bluuebunny/crossref_metadata_2025 huggingface dataset:
ENERGY DISTRIBUTION IN REPRODUCTIVE STRUCTURES OF AMARYLLIS
Authors: Smith Carey A. , Evenson William E.
Published: January 2018

Energy content of tissue produced in male and female reproductive structures as well as in associated flower parts of Amaryllis was measured with an oxygen bomb calorimeter. In typical flowers, 6.6% of their total energy (2,880 cal) was in pollen, 4.9% in anther walls, 4.6% in ovules and placentae, and 12.6% in ovary walls and septa. Ovules were estimated to contain only about one‐third as much energy as pollen. Mature seeds typically contained about 100 times as much energy as ovules. Total energy in mature seeds per flower was approximately equal to total energy in flower tissues. Proportional allocation of anther energy to pollen increased with anther size. The biological significance of these results is discussed.
COMPARATIVE ANATOMY OF EUCRYPHIACEAE
Authors: Dickison William C.
Published: January 2018

Aspects of vegetative and floral morphology and anatomy of five species of Eucryphia Cav. are described. Differences in wood structure, type and complexity of petiole and leaf vascularization, presence or absence of complex abaxial cuticular protrusions on the leaves, and patterns of floral vasculature are useful in species delimitation. Anatomical data are in agreement with the inclusion of Eucryphiaceae in the Rosales near Cunoniaceae.
STRUCTURE AND ONTOGENY OF LATICIFERS IN CICHORIUM INTYBUS (COMPOSITAE)
Authors: Vertrees Gerald L. , Mahlberg Paul G.
Published: January 2018

The branched anastomosed laticifer system in the primary body of Cichorium intybus L. originates in embryos from files of laticiferous members at the boundary between phloic procambium and ground meristem. Upon seed germination, laticiferous members develop perforations in the end walls which become entirely resorbed. Perforations also develop in the longitudinal walls of contiguous laticiferous members and from lateral connections between developing laticifer branches. Additional laticiferous members originate as procambium differentiation proceeds, and their differentiation follows a continuous acropetal sequence in leaf primordia of the plumule. In roots, laticifers closely associated with sieve tubes in the secondary phloem originate from derivatives of fusiform initials in the vascular cambium. These laticifers develop wall perforations and in a mature condition resemble laticifers in the primary body. As the girth of the root increases, laticifers toward the periphery, unlike associated sieve tubes, resist crushing and obliteration. Laticifers vary in width from about 4 to 22 μm; the widest ones occur in involucral bracts and the narrowest ones in florets. There was no evidence that intrusive growth occurs during development of the laticifer system, although such growth may occur during development of occasional branches which extend through ground tissue independent of phloem and terminate in contact with the epidermis. Presence of amorphous callose deposits is related to aging of laticifers and mechanical injury.
HYPERPLASTIC PHLOEM IN SUGARBEET LEAVES INFECTED WITH THE BEET CURLY TOP VIRUS
Authors: Esau Katherine , Hoefert Lynn L.
Published: January 2018

Electron microscopy of sugarbeet leaves infected with the beet curly top virus confirmed earlier findings by light microscopy that the hyperplastic phloem consists mainly of sieve elements that are more or less abnormal in structure. Some parenchyma cells and occasional companion cells may be present. The hyperplastic phloem develops in the place of normal phloem and sometimes in the adjacent ground tissue and the xylem. The sieve elements vary in shape and may be haphazardly arranged. The protoplasts of the sieve elements have the usual characteristics of this type of cell. The sieve element plastids develop from chloroplasts if the hyperplasia occurs in chloroplast‐containing parenchyma cells. The cell walls have sieve areas that often are less well differentiated than those of normal sieve elements. The hyperplastic growth in the phloem of curly top diseased plants is discussed with reference to plant tumors induced by certain other plant viruses.
THE SHOOT APEX OF BOUGAINVILLEA SPECTABILIS
Authors: Stevenson Dennis Wm.
Published: January 2018

The shoot apex of Bougainvillea spectabilis consists of five zones: A two‐ or occasionally three‐layered tunica, a central mother cell zone, a cambium‐like zone, a rib meristem (central meristem), and a peripheral meristem. The presence of a cambium‐like zone is somewhat unusual in the apex of vascular plants, having only been reported for a few taxa. In B. spectabilis the cambium‐like zone is consistently present throughout the plastochron and all yearly seasonal periods.
PETRIFIED NEUROPTERID FOLIAGE FROM A MIDDLE PENNSYLVANIAN COAL BALL
Authors: Reihman M. A. , Schabilion J. T.
Published: January 2018

Petrified specimens of pteridosperm foliage assignable to Reticulopteris muensteri (Eichwald) Gothan and Neuropteris rarinervis Bunbury were found in a Middle Pennsylvanian age coal ball from central Iowa. The presumed close affinity of these two foliage taxa is supported by various anatomical similarities including hydathode‐like vein terminations and non‐papillate lower epidermises with high stomatal density. Comparison of the foliar anatomy of these neuropterids to that of the xeromorphic taxa Alethopteris sullivanti (Lesquereux) Schimper and A. lesquereuxi Wagner show striking differences which suggest that these neuropterid and alethopterid taxa were adapted to markedly different habitats.
TRITICUM URARTU AND GENOME EVOLUTION IN THE TETRAPLOID WHEATS
Authors: Johnson B. L. , Dhaliwal H. S.
Published: January 2018

The A genome of the tetraploid wheats (AABB, 2n = 28) shows 5‐6 bivalents in crosses with Triticum boeoticum (2n = 14) and various Aegilops diploids (2n = 14). The B genome has never been similarly identified with any species, and is commonly thought to have been modified at the tetraploid level. Triticum boeoticum was presumably accepted as the A‐genome donor because of its morphological similarity to the wild tetraploids and because it was formerly the only known wild diploid wheat. The B donor has been thought to be Ae. speltoides or another species of the Sitopsis section of Aegilops, but these diploids show pairing affinity with A rather than B. More recently, another diploid wheat, T. urartu, was found to be sympatric with T. boeoticum throughout the natural range of the tetraploids. The synthetic boeoticum‐urartu amphiploid was virtually identical morphologically with the wild tetraploid wheats, whereas various boeoticum‐Sitopsis amphiploids were markedly different. But the urartu genome, like those of T. boeoticum and Sitopsis, paired with A and not with B. However, cytological evidence also shows (1) that the genomes of any plausible parental combination pair with one another, (2) that the A and B genomes of the tetraploid wheats pair with one another in the absence of the gene Ph, and (3) that homoeologous chromosomes of the tetraploids have differentiated further, presumably as a result of diploidization. Consequently, chromosome pairing at Meiosis I can be expected to give ambiguous evidence regarding the identity of the tetraploid genomes with their parental prototypes. A hypothesis regarding the expected pairing affinities between tetraploid homoeologues that have differentiated from closely related parental chromosomes is advanced to explain the anomalous pairing behavior of the A and B genomes. Triticum boeoticum and T. urartu are inferred to be the parents of the tetraploid wheats.
MORPHOLOGICAL DIFFERENTIATION AND NEIGHBORHOOD SIZE IN LIATRIS CYLINDRACEA
Authors: Schaal Barbara A. , Levin Donald A.
Published: January 2018

Pollinator flight and seed dispersal distributions are leptokurtic in the perennial, prairie herb Liatris cylindracea Michx. (Compositae). From these dispersal data neighborhood size and area were determined to be 165 plants and 33 m2, respectively. An analysis of morphological variation along three transects of an edaphic gradient indicates that significant local differentiation for several characters occurs at the study site. The pattern of local differentiation is unrelated to edaphic factors.
MORPHOLOGY OF SACCHARUM‐SORGHUM HYBRID DERIVATIVES
Authors: Gupta S. C. , de Wet J. M. J. , Harlan J. R.
Published: January 2018

The intergeneric hybrid between sugarcane (Saccharum sp.) and sorghum (Sorghum bicolor (L.) Moench.) was produced by pollinating sugarcane inflorescences of clone F 36‐819 (2n = ca. 112) with diploid (2n = 20) ‘Rex’ sorghum pollen. The backcross four (BC4) population, produced by back‐crossing twice with diploid and then twice more with tetraploid (2n = 40) ‘Rio’ sorghum, combined 40 Sorghum and 4‐10 Saccharum chromosomes. Different BC4 individuals were morphologically distinct within and between chromosome complexes, indicating that their genomes must comprise different combinations of Sorghum and Saccharum chromosomes. Selfing for one or more generations results in almost complete elimination of Saccharum chromosomes and morphologically modified sorghums are recovered. Modified sorghums have various combinations of Saccharum characteristics superimposed on a basic Sorghum morphology. The presence of Saccharum characters in some of the recovered sorghums with 2n = 40 chromosomes indicates the potential for a gene transfer from sugarcane to sorghum.
ALLOCATION, GROWTH RATES AND GAS EXCHANGE IN SEEDLINGS OF STEPHANOMERIA EXIGUA SSP. CORONARIA AND ITS RECENT DERIVATIVE S. MALHEURENSIS
Authors: Gottlieb L. D.
Published: January 2018

The annual diploid plant species Stephanomeria malheurensis is known only from a single locality where it grows interspersed with its progenitor S. exigua ssp. coronaria. S. malheurensis is thought to have originated recently at its present site and, consequently, serves as a model to study how the phenotype of a species is assembled following its origin. The following were examined in the present study: dry matter allocation, growth parameters, net photosynthesis, and dark respiration of seedlings under three temperatures in order to identify specific features of the new species that might relate to its ecological properties. Under each test condition, S. malheurensis had leaves with a significantly smaller surface area, greater dry weight per unit area, heavier roots, and a higher root/shoot ratio. Both species had similar relative growth rates during the measured period of rosette growth, but in S. malheurensis this resulted from the combination of a lower leaf area ratio and a higher net assimilation rate, whereas in ssp. coronaria it resulted from the opposite combination. The mean rates of apparent net photosynthesis and dark respiration were similar in both species. The differences between the species may reflect the establishment of genes in S. malheurensis which still are present in ssp. coronaria. The implications of this and the possible ecological significance are discussed.
LATICIFER ULTRASTRUCTURE AND DIFFERENTIATION IN SEEDLINGS OF PAPAVER BRACTEATUM LINDL., POPULATION ARYA II (PAPAVERACEAE)
Authors: Nessler Craig L. , Mahlberg Paul G.
Published: January 2018

Laticifers of Papaver bracteatum Lindl., population Arya II, seedlings were examined by electron microscopy. Laticifers were first differentiated in procambium of the radicle associated with phloem about 72 hr after seeds were sown. Proliferation of membrane‐bound vesicles of apparent endoplasmic reticulum origin distinguished laticifers from adjacent cells. Vesicles developed electron‐dense caps from the internal condensation of small particles. Laticifer initials possessed the usual complement of organelles that became obscured in mature cells by the large, closely packed vesicles. Plastids contained an electron‐dense, membrane‐bound inclusion, but never developed lamellae or starch grains. Articulation and anastomoses between laticifer elements resulted from gradual removal of wall materials by both cells on opposite sides of the common walls at a perforation site. Differentiation of the laticifer initials and the micromorphology of the protoplast of P. bracteatum is similar to that reported for P. somniferum.
ORIGIN AND DEVELOPMENT OF POLLEN EMBRYOIDS AND POLLEN CALLUSES IN CULTURED ANTHER SEGMENTS OF HYOSCYAMUS NIGER (HENBANE)
Authors: Raghavan V.
Published: January 2018

The dedifferentiation of pollen grains of Hyoscyamus niger (henbane) into embryoids and calluses was examined by culturing identical segments of the same anther in a mineral salt‐sucrose basal medium and in the basal medium supplemented with 2.0 mg/l 2,4‐dichlorophenoxyacetic acid, respectively. Addition of auxin enhanced anther efficiency but did not affect the number of embryogenic pollen grains of an anther segment transformed into calluses. In anther segments cultured in the basal medium, the organogenetic part of the pollen embryoid was formed by the division of the generative cell alone, or by the division of both generative and vegetative cells. More or less similar pathways were followed by pollen grains of anther segments cultured in a medium containing auxin to form calluses. Culture of anther segments in a medium containing a high concentration of auxin (50.0 mg/l) led to a significant reduction in the yield of calluses which were formed almost entirely by the division of both generative and vegetative cells. The bearing of these observations on the role of auxin in determining the pathway of differentiation of embryogenic pollen grains in cultured anther segments is considered. The appearance of embryogenic pollen grains in close proximity to the tapetum as seen in longitudinal sections of cultured anther segments has suggested a role for a gradient of tapetal factors in embryogenic induction.
FRUITING AND TWIG DIAMETER IN CITRUS
Authors: Jahn Otto L.
Published: January 2018

On orange and grapefruit trees, fruiting was associated with an increase in diameter of the twig. On twigs with lateral fruit, this increase was restricted to that part of the twig below the point of attachment of the fruit. Possibly, fruit development induces orientation of vascular tissues and, hence, translocation toward the fruit.
ULTRASTRUCTURAL STUDIES OF PINUS PINASTER NEEDLES: THE ENDODERMIS
Authors: Carde Jean‐Pierre
Published: January 2018

The endodermis in the needles of Pinus pinaster was examined with light and electron microscopy. The endodermis is composed of very long, radially flattened cells, filled with a large central vacuole, which contains spherical dense bodies whose concentration decreases from the ends of the cell to the middle part. They are individually surrounded by a fine granular matrix. The central vacuole is bounded by a thick tonoplast. Other small, clear vacuoles are limited by a thin tonoplast. The parietal cytoplasm contains relatively few ribosomes, long slender chloroplasts, and lipid bodies. The smooth endoplasmic reticulum is highly developed along the tangential walls and frequently connected, or apposed, to the plasma membrane. Numerous primary pit fields are seen in the radial walls which are lignified and in the tangential walls; the latter exhibit a characteristic loosening of the outer layer of the wall. The lipid bodies are connected to endoplasmic reticulum tubules. The role of the endodermis in the active transport of water inside the needle is discussed in reference to previous physiological studies. The chemical composition of the vacuolar dense bodies is as yet unknown.
ULTRASTRUCTURE OF EXINE‐LESS POLLEN: HELICONIA (HELICONIACEAE)
Authors: Kress W. John , Stone Donald E. , Sellers Susan C.
Published: January 2018

Pollen of Heliconia and many of its relatives in the Zingiberales is virtually devoid of a conspicuous, protective exine. The exine is relegated to a few spinules and a thin, electron‐dense layer (0.08 μm), whereas the intine can be up to 100 times as thick (8 μm) and structurally complex. Comparative ultrastructural observations on the sporoderm and protoplast are presented for three species and discussion focuses on the possible adaptive significance of the elaborated intine and its potential usefulness in systematic studies.
CELL CYCLE KINETICS OF ENDOREDUPLICATION IN GAMMA‐IRRADIATED ROOT MERISTEMS OF PISUM SATIVUM
Authors: Evans Lance S.
Published: January 2018

Label and mitotic indices and microspectrophotometry of unlabeled interphase cells were used to measure the proportion of root meristem cells of Pisum sativum in each cell cycle stage after exposure to protracted gamma irradiation. Three seedling types were investigated: 1) intact seedlings, 2) seedlings with cotyledons detached and treated with lanolin paste applied to the area of cotyledon excision, and 3) seedlings with detached cotyledons and treated with a G2 Factor applied to the area of cotyledon excision in lanolin paste. In intact seedling meristems, predominant cell arrest occurred with a 4C amount of DNA while 0.30 of the cells underwent endoreduplication to arrest with an 8C amount of DNA. Only 0.07 cells arrested with a 2C amount of DNA. Polyploid cells were produced several days after the start of irradiation and were derived from a diploid cell population. In seedlings exposed to lanolin only, without cotyledons, most cells arrested with a 2C amount of DNA with no polyploid cells. In seedlings exposed to a G2 Factor in lanolin after cotyledon excision, most cells arrested with a 4C amount of DNA but no cells underwent endoreduplication. These experimental results suggest that the G2 Factor derived from cotyledons of Pisum sativum was necessary for predominant cell arrest in G2 but alone was not sufficient for the polyploidization step.
FURTHER STUDIES OF THE UNUSUAL TYPE OF LATICIFEROUS CANALS IN MAMMILLARIA (CACTACEAE): STRUCTURE AND DEVELOPMENT OF THE SEMI‐MILKY TYPE
Authors: Mauseth James D.
Published: January 2018

The development and structure of the laticifers in several species of the section Subhydrochylus of the genus Mammillaria (Cactaceae) were examined. These laticifers were found to be similar to those of the section Mammillaria in that both types develop from the complete lysis of several rows of parenchyma cells, and both types consist of long, branching, tubular lumens which are lined by epithelia. The laticifers of the section Subhydrochylus differ from those of the section Mammillaria in that those of the former are more irregular in shape, lumen development, and epithelium form. Also, the Subhydrochylus laticifers occur only as a single ring in the outermost cortex and tubercle bases, whereas those of section Mammillaria can be found in pith, medullary rays, cortex and throughout the tubercles. Because the structure of the laticifers in the section Mammillaria is much more regular and orderly, it is postulated that they are the derived type and that the laticifers of the section Subhydrochylus more closely resemble the ancestral condition. Two species, M. elegans and M. tegelbergiana, were found to be intermediate in nature, having characteristics of both types of laticifer systems. Solista pectinata was found to have laticifers similar to those in section Subhydrochylus.
THE ORIGIN OF COASTAL SAGE VEGETATION, ALTA AND BAJA CALIFORNIA
Authors: Axelrod Daniel I.
Published: January 2018

Coastal sage is a new pioneer‐type vegetation that only spread widely after the Early Quaternary, when species on the dry open borders of forest, woodland and arid tropic scrub vegetation shifted into expanding dry sites there and in adjacent grasslands. These new sites were created by a coincidence of major climatic and tectonic events and by accompanying erosion and mass movement on steep new slopes. Attaining most of its present area during the hot, dry Xerothermic, coastal sage scrub spread further as man's activities disturbed the landscape.
AUXIN, CYTOKININ AND GROWTH OF EXCISED ROOTS OF BRYOPHYLLUM CALYCINUM
Authors: Robbins William J. , Hervey Annette
Published: January 2018

Excised roots 1 cm long of Bryophyllum calycinum required exogenous auxin (α‐naphthaleneacetic acid) for growth in still culture in a medium of sucrose, mineral salts and vitamins. Little or no growth occurred with the addition of cytokinin (6‐benzylaminopurine) alone to the basal medium. Best growth was obtained with combinations of 1 μg of auxin and 1 or 2 μg of cytokinin in 50 ml of medium. Larger amounts of the two phytohormones resulted in reduced growth.
STEM FORMATION FROM A SUCCULENT LEAF: ITS BEARING ON THEORIES OF AXIATION
Authors: Green Paul B. , Brooks Kenton E.
Published: January 2018

The radial symmetry of shoots and roots arises from a center of symmetry within the apical meristem. When a lateral axis forms at a distance from the tip, a new center of radial symmetry must arise. We have studied the biophysics of this kind of transformation in the epidermal layer of the succulent Graptopetalum where a stem “regenerates” from organized leaf tissue. Study of the epidermal cell pattern (with scanning electron microscopy) shows that reorganization involves neither a cellular pre‐pattern blocked out by oriented cell divisions nor a callus‐like stage where cell files, expansion direction, and primary cell wall cellulose orientation are randomized throughout. Rather, developmental events are a function of initial position. In regions of geometrical compatibility between parent axis and prospective lateral, there is little or no modification of files, expansion, or cellulose. In regions requiring 90° changes in orientation, cellulose orientation (studied with polarized light) conforms to the new symmetry first. This is followed later by changes in the surface growth pattern and in the cell division pattern. The early establishment of a circumferential cellulose pattern in the epidermal layer could account for both the cylindrical shape of the new axis and the subsequent rearrangement of directional growth and cell file pattern.
OCCURRENCE OF A STELAR LESION DURING IMBIBITIONAL CHILLING OF ZEA MAYS L.
Authors: Cohn Marc Alan , Obendorf R. L.
Published: January 2018

Radicle growth of the corn inbred Oh51A was reduced by imbibitional chilling at 5 C. The effect was mediated by the initial moisture of the kernel prior to hydration. Five percent initial moisture kernels were injured while 13% initial moisture kernels were not. The formation of a structural lesion in the radicle during the first 24 hr of hydration at 5 C of 5% initial moisture kernels was correlated with subsequent radicle growth reduction at 25 C. The lesion did not form during hydration of 13% initial moisture kernels at 5 C, in kernels hydrated at 25 C, in unimbibed kernels, or in heat‐killed, cold‐imbibed kernels. The lesion also did not appear during the imbibitional chilling of the corn inbred B8 which did not exhibit radicle growth reduction. Two sources of Oh51A with similar lesion frequencies were different in the severity of growth reduction. While the lesion became sealed at 25 C subsequent to cold hydration, growth reduction differences were not fully explained by this phenomenon. In one source more seedlings exhibited reduced growth than expected from the frequency of observable lesions. Therefore, other types of damage contributed to the reduction of radicle growth.
POLLINATION INTERACTIONS IN SYMPATRIC DICENTRA SPECIES
Authors: Macior Lazarus Walter
Published: January 2018

The pollination of a large mixed population of Dicentra canadensis and D. cucullaria was studied in a beech‐maple forest in southwestern Ohio. Analyses of pollinator frequencies and species, pollinator behavior, sugar components and concentrations in nectar, corbicular pollen loads carried by pollinators, spectral reflectance from corollas including ultraviolet reflectance, fragrance, blooming phenology, insect‐related fertility, and hybridization potentials suggested that these sympatric Dicentra species are reproductively isolated by internal mechanisms but not by external barriers to hybridization. Both species were exclusively and obligately dependent upon queen bumblebees for their pollination unlike other members of the spring ephemeral flora to which they belong. The occurrence of one or both species in one area is considered primarily the result of their adaptive preference for different edaphic and possibly climatic situations and not the consequence of competitive exclusion by pollinator behavior.
SYMBIOTIC NITROGEN FIXATION IN CEANOTHUS ROOTS
Authors: Kummerow Jochen , Alexander James V. , Neel James W. , Fishbeck Kathleen
Published: January 2018

Ceanothus greggii var. perplexans is a common shrub in the southern California chaparral. Clusters of nodules found under the canopy of this species are modified roots which contain a nitrogen‐fixing endophyte, Frankia ceanothi (Actinomycetales), within the cortex. The nodule density per m2 obtained from root system excavations is much lower than that reported for different Ceanothus species in northern California. Field observations indicate that soil moisture is an important factor in nodule formation. Anatomical studies with the scanning electron microscope and acetylene reduction assays support the hypothesis that the vesicles, spherical swellings of hyphal endings (1.2–3.0 μm in diam), are indeed the sites of N2 fixation. No bacteria‐like bodies were found. The acetylene reduction rates of C. greggii endophytes were of the same order of magnitude as those reported for other members of the genus Frankia. It is estimated that 100 grams of nitrogen are fixed per year per hectare for a specific area in the southern Californian chaparral where C. greggii comprises 1/3 of the ground cover. This amount appears to be large enough to replace the nitrogen that is lost annually by drainage and runoff from winter rain storms.
TAXONOMIC CHARACTERISTICS OF SPHENOPHYLLALEAN CONES
Authors: Good Charles W.
Published: January 2018

The range of variability in the taxonomic characteristics traditionally used to establish genera and species of Sphenophyllum cones is studied from specimens of Bowmanites dawsoni, B. trisporangiatus, B. bifurcatus, Litostrobus, and Sphenostrobus. Taxonomic criteria examined include configuration of the cone stele, number of sporangiophores per bract, anatropous vs. orthotropous sporangium attachment, number of appendages per node, and spore morphology. Because of the large degree of variability observed, these characteristics do not appear to adequately differentiate between the genera Litostrobus and Sphenostrobus, so these genera are combined under Sphenostrobus. A new combination, S. iowensis, is proposed for specimens previously described as L. iowensis, L. paulus, and B. moorei. It is suggested that species currently placed in the genus Bowmanites may represent several distinct natural genera of sphenophyllalean cones.
POLLINATION OF ANGIOSPERMS IN CONTRASTING CONIFEROUS FORESTS
Authors: Moral Roger del , Standley Lisa A.
Published: January 2018

We studied the distributions of flower color, flower morphology, and putative pollinators in eight communities in the western Cascades of Washington and 14 communities in the eastern Cascades. These two forested regions differ in the proportions of species in each flower color and morphological type such that the eastern region is more complex. The putative pollinators of each species were determined from morphological and color properties of the flowers and from the recent, extensive literature. The floristic complement of the western region appears to be serviced by a collection of pollinators that is less diverse than that of the east. In each region there is a strong positive correlation between species richness and flower color diversity, floral morphology diversity, and putative pollinator diversity, respectively. These comparisons suggest the competition for pollinators has led to greater niche differentiation in the eastern regions and that this factor, combined with greater habitat complexity, results in the far greater species richness of the eastern region.
EFFECT OF DESICCATION AND SCARIFICATION ON THE PERMEABILITY AND STRUCTURE OF THE SEED COAT OF CUSCUTA CAMPESTRIS
Authors: Hutchison James M. , Ashton Floyd M.
Published: January 2018

Changes occurring within the seed coat of Cuscuta campestris Yunkr. during desiccation were correlated with a decrease in germinability. Germination initially increased as the embryo matured, but then decreased as the testa dried. Completion of macrosclereid development signaled the onset of dormancy. Mechanical scarification with sandpaper or immersion in concentrated H2SO4 broke dormancy. The impermeable layer is a region above the light line and at the junction of the hypodermis and the palisade cell layers. This region appeared to be deposited during desiccation of the hypodermis. Overwintering or a period of cold storage also broke dormancy. The change in permeability was found throughout the testa rather than in a specific area.
ULTRASTRUCTURAL CHANGES OF CHLOROPLASTS IN ATTACHED AND DETACHED, AGING PRIMARY WHEAT LEAVES
Authors: Hurkman W. J.
Published: January 2018

Degradation of chloroplasts is shown in mesophyll cells of primary leaves of wheat. The sequence of ultrastructural changes in chloroplasts of naturally senescing leaves is compared with that of detached, aging leaves. In chloroplasts of naturally senescing leaves, the first indications of aging are the appearance of osmiophilic globuli and reorientation of the thylakoidal system. The membranes of the grana and intergrana lamellae then become distended and later dissociate into distinct vesicles. Concurrent with these membrane changes, osmiophilic globuli increase in size and number, and the stroma breaks down. Finally, the chloroplast envelope ruptures and plastid contents disperse throughout the cell's interior. In chloroplasts of mesophyll cells in detached, aging leaves, initial changes also include appearance of osmiophilic globuli, but later stages of chloroplast degradation are different. The chloroplast envelope ruptures before the lamellae break down. Swelling of grana and intergrana lamellae is not pronounced and, additionally, the thylakoidal system degenerates without forming vesicles or numerous osmiophilic globuli. These differences in the sequence of chloroplast degradation indicate that naturally senescing leaves rather than detached, aging leaves should be used in studies of chloroplast senescence.
ULTRASTRUCTURAL DEVELOPMENT OF THE BEETLE FOOD TISSUE OF CALYCANTHUS FLOWERS
Authors: Rickson Fred R.
Published: January 2018

The flower of Calycanthus traps a wide variety of beetles which, while imprisoned, effect pollination. During their occupancy the insects eat a protein‐rich tissue developed at the tips of the inner tepals, stamens, and staminodia. Cells of this food tissue differentiate a large number of cytoplasmic protein tubules by using a protein vacuole as an assembly site. The cells comprising the food tissue represent a very specialized plant cell type and one which facilitates this particular plant/insect relationship.
DIURNAL VARIATION IN THE ESSENTIAL OILS OF VALENCIA ORANGE LEAVES
Authors: Hopfinger J. A. , Kumamoto J. , Scora R. W.
Published: January 2018

Diurnal variations in the leaf oils of Valencia oranges [Citrus sinensis (L.) Osbeck] were studied over a period of 4 years. Depending on the season of harvest, a twofold diurnal change in amount of oil can be observed. A quiescent period between flushes was observed in June. The amount of the main individual components varies with the total oil so that the composition of oil shows only small variations. One suggested function for the oil could be as a precursor for higher isoprenoid biosynthesis.
UNDERGROUND BIOMASS PROFILES AND PRODUCTIVITY IN ATLANTIC COASTAL MARSHES
Authors: Gallagher John L. , Plumley F. Gerald
Published: January 2018

An underground biomass profile and productivity study involved year‐long sampling programs in 18 stands of salt marsh plants in Georgia, Delaware, and Maine. As the result of the monthly or bimonthly marsh coring program three types of underground biomass profiles were found. In the first, the concentration of macro‐organic matter (MOM) was uniform with depth; the notable example of this type was creekbank Spartina alterniflora in the southern part of the coast. A second type had a high MOM concentration at the surface which decreased with depth. This, the most common type of profile, was exemplified by Spartina patens, S. alterniflora from the high marsh along the southern coast (Georgia), and creekbank S. alterniflora from the northern part of its range (Maine). The third type of profile was seen where a large rhizome mat developed 15–20 cm below the surface. Spartina cynosuroides and Phragmites communis were typical examples of this type of profile, resulting in a low biomass at the surface, a higher biomass somewhat below the surface, and a low concentration at depth. The annual maxima and minima of MOM biomass were used to calculate annual increments, which can be considered minimum annual production values. These productivity values ranged from a low of 80 g C/m2 for creekhead S. alterniflora in Maine to a high of 1690 g C/m2 for Juncus gerardi in Maine. The mean for all plant stands was 650 g C/m2. Since the average carbon content of the MOM was 35.3%, this corresponds to 1850 g dry weight/m2 per year. As a measure of the relative activity of the total pool of macro‐organic material in the soil, turnover times were calculated by dividing the total macro‐organic matter by the annual increments. Within the MOM pool there are several components with turnover times varying from days to years. The turnover time for the entire pool ranged from 18 months in two Georgia salt marsh plant stands to 224 months for one in Maine. In the two instances where values for a species could be compared between Maine and Georgia, the turnover time was shorter at the more southerly site. These results can probably be attributed to slower microbial decay rates in the cooler climate. In Georgia and Maine where the turnover values for a species were determined for two elevations, the time was shorter at the lower elevation.
CHROMOSOME NUMBERS IN SOUTH AMERICAN COMPOSITAE
Authors: Turner B. L. , Bacon J. , Urbatsch L. , Simpson B.
Published: January 2018

Original chromosome counts are reported from 91 populations and 73 taxa distributed among 46 genera. Most of these were obtained from meiotic material and are first reports. Some of the more interesting counts are from genera with amphitropical distributions such as Gaillardia and Helenium. When appropriate, systematic implications of the data are discussed.
FLAVONOIDS AND TAXONOMY OF THE LIMNANTHACEAE
Authors: Parker William H. , Bohm Bruce A.
Published: January 2018

To help clarify relationships within the Limnanthaceae, all 19 taxa were compared on the basis of flavonoids occurring in all tissues, and 14 of these taxa were additionally compared on the basis of flavonoids occurring only in the petals. Of the 46 flavonol glycosides encountered, 35 were identified as derivatives of six flavonol aglycone types: syringetin, isorhamnetin, kaempferol, laricytrin (myricetin 3'‐methyl ether), quercetin and myricetin, all glycosylated with combinations of glucose and rhamnose. Varimax Factor Analysis with rotation of the flavonoid data indicated that the family probably contains 3 phyletic lines, an observation inconsistent with the conventional 2‐generic interpretation of the family. Mason's sectional treatment of Limnanthes is supported by petal flavonoid results, but not by whole‐plant flavonoid results, indicating that petal flavonoids more clearly reflect natural relationships in Limnanthes. Evolution of whole‐plant flavonoids of Limnanthes appears to be partly linked to changes in breeding system.
CHARACTERIZATION OF POLLEN ANTIGENS FROM AMBROSIA L. (COMPOSITAE) AND RELATED TAXA BY IMMUNOELECTROPHORESIS AND RADIAL IMMUNODIFFUSION
Authors: Lee Yoo Sung , Dickinson David B.
Published: January 2018

The pollen antigens of various Ambrosia and related species were studied to learn whether substances closely related to antigen E (the major allergen of Ambrosia artemisiifolia) were present. After conventional immunoelectrophoresis, pollen extracts from six Ambrosia species each produced at least one pronounced precipitin line with antiserum for purified antigen E. Electrophoretic mobility was the same for several species (A. artemisiifolia, A. bidentata, A. psilostachya, and A. trifida) but was relatively lower for A. acanthicarpa and A. ambrosioides. Precipitin rings were also produced when pollen extracts of the various Ambrosia species were subjected to radial immunodiffusion in agarose which contained antiserum for purified antigen E. There was great variation among the Ambrosia species with respect to precipitin ring diameters. The variation may be due to differences among species in content of the antigen E‐like substances or to altered interaction with the immobilized antibody. Crossed (2‐dimensional) immunoelectrophoresis was shown to be useful for characterizing Ambrosia pollen antigens. Pollen extracts from A. artemisiifolia produced eight pronounced precipitin bands and at least eight faint, relatively fast‐moving bands after crossed immunoelectrophoresis with antiserum against a whole pollen extract from the same species. One of the pronounced bands contained antigen E.
A COMPARATIVE LIGHT‐ AND ELECTRON‐MICROSCOPIC STUDY OF MICROSPOROGENESIS IN MALE STERILE (MS,) AND MALE FERTILE SOYBEANS (GLYCINE MAX (L.) MERR.)
Authors: Albertsen Marc C. , Palmer Reid G.
Published: January 2018

A comparative study of microsporogenesis in fertile and in male sterile (ms1) soybean plants (Glycine max (L.) Merr.) was conducted by using various microscopic techniques. Once the developmental pattern for fertile microsporogenesis was established, it was compared with the developmental pattern in sterile plants to determine the time of microsporogenesis breakdown. Sterility of the ms1 mutant is caused by failure of cytokinesis after telophase II. The four nuclei resulting from meiosis become enclosed in a single‐celled structure, termed a coenocytic microspore. These microspores develop a pollen‐like wall and become engorged with lipid and starch reserves. Coenocytic microspores usually degenerate after engorgement. This study of fertile and sterile (ms1) microsporogenesis has shown that nuclear and cytoplasmic events must occur at precise times for the successful development of 1n pollen grains from 2n sporogenous cells. Any disruption during this process leads to sterility.
PLASTIDS IN LATICIFERS OF PAPAVER. II. ENZYME CYTOCHEMISTRY OF MEMBRANE‐BOUND INCLUSIONS OF LATICIFER PLASTIDS IN P. BRACTEATUM LINDL. (PAPAVERACEAE)
Authors: Nessler Craig L. , Mahlberg Paul G.
Published: January 2018

Membrane‐bound inclusions in laticifer plastids of Papaver bracteatum Lindl. were examined by electron microscopic enzyme cytochemistry. Electron‐opaque reaction products were observed in the plastid inclusions of laticifers in tissues incubated in 3,4 dihydroxyphenylalanine (dopa), tyrosine, or 3,3 diaminobenzidine (DAB). The enzymatic basis for substrate oxidation was confirmed by the absence of reaction product in boiled controls. Oxidation of dopa and tyrosine in plastid inclusions was not inhibited by sodium diethyldithiocarbamate (DDC), although DDC did inhibit the formation of reaction product between chloroplast lamellae in non‐laticiferous cells. Reaction product was also observed in tissues incubated in dopa and subsequently treated with catalase or catalase plus DDC. DAB oxidation was observed at pH 9.0 and 7.3, in tissues preincubated in aminotriazole (AT) and when hydrogen peroxide was omitted from the DAB medium. The results suggest that peroxidases in the inclusions of laticifer plastids may be responsible for substrate oxidation, even though exogenously applied catalase failed to inhibit dopa oxidation.
DEVELOPMENT OF THE INFLORESCENCE AND “CROWN” OF ANANAS COMOSUS AFTER TREATMENT WITH ACETYLENE, NAA, AND ETHEPHON
Authors: Wee Y. C. , Rao A. N.
Published: January 2018

The vegetative apex of the Masmerah cultivar of pineapple, Ananas comosus (L.) Merr., is dome‐shaped and has the typical tunica‐corpus organization. Treating the plant with acetylene, NAA or ethephon transforms the vegetative apex to a reproductive one. As early as two days after treatment the apical height and width increase, attaining maximum dimensions in 8–14 days, after which they progressively decrease. During 4–6 weeks, when the full complement of florets has been initiated, the dimensions of the apex are again increased and leaves that form the fruit crown are initiated. A cambium‐like zone at the base of the corpus is noticed 2–4 days after the application of acetylene and ethephon. Acetylene and NAA result in a more pointed apex initially, while ethephon results in a more broadened apex. The largest increase in apical height and width is seen when NAA is used. The development of the inflorescence from the time the full complement of florets is formed to fruit maturity is described. Cell multiplication is the main cause of peduncle elongation and inflorescence head enlargement, although towards the later stages of growth, cell enlargement contributes more to the increase in size of the organs.
ECOLOGICAL GENETICS OF THE COLONIZING ABILITY OF ROSE CLOVER (TRIFOLIUM HIRTUM ALL.)
Authors: Jain S. K. , Martins P. S.
Published: January 2018

Thirteen populations sampled from among the oldest plantings of rose clover (Trifolium hirtum All.), introduced into the California range during the late 1940's, and 12 roadside populations established through natural colonization were compared for their genetic and demographic features. Roadside colonies showed a greater amount of reproductive effort in terms of a larger number of heads per plant and larger calyx, lower rate of seed carryover, higher and more stable plant density, lower seedling survivorship, and earlier flowering. The calyx was more hirsute in roadside collections and remained attached with the seed, a feature accounting for higher germination probabilities on the soil surface or in litter along the roadsides, in contrast to the range where grazing animals would often work the seed into the soil. Outcrossing rates are slightly higher in roadside colonies in which genetic polymorphisms at three marker loci represented as high levels of genetic variability as in the range populations. The colonizing success of rose clover seems to be largely determined by a few and rapid morphological changes and by the retention of some outbreeding and genetic variation. Such joint analyses of genetic and demographic features of colonizing species are needed to support various deductions about the characteristics of “ideal” weeds and colonizers.
RADIOACTIVE TRACER STUDY OF SPOROPHYTE NUTRITION IN HEPATICS
Authors: Thomas Robert J. , Stanton David S. , Grusak Michael A.
Published: January 2018

Sporophytes of Fossombronia foveolata, Lophocolea heterophylla, Pellia epiphylla, Ptilidium pulcherrimum, and Riella affinis were surgically isolated from host gametophyte tissues and treated with 14CO2. Sporophytes of all five species are capable of fixing CO2 in the light. Sporophyte/gametophyte ratios for 14CO2 fixation/mg fresh weight range between 0.12 and 0.39. Corresponding ratios for chlorophyll content are 1.07 to 3.30. Of the total 14CO2 fixed by excised Lophocolea sporophytes, 40% can be attributed to the photosynthetic activity of haploid spores. Enveloping gametophytic tissues (calyptra and pseudoperianth) inhibit photosynthesis of attached sporophytes by as much as 50%. For sustained growth, sporophytes rely on organic nutrients supplied by the gametophyte: radioactivity of Lophocolea sporophytes increases significantly after application of 14C‐glucose to host gametophytes. Surgically isolated sporophytes develop slowly in mineral culture, without significant increase in dry weight. The assumption that hepatic sporophytes are at least partly autonomous with respect to organic nutrition (an assumption that figures prominently in speculation on the evolutionary origin of the sporophyte) is confirmed.
GLANDULAR LEAF STRUCTURE OF TRIPHYOPHYLLUM PELTATUM (DIONCOPHYLLACEAE): A “FLY‐PAPER” INSECT TRAPPER
Authors: Marburger Joy E.
Published: January 2018

Certain leaves of Triphyophyllum peltatum (Hutch. & Dalz.) Airy Shaw (Dioncophyllaceae) have an extended, erect midrib covered with stalked and sessile glands exhibiting insect‐trapping ability. The stalked glands secrete a sticky, acid mucilage to which numerous insects in various stages of decay were observed adhering. The morphology and anatomy of the glandular leaves were investigated with light and scanning electron microscopy. The midrib and the lamina in the lowermost part of the leaf bear stomata. Those of the midrib are transitional between actinocytic and cyclocytic in type. Parenchyma cells in mature and immature portions of the midrib and in the glands contain numerous crystals and amyloplasts. The anatomy of the stalked and sessile glands is remarkably similar to that of Drosophyllum lusitanicum (L.) Link. (Droseraceae). A distinct cuticle covers the gland head, but no pores are visible. Three distinct layers underlie the cuticle: a definite epidermal layer with irregularly thickened cell walls, and two layers of more loosely arranged cells. A fourth layer, endodermoid in nature with radially thickened cell walls, connects the head and stalk of the stalked glands and the head and midrib parenchyma of the sessile glands. Vascular elements (including helical and scalariform tracheary elements) reach the endodermoid layer. According to recent studies, Triphyophyllum and Drosophyllum have different phylogenetic origins; the morphological and anatomical similarities in the insect‐trapping glandular leaves show more support for their convergent evolution rather than for an alliance of the Dioncophyllaceae with the Droseraceae.
VARIATION OF SHOOT MORPHOLOGY AND BIFURCATION RATIO IN SUGAR MAPLE (ACER SACCHARUM) SAPLINGS
Authors: Steingraeber David A. , Kascht Lawrence J. , Franck Daniel H.
Published: January 2018

Open‐grown sugar maple saplings differ qualitatively in their gross morphology when compared with saplings growing in shaded forest understories. Forest‐grown saplings have their leaves distributed in a few planar layers, while open‐grown saplings exhibit fuller crowns and more profuse branching. In order to quantify these observed differences in branching patterns, ordering methods were applied to twenty saplings each from forest and open sites. Bifurcation ratio, an index of branching previously assumed to be species constant, differed significantly between forest‐grown and open‐grown saplings. Bifurcation ratios for forest‐grown saplings were low, with a mean of 3.19. Values for open‐grown saplings were generally higher, with a mean of 7.05. This variation of bifurcation ratio between forest‐grown and open‐grown sugar maple saplings is the first such variation within any species to be reported. In addition, open‐grown saplings were characterized by more extension growth of terminal shoots than forest‐grown saplings. These results suggest that sugar maple has a range of branching and light interception characteristics that suit it well in different microenvironments.