bluuebunny/crossref_metadata_2025 huggingface dataset:
EFFECTS OF 2,3,5‐TRIIODOBENZOIC ACID ON THE STRUCTURE OF SOYBEAN LEAVES
Authors: Krause Bernard F. , Boke Norman H.
Published: January 2018

The effects of 2,3,5‐triiodobenzoic acid (TIBA) on soybean leaves (Glycine max. [L.] Merrill ‘Harosoy‘) include thickening with intensification of color and some raised intercostal regions, giving a wrinkled appearance. These effects are not restricted to early stages of leaf development but are pronounced during and after unfolding of the leaf. Proliferation of tracheary elements, increased procambial activity, and hypertrophy of bundle sheath extension cells occurred in the leaflet midvein of the youngest expanded leaf treated with 50 ppm or 100 ppm of TIBA. The youngest treated leaves exhibited differential growth rates and expansion within the palisade and spongy layers. Hypertrophy of spongy cells in these leaves occurred independently or simultaneously with elongation of the upper and lower palisade layers. The palisade and spongy tissues had undergone cell division and expansion at a greater pace than the epidermal layers. This, along with hypertrophy in the bundle sheath extension cells, would explain the wrinkled appearance of the lamina. The treated leaf became thicker than the control as a result of the increased number of cells in the spongy layer and elongation in the palisade layer. The observed aberrations in leaf structure suggest that TIBA interferes with some auxin‐translocating system within the plant.
DEVELOPMENT, STRUCTURE AND FUNCTION OF SECRETORY TRICHOMES IN PSYCHOTRIA BACTERIOPHILA (RUBIACEAE)
Authors: Horner Harry T. , Lersten Nels R.
Published: January 2018

Mucilage‐secreting dendroid trichomes develop from the adaxial epidermis of young stipules surrounding the shoot apex. Each trichome consists of a multicellular stalk from which radiate many branch cells. The trichome has no cuticle and the branch cell walls distally are loose cellulosic frameworks. Dictyosomes produce vesicles whose products are secreted through the plasma‐lemma and cell wall. Enlarged portions of the ER are frequently associated with dictyosomes and may be part of the system for synthesis and transport of secretion products. Bacteria, which later occur in leaf nodules, are present in the mucilage surrounding trichomes and young leaves. The latter develop stomata through which the bacteria enter. As stipules and leaves grow out of the apical region, the secretory trichomes degenerate and are replaced by non‐secretory ones.
ONTOGENY OF THE TENDRIL IN VITIS VINIFERA
Authors: Tucker Shirley C. , Hoefert Lynn L.
Published: January 2018

The apical meristem of the grape tendril possesses several remarkable features: bilateral symmetry, a minimal number of appendages, and an exceedingly brief period of apical meristem activity. The cellular configuration of the apex changes from tunica‐corpus to zonate, as rudimentary leaves and branch‐tendril apices are initiated. Eventually the apical meristem of the tendril itself ceases meristematic activity and differentiates as a large hydathode. Typical spongy epithem tissue, copious xylary tissue, and water‐pores in the epidermis characterize the hydathode. Numerous vascular strands traverse the length of the tendril and terminate in enlarged tracheary elements adjacent to the epithem. Cessation of meristematic activity follows lowered mitotic rate in the summit and accelerated differentiation below and within the meristem.
MORPHOGENETIC ASPECTS OF A LEAFLESS MUTANT IN TOMATO I. GENERAL PATTERNS IN DEVELOPMENT
Authors: Caruso John L.
Published: January 2018

The embryo of the reduced form of the lanceolate mutant in tomato fails to undergo the heart‐shaped stage of development. Cells in the shoot apical region of this leafless mutant lose their meristematic character and develop into mature parenchyma during embryogenesis. This early loss of meristem tissue leads to the determinate growth which is evident in the seedling. In contrast to normal, starch grains are visible with the light microscope in cells of the shoot tip of the mutant hypocotyl from early embryogeny up to and including the seedling stage, and protein bodies are abundant in the same tissue of fully developed mutant embryos. The shoot apical region in homozygous mutant embryos with cotyledons or cotyledon‐like structures exhibits some cytochemical and morphological similarity with the normal shoot apex. Morphological variation in these forms appears to be in a continuous pattern. The extent of their development and consequent longevity is related to possible differences in rates of cell expansion and variation in environmental factors during the early stages of embryogenesis.
LOSS OF GIBBERELLINS BY LEACHING FROM STEMS AND FOLIAGE OF CHRYSANTHEMUM MORIFOLIUM ‘PRINCESS ANNE’
Authors: Kozel P. C. , Tukey H. B.
Published: January 2018

Structurally complex metabolites such as carbohydrates, organic acids, and amino acids are leached from plants by rain and dew. Applied GA3 (1 mg/ml) absorbed by a 5‐cm stem segment of Chrysanthemum morifolium and translocated to a single attached leaf was leached from the leaf with distilled water. To detect endogenous gibberellins in plant leachates, Chrysanthemum morifolium ‘Princess Anne’ plants were leached under 8‐hr and 18‐hr photoperiods. The leachates were collected and extracted at pH 8.2 with methylene chloride to*** remove inhibitors and at pH 3.0 to remove gibberellins. The extract containing the gibberellins was fractionated on a silica gel column by an eluting phase of 0 to 100% ethyl acetate‐n‐hexane solutions. The presence of gibberellin‐like substances was confirmed by their elution pattern from the silica gel column and by two bioassays, the lettuce hypocotyl and the Rumex bioassays. The results suggest that substances similar to GA1–3 and GA5 were leached from plants growing under an 18‐hr photoperiod. The leachate from plants growing under an 8‐hr photoperiod contained gibberellin‐like substances similar to GA1–3 and GA6.
A NEW NEMATODE‐DESTROYING HARPOSPORIUM
Authors: Drechsler Charles
Published: January 2018

A mucedinaceous parasite, observed destroying eelworms in a maize‐meal‐agar plate culture prepared by the addition of some forest duff from western Maryland, is newly described as Harposporium cycloides. Its conidia differ from the crescentic or semicircular conidia of the familiar H. anguillulae in that their curvature extends to an angular magnitude of approximately a full circle. Its chlamydospores, though sometimes found united in pairs, are much more often produced singly than are the chlamydospores of H. anguillulae.
THE EFFECT OF 3‐AMINO‐1,2,4‐TRIAZOLE ON THE ULTRASTRUCTURE OF PLASTIDS OF TRITICUM VULGARE SEEDLINGS
Authors: Bartels Paul G. , Weier T. E.
Published: January 2018

The application of sublethal doses of 3‐amino‐1,2,4‐triazole (AT) to germinating, light‐grown wheat grains causes chlorosis of the resulting leaves. An ultrastructural examination of the leaf tissue reveals that the plastids lack normal grana‐fret membrane systems and chloroplast ribosomes. A few disorganized membranes are always present in these chloroplasts. However, AT‐treated, dark‐grown seedlings contain proplastids with non‐crystalline prolamellar bodies and ribosomes. When these etiolated, treated plants are exposed to 600 ft‐c light for various periods of time, the proplastids fail to develop into normal, grana‐containing chloroplasts.
CYTOPLASMIC ORGANIZATION AND RHYTHMIC STREAMING IN GROWING BLADES OF CAULERPA PROLIFERA
Authors: Dawes Clinton J. , Barilotti D. Craig
Published: January 2018

Light‐ and electron‐microscopic studies of the growing blades and their meristematic tips in Caulerpa prolifera have been correlated with time‐lapse photographic studies. The growing blade may be divided into three zones based on the level of maturation. A “meristemplasm” is present at the tip of the growing blade and at sites of wounding. The cytoplasm of these growing regions has an abundant endoplasmic reticulum, Golgi bodies, amyloplasts, and nuclei, but lacks chloroplasts and a central vacuole. An intermediate zone lies between the white meristemplasm and the green, mature basal zone. The basal zone contains a parietal cytoplasm with organelles typical of the Chlorophyta and a dominant central vacuole. Two distinct systems of cytoplasmic streams occur in the basal zone and both contain packets of microtubules orientated parallel to the axis of the streams. As the blade matures and growth ceases, the dominant central vacuole forms up to the tip. In developing blades the tips become white in the absence of light as a result of basipetal movement of the chloroplasts. In plants kept on a 12‐hr L: 12‐hr D cycle, blade growth and chloroplast migration at the blade tip are rhythmic, and the peak occurs about 2‐4 hr after initiation of the dark phase. Experiments are reported using continuous light or darkness after three 24‐hr periods of 12‐hr L: 12‐hr D phasing.
DIURNAL PATTERNS OF POLLEN EMISSION IN AMBROSIA, PHLEUM, ZEA, AND RICINUS
Authors: Ogden Eugene C. , Hayes Janet V. , Raynor and Gilbert S.
Published: January 2018

Hourly measurements of pollen emission were made from cultivated plots of Ambrosia, Phleum, Zea, and Ricinus over the course of several pollination seasons as part of a study of pollen dispersion from known sources. A characteristic diurnal emission pattern was found for each genus. Ambrosia pollen emission normally begins an hour or two after sunrise, peaks a few hours later, and decreases through the afternoon. Phleum starts during the night, peaks about 2 hr after sunrise, and declines slowly through the day. Zea emits pollen fairly uniformly during the period from 2 hr after sunrise to about sunset, while Ricinus pollen was collected from several hours after sunrise to late afternoon with a peak in mid‐morning. Daily patterns often vary from the seasonal mean in response to changing meteorological conditions.
ACTIVITY OF MARGINAL AND PLATE MERISTEMS DURING LEAF DEVELOPMENT OF XANTHIUM PENNSYLVANICUM
Authors: Maksymowych Roman , Wochok Zachary S.
Published: January 2018

The mitotic and biosynthetic activities of the marginal and plate meristems were studied during the entire course of leaf development of Xanthium pennsylvanicum. In contrast to statements in the literature, marginal meristem activity is long in duration, as assayed by the mitotic counts and H3‐thymidine incorporation. This me istem is active 23 days. The plate meristem is active for an additional 3 days after cessation of cell division in the marginal meristem, but the total duration of its mitotic activity is also approximately 23 days. Numerous periclinal cell divisions of the plate meristem form additional cell layers and contribute to the growth of the lamina in thickness. Incorporation of H3‐thymidine increased during the course of leaf development. Cells between plastochronic ages 0 and 2.0 incorporated more of the radioisotopic precursor than those of younger leaf primordia. The uptake and incorporation of H3‐thymidine into nuclear DNA was more sluggish during the early stages of development than in the more expanded leaves. No DNA synthesis was demonstrated after cessation of cell division in the leaf lamina. Metabolic or endomitotic DNA synthesis after leaf plastochron index (LPI) 3.0 seems improbable. No significant differences in the incorporation of H3‐thymidine could be demonstrated between the marginal and plate meristems. This would indicate no distinct biosynthetic differences between the two meristems. The definitions of the marginal and plate meristems of Xanthium leaves were formulated in view of the above findings.
CYTOLOGY AND REPRODUCTIVE CHARACTERISTICS IN PENNISETUM SETACEUM
Authors: Simpson C. E. , Bashaw E. C.
Published: January 2018

A green ecotype of fountaingrass, Pennisetum setaceum (Forsk.) Chiov., was found to be triploid (3x = 27) with 9 II + 9 I at metaphase I. Meiotic behavior of the bivalents was normal, but the univalents lagged and divided precociously at anaphase I. The univalent halves lagged at anaphase II and were distributed at random. Micronuclei were common, and stainable pollen was approximately 40%. The green type produced four progeny with 54 chromosomes. A purple strain of P. setaceum was found to be hexaploid (6x = 54) with varying chromosomal associations. Meiotic behavior was highly irregular and stainable pollen was almost zero. Megasporogenesis was initiated in both types, but the megaspores degenerated and nucellar and integument cells developed into four‐nucleate, aposporous embryo sacs. Following self‐pollination, the green type set approximately 10% seed and the purple type set 0.05% seed. Purple fountaingrass set as high as 18% seed following the application of pollen from Pennisetum ciliare (L.) Link (4x = 36), exemplifying a rare form of pseudogamy between two species. Improvement of P. setaceum through a standard breeding program appears unlikely.
GENETIC AND ENVIRONMENTAL CONTROL OF GLYCOLIC ACID OXIDASE ACTIVITY IN ECOTYPIC POPULATIONS OF TYPHA LATIFOLIA
Authors: McNaughton S. J.
Published: January 2018

Glycolic acid oxidase activity at 25 C in leaf homogenates of ecotypic populations of Typha latifolia varied according to native climate of the population and current growing conditions. Activity of plants grown under warm/short day conditions was positively correlated with maximum summer temperature at the site of population origin. Activity of plants grown under cool/ long day conditions was negatively correlated with length of growing season at the site of origin. Populations from sites characterized by a long growing season are much less susceptible to environmental regulation of enzymic level than populations originating in short growing season sites. Enzyme activity is not a secondary reflection of differentiation at the level of chlorophyll or cofactor concentration. Enzymic differences between ecotypic populations reflect differences in control systems at the level of protein synthesis and genetic structure.
CELL POPULATION KINETICS IN CALLUS TISSUES OF CULTURED PEA ROOT SEGMENTS
Authors: Hof J. Van't , McMillan B.
Published: January 2018

Two callus tissues, one composed of diploid and the other of a mixture of diploid and polyploid cells, were derived by culturing 1‐mm pea root segments; the mixed callus tissues were obtained by incorporation of kinetin in the culture medium. The callus tissues were used to determine (a) if cell proliferation was altered with the change in cell constituents of a callus; (b) the rate at which polyploid cells increased after kinetin stimulation; (c) the nature of the mitotic cycle in the diploid and mixed polyploid callus tissues; and (d) if the mitotic cycle changed as the tissue aged. Histological, cytological, radioisotope, and radioautographic analyses were made on callus tissue ranging from 1 to 4 days old. The results indicated that gross morphological changes were associated with the anatomical location of the proliferative cells. They showed that the percentage of polyploid division figures after stimulation by kinetin increased rapidly during the first 6 to 7 days in culture and then continued to increase at a much reduced rate. Cell counts revealed that cell proliferation in the mixed callus tissue was initially delayed when compared with the diploid tissue, but that after the delay was overcome cell number increased in each in similar manner. Analysis of the number of DNA‐synthesizing cells showed that their percentage was highest during the first 2 days of culture and then leveled off at a value of about 10%. Mitotic cycle analysis indicated that it could be accurately measured only in the younger diploid callus tissues and that it increased in variability with increased age.
LEAF INITIATION RATES AND VOLUME GROWTH RATES IN THE SHOOT APEX OF CHRYSANTHEMUM
Authors: Berg A. R. , Cutter E. G.
Published: January 2018

The leaf initiation rate and apical volume growth rate of lateral shoots of Chrysanthemum morifolium ‘Improved Albatross III’ were determined for plants growing under controlled environment conditions. After removal of the terminal bud, the top two lateral buds produced leaves at a rate of 1.4 to 1.6 leaves/day for the first 9 or 10 days. At about the 10th day there appeared to be an abrupt shift to a lower initiation rate of 0.7 to 0.8 leaves/day. Defoliation by periodic removal of leaves larger than 1 cm caused a statistically significant increase in initiation rate, but not to as high a rate as that of the first 10 days of bud growth. Volume growth rates of the apical region were determined from transverse sections of five apices, according to the method of Richards (1951). The apical region was found to have a radial expansion rate of 0.1623/plastochron and a vertical expansion rate of 0.0494/plastochron. The volume growth rate was calculated to be 0.3740/plastochron and the volume doubling time to be 1.85 plastochrons or 56 to 63 hr.
PEROXIDASE LOCALIZATION, ACTIVITY, AND ISOZYME PATTERNS IN THE DEVELOPING SEEDLING OF VANDA (ORCHIDACEAE)
Authors: Alvarez Marvin R. , King Dan O.
Published: January 2018

Peroxidase activity in the seedling of Vanda was investigated at various stages of development. Active sites were demonstrated histochemically and soluble proteins and peroxidase isozymes were resolved by disc electrophoresis at progressive stages of growth. Activity, which is highest in the early stages of development and lowest at the stage when maximum differentiation occurs, is confined to the epidermal layer and outer surface of the seedling in early stages of development, It is also present in the vascular tissues of the leaves, root, and parenchymatous region at later stages. Indoleacetic acid raises peroxidase activity when present in the growth medium in physiological concentrations. The number of isoperoxidases varies with developmental stage and is lowest in the stage at which leaves and roots are initiated. These observations are discussed in relation to the hypothesis that the peroxidases play a role in morphogenesis as a part of the indoleacetic acid‐oxidase system.
ZOOSPORIC FUNGI OF OCEANIA. VII. FUSIONS IN RHIZOPHLYCTIS
Authors: Karling John S.
Published: January 2018

Clumping, pairing, and fusion of zoospores occur commonly in three isolates of Rhizophlyctis occanis sp. n., as well as in R. ingoldii Sparrow from the South Pacific islands and New Zealand. At present the fusions are interpreted to be gametic, but this interpretation has not been substantiated fully because it has not been possible so far to bring the fusion products to maturity and demonstrate conclusively that resting spores are sexually formed. The motile cells appear to be facultative. They may function as zoospores and develop directly into sporangial thalli or fuse to form young zygote‐like thalli. In this respect they are very similar to those of some members of the Olpidiaceae and Synchytriaceae. The fusing cells lose their morphological identity as such in the process of fusion as in members of these families, and in this respect they are unlike most of those of the family Rhizidiaceae in which Rhizophlyctis is commonly classified. The fusions in R. occanis and R. ingoldii are strikingly similar to those in Karlingia dubia Karling, an operculate species, which indicates that Rhizophlyctis and Karlingia are closely related genera.
GROWTH AND HABITUATION IN TISSUE CULTURES OF ENGLISH IVY, HEDERA HELIX
Authors: Stoutemyer V. T. , Britt O. K.
Published: January 2018

Tissue cultures from both juvenile and adult stems of English ivy, Hedera helix L., were established in White's medium supplemented by coconut water and auxin (usually naphthalene acetic acid). With repeated transfers, cultures were habituated in less than a year to grow well without coconut water by using an auxin and kinetin. Cultures from juvenile seedlings were less demanding in requirements for growth. In all types of cultures occasionally small areas of rapidly growing cells were noticed. These when isolated gave rise to rapidly growing cultures with many cells of unusual appearance. Abnormally long cells and chain‐type cells were abundant. When 0.1 mg/ liter of kinetin was added to the medium, these cells grew well without auxin and coconut water.
CHLOROPLAST DEVELOPMENT IN NICOTIANA TABACUM ‘MARYLAND MAMMOTH’
Authors: Stetler D. A. , Laetsch W. M.
Published: January 2018

The development of chloroplasts in light‐grown and in previously etiolated tissues of tobacco has been studied. A single membrane‐bound body is found in the developing plastids of both light‐ and dark‐grown tissue. The contents of the body appear homogeneous, becoming progressively granular as the chloroplast develops. In the mature chloroplast the body contains a fibrillar network resembling strands shown to be DNA by other workers. The prolamellar body persists even in moderately well developed chloroplasts in light‐grown plants. Frequently the prolamellar body is connected to the membrane‐bound body as well as to the grana. Relatively mature chloroplasts are seen to divide in this tissue. The membrane‐bound body may have a role in the formation of lamellae, but the nature of its contents is yet to be determined.
EFFECTS OF CA AND SR ON ZEA MAYS SEEDLING PRIMARY ROOT GROWTH
Authors: Bonds Eldon , O'Kelley Joseph C.
Published: January 2018

Either Ca or Sr in a mineral nutrient medium prevented toxic effects of other nutrient ions on aerated primary roots of maize; other monovalent or divalent, cations substituted for Ca did not. Calcium in the complete nutrient solution, or as CaCl2 alone, stimulated the division of apical meristem cells in these roots, as compared to division in water alone, but Sr did not. However, the replacement of Ca in the nutrient medium by Sr resulted in the development of additional secondary roots, probably in part by decreasing the rate of cell division in the apical meristem of the primary root and thereby diminishing apical dominance.
THE ULTRASTRUCTURE OF MITOSIS IN MYXAMOEBAE AND PLASMODIA OF PHYSARUM FLAVICOMUM
Authors: Aldrich Henry C.
Published: January 2018

Electron microscopy of glutaraldehyde‐osmium‐fixed samples of haploid myxamoebae and diploid plasmodia of the myxomycete Physarum flavicomum Berk. reveal dissimilar spindle apparatus during mitosis in the two cell types. Myxamoebae exhibit an astral type of mitosis with centrioles at the poles and nuclear envelope breakdown during prophase. Plasmodial nuclei lack centrioles at mitosis and have an intranuclear spindle, with nuclear envelope persisting during the entire division. Coated vesicles are noted during prophase and telophase in myxamoebae and their role in spindle formation and dispersion is suggested.
A CHROMATOGRAPHIC INVESTIGATION OF INTERSPECIFIC RELATIONSHIPS IN PINUS (SUBSECTION SYLVESTRES)
Authors: Thielges Bart A.
Published: January 2018

The foliage polyphenols of 16Pinusspecies were compared by two‐dimensional paper chromatography. The general patterns of chemical similarity were correlated with the geographic distributions of the species; sympatric species generally had greater chemical affinity than did allotropic species. This relationship did not always correspond to hybridization patterns and morphological similarities. The distinctive chromatographic patterns of the Southeast Asian species(P. insularis, P. luchuensis, P. merkusii)and their generally low affinities with species of Europe and the Asian mainland suggest that further investigation of the morphological relationships and the genetic compatibility of these species with otherSylvestresspecies is warranted. The chemical relationships ofP. halepensisandP. heldreichiito otherSylvestresspecies were also unclear. The qualitative differences in polyphenols among species are consistent and of sufficient magnitude to enable the application of chromatographic analysis to studies of interspecific hybridization inPinus.
BIPOLAR INCOMPATIBILITY IN THE HYMENOMYCETE POLYPORUS PALUSTRIS
Authors: Flexer Abraham S.
Published: January 2018

The basic features of bipolar incompatibility in the hymenomycete, Polyporus palustris (Berk. and Curt.), have been investigated by a comparison of compatible and incompatible interactions leading to the formation of dikaryons and common‐factor heterokaryons, respectively. Nuclear migration is severely restricted and nuclear pairing and conjugate nuclear division fail to occur in the interaction of incompatible homokaryons. It is suggested that the single incompatibility factor of P. palustris combines the functions of the two incompatibility factors of tetrapolar species.
COMPARATIVE ANATOMY OF THE SEED COATS OF GNETUM AND THEIR PROBABLE EVOLUTION
Authors: Rodin R. J. , Kapil R. N.
Published: January 2018

The seed coats of Gnetum gnemon L., G. ula Brongn., G. montanum f. parvifolium (Warb.) Mgf. and G. neglectum Bl. consist of three layers. The outer layer or sarcotesta is mostly parenchyma but contains some sclereids and fibers and a series of simple vascular bundles. The middle sclerotesta forms masses of sclereids in varying shapes and numbers, sometimes extending as a basal plate, and is usually thicker near the micropylar tube. The second layer also contains a series of small vascular bundles that reach the apex. Depending on the species, the middle layer is sometimes nearly free from the outer layer, may be partially fused with it, or completely fused to it at maturity. The innermost layer of the seed coat constitutes the endotesta which is membranous and only rarely contains sclerenchyma. It possesses a dichotomous venation system with varying degrees of anastomosing, depending upon the species. The above species show qualitative and quantitative differences in their sclerenchyma and laticifers. Seed coat anatomy may be useful in the diagnosis of some species. The trends of evolution of seed coat structure within these four species of Gnetum are discussed, and a comparison of tissue layers and vasculature with certain fossil pteridosperms is made, especially in the Trigonocarpales
CRENATICAULIS, A NEW GENUS OF DEVONIAN PLANTS ALLIED TO ZOSTEROPHYLLUM, AND ITS BEARING ON THE CLASSIFICATION OF EARLY LAND PLANTS
Authors: Banks H. P. , Davis M. R.
Published: January 2018

The name Crenaticaulis verruculosus is proposed for slender, pseudomonopodially and dichoto‐mously branching plants that bore opposite to subopposite sporangia along the stem and two rows of prominent, multicellular teeth on opposite sides of the terete axis. Epidermal cells were either narrow and elongate parallel to the stem or short with a papillate outer tangential wall. Axillary tubercles were present on one side of the stem near lateral branches. Some tubercles bore remnants of branches. Sporangia dehisced along their distal margins into two unequal halves. No spores were found. Occasional short lengths of stem were petrified by iron pyrite. Sections revealed a cortex consisting of four to six rows of thick‐walled cells and a xylem strand. The strand was elliptical in transverse section and maturation was exarch. Tracheids were chiefly scalariform. It is suggested that the so‐called axillary tubercles, known in several plants of Devonian age, were scars of rhizophores like those in the modern genus Selaginella. The plant is referred to the subdivision Zosterophyllophytina.
DEVELOPMENT OF CHLOROPLAST FINE STRUCTURE IN ASPEN TISSUE CULTURE
Authors: Blackwell Steven J. , Laetsch W. M. , Hyde Beal B.
Published: January 2018

Chloroplast ontogeny has been examined in 42‐day etiolated triploid aspen callus (Populus tremuloides Michx.) subjected to two different light conditions. White and low‐intensity red illumination showed little differences in their stimulatory effects on plastid development, the red light‐irradiated plastids developing only slightly more slowly. Asynchronous plastid development was noted in both lighting systems. Etioplasts contained an interconnected tubular net, phytoferritin aggregates, electron‐transparent vesicles which seem to invaginate from the inner plastid membrane, membrane‐bound homogeneous spheroids and starch grains. Irradiation caused various morphological changes within the proplastids; the tubular complex became transformed into the more ordered prolamellar body‐like structure from which radiated membrane‐bound sacs filled with electron‐dense material. These sacs, characterized as thylakoid precursors, were transformed into a thylakoidal system typical of mature chloroplasts. This ontogenetic scheme represents an additional pathway for the development of photosynthetic lamellae. Other light‐induced changes in the developing plastid include disappearance of phytoferritin particles and homogeneous spheroids, decrease in starch content, and appearance of osmiophilic droplets.
SPIRAL DEVELOPMENTAL PATTERNS IN THE STEM AND INFLORESCENCE OF LILIUM TIGRINUM
Authors: Greller Andrew M.
Published: January 2018

Extensive correlations in spirality were observed among vegetative and floral organs in Lilium tigrinum Ker. Organs involved were vegetative leaves, bracts, and bracteoles. These correlations varied in their degree of constancy depending upon the organs involved. The mature inflorescences of L. tigrinum appeared to fit the common definition of a raceme. In 67.3% of the flowers at node 3 on the raceme, the bract‐bracteole spirals reversed the spiral of vegetative leaves on the stem. These reversals resembled those observed on essentially cymose inflorescences of certain members of the Caryophyllaceae. Cymose branching was found to be an invariable feature of the inflorescence of L. tigrinum when secondary flowers appear. The apparently indeterminate tips of inflorescence main axes were interpreted as exhibiting stages in progression from a basically determinate (cymose) inflorescence. It was concluded that the ancestors of L. tigrinum had well‐developed cymose branching patterns in the inflorescence. Reversal of stem spirals by the bract‐bracteole spirals at the apices of many inflorescences was considered to be the result of complete utilization of the inflorescence meristem. Explanations for those reversals were provided by the field theory and by the theory of the first available space.
CHROMOSOME PAIRING IN NATURAL FIRST AND ADVANCED GENERATION LIATRIS HYBRIDS
Authors: Levin Donald A.
Published: January 2018

Chromosome pairing was analyzed in natural F1 and advanced generation hybrids of crosses between Liatris aspera and L. spicata, and L. aspera and L. cylindracea. The status of the hybrids was determined on the basis of morphological and chromatographic criteria. The F1 hybrids of L. aspera × L. spicata contained pairing irregularities in 30% of their PMC's as compared to 10% in the hybrid segregates. Notably, translocation figures appeared in 7% of the F1 PMC's as compared to 0.6% in the segregate PMC's. The F1 hybrids of L. aspera × L. cylindracea contained irregularities in 19% of their PMC's as compared to 7% in the segregates. Translocation figures occurred in 6% of the F1 PMC's, but only in 0.7% of the segregate PMC's. The incidence of pairing and level of structural heterozygosity was far lower in the hybrid segregates than was anticipated on the basis of F1 pairing relationships. Thus it would appear that there is selection for structural homozygosity in the hybrid segregates.
CYTOLOGY AND MORPHOGENESIS IN THE RHIZOMORPH OF ARMILLARIA MELLEA
Authors: Motta Jerome J.
Published: January 2018

Aided by the techniques of thin sectioning and electron microscopy, the apical region of the rhizomorph ofArmillaria melleahas been examined. This region is composed of concentric zones of morphologically distinct tissues derived from a subapical meristematic zone designated the apical center. Meristematic activity is of two types: (1) primary, localized in the apical center, in which new hyphal elements are formed from apical initials, and (2) secondary, localized in the lateral regions of the apex, in which elaboration of the hyphal elements by means of elongation and secondary crosswall formation takes place. From these meristematic zones the tissues of the mature rhizomorph are derived and include: (a) peripheral hyphae, (b) cortex, (c) subcortex, and (d) primary and secondary medulla. The manner of differentiation of an apical initial appears unique and involves synchronous nuclear divisions accompanied by segmentation in many planes. The result of this activity is the formation of multinucleate hyphae. Apical initials are usually highly cytoplasmic and possess peculiar non‐membrane‐bound fibrous bundles, but in all other respects they resemble the hyphae of most Basidiomycetes thus far examined with the electron microscope.
ORCHID EMBRYOLOGY: MEGAGAMETOPHYTE OF EPIDENDRUM SCUTELLA FOLLOWING FERTILIZATION
Authors: Cocucci Alfredo , Jensen William A.
Published: January 2018

The megagametophyte of Epidendrum scutella, an orchid, was examined with the electron microscope after the entrance and discharge of the pollen tube. The pollen tube enters the embryo sac by growing through the filiform apparatus of a synergid and discharges through a terminal pore into the degenerating cytoplasm of the synergid. The synergid nucleus appears pushed to one side by the discharge of the pollen tube. What is believed to be the remains of the vegetative nucleus has been found in the degenerate synergid, but no trace of the sperm cytoplasm has been seen. The zygote is approximately the same size as the egg. The ribosomes become grouped into polysomes. Both the egg and the zygote apparently completely lack dictyosomes. The polar nuclei partially fuse before fertilization, but fusion of the sperm nucleus with the polar nuclei does not occur and no endosperm is produced. Polysome formation occurs in the central cell and large amounts of tubular, smooth ER are seen. The antipodals remain following fertilization, undergoing ultrastructural changes similar to the central cell.
THE FEMALE GAMETOPHYTE OF MACHAERANTHERA PATTERSONII (ASTER PATTERSONII) AND OF M. TANACETIFOLIA
Authors: Howe Thomas D.
Published: January 2018

The nucellus of Machaeranthera pattersonii (A. Gray) Greene (Aster pattersonii A. Gray) contains only one megaspore mother cell, and the female gametophyte develops from the chalazal megaspore of a row of four, thus conforming to the Polygonum type of development. These observations are contrary to the older work of Palm. Three nuclear divisions produce the typical eight nuclei with the egg apparatus, primary endosperm cell with two polar nuclei, and two antipodal cells, the micropylar one containing two nuclei. Usually no more antipodal cells are formed, although there is further nuclear division, apparently followed by nuclear fusion. The antipodal cells remain about the same size without forming an antipodal haustorium. Cell division accompanies the first division of the primary endosperm nucleus. The early stages of the embryo resemble those of other Compositae. Machaeranthera tanacetifolia (HBK) Nees also shows the Polygonum type of development of the female gametophyte. It is suggested that Palm may have been working on some species of Erigeron that had been wrongly identified, which would account for the difference in observations.
THE SPORE PATTERN IN SOME SPECIES OF CHEILANTHES
Authors: Knobloch Irving W.
Published: January 2018

Of the 32 taxa examined, 13 contained 32 spores in each sporangium and are considered apo‐gamous, 14 were sexual species with 64 spores per sporangium, and 5 had 32 spores in some sporangia and 64 in others. When considered as a whole, the spores ranged in size from 29.9 to 74.88μ. Most species had oval or globose spores but several had tetrahedral spores. The spores of all were radially symmetrical. Almost all of the species possessed a crassimarginate type of laesura and all except C. cooperae and C. viscida had a perispore. The ornamentation of the perispore showed the following patterns: napate, granulate, psilate, lobate, foveate, and echinate. The exine pattern was predominantly psilate but foveate, rugulate, napate, and granulate conditions were observed. Seventeen taxa were found to have some degree of spore abortion.
PSEUDOBRYOPSIS MYURA AND ITS REPRODUCTION
Authors: Feldmann Jean
Published: January 2018

Pseudobryopsis myura, type of the genus, is monoecious; male and female gametocysts occur on the same plant; there is definite anisogamy and only macrogametes possess a stigma. The mode of extrusion of the gametes differs both from the Bryopsis‐type and from the Codium‐type. As in Codium the discharge of the gametocyst is due to internal pressure. Gametes become motile only after their extrusion from the gametocyst.
INVESTIGATIONS ON THE ROOT FORMATION IN THE TISSUES OF HELIANTHUS TUBEROSUS CULTURED IN VITRO
Authors: Gautheeet R. J.
Published: January 2018

Excised rhizome fragments of Helianthus tuberosus ‘Violet de Rennes’ produce roots in vitro; the sequence of morphogenetic phenomena is as follows: proliferation, differentiation of phloem and tracheids, organization of cambiums, and formation of root primordia from cambiums. This rhizogenesis is conditioned by five limiting factors: mineral salts, sugar, auxin, temperature, and light. The optimum level of each of these factors was determined and in certain cases also the threshold of action. For white light the beginning was about 1/1000 lux. These five limiting factors do not represent the same site of action. The mineral salts, especially nitrogen and calcium, have their effect when the cambiums have been organized. The sugars act before the formation of cambiums. Light operates principally upon cambium and this action is independent of photosynthesis. It was not possible to determine whether the auxin has a preferential site of action. A temperature higher than 15 C is essential to obtain the formation of cambiums but further production of roots is possible at 15 C or even less. The variations in temperature more or less around the optimum stimulate rhizogenesis. The supra‐optimal temperatures mainly have their effect before the formation of cambiums and infra‐optimal temperatures after. The effect of light can be exhibited at low temperature. Gibberellic acid in association with auxin favors root formation in the dark whereas in light it exhibits inhibiting properties. Rhizogenetic potentialities of tissues are reduced when these are cultured in the dark in presence of auxin. On the other hand, if auxin is applied after the isolation of explants, rhizogenesis is stimulated and the tissues are able to produce roots even in the dark. The action of light and of auxin can be dissociated; when the explants having absorbed a small quantity of auxin are transferred to a medium without auxin for 60 days in the dark, they conserve the rhizogenetic potential which is expressible on transferring them to light. Finally, grafting experiments suggested that light could induce the formation of a rhizogenetic factor in the tissues which is transmittable from cell to cell. These experiments have definitely established that the induction of root formation is governed by several factors which have complex interactions.
REMARKABLE EXAMPLES OF SPECIATION IN ASIATIC PLANTS
Authors: Hara Hiroshi
Published: January 2018

The nature, extent, and tempo of speciation differ from one plant group to another, and some noteworthy examples studied in Asiatic flowering plants are considered. In the Rubia cordifolia group, Himalayan plants have epigeous cotyledons, while all Japanese plants have hypogeous cotyledons; in both groups polyploidy seems to have occurred parallelly. The pollen pattern varies in some groups correlated with polyploidy, and an example is observed within a species (Anemone hepatica) or a genus (Isopyrum, etc.). Representative examples in which polyploidy plays an important role in speciation are explained in such genera as Aucuba, Helwingia, Duchesnea, Agrimonia and Suaeda. Dysoploidy and amphiploidy are also important, and establishment of new basic numbers is occasionally found in closely allied species as exemplified in Lysimachia and Chrysosplenium, or even in one species, Chionographis japonica. As a striking example of an exceedingly polymorphous species which is considered to be undergoing speciation, the variations in Paris polyphylla are reviewed. On the contrary, Phryma leptostachya is not highly differentiated, although it occurs in two widely separated regions, and must be of very old origin.
ON THE STRUCTURE OF A SILICIFIED STEM OF PROTOPITYS AND ROOTS ASSOCIATED WITH IT FROM THE CARBONIFEROUS LIMESTONE, LOWER CARBONIFEROUS (MISSISSIPPIAN) OF YORKSHIRE, ENGLAND
Authors: Walton John
Published: January 2018

This investigation of fossils belonging to the genus Protopitys found in Lower Carboniferous (Mississippian) strata in Yorkshire reveals features hitherto not described in this genus. By comparison of cellular elements with those of the stem, closely associated roots are evidently parts of the same species as the stem which is undoubtedly Protopitys Buchiana. The Yorkshire specimens had been given the name of Protopitys radicane Kidston M.S., by Scott without adequate description. This name must now be dropped. The cambium region and the secondary tissues of the stem are well preserved and they exhibit unusual features. The roots are of various sizes and stages of development. They have no secondary tissues and resemble those of Pteridophytes more closely than those of gymnosperms.
DEVELOPMENT AND STRUCTURE OF PHLOEM IN THE PETIOLE OF LUFFA CYLINDRICA
Authors: Shah J. J. , Jacob Raju
Published: January 2018

Differentiation of external phloem is earlier than that of internal phloem in the young petiole of Luffa cylindrical. For a single sieve‐tube element, one to six companion cells are present. The young sieve element shows many globular slime bodies which fuse longitudinally and disperse into the cytoplasm. Simultaneously the nucleus loses its stainable contents and later disorganizes. The contents of the sieve element are in the form of plugs, strands or a granular mass. Undispersed slime in the form of discrete bodies along the lateral walls is also observed. During one stage, at least, the dispersed slime and other contents of a mature sieve element lie at the periphery around a central cavity. A special type of phloem‐parenchyma cell shows disorganizing chloroplasts, an extruded nucleolus, and callose on primary pit fields.
GENETIC VARIATION IN THE ORIENTATION OF NUCLEAR SPINDLES DURING THE DEVELOPMENT OF ASCI IN NEUROSPORA
Authors: Pincheira Guido , Srb Adrian M.
Published: January 2018

The effect of a single mutant gene, peak‐2, in Neurospora crassa is to alter the ascus from one in which the eight spores are linearly arranged to one in which the eight spores are arranged non‐linearly. The same gene transferred to N. tetrasperma determines an ascus similar to that of the mutant N. crassa but in striking contrast to the normal ascus for N. tetrasperma, which includes four heterokaryotic spores, linearly arranged. A comparative cytological study has been made on asci from both species, including material from zygotes that are homozygous normal, heterozygous for peak‐2, and homozygous for peak‐2. The observed morphogenetic differences are closely related to differences in nuclear spindle orientation, which in turn are correlated with the geometry of the cell. The observations are shown to bear on the basis of pseudohomothallism in N. tetrasperma. Speculations on the importance of the cell wall in relation to spindle orientation are presented. Differences of expression of peak‐2 in the different species are discussed.
POLLINATION ADAPTATION IN PEDICULARIS LANCEOLATA
Authors: Macior Lazarus Walter
Published: January 2018

Cinematographic, stereophotographic, and visual observations have revealed that the zygomorphic, nectarless flower of Pedicularis lanceolata Michx. is pollinated in northeastern Ohio by pollen‐foraging workers of three Bombus species. Foragers hang inverted from the asymmetrical corolla and remove pollen with their front and middle legs from anthers concealed by the galea. The stigma contacts pollen deposited especially on the median portion of the forager's first abdominal sterilite. Insect exclosures and pollinator collections demonstrated the obligate pollination dependence of the flower on Bombus workers. Of 152 corbicular pollen loads from workers foraging on P. lanceolata, Gentiana andrewsii, Prunella vulgaris and five composite species in the same habitat, 84.2% contained P. lanceolata pollen; 75.8% of the latter contained P. lanceolata pollen exclusively. Possible coadaptive relationships of Pedicularis flowers and pollinators are discussed.
INTERACTION OF LIGHT QUALITY AND NUCLEASES IN THE GROWTH OF THE GAMETOPHYTES OF ASPLENIUM NIDUS
Authors: Raghavan V.
Published: January 2018

Appropriate concentrations of ribonuclease A and B selectively inhibited initiation of two‐dimensional morphology in the gametophytes of Asplenium nidus, grown under a photoperiod of 5½ hr white light. Filamentous growth was promoted in such sporelings, the individual cells of which were significantly longer than corresponding cells of the control. Higher concentrations of enzymes were required to inhibit two‐dimensional growth in the gametophytes grown in blue light. Concentrations of ribonuclease A or B which inhibited two‐dimensional growth in white light promoted growth in length of the protonema in red light. Growth modifications in the sporelings induced by deoxyribonuclease in different light conditions were similar to those induced by the ribonucleases. The results lend further support to the postulated role of RNA in the regulation of two‐dimensional growth in fern gametophytes.
PIGMENTS AND PLASTIDS IN CULTURES OF TOTIPOTENT CARROT CELLS
Authors: Israel H. W. , Mapes Marion O. , Steward F. C.
Published: January 2018

Cells from a strain of carrot which was prone to form deep‐seated chlorophyll in its storage organ have been cultured in a manner that promoted them to organize into plantlets. Whereas the free cells contained only chloroplasts, the plantlets derived from these cells formed all types of plastids (“proplastids,” leucoplasts, chromoplasts, and chloroplasts) in accordance with the location of the cells in question in the developing plant body. The developmental history of the plastids has been traced with the electron microscope. The events of chloroplast development, previously described by Israel and Steward (1967) for cultured carrot explants, have been verified. The bearing of this new evidence upon the control of plastid development and biochemistry is discussed and related to other recent studies. The conclusion is that all totipotent carrot cells have plastids as essential organelles but that their final form and content are sharply defined by the factors inherent in the location of the cells in the plant body as it emerges.
REGULATION OF GROWTH AND CELLULAR DIFFERENTIATION IN DEVELOPING AVENA INTERNODES BY GIBBERELLIC ACID AND INDOLE‐3‐ACETIC ACID
Authors: Kaufman Peter B. , Petering Louise B. , Adams Paul A.
Published: January 2018

Auxin (IAA) at physiological concentrations causes significant reduction of GA3‐promoted growth in excised Avena stem segments. IAA is thus considered to be a gibberellin antagonist in this system. It was found to act non‐competitively in repressing GA3‐augmented growth in these segments. In intercalary meristem cells at the base of the elongating internode, GA3 blocks cell division activity and causes a marked increase in cell lengthening. IAA substantially promotes lateral expansion in comparable intercalary meristem cells, particularly in the vicinity of vascular bundles underlying the epidermis. It also alters the plane of cell division in differentiating stomata. IAA at high concentrations (10−3, 10−4 m), in combination with GA3, overrides the effects of GA3 on cell lengthening, while with low concentrations of IAA (10−9, 10−10m), the effects of GA3 are clearly dominant. At intermediate concentrations of IAA (10−6, 10−7m), in the presence of GA3, the effects of this treatment on cell differentiation closely parallel the pattern of differentiation in untreated tissue. It is postulated that a lateral gradient of auxin and gibberellin could control cell expansion in long epidermal cells during intercalary growth of the internode.