bluuebunny/crossref_metadata_2025 huggingface dataset:
FUCHSIA POLLEN FROM THE EARLY MIOCENE OF NEW ZEALAND
Authors: Daghlian Charles P. , Skvarla John J. , Pocknall David , Raven Peter H.
Published: January 2018

Fossil pollen of Diporites aspis Pocknall & Mildenhall, from the early Miocene of New Zealand, was examined by combined light, scanning, and transmission electron microscopy, in order to determine its relationship to extant Fuchsia pollen. Based on overall morphology, exine structure, exine surface sculpture, viscin thread morphology, and apertural features, the fossil pollen definitely can be considered to represent Fuchsia. Parallel studies of extant Fuchsia pollen indicate that a more precise identification of the fossils is not possible. With the examination of additional fossil material, it should be possible to learn a great deal about the timing of origin and migration of the genus Fuchsia, but not of its constituent parts.
CELL CYCLE DURATION IN THE MERISTEM OF NEPHROLEPIS BISERRATA STOLONS: THE ROLE OF THE APICAL CELL
Authors: Seilhean V. , Michaux‐Ferriere N.
Published: January 2018

The stolons of Nephrolepis biserrata (sw.) Schott are thin axes that grow rapidly (from 2 to 4 mm per day) in the controlled conditions applied. In the cylindro‐conical meristem, three histological zones are defined. Cell cycle duration was determined for each zone by autoradiographic methods after incorporation of tritiated thymidine and confirmed by the colchicine‐induced metaphase‐accumulation technique. The apical cell and its derivatives (Zone 1) are mitotically more active (cell cycle duration: 80 hr) than the cells of the subapical zones (2 and 3), where cell cycle lengths are 142 hr and 95 hr respectively. These data, compared to previous results, give evidence for the main role played by the relative rate of division of the apical cell compared to that of lateral cells in the organization and the shape of the meristem of pteridophytes. Moreover, the apical cell appears to be unique in having a differentiated cytological aspect not usually associated with an intensely proliferating cell.
THE ROLE OF MUCILAGE IN THE GERMINATION OF CUIPO, CAVANILLESIA PLATANIFOLIA (H. & B.) H. B. K. (BOMBACACEAE), A TROPICAL TREE
Authors: Garwood Nancy C.
Published: January 2018

The mucilage in the fruits of cuipo, Cavanillesia platanifolia, is an adaptation to the unpredictable rainfall at the beginning of the rainy season in the tropical moist forests of central Panama. It allows cuipo to germinate rapidly following rains in the early rainy season, before other potential competitors. Mucilage comprises ~27% of the mass of the large (~3.5 g) wind‐dispersed fruits of cuipo. Water uptake capacity of cuipo fruits (7 g water/g fruit in 10 min) was greater than that of the diaspores of five wind‐dispersed species sympatric with cuipo. Diaspores of these five species lost all their absorbed water within 2 days but cuipo retained it for 2 wk. Experiments using two mucilage treatments (seeds within fruit and seeds alone) and three watering treatments (daily, weekly, and biweekly) indicated that 1) neither mucilage nor watering treatments altered percent germination; 2) the presence of mucilage‐rich fruits lessened the effects of drought on seedling development and decreased the degree of wilting; and 3) both treatments interacted in their effects on percent and cause of mortality.
CHIMERAL NATURE OF THE PINWHEEL FLOWERING AFRICAN VIOLETS (SAINTPAULIA, GESNERIACEAE)
Authors: Lineberger R. Daniel , Druckenbrod Mark
Published: January 2018

Pinwheel flowering African violets are bicolor forms that have a patterned arrangement of colors on the corolla segments. A median band of one color extends radially from the central portion of the corolla on each corolla segment and contrasts with the marginal color. In vitro culture of various tissues was accomplished, and observation of the flowering patterns of the regenerated plants supports the hypothesis that the cultivars ‘Valencia’, ‘Dardevil’, and ‘Desert Dawn’ are periclinal chimeras. Adventitious plants display a high proportion of monochromatic flowers of the same color as the lateral margin of the corolla segments. Petiole cultures from which the epidermal layers were removed yielded plants with flowers of the color of the central stripe of the corolla segments. Pinwheel flowering plants were regenerated through short‐term culture of whole inflorescences, suggesting that the African violet inflorescence may possess axillary vegetative meristems. These results support the contention that adventitious shoots may arise from the epidermal layer only (L.I), or with the participation of the epidermal and subjacent layers (L.I and L.II). These results contradict the recent conclusion that all three histogen layers of African violet participate in adventitious shoot organization.
FUNGAL ENDOPHYTES OF CYPERUS AND THEIR EFFECT ON AN INSECT HERBIVORE
Authors: Clay Keith , Hardy Tad N. , Hammond Abner M.
Published: January 2018

Populations of the sedges Cyperus virens Michx. and C. pseudovegetus Steud. (Cyperaceae) in Louisiana often contain individuals infected by the systemic fungal endophyte Balansia cyperi Edg. (Clavicipitaceae, Ascomycetes). Related fungal endophytes infecting grasses are known to have detrimental effects on insect and mammalian herbivores consuming infected plants. In this study herbivory of infected and uninfected sedges was compared in two laboratory experiments. Newly hatched larvae of the fall armyworm (Spodoptera frugiperda [J. E. Smith], Noctuidae, Lepidoptera) were reared on leaves from either infected or uninfected plants of C. virens and C. pseudovegetus grown in the greenhouse. Survival, growth, and development of each insect were monitored. For both sedges larval survival and rate of weight gain were reduced, and length of the larval period was increased for larvae reared on leaves from infected plants compared to larvae reared on leaves from uninfected plants. The results of this study parallel results obtained from grasses, suggesting that the endophyte may defend its host against herbivory in natural populations.
EVIDENCE FOR SIGNIFICANT DIFFERENCES IN NUCLEAR DNA CONTENT BETWEEN TWO GEOGRAPHICALLY ISOLATED CLONES OF ARMILLARIA MELLEA
Authors: Motta Jerome J.
Published: January 2018

Several collections of Armillaria mellea (Vahl: Fr.) Kummer basidiocarps were screened for relative nuclear DNA content using microspectrophotometric techniques. One collection from the Pacific Northwest showed relative DNA values approximately 30% higher than a reference collection from College Park, Maryland. Corresponding differences in nuclear volumes were also observed. It is postulated that the Washington isolate may represent a stable aneuploid or polyploid clone of the species.
GRAVITROPISM IN ABSCISIC‐ACID DEFICIENT SEEDLINGS OF ZEA MAYS
Authors: Moore Randy , Smith J. D. , Fong Franklin
Published: January 2018

We did not detect any abscisic acid (ABA) in roots or leaves of carotenoid‐deficient mutants of Zea mays. Similarly, we did not detect any ABA in roots or leaves of seedlings treated with Fluridone (an inhibitor of carotenogenesis) even after subjecting them to polyethylene glycol (PEG)‐induced moisture stress. Primary roots of untreated, Fluridone‐treated, and mutant seedlings were strongly graviresponsive. These results suggest that 1) ABA is not necessary for positive gravitropism by primary roots of these cultivars of Z. mays, and 2) ABA is synthesized via the carotenoid pathway.
APOMIXIS IN AMELANCHIER LAEVIS, SHADBUSH (ROSACEAE, MALOIDEAE)
Authors: Campbell Christopher S. , Greene Craig W. , Neubauer Benedict F. , Higgins Jean M.
Published: January 2018

We studied ovule and megagametophyte development in tetraploid (n = 34) individuals of Amelanchier laevis in Maine. Nomarski differential interference contrast microscopy of cleared, whole ovules and conventional microscopy of sectioned, stained material show no clear evidence for the successful completion of meiosis. Instead, the megasporocyte or its derivatives degenerate and one to six nearby cells develop into aposporous initials. Usually more than one of these divide to form eight‐nucleate, Polygonum‐type megagametophytes. The egg apparently forms a proembryo parthenogenetically, but seed maturation requires pollination. This evidence for apospory and pseudogamy, the first to be reported in Amelanchier, conforms to the general pattern found in other apomictic genera of the Maloideae.
DYNAMICS OF A HYBRID ZONE IN PHLOX: AN EXPERIMENTAL DEMOGRAPHIC INVESTIGATION
Authors: Levin Donald A. , Schmidt Kurt P.
Published: January 2018

The dynamics of a narrow hybrid zone between Phlox drummondii ssp. drummondii and ssp. mcallisteri was investigated using an experimental demographic approach. Three populations of each subspecies as well as those from the hybrid zone were involved. Experimental plots containing seeds from each of the nine populations were established in each of the eight sites. Germination, survivorship to reproduction, and fecundity were monitored at 4–6 wk intervals. Finite rates of increase were estimated from these data. There were significant site effects for each demographic variable and rate of increase as well as significant population effects for germination and finite rate of increase. Although there were population effects, no significant differences were found between plant types in sites of the subspecies or the hybrid zone. We reject the hypothesis that the narrow width of the hybrid zone is the result of hybrid disadvantage. We propose that the narrow width is a result of restricted gene flow and discuss the supporting evidence.
THE MEAN INNER RADIUS OF SUN AND SHADE ILEX OPACA LEAVES
Authors: Supnick Martin
Published: January 2018

The mean inner radius of thickness M, a shape measure defined as the mean of the shortest distances d to the border from all internal points Pi of an object, was applied in its dimensionless form D0M to Ilex opaca sun and shade leaves. This measure has the following attributes: 1) ubiquitous input; 2) the point function f(P) = d is always single valued; 3) it is an intrinsic measure; 4) it is nondirectional; 5) the same definition may be used for any dimension number and be extended to other functions of d.

Since Ilex opaca is found in hot, sunny environments, one might predict its sun leaves to be smaller in area and “narrower” in shape (lower D0M) than shade leaves, making them better convective coolers. Although sun leaves of Ilex opaca have been shown to be smaller in area, their D0M was unexpectedly greater than shade leaves.
CHANGES INDUCED BY WATER ON EUPHORBIA SUPINA SEED COAT STRUCTURES
Authors: Jordan Lowell S. , Jordan James L. , Jordan Catalina M.
Published: January 2018

Moisture applied to dry seeds of Euphorbia supina Raf. caused helices embedded in the seed coat to elongate. The helices consist initially of tightly coiled strands that loosen when moistened. The helices can repeatedly elongate and contract, but their configuration and expandability gradually changes as the strands coalesce to form thin plates. With prolonged exposure to moisture and drying, the plates, in turn, coalesce into an amorphous layer that covers the seed. Periodic Acid‐Schiff test produced red coloration, which indicates the helices contain polysaccharides, probably mucilage.
PATTERNS OF FLORAL NECTAR‐SUGAR COMPOSITION OF IPOMOPSIS LONGIFLORA (POLEMONIACEAE) NEAR THE CONTACT ZONE OF ITS SUBSPECIES LONGIFLORA AND AUSTRALIS
Authors: Freeman C. Edward , Reid William H. , Worthington Richard D.
Published: January 2018

The nectar‐sugar compositions of 338 individuals from 27 populations in two subspecies of Ipomopsis longiflora from Arizona, New Mexico, Texas, and Chihuahua were determined by high‐performance liquid chromatography. Mean sucrose compositions of populations ranged from 73.2% to 91.9%, and the standard deviations ranged from 1.9% to 9.1%. Pairs and aggregates of populations were statistically compared. The nectar‐sugar compositions of the two subspecies were significantly different as aggregates. Subspecies australis averaged 9.5% fructose, 7.9% glucose, and 82.6% sucrose while subspecies longiflora averaged 7.8% fructose, 5.7% glucose, and 86.5% sucrose. Each subspecies was found to have two groups of populations. Groups of higher sucrose populations were found along the contact zone of the subspecies; away from the contact zone both subspecies had groups of lower sucrose populations. The data show that significant variability exists in this biochemical character, and the pattern of variation is clearly related to the geographic distribution of the populations. The genetic and selective mechanisms involved are unknown.
ONTOGENETIC CHANGES IN DNA CONTENT IN ROOTS OF THE WATER FERN AZOLLA FILICULOIDES
Authors: Kurth Eva , Gifford Ernest M.
Published: January 2018

The DNA content of the apical cell and various other cells in the roots of Azolla filiculoides was determined by two‐wavelength cytospectrophotometry. DNA content decreased markedly with increasing age of the apical cell; there was a similar but less pronounced trend in the other cell populations studied. These findings suggest the possibility of DNA amplification in very young roots with rapidly dividing cells.
EFFECT OF SEED SIZE ON HETEROBLASTIC DEVELOPMENT IN SEEDLINGS OF DESMODIUM PANICULATUM
Authors: Wulff Renata D.
Published: January 2018

Seedlings of Desmodium paniculatum derived from different seed sizes differed in heteroblastic development. The transition from juvenile to adult leaves took place at the fourth node in seedlings derived from larger seeds and at the fifth or sixth node in those derived from smaller ones. Cotyledon removal had no effect on this condition, but growth under reduced irradiance delayed the formation of adult leaves in seedlings from larger seeds. Simple and compound leaves had similar unit area photosynthetic rates and stomatal conductance values, but compound leaves had a 30% higher total area. The earlier production of adult leaves would thus give seedlings from larger seeds an advantage in terms of total carbon gain.
RECIPROCAL TRANSPLANT EXPERIMENTS WITH DELPHINIUM NELSONII (RANUNCULACEAE): EVIDENCE FOR LOCAL ADAPTATION
Authors: Waser Nickolas M. , Price Mary V.
Published: January 2018

Reciprocal seed transplants suggest that there is fine‐scale adaptation in Colorado populations of the perennial herb Delphinium nelsonii. In four experimental plots, seeds planted within 1 m of the maternal parent produced seedlings that began flowering at a younger age and produced more flowers over their lifespan than those derived from maternal parents growing 50 m away. These “resident” seedlings also survived as well or better than the “nonresidents.” Resulting selection coefficients against nonresidents averaged 34%. Species composition of the herbaceous flora was found to vary substantially over short distances in subalpine meadows where D. nelsonii grows, indicating that the biotic environment varies and that physical factors probably do as well. Thus, spatial heterogeneity in selective forces may be substantial, which should foster the sort of local adaptation documented for D. nelsonii.
DOES INTERFERENCE CAUSE NICHE DIFFERENTIATION? EVIDENCE FROM SUBALPINE PLANT COMMUNITIES
Authors: Moral Roger del , Clampitt Christopher A. , Wood David M.
Published: January 2018

The effects of interference on community structure of subalpine meadows were investigated. Adults greatly reduced seedling survival in the greenhouse, and natural seedling survival was low. In fell fields, nurse plant effects were common, while survival was confined to gaps in productive meadows. A greenhouse experiment demonstrated that community dominants were strong competitors able to suppress subordinates. Simulated grazing of Festuca, a dominant, reduced its yield relative to most subordinates. Interference intensity appears to be a function of productivity and proximity. The proportion of negative species associations increased as productivity increased. Morphological similarity between species is least in the most productive community, but greatest where productivity is only moderate. Interference may permit only relatively dissimilar species to coexist unless it is ameliorated by factors such as grazing or heterogeneity. Spacing patterns suggest that minimal contact between dominants and other species is a characteristic of communities with intense interference. The evidence points to this hypothesis: interference acts contemporaneously to limit niche width in productive communities, but evolutionary changes are unlikely where complete dominance is possible and specialization is not a viable option. In contrast, species in unproductive communities, where abiotic stress is likely to have been an evolutionary force, appear genetically more niche differentiated. Where contemporary interference is moderate, evolutionary effects are possible because species may use resources not preempted by the dominants.
PHENOTYPIC VARIATION WITHIN “INDIVIDUAL” LICHEN THALLI
Authors: Larson D. W. , Carey C. K.
Published: January 2018

“Individual” large diam lichen thalli of Umbilicaria vellea (L.) Ach. and U. mammulata (Ach.) Tuck. are not uniform in physiological activity or enzymatic phenotype. Horizontal variation in net photosynthetic rates and dark respiration rates was found, but this was independent of the mass of the photosynthesizing or respiring tissues. In addition, sublethal temperature pretreatments reduced the net photosynthetic and respiratory rates of some areas of the thallus, but increased others.

Assays of isoenzyme phenotypes showed that all large diam thalli are extensively polymorphic while young, small diam thalli are mainly monomorphic. Taken together, the results say that the concept of the “individual” may be inappropriate for these organisms.
MORPHOMETRIC ANALYSIS OF SHAPE OF SPECIMENS FROM THE NEOTYPE OF TABELLARIA FLOCCULOSA (BACILLARIOPHYCEAE)
Authors: Theriot Edward , Ladewski Theodore B.
Published: January 2018

Shape variation of 67 specimens from the neotype slide of Tabellaría flocculosa was analyzed by computer‐assisted morphometric techniques. Coefficients of a Legendre polynomial expansion of specimen shapes are shape descriptors used in principal component analysis (PCA). The first PC axis (PC1) is highly correlated with valve length. Variation along PC, is a combination of increase in width with a reduction in the distance between central and terminal inflations. The second axis (PC2) is the major length‐free component of shape variation. Variation in PC2 scores is related to the degree of constriction between the poles and the center. Shape variability increases as specimen length decreases. Three nonexclusive hypotheses can explain this: 1) different genetic entities are involved, 2) control of shape is strict in specimens longer than 35 μm, but not for those less than 35 μm, 3) the pattern of variation reflects environmental variation during the period of development of the population.
SYSTEMATIC STUDIES IN THE PHACELIA HUMILES GROUP (HYDROPHYLLACEAE): COROLLA VENATION PATTERNS
Authors: Lee Gregory J.
Published: January 2018

A survey of corolla venation patterns in the Phacelia Humiles group (Hydrophyllaceae) revealed considerable diversity, ranging from open venation and no interpetal vascular connections in some taxa to closed venation and interpetal vascular connections in others. In general, the distribution of the different venation patterns agrees with recent taxonomic treatments and provides evidence for the artificiality of sections based on ovule number. In several cases where the affinity of a species was ambiguous, the venation pattern of its corollas provides evidence for its placement.
A SCANNING ELECTRON MICROSCOPIC STUDY ON THE INITIATION AND DEVELOPMENT OF FLORAL ORGANS OF BRASSICA NAPUS (CV. WESTAR)
Authors: Polowick P. L. , Sawhney V. K.
Published: January 2018

The initiation and development of the floral organs of Brassica napus L. (cv. Westar) were examined using the scanning electron microscope. After transition of the vegetative apex into an inflorescence apex, flower primordia were initiated in a helical phyllotactic pattern. The sequence of initiation of the floral organs in a flower bud was that of sepals, stamens, petals and gynoecium. Of the four sepal primordia, the abaxial was initiated first, followed by the two lateral and finally the adaxial primordium. The four long stamens were initiated simultaneously in positions alternating with the sepals. The two short stamens were initiated basipetal to and outside the long stamens, and opposite the lateral sepals. The petals arose on either side of the two short stamens and the gynoecium was produced from the remainder of the apex. During development, the sepal primordia curved sharply at the tips and tightly enclosed the other organs. Stamen primordia developed tetralobed anthers at an early stage while filament elongation occurred just prior to anthesis. A unique pattern of bulbous cells was present on the abaxial surface of the anther. Growth of petal primordia lagged relative to the other floral organs but expansion was rapid prior to anthesis. The gynoecium primordium was characterized by an invagination early in development. At maturity, there was differentiation of a papillate stigma, an elongated style and a long ovary marked externally by sutures and divided internally by a septum. Distinct patterns of cuticular thickenings were observed on the abaxial and adaxial surfaces of the petals and stamens and on the surface of the style. The patterns were less obvious on the sepals and ovary. Stomata were present on both surfaces of the mature sepals, on the style and restricted areas on the abaxial surface of the anthers and nectaries but were absent from the petals, the adaxial surface of the stamens and the ovary. No hairs were present on any of the floral organs.
SEED BANK DYNAMICS IN A SOUTHEASTERN RIVERINE SWAMP
Authors: Schneider Rebecca L. , Sharitz Rebecca R.
Published: January 2018

Seed banks were examined in a Taxodium distichum L.‐Nyssa aquatica L. (cypress‐tupelo) swamp forest and an adjacent bottomland hardwood forest on the floodplain of the Savannah River in South Carolina. Thirty 0.01 m2 soil cores were collected in each community at each of three sampling times: before seed fall, after seed fall, and after an early spring river level rise had inundated both communities. Germination and sieving techniques were used to enumerate seeds in each sample. Woody seed banks of the two communities were dissimilar in species composition with both underrepresenting the species composition of the standing vegetation. In contrast, herbaceous seed banks of both communities were similar in species composition with greater species diversity in the seed banks than in the standing vegetation. Both the herbaceous and woody seed banks of the hardwood community changed significantly in seed densities across the three collection dates. Densities increased from September to December, after seed fall for many species, but decreased in April after the early spring water level rise. Seed densities did not change significantly in the cypress‐tupelo community across the three collections. Hydrologic regime appears to have a major influence on seed bank composition and dynamics in southeastern riverine swamps.
BERTRAM WHITTIER WELLS (1884–1978): A STUDY IN THE HISTORY OF NORTH AMERICAN PLANT ECOLOGY
Authors: Troyer James R.
Published: January 2018

The botanist Bertram Whittier Wells belonged to the first generation of North American plant ecologists who worked in the period 1900–1950. As such he approached plant communities descriptively, with emphasis on their qualitative composition, distribution with respect to habitat factors, and successional relations. He pioneered in the study of the ecology of the vegetation of the southeastern United States, especially of the coastal plain. His principal contributions lay in establishing early foundations for understanding a number of problems: the role of pine communities, the interaction of pyric with topographic and edaphic factors, secondary succession in old fields, the origin and maintenance of mountain grassy balds, the salt‐spray factor in coastal ecology, and the origin and history of lakes of the Carolina bays. Wells worked essentially alone, apart from the ecological schools and doctrinal networks which characterized his time. He received little contemporary recognition from his fellow ecologists, and in later years even acquired a negative reputation. The work of Wells is examined both for itself and for the insight it and its reception afford into the history of the initial half‐century of North American plant ecology. A complete list of Wells' ecological publications is presented.
FACTORS INFLUENCING SEED GERMINATION IN SALICORNIA PACIFICA VAR. UTAHENSIS
Authors: Khan M. Ajmal , Weber Darrell J.
Published: January 2018

The halophyte, Salicornia pacifica var. utahensis (Tiderstorm) Munz produces seed under high salinity conditions, and deposits its seed on saline soil. Experiments were conducted to determine the effect of salinity, temperature and growth regulators on germination. Results indicate that the seeds can germinate at very high salt concentration (5% NaCl). Germination was sensitive to the changes in temperature regimes. At higher 30–20 C, light‐dark sequence, no germination occurred at 3, 4 and 5% NaCl treatments. On the other hand, 30% germination did occur at 5% NaCl treatment at a temperature regime of 15–5 C. These seeds required light for germination. Only 50% germination occurred in the non‐saline control in the dark and the addition of NaCl further reduced germination. The GA3 partially alleviated the inhibitory effect of NaCl and darkness. Kinetin did not promote germination.
LIPID RESERVES OF SEEDS OF IMPATIENS CAPENSIS AND I. PALLIDA (BALSAMINACEAE): DEVELOPMENTAL ASPECTS
Authors: Nozzolillo Constance , Rahal Hussain , Llljenberg Conny
Published: January 2018

It has been known since 1948 that seeds of Impatiens species (family Balsaminaceae) contain a polyconjugated 18:4 fatty acid, α‐parinaric acid. Content of this acid is high in seeds of the two species of Impatiens native to eastern North America, I. capensis Meerb. and I. pallida Nutt. The cotyledons of these seeds also have an unusual blue pigmentation that disappears when lipids are extracted. Deposition of oil reserves and appearance of cotyledon color was observed during fruit development. Pods of I. capensis and I. pallida were measured daily after anthesis. Length increased linearly to a maximum of about 27 mm (I. capensis) and 30 mm (I. pallida) by day 10 after which increase in girth and fresh weight of pods, and fresh weight of seeds, increased exponentially. At maturity (15 days) seeds of I. pallida were twice the weight of seeds of I. capensis. Lipid reserves, extracted with chloroform‐methanol, were detectable by day 6 and increased rapidly to 28% fresh weight (2 mg/seed) in seeds of I. capensis and to 24% (4 mg/seed) in I. pallida. The characteristic ultra‐violet (uv) spectrum of α‐parinaric acid was already present by day 6, and content of this acid increased to 42% of total lipids in I. capensis and to 30% in I. pallida at maturity. Fatty acids as determined by gas chromatography of oil of mature seeds were 16:0 (13%, I. capensis; 11%, I. pallida); 16:1 (trace); 18:0 (2%); 18:1 (20%, 25%); 18:2 (17%, 14%); 18:3 + 18:4 (48%, 47%). Electron micrographs of mature seeds of I. capensis showed abundant oleosomes and protein bodies. The blue color of the cotyledons was faint at day 11 and then intensified with age. It was somewhat paler in I. pallida than in I. capensis, suggesting that it may be associated with the presence of α‐parinaric acid.
ROLE OF PARENCHYMA IN LINUM USITATISSIMUM LEAF TRACE PATTERNS
Authors: Meicenheimer Roger D.
Published: January 2018

A new notation for leaf trace patterns was developed which is consistent with contemporary contact parastichy phyllotaxis notation. New computer‐aided methods for generating accurate stem tissue maps were developed. Application of these methods resulted in clarification of the role that parenchyma differentiation plays in delimiting the procambial template for Linum usitatissimum L. stem vasculature through ontogeny. Study of the tissue maps for the various leaf trace patterns exhibited by Linum stems through ontogeny generated a set of observations which permits more rigorous definition of the developmental rules for vascular pattern formation. Long‐known geometric principles of phyllotaxis were found applicable to leaf trace patterns.
POLLEN‐OVULE RATIOS IN THE CRUCIFERAE
Authors: Preston Robert E.
Published: January 2018

Several recent studies have revealed sources of variation in pollen‐ovule ratios that might limit their usefulness as breeding system indicators. In this survey, pollen‐ovule ratios were determined for 66 crucifer taxa (Cruciferae) with known breeding systems to establish whether a clear distinction could be made between the pollen‐ovule ratios of allogamous and autogamous crucifers and whether this was sufficient to allow a standard to be set for the Cruciferae. Both the mean number of pollen grains per flower and the pollen‐ovule ratio were significantly larger in the allogamous taxa than in the autogamous taxa, whereas the mean number of ovules per flower was not significantly different. However, the pollen‐ovule ratio was found to be a much better indicator of the breeding system than the mean number of pollen grains by itself, based on the degree of overlap between the values for the allogamous and autogamous taxa. Variation in the amount of pollen produced by different sets of stamens and a correlation between the pollen‐ovule ratio and seed size were identified as potential sources of error in calculating and interpreting the pollen‐ovule ratios. This survey suggests that the pollen‐ovule ratios of allogamous crucifers are typically greater than 3,500, that those of autogamous crucifers are typically less than 1,000, and that these standards can be used for indicating the breeding systems of other species in the Cruciferae.
RELATIONSHIPS BETWEEN PHOTOSYNTHETIC CAPACITY AND LEAF STRUCTURE IN SEVERAL SHADE PLANTS
Authors: Araus Jose L. , Alegre Leonor , Tapia Luis , Calafell Ramon , Serret Maria D.
Published: January 2018

Leaf structure, photosynthetic characteristics and related physiological parameters have been studied in three ornamental shade species:Fatsia japonica, Cissus rhombifolia(relatively light‐tolerant plants), andPhilodendron scandens(obligate shade plant). Species were grown in a shadehouse. Maximum photosynthetic photon flux density was 470 μmol m‐2s‐1. Net rate of CO2uptake at light saturation (maximum Pn) inFatsiawas 6.90 ± 1.27 μmol m‐2s‐1. InCissusandPhilodendronvalues were about 30% and 63% less respectively, than those measured inFatsia.The nitrogen content, relative dry wt, specific leaf dry wt (SLDW), chlorophyll a/b ratio, and nitrogen to chlorophyll ratio were lower inPhilodendron.However, leaf thickness inPhilodendron(296 ± 17 μm) was about 54% and 160% higher, respectively, than inFatsiaandCissus, and the ratio between mesophyll cell area and leaf surface area (Ames/A) was nearly similar in the three species. HoweverPhilodendronexhibited a percentage of palisade parenchyma about three times lower than that observed in the two other species. The chloroplast number per mm of cell wall in transverse sections (chloroplast density) in the palisade parenchyma was fairly constant (about 65), irrespective of species. The “chloroplast density” in the spongy parenchyma ofPhilodendronwas about 53% and 63%, respectively, ofFatsiaandCissusvalues. InFatsiaandCissuschloroplast ultrastructure seems to change gradually and continuously from sun to shade type with the depth from the adaxial to abaxial surface. Special emphasis was given in order to determine the structural parameters best correlated with maximum Pn between the different species. In this way chloroplast number in transverse sections (chloroplast number) and the ratio between chloroplast area and leaf surface area (Achl/A) were the parameters best correlated with maximum Pn, and stomatal frequency was also a good determinant of maximum Pn. However, leaf thickness, SLDW, and even Ames/A ratio were weakly correlated with maximum Pn.
FLUID FLOW IN THE OUTERMOST XYLEM INCREMENT OF A RING‐POROUS TREE, ULMUS AMERICANA
Authors: Ellmore George S. , Ewers Frank W.
Published: January 2018

Hydraulic conductivity through the outermost growth ring of Ulmus americana was quantified to determine the significance of this single growth increment to fluid flow in xylem of a ring‐porous tree. Gravity flow rates through trunks deprived of the outermost growth ring dropped to 8% of the rate achieved in control trunks whose cross section was intact. However, colored dye, fed through stem segments, appeared in up to 4‐yr old wood, corroborating earlier reports that fluid flows through more than just the outermost growth ring of ring‐porous trees. Finally, the pathway of flow through older rings was shown to consist of narrow latewood elements while the wider and more hydraulically significant earlywood vessels came into play only in the outermost growth ring of U. americana. These data indicate that the outermost growth ring of Ulmus is responsible for over 90% of xylem transport in this ring‐porous tree, because wide earlywood vessels function only for one growth season.
ENDOSPERM STRUCTURE AND STORAGE RESERVE HISTOCHEMISTRY IN THE PALM, WASHINGTONIA FILIFERA
Authors: DeMason Darleen A.
Published: January 2018

The endosperm of Washingtonia filifera consists of living cells with the same general cellular structure throughout the seed. The major storage reserves are carbohydrate, stored in the form of thickened walls; lipid, stored as numerous small lipid bodies which fill the cytoplasm; and protein, stored as large, but variably‐sized, protein bodies. The protein bodies contain two types of inclusions: prismatically‐shaped denser protein crystalloids and small crystalline deposits presumed to be phytic acid. The X‐ray microanalysis shows these crystalline inclusions do contain P, Ca, Mg, and Fe. Protein bodies are positively stained with PAS. Nuclei are present in all cells, but stain very palely. Plastids and mitochondria are present, but infrequently seen. The plastids have few, poorly developed membranes. Endoplsasmic reticulum and dictyosomes are lacking. The cell wall is thick except in areas of pit fields and consists of three layers which differ in their staining with toluidine blue and in their ultrastructural characteristics: middle lamella, thickened outer wall, and thin inner wall. All wall layers are positively stained with PAS and calcofluor. Although general structural features of the endosperm in Washingtonia filifera are similar to those in date seeds, the composition of the wall polysaccharides and protein bodies appear to differ somewhat.
ANALYSIS OF STARCH CONTENT IN CHLORELLA PYRENOIDOSA (CHLOROPHYTA) BY MORPHOLOGICAL AND QUANTITATIVE TECHNIQUES
Authors: Rosen Barry H. , Berliner Martha D. , Petro Michael J.
Published: January 2018

Chlorella pyrenoidosa (Chick) was grown heterotrophically in batch culture on defined medium with glucose. Morphometric analysis of cells in the exponential growth phase showed that starch accounted for 57% of the volume of the chloroplast and 36% of the total cell volume. During the stationary growth phase, the amount of starch accounted for only 36% of the chloroplast volume and 13% of the total cell volume. This represented a 36% decrease in the amount of starch/cell between the exponential and stationary phase. Determination of starch as grams/cell using quantitative techniques on cell extracts showed a comparable decrease in the amount of starch during this same transition. Based on these results, morphometric techniques provided an accurate assay of starch and have the added advantage of visualization of cellular structures not available when quantitative techniques are used.
EFFECT OF PETIOLE PHLOEM DISRUPTION ON STARCH AND MINERAL DISTRIBUTION IN SENESCING SOYBEAN LEAVES
Authors: Wood L. J. , Murray B. J. , Okatan Y. , Noodén L. D.
Published: January 2018

Normally, starch (sugars) and minerals are redistributed from the leaves to the pods during monocarpic senescence in maturing soybean plants. Petiole phloem destruction (steam girdling), which blocked this redistribution by interrupting export through the petiole, altered the foliar senescence pattern producing a distinctive interveinal yellowing with green areas along the veins on pod‐bearing plants. This suggests that blockage of the petiole phloem may cause nutrients to accumulate in the green zones along the leaf veins instead of being redistributed to the pods. In the leaves of untreated plants, starch showed the same distribution pattern as chlorophyll; however, starch was preserved in yellow areas as well as the green zones of the steam‐girdled leaves. Mineral analyses of the veinal and interveinal zones of treated leaves and controls showed that the veinal green zones and interveinal yellowing in treated plants were not respectively enriched and depleted in minerals corresponding to a redistribution of minerals within the leaves. Depodding also blocked leaf yellowing, net mineral redistribution and starch breakdown. Thus, the pods are able to induce chlorophyll breakdown without net mineral redistribution or starch loss in leaves with petiole phloem destruction. This shows that chlorophyll breakdown is not obligatorily coupled with mineral redistribution or starch breakdown.
VARIATION OF STOMATAL DISTRIBUTION IN CAREX AQUATILIS (CYPERACEAE)
Authors: Standley Lisa A.
Published: January 2018

The density and distribution of stomates in Carex aquatilis Wahl. in the Pacific Northwest were examined using epidermal peels of samples of leaves from natural populations, from greenhouse‐grown transplants and from seedling families grown under controlled conditions. These were compared to stomatal distributions of populations in eastern North America.

Populations of Carex aquatilis Wahl. form 2 groups based on the distribution and density of stomates. Carex aquatilis var. dives (Holm) Kükenthal is epistomatic, with adaxial stomatal densities of 28.7–48.5/0.1 mm2. The C. aquatilis var. aquatilis is amphistomatic, with adaxial stomatal densities of 8.1–22.2/0.1 mm2 and abaxial densities of 11.3–24.5/0.1 mm2 in the Pacific Northwest. Total stomatal frequencies are similar in both groups. Stomatal distribution and densities are here shown to not vary significantly within populations and appear to be genetically determined, as shown by progeny tests and growth of seedlings under uniform and experimental conditions. Stomatal distribution in Carex aquatilis appears to be adaptive, and intraspecific variation provides a system for determining the adaptive significance of differences in stomatal patterns.
VEGETATIVE AND FERTILE STRUCTURES OF CYATHOTHECA VENTILARIA FROM THE UPPER PENNSYLVANIAN OF THE APPALACHIAN BASIN
Authors: Mickle James E. , Rothwell Gar W.
Published: January 2018

Permineralized stems, leaves and a fertile structure assignable to Cyathotheca Taylor are described from the Late Pennsylvanian Duquesne Coal of eastern Ohio. The new material, C. ventilaria sp. nov., provides the first evidence of vegetative structures for the genus. Vegetative parts are referred to the fertile fragments based upon distinctive vascular morphology, common histological features, and close association. Stems are up to 5.0 mm in diam and have an apparently endarch dictyostele with scalariform metaxylem tracheids. Secondary xylem consists of tracheids with bordered pitting and uniseriate, parenchymatous rays 1–9 cells high. Leaves are arranged in a 3/8 pattern. They are small, pinnately‐lobed, and vascularized by an U‐shaped bundle. Distal to divergence, one of the apparent leaf traces becomes radial to resemble the base of a fertile structure. This implies a mode of attachment for the fructification and suggests evidence to interpret its homologies. The fertile specimen consists of laminae that diverge from a short stalk, and bifurcate distally. Laminae bear sporangia 0.6–0.7 mm in diam attached adaxially by vascularized pedicels. Spores average 36 μm in diam and are of the Kewaneesporites type. The combination of features now known for Cyathotheca exclude it from assignment to a currently‐recognized major group of vascular plants, thus emphasizing that the Pennsylvanian coal swamp flora included a greater diversity than commonly is interpreted.
RESPONSE OF TWO OLD FIELD PERENNIALS TO INTERACTIONS OF CO2 ENRICHMENT AND DROUGHT STRESS
Authors: Wray Susan M. , Strain Boyd R.
Published: January 2018

Aster pilosus Willd. (aster, C3) and Andropogon virginicus L. (broomsedge, C4) were grown in growth chambers at 26/20 C day/night temperatures with a PPFD of 1,000 μmol s–1 m–2. Water was withheld for a 2‐wk drought period under three CO2 concentrations (approximately 380, 500, and 650 μl 1–1). There were significant effects of CO2 enrichment on aster so that drought stress did not occur in plants grown with CO2 enrichment. Non‐watered plants with CO2 enrichment had greater leaf water potentials, greater photosynthetic rates, and greater total dry wt than non‐watered plants grown at 380 μl 1–1 CO2. The response of broomsedge to drought was the same in all CO2 treatments and there was no significant interaction of CO2 enrichment and drought. The decreased severity of drought stress and the increased growth of aster with CO2 enrichment may increase its competitive ability during droughts, allowing it to persist for longer periods during succession in abandoned fields.
ULTRASTRUCTURAL STUDIES OF FOSSIL PLANT CUTICLES. II. TARPHYDERMA GEN. N., A CRETACEOUS CONIFER FROM ARGENTINA
Authors: Archangelsky Sergio , Taylor Thomas N.
Published: January 2018

Tarphyderma glabra is a leafy shoot of early Cretaceous age from Santa Cruz, Argentina. The leaves, often found isolated, are hypostomatic with the guard cells more or less deeply sunken in suprastomatal chambers. Each chamber is formed by a ring of irregularly elongated cells that may have regulated the opening of the stoma. The cuticle membrane of both the upper and lower surface is thick and can be subdivided into distinct layers based on ultrastructural features and position on the leaf. A cutinized hypodermis is present. The plant, a conifer of uncertain affinities, is compared with other taxa characterized by deeply sunken guard cells.
RE‐EVALUATING THE SIGNIFICANCE OF CORRELATIONS BETWEEN SEED NUMBER AND SIZE: EVIDENCE FROM A NATURAL POPULATION OF THE LILY, CLINTONIA BOREALIS
Authors: Galen Candace , Weger Harold G.
Published: January 2018

The basis for the negative correlation between seed number and seed size was experimentally investigated in a natural population of Clintonia borealis. Clones of this species vary significantly in estimated self‐compatibility (ratio of seed set with selfing to that with outcrossing) and this appears to affect the number and size of seeds set in individual flowers of each. Clones estimated to be largely self‐compatible set more seeds per flower than incompatible ones under natural pollination. However, naturally pollinated flowers of self‐compatible clones set smaller seeds than those of incompatible clones, and the significance of the negative relationship between seed number and size in individual flowers was removed by holding variation due to compatibility constant. Supplementing resources per flower (by reducing the number of fruits competing for resources per stem) significantly increased total seed mass but had no effect on the negative relationship between seed number per flower and seed size. In contrast, supplementing cross pollination did not significantly influence total seed mass per flower but changed the relationship between seed number and size to positive, regardless of resource level. In other words, with plentiful cross pollination maternal genets capable of setting more seeds per flower also produced heavier ones. Thus, evidence is provided that the balance between seed number and seed size in this population is regulated by the interaction of maternal self‐compatibility with natural pollination.
EFFECTS OF CANOPY POSITION AND IRRADIANCE ON THE LEAF PHYSIOLOGY AND MORPHOLOGY OF PENTACLETHRA MACROLOBA (MIMOSACEAE)
Authors: Oberbauer Steven F. , Strain Boyd R.
Published: January 2018

Pentaclethra macroloba (Willd.) Kuntze (Mimosaceae) is a dominant late‐successional tree species in the Atlantic lowland forests of Costa Rica. Leaves of P. macroloba from three heights in the forest canopy were compared with leaves of seedlings grown in controlled environment chambers under four different irradiance levels. Changes in leaf characteristics along the canopy gradient paralleled changes resulting from the light gradient under controlled conditions. The effect of light or canopy position on light‐saturated photosynthesis was small, with maximum photosynthesis increasing from 5 to 6.5 μmol m−‐2 s−‐1 from understory to canopy. Both chamber grown and field leaves showed large adjustments in photosynthetic efficiency at low light via reductions in dark respiration rates and increases in apparent quantum yields. Light saturation of all leaves occurred at or below 500 μmol m−‐2 s−‐1. Leaf thickness, specific leaf weight, and stomatal density increased to a greater extent than saturated photosynthesis with higher irradiance during growth or height in the canopy. As a result, there was a poor correspondence between leaf thickness and light‐saturated photosynthesis on an area basis. It is concluded that Pentaclethra macroloba possesses the characteristics of a typical shade‐tolerant species.
DIFFERENTIAL OXIDATION OF MANGROVE SUBSTRATE BY AVICENNIA GERMINANS AND RHIZOPHORA MANGLE
Authors: Thibodeau Francis R. , Nickerson Norton H.
Published: January 2018

Both Avicennia germinans (black mangrove) and Rhizophora mangle (red mangrove) are commonly found in anaerobic substrate. Black mangrove roots create oxidized rhizospheres substantially larger than those described for other plant species. When air cannot enter the root system through the pneumatophores, the rhizospheres become as reduced as nearby un vegetated soil. The presence of red mangrove, in contrast, appears to have no effect on the oxidation state of surrounding anaerobic soils. It is likely that these data help to explain the distributions of both species in intertidal associations.
EVOLUTIONARY MODIFICATION IN CLARKIA I. SELECTION FOR HAIRLESSNESS
Authors: Vasek Frank C.
Published: January 2018

Plants of Clarkia unguiculata with moderate numbers of long hairs on the ovary and calyx were selected for relative “hairlessness” through 11 generations. Inbreeding depression, manifested as a high degree of sterility, necessitated co‐selection for fertility. The proportion of fertile plants among families ranged from 0–50% in the 5th selected generation and increased to a range of 53–100% in the 10th selected generation. At the same time, the mean number of hairs on the ovary decreased from a range of 0.0–1.1 to a range of 0.0–0.2; and the mean number of hairs per sepal from 0.5–16.0 to 0.1–2.2. The percentage of plants per family with no hairs on the ovary and no hairs on the calyx increased from a range of 0–63 in the 5th selected generation to a range of 4–88 in the 10th selected generation. Nonselected progenies have long hairs on both ovary (mean 10–17) and sepals (mean 46–50) in all plants. The demonstrated response to selection has important implications regarding catastrophic selecion and the evolution of Clarkia species in marginal habitats.