitotically arrested by continuous irradiation with gamma rays. The experiments were designed to determine if the arrested cells accumulated in a certain part of interphase, to determine the effect on DNA, RNA and protein synthesis, to find out if the effects were temperature dependent, and finally to reveal possible relationships between growth inhibition and altered synthesis. The results showed that the incorporation of DNA and RNA precursors was impaired by irradiation and that decreased temperature further increased radiation impairment of DNA synthesis. Protein synthesis on the other hand was not impaired by irradiation at either temperature. Irradiation at 20C reduced the number of DNA‐synthesizing cells; at 10C this number was reduced to near zero. Although irradiated cells synthesizing RNA showed a reduction in grain counts when compared to the controls, they still retained the ability to incorporate tritiated uridine at 10C. It was hypothesized that the combination of reduced DNA and RNA synthesis and unaffected protein synthesis resulted in precocious maturation of the arrested meristem cells. Growth which occurred in the absence of cell division was attributed to meristematic cells which precociously matured and cells which were in the region of elongation.
CINE‐PHOTOMICROGRAPHY OF LOW TEMPERATURE EFFECTS ON CYTOPLASMIC STREAMING, NUCLEOLAR ACTIVITY AND MITOSIS IN SINGLE TOBACCO CELLS IN MICROCULTURE
Authors: Das T. M. , Hildebrandt A. C. , Riker A. J.
Published: January 2018

Living, unstained, single tobacco (Nicoliana tabacum × N. glutinosa) cells (clone H‐196) were grown in microcultures in liquid medium containing sucrose, mineral salts, coconut milk and 2,4‐dichlorophenoxyaeetic acid. Time‐lapse motion pictures were taken through interference and phase microscopes. The movement of cytoplasm and cell organelles gradually slowed and ultimately completely ceased as the cell was cooled by dry ice. The cessation of the movement of cell organelles took place between 5 and –7C. The typical cytoplasmic morphology was lost as the movement slowed. The cytoplasmic strands thinned out and numerous small vacuoles formed. During rewarming of the cell to room temperature, the vacuoles were replaced by numerous small globular masses of cytoplasm which reorganized into cytoplasmic strands. The normal movement of cytoplasmic strands and cell organelles was resumed. A number of small nucleolar vacuoles at room temperature gradually expanded and coaleseed to form a large central vacuole which underwent further expansion and then contracted rapidly. Four different concentric zones were visible across the nucleolar region. A white, highly reflecting, glossy substance appeared on the surface of the expanding vacuole. The position of the nucleus during contraction and expansion was never stationary. Some nucleolar vacuoles remained open for an indefinite period of time when the cell was cooled to 5C. No change was noticed during cooling, but during rewarming to room temperature, the nucleolar vacuole was partially closed. The pumping action of the nucleolar vacuole suggested important exchanges of metabolites between the nucleolus and the cytoplasm. A single cell of tobacco did not divide at –10C, but mitosis proceeded upon cooling the cell to – 12–15C for a brief period. Different phases of mitosis, specifically formation of the cell plate, cell wall, and separation of nuclei, were delayed by low temperature treatment.
ELECTRON MICROSCOPY OF CYTOPLASMIC INCLUSIONS IN CELLS INFECTED WITH ROD‐SHAPED VIRUSES
Authors: Edwardson John R.
Published: January 2018

Thin sections of leaf tissue infected with 12 rod‐shaped viruses varying from 180 mμ to 750 mμ in length were examined in the electron microscope. Neither intranuclear nor cytoplasmic inclusions occurred in healthy tissue. Intranuclear inclusions were observed only in material infected with tobacco etch virus. Several types of cytoplasmic inclusions were induced by the group of viruses varying in length from 730 mμ to 750 mμ; however, only one type of inclusion was common to all seven viruses of this group. It is proposed that this inclusion, which appears as a pin‐wheel in cross section and as a bundle in longitudinal section, is diagnostic for infection with viruses of the potato Y group, i.e., rod‐shaped viruses whose lengths vary from 730 mμ to 750 mμ.
THE DISTRIBUTION OF LATERAL ROOTS IN MUSA ACUMINATA ‘GROS MICHEL’
Authors: Riopel James L.
Published: January 2018

Studies of the distribution of lateral roots in banana show that they are initiated along the pericycle in a non‐random, dispersed pattern. This is demonstrated by the failure of laterals to conform to a Poisson distribution and by a nearest neighbor analysis in which the mean distance for nearest laterals is found to be consistently greater than the expected distance based on random association. The slight degree of dispersion indicates that the protoxylem positions adjacent either radially or longitudinally to existing laterals are not as favorable as the remaining protoxylem positions for the development of the next acropetal lateral. Results which show a greater longitudinal distance between successive laterals that form in the same segment of the root, and a tendency for each lateral to form at an angle greater than 30° from the previous one offer further evidence that established lateral primordia may influence the site where the next lateral will arise. It is concluded that the regulation of the positions for lateral roots in banana is dependent both on the presence of special conditions in cells of the pericycle opposite the protoxylem and also on the location of the previous lateral.
AN ENDOGENOUS RHYTHM IN THE HILL‐REACTION ACTIVITY OF TOMATO CHLOROPLASTS
Authors: Hoffman Frank M. , Miller John H.
Published: January 2018

When tomato plants are grown under alternating light‐dark conditions there is a diurnal rhythm in the dichlorophenol indophenol–Hill‐reaction activity of chloroplasts isolated from the plants. The activity rises to a peak about 4 hr after the light period begins and then falls, and a second peak occurs during the dark period. When plants grown in alternating light‐dark are placed under conditions either of continuous darkness and constant temperature or of continuous low‐intensity light and constant temperature, the rhythm persists with a period of approximately 12 hr. This rhythm occurs only in plants up to about 4 weeks of age, and no rhythm in Hill‐reaction activity is found in chloroplasts isolated from plants grown under continuous light. However, when continuous‐light plants are placed in continuous darkness a rhythm is initiated which seems to be quite similar to the rhythm observed with chloroplasts from alternating light‐dark plants. Fluctuating temperatures do not replace light‐dark alternation in initiating the rhythm.
THE NUCLEI AND PARASEXUALITY IN PHYMATOTRICHUM OMNIVORUM
Authors: Hosford Robert M. , Gries George A.
Published: January 2018

An active parasexual cycle in Phymatotrichum omnivorum is indicated by the presence of haploid, diploid, aneuploid and other rare polyploid nuclei in the multinucleate mycelial cells, migration of nuclei through the central pore of the transverse hyphal septum, anastomosis of the hyphae, and strain differences. The haploid nuclei divide by mitosis, and the haploid chromosome number is four. Diffuse nuclei, each containing many very small dark‐staining bodies, are also common in the mycelium. As the “spore mat” matures vesicles are extruded through the walls of its conidiophores and hyphae. One, two, or rarely three nuclei migrate into each enlarging vesicle to form conidia. Almost all the nuclei migrate progressively from the hyphae into the conidiophores and then into the conidia. The nuclei of the ungerminated strands and sclerotia are dark‐staining spheres and ovals, although a few are similar to those mycelial nuclei which have evident chromosomes. As the sclerotia germinate, nuclei of the latter appearance become common in the pseudoparenchymatous cells, align in a row, and apparently reduce in size. Hyphae form in the pseudoparenchymatous cells and contain nuclei similar to those of the vegetative mycelium. The hyphae of the Sclerotium form a mycelium. The nuclei of the various stages of the life cycle were stained by one to three procedures (Feulgen, aceto‐orcein, and haematoxylin). Treatment of some sections of mycelium with deoxyribonuclease prior to staining by Feulgen technique resulted in the absence of staining or observable nuclei, while similar treatment with ribonuclease had no effect on the appearance of the nuclei.