bluuebunny/crossref_metadata_2025 huggingface dataset:
REGENERATION RESPONSES IN PEA ROOTS AFTER TIP EXCISION AT DIFFERENT LEVELS
Authors: Reihman Mary Ann , Rost Thomas L.
Published: January 2018

Root tips of Pisum sativum cv Alaska were excised at seven excision distances ranging from 250 to 5,000 μm from the root cap/body junction. Three response types resulted: 1) Type A— One to three regenerated apices grew in the same plane as the root axis; 2) Type B—One to three regenerates emerged either longitudinally from a swollen wound site or at angles >90“° from the root longitudinal axis; 3) Type C—One to three lateral roots emerged at 90° from the root axis. The response type was dependent on the excision distance: Type A response resulted after excisions of 250 and 500 μm, Type B after excisions of 1,000 and 1,500 μm, and Type C after excisions of > 1,500 μm. The vascular patterns of the regenerated roots varied with excision distance. Most regenerates resulting after being excised at 250 μm exhibited variations in xylem strand number. Most of those resulting after being excised at 500 μm were ”polystelic“ and few of these showed variation in xylem strand number. With increasing excision distance the number of regenerates with variation in xylem stand number or with a ”polystelic“ condition decreased. Both the type of regeneration response and the vascular patterns within the regenerates correlated with the state of differentiation of cells at each excision distance.
EVOLUTION OF POPULUS NIGRA (SECT. AIGEIROS):INTROGRESSIVE HYBRIDIZATION AND THE CHLOROPLAST CONTRIBUTION OF POPULUS ALBA (SECT. POPULUS)
Authors: Smith Randy L. , Sytsma Kenneth J.
Published: January 2018

Restriction site variation in chloroplast DNA and nuclear ribosomal DNA was examined in 16 accessions from the Salicaceae comprising ten species of Populus and one outgroup species of Salix. Forty‐nine restriction site mutations in the chloroplast DNAs were used to generate one most parsimonious phylogenetic tree. This tree indicates that all varieties of P. nigra (black poplars of sect. Aigeiros) have a chloroplast genome, maternally inherited, derived from the clade including the white poplars (P. alba and segregate species of sect. Populus) and divergent from the American cottonwoods of their own section. Twenty‐one restriction site mutations in the nuclear ribosomal DNAs generated a single most parsimonious phylogenetic tree that indicates that the nuclear genome ofP. nigra is distinct from both the white poplars and American cottonwoods. The incongruity of these independent molecular phylogenies provides evidence for an unusual origin of the black poplars. Populus alba or its immediate ancestor acted as the maternal parent in a hybridization event with the paternal lineage of P. nigra. Subsequent backcrosses to the paternal species gave rise to the extant P. nigra with a chloroplast genome of P. alba and the nuclear genome of the paternal species. These hybridization and introgression events must have pre‐dated the divergence of the black poplar varieties. The biphyletic nature of the P. nigra genomes suggests that dependency on one class of molecular or morphological markers or the merging of the two kinds of data sets to derive accurate estimates of true phylogenies could be misleading in plants.
COMPARATIVE STUDY OF THE FLORAL VASCULATURE IN SAURURACEAE
Authors: Han‐Xing Liang , Tucker Shirley C.
Published: January 2018

The floral vascular systems are compared among all six taxa of Saururaceae, including the two species of Gymnotheca which have not been studied previously. All are zygomorphic (dorsiventrally symmetrical), not radial as sometimes reported, in conformity with dorsiventral symmetry during organogenesis. Apocarpy in the two species of Saururus (with four carpels and six free stamens) is accompanied by a vascular system of four sympodia, each of which supplies a dorsal carpellary bundle, two ventral carpellary bundles, and one or two stamen traces. The level at which the ventral bundles diverge is the major difference in vasculature between the two species. The other four taxa are all syncarpous, and share some degree of stamen adnation and/or connation. The vascular systems also show varying degrees of fusion. The two species of Gymnotheca (with four carpels and six stamens) are very similar to each other; in both, the ventral traces of adjacent carpels fuse to form a placental bundle, which supplies the ovules and then splits into a pair of ventral strands. The flowers of Houttuynia cordata (with only three carpels and three adnate stamens) are sessile. Each flower is vascularized by three sympodia; the median adaxial sympodium is longer than the other two sympodia before it diverges to supply the adaxial organs. Three placental bundles also are formed in Houttuynia, but the three bundles differ in their origin. The median abaxial placental bundle diverges at the same level as the three sympodial bundles of the flower, while the other two lateral placental bundles diverge at a higher level from the median adaxial sympodium. Anemopsis californica, with an inferior ovary of three carpels, sunken in the inflorescence axis, and six stamens adnate to the carpels, has a vascular system very similar to that of Houttuynia cordata. The modular theory of floral evolution is criticized, on the bases of the known behavior of apical meristems and properties of vascular systems. The hypothesis is supported that saururaceous plants may represent a line of angiosperms which diverged very early.
COMPARATIVE ONTOGENY OF THE PERIANTH IN MIMOSOID LEGUMES
Authors: Ramírez‐Domenech Jose I. , Tucker S. C.
Published: January 2018

Comparative ontogeny of the perianth is reported for representative genera and species among mimosoid legumes in order to elucidate intertribal relationships and also relationships to the other two subfamilies of legumes. Initiation of the perianth is acropetal in two whorls. The calyx arises first followed by the corolla. Order of initiation of both calyx and corolla is determined during early ontogeny. Four different types of order of initiation have been found in the calyx: helical, simultaneous within one whorl, bidirectional, and ring meristem. Helical initiation is considered primitive; simultaneous within one whorl, bidirectional, and ring meristem are considered derived. Differences during early organogeny in the calyx among mimosoids result in similar morphologies of the mature calyx which indicates that parallel evolution may have played a major role in evolution of radial symmetry within the group. Order of initiation of the corolla is uniformly simultaneous whorled with one exception. Position of organs is a significant feature which separates mimosoids from caesalpinioids and papilionoids. In mimosoids the median sepal is located abaxially and the median petal adaxially in relation to the subtending bract. In both caesalpinioids and papilionoids the median sepal is located abaxially and the median petal adaxially in relation to the subtending bract. Fusion of the calyx in some taxa can be interpreted as an example of acceleration.
LEAF VASCULATURE IN BARLEY, HORDEUM VULGARE (POACEAE)
Authors: Dannenhoffer Joanne M. , Ebert Wesley , Evert Ray F.
Published: January 2018

The vascular system of the Hordeum vulgare L. leaf consists of multiple longitudinal strands interconnected by transverse bundles. In any transverse section, the longitudinal strands can be categorized into three bundle types: small, intermediate, and large. Individual longitudinal strands intergrade structurally from one bundle type into another as they descend the leaf. At their distal ends, they have the anatomy of a small bundle. As they descend the leaf, most intergrade into intermediate bundle and then into large bundle types. All strands with large bundle anatomy extend basipetally into the stem. Typically, the other longitudinal strands, which do not intergrade structurally into large bundles, do not enter the sheath, but fuse with other longitudinal strands above the junction of the blade with the sheath. Despite the decrease in number of longitudinal bundles entering the sheath, an increase takes place in the total crosssectional area of sieve tubes and tracheary elements. A linear relationship exists between leaf width and total bundle number in the blade but not in the sheath. Moreover, a linear relationship exists between cross‐sectional area of vascular bundles and both total and mean cross‐sectional area of tracheary elements and thin‐walled sieve tubes.
FOSSIL MASTIXIOID (CORNACEAE) ALIVE IN EASTERN ASIA
Authors: Eyde Richard H. , Qiuyun Xiang
Published: January 2018

The tree species Diplopanax stachyanthus, wrongly placed in the Araliaceae, belongs in fact to the mastixioid subfamily of Cornaceae. Fruit features make it congeneric with Mastixicarpum, part of a woody‐fruited complex known heretofore from Tertiary fossils.
ORIGIN AND DEVELOPMENT OF LATERAL ROOTS IN TYPHA GLAUCA
Authors: Seago James L. , Marsh Leland C.
Published: January 2018

Lateral roots of Typha glauca arose from the pericycle of the parent adventitious root. Periclinal divisions of the pericycle gave rise to two layers; the outermost initially produced the ground meristem and protoderm, and the innermost produced the procambium. The immature endodermis of the parent root contributed to the early stages of the root tip as an endodermal covering. Prior to emergence, the ground meristem/protoderm produced cells into the endodermal covering. After emergence, the endodermal covering was replaced by a calyptrogen, which was derived from the ground meristem/protoderm and which, in turn, formed the rootcap. A typical monocotyledonous three‐tiered meristem was then produced. An outer ground meristem also arose before emergence to form a hypodermis in many lateral roots; in these, crystalliferous cell production began in midcortex cells before emergence, and a small aerenchyma developed in their cortices. The rootcap columella stored small amounts of starch shortly after emergence. Lateral roots of T. glauca were smaller than their parental adventitious roots; they normally had only two to six poles of xylem and phloem, and the cortex was less than six cells across. During 1–3‐cm elongation, the lateral root apical meristem and mature regions narrowed, stored starch disappeared, fewer crystals formed, aerenchyma production ceased, and the roots stopped elongation.
ANATOMY AND ASPECTS OF DEVELOPMENT OF THE STAMINATE INFLORESCENCES AND FLORETS OF SEVEN SPECIES OF ALLOCASUARINA (CASUARINACEAE)
Authors: Flores Eugenia M. , Moseley Maynard F.
Published: January 2018

The morphology, ontogeny, and vascular anatomy of the staminate inflorescences and florets of seven species of Allocasuarina are described. The generally terminal but open‐ended inflorescences occur on monoecious or staminate dioecious trees and consist of whorls of bracts, each subtending a sessile axillary floret. Each floret consists of one terminal stamen with a bilobed, tetrasporangiate anther enclosed typically by cuculliform appendages, commonly considered bracteoles, an inner median pair and an outer lateral pair. The mature stamen is exerted, the anther is basifixed and is extrorsely dehiscent. In early development of a male inflorescence very little internodal elongation occurs and enclosing cataphylls appear. The inflorescence apex is a low dome with a uniseriate tunica and a small group of central corpus cells. Bract primordia are initiated by periclinal divisions of C1 followed by further divisions of the corpus and anticlinal divisions in the tunica. The bracts are epinastic and become gamophyllous except apically by cell divisions in both sides of each primordium. Stomata are restricted to the axis furrows and the abaxial tips of the bracts. The axillary florets arise in acropetal succession initiated by periclinal divisions in C1 accompanied by anticlinal divisions in the tunica. The lateral floral appendages are also initiated by C1 followed by anticlinal divisions in the tunica. They become adnate basally later with the subtending bract. The median sterile appendages are initiated in a manner similar to the initiation of the outer appendages. The stamen is initiated by divisions in the outer layers of the corpus and in the tunica, and then develops first by apical growth followed by intercalary growth. The vascular system of the inflorescence is identical to that of the vegetative stem. Each floret is supplied by a single bundle that has its source in a branch from each of the two traces supplying a bract. Six bundles arise from the floral bundle; four of these terminate in the base of the stamen and two form an amphicribal bundle that supplies the anther. Pollen is binucleate, 3‐ to 7‐porate. The exine is tegillate.
SPERMATOGENESIS IN A HOMOSPOROUS FERN, ONOCLEA SENSIBILIS
Authors: Kotenko Jane L.
Published: January 2018

A detailed study of spermatogenesis in a homosporous fern, Onoclea sensibilis L., is presented from the formation of the first spermatogenous cell to the release of the sperm. Two different walls are deposited around the developing spermatids at specific developmental stages as opposed to one wall reported for other species. Most ultrastructural changes that occur in Onoclea during spermatid differentiation resemble those described in previous studies on other fern species, with the following exceptions: 1) A previously undescribed structure appears during midspermatid stage. This dense layer of amorphous material with a row of evenly spaced light areas occurs between the anterior portion of the mitochondrion associated with the multilayered structure and the anterior plasmalemma of the spermatid. 2) An early stage in blepharoplast formation resembles that which occurs in the heterosporous fern Marsilea, in contrast to that which has been reported in Platyzoma, the only other homosporous fern studied at this stage. 3) The osmiophilic crest does not form as early as reported in other ferns. 4) The cap cell of Onoclea is removed intact, rather than collapsing or forming a pore during sperm release. Observations are reported on the number of sperm per antheridium, the time course of spermatogenous cell mitosis, and of differentiation of spermatids into sperm. In Onoclea, an antheridium may contain either 32 or 64 sperm. Regardless of the final number of sperm, each has approximately the same volume.
DNA “FINGERPRINTS” REVEAL GENOTYPIC DISTRIBUTIONS IN NATURAL POPULATIONS OF BLACKBERRIES AND RASPBERRIES (RUBUS, ROSACEAE)
Authors: Nybom Hilde , Schaal Barbara A.
Published: January 2018

The genotypic distributions in a population of Rubus occidentalis L. and R. pensilvanicus Poiret were analyzed by using DNA “fingerprinting.” The number of genotypes found was related to the mode of reproduction; 20 plants of the sexual R. occidentalis comprised 15 genotypes, whereas 20 plants of the presumably apomictic R. pensilvanicus comprised only five genotypes. DNA “fingerprinting” appears to be a useful tool in the understanding of population structure.
NEW ANGIOSPERM RECORDS FROM THE CARIBBEAN TERTIARY
Authors: Graham Alan
Published: January 2018

Thirteen taxa represented by fossil palynomorphs that either have no previous fossil record or were unknown as microfossils in the region have been recovered from Gulf/Caribbean Tertiary deposits and processed by acetolysis. Twelve of these are from the Pliocene Gatun Formation in the Canal region of Panama: Aegiphila (Verbenaceae), cf. Bucida (Combretaceae), Cabomba (Cabombaceae/Nymphaeaceae), Casimiroa (Rutaceae), Cosmibuena (Rubiaceae), Cymbopetalum (Annonaceae), Faramea (Rubiaceae), Mutisieae type (Compositae), Petrea (Verbenaceae), Posoqueria (Rubiaceae), and Symplocos (two types, Symplocaceae). The other (Hygrophila, Acanthaceae) is from the Miocene Artibonite Group of Haiti. These new records support emerging concepts concerning the biogeography and paleoenvironments of proto‐Central America based on previous studies: a Tertiary vegetation with predominantly Central American and Mexican affinities; little evidence of extensive arid or savanna vegetation; a paleophysiography of low to moderate altitudes; and an essentially modern tropical climate for the southern part of present‐day Central America, which on the basis of plate tectonic evidence, consisted mostly of volcanic islands until about 3.8 Myr.
SEEDLING GROWTH AND SURVIVAL OF RED AND WHITE FIR IN A SIERRA NEVADA ECOTONE
Authors: Barbour M. G. , Pavlik B. M. , Antos J. A.
Published: January 2018

We hypothesized that differential seedling establishment was responsible for the transition from white fir‐ to red fir‐dominated forest. Nearly 2,000 seeds of each species were sown within six fenced gardens that spanned the ecotone (1,902–2,073 m). Germination and seedling mortality were monitored through the first growing season. Red fir germination percentage exceeded that of white fir in all gardens in sites dominated by red fir saplings and overstory trees, and a similar pattern was true for white fir. Survival at the end of the first growing season was low and statistically similar for both species, as was the average length of life for seedlings and the causes of mortality. Relative demographic performances (an integrated measure of germination and survivorship over time) suggest that: 1) open/xeric microhabitats within the ecotone favor white fir over red fir; 2) both open/mesic and shaded/xeric microhabitats favor red fir over white fir; and 3) shaded/mesic microhabitats are equally favorable for both species. Seedlings of red and white fir were grown for 6 mo in a growth chamber that imitated early summer temperature and soil moisture conditions. Red fir seedlings were consistently heavier than white fir seedlings, in part a result of the 2.5 × greater caloric content of red fir seed. Relative growth rates were similar for both. Allocation of photosynthate to roots was greater for red fir than white fir, a result contrary to the expected pattern, given that white fir occurs at more xeric, lower elevations than red fir. No consistent differences between the species occurred in root growth or morphology.
TRANSPORT OF CARBON AMONG CONNECTED RAMETS OF EICHHORNIA CRASSIPES (PONTEDERIACEAE) AT NORMAL AND HIGH LEVELS OF CO2
Authors: Alpert Peter , Warembourg Fernand R. , Roy Jacques
Published: January 2018

The floating, stoloniferous plant, Eichhornia crassipes, has high rates of productivity and rapidly invades new sites. Because the transport of carbon among connected ramets is known to increase the growth of clonal plants, we asked whether there is intraclonal carbon transport in E. crassipes. Because net photosynthesis of E. crassipes is significantly higher at high levels of atmospheric CO2, we also asked if high CO2 can change patterns of carbon transport in ways that might modify clonal growth. We exposed individual ramets within groups of connected ramets to 14CO2 for 15–45 min and measured the distribution of 14C in the group after 4 days of growth at 350, 700, 1,400, or 2,800 μ1 1−‐1 CO2. At 350 μ1 1−‐1 CO2, a parent ramet exported approximately 10% of the 14C that it assimilated to its first rooted offspring ramet. The offspring exported a similar percentage of the l4C it assimilated toward the parent; two‐thirds of this 14C was retained by the parent, and one‐third moved into new offspring of the parent. In all ramets, imported carbon moved into leaves as well as roots. At the higher levels of CO2, the percentage of assimilated carbon exported from a parent ramet to the leaf blades of its first offspring was lower by half. High CO2 had little other effect on carbon transport. E. crassipes maintains bidirectional transport of carbon between ramets even under uniform and favorable environmental conditions and when external CO2 levels are very high.
EARLY SENESCENCE OF CORTICAL CELLS IN THE ROOTS OF CEREALS. HOW GOOD IS THE EVIDENCE?
Authors: Wenzel C. L. , McCully M. E.
Published: January 2018

There are numerous reports that cortical cells senesce in young, otherwise healthy main roots of cereals, including corn. These are based on apparent absence of nuclei in root segments or transverse sections after acridine‐orange staining. Senescence is said to progress from the outer to the inner cortex basipetally from the root tip, except cells around branch bases where nuclei always stain. We studied axile roots of soil‐grown cereals using various methods to detect nuclei primarily in longitudinal sections. No senescence marked by nuclear loss was found in healthy‐looking intact cortices. Cortical cells of mature corn roots remained alive except where aerenchyma developed. No cortical death had occurred in barley, wheat, or oat seminal roots in 15‐,17‐, and 20‐day‐old plants, respectively, but cortical cells in older regions of seminal and nodal roots did collapse and slough off, but with no evidence for earlier loss of nuclei. Failure to detect acridine‐orange‐stained nuclei may not indicate that cells are senescent, and can be an artifact caused by sectioning method and wall impermeability. The effectiveness of other methods for evaluation of root cell vitality is discussed.
AGAMOSPERMY AND THE LOSS OF DISTYLY IN ERYTHROXYLUM UNDULATUM (ERYTHROXYLACEAE) FROM NORTHERN VENEZUELA
Authors: Berry Paul E. , Tobe Hiroshi , Gómez José A.
Published: January 2018

Erythroxylum undulatum is a gametophytic apomict that produces about 15% seed set independently of pollination. Embryo sac formation is aposporous, and the plants are largely pollen‐sterile, which may be a result of polyploidy and hybrid origin. It appears to be derived from a distylous ancestor, as all other known species of Erythroxylum are distylous or secondarily dioecious, and all examined individuals of E. undulatum correspond to the normal long–styled morph. This is the first clearly documented case of agamospermy derived from distyly.
TRANSPORT OF IAA AND ACC IN FLORAL ORGANS OF IPOMOEA NIL (CONVOLVULACEAE)
Authors: Kiss Helen Guiragossian , Koning Ross E. , Daie Jaleh
Published: January 2018

The involvement of the stamens as transporters of plant growth regulators in flowers was examined by measuring the movement of 14C‐indole‐3‐acetic acid (IAA) and l4C‐l‐aminocyclopropane‐1‐carboxylic acid (ACC) through floral organs of Ipomoea nil. During the transport of 14C‐IAA through isolated filament segments, the polar accumulation of 14C‐IAA in receiver blocks increased with time during filament development, which correlated with polar efflux rates at older stages of filament development. An inhibitor of polar IAA transport, 2,3,5‐triiodobenzoic acid, disrupted the polarity of auxin transport by reducing the movement of 14C‐ IAA from filaments into receiver blocks. Transport of both 14C‐IAA and l4C‐ACC through filaments into other floral organs also was monitored in isolated flower buds in the laboratory and intact buds in the greenhouse. In isolated and intact buds 21 hr before anthesis, substantially higher levels of isotope were recovered in corolla tissue when 14C‐ACC was transported through the filaments than when 14C‐IAA was transported from the filaments. In isolated buds, substantial levels of both isotopes accumulated in the pistil (69 hr and 45 hr before anthesis), but minimal amounts were observed in receptacle and calyx tissues (69 hr to 21 hr before anthesis). In intact buds, high levels of both isotopes were recovered in receptacle, calyx, and pistil tissues (69 hr to 21 hr before anthesis). The results from this study support the hypothesis that Ipomoea stamens are transporters for ACC and IAA to regulate ethylene production in the corolla and other floral tissues.
LIFE HISTORY VARIATION WITHIN POPULATIONS OF AN ASEXUAL PLANT, ERIGERON ANNUUS (ASTERACEAE)
Authors: Stratton Donald A.
Published: January 2018

Genetic variation was measured for several morphological and life history characters in Erigeron annum, a triploid and obligately apomictic species. There was significant genetic variation for nearly all characters measured, including plant size, growth rate, time of flowering, biomass allocation to roots and shoots, seed weight, and germination response to temperature. Variance among genotypes accounted for up to 55% of the total phenotypic variance, well within the range of heritabilities observed for sexual species. These estimates of broad‐sense heritability predict substantial short‐term response to selection on life history characters in this asexual species.
REPRODUCTIVE AND VEGETATIVE STRUCTURE OF NORDENSKIOLDIA (TROCHODENDRACEAE), A VESSELLESS DICOTYLEDON FROM THE EARLY TERTIARY OF THE NORTHERN HEMISPHERE
Authors: Crane Peter R. , Manchester Steven R. , Dilcher David L.
Published: January 2018

Nordenskioldia borealis Heer is described and its systematic position is reassessed based on examination of the type material and specimens recently collected from three Paleocene localities in North America (Almont, North Dakota; Melville, Montana; Monarch, Wyoming). The morphology of Nordenskioldia infructescences and fruits is clarified, and in particular, silicified specimens from Almont provide new details of fruit and seed anatomy. Fruits are schizocarpic, and individual fruitlets also dehisce to release flat reticulate seeds. These seeds occur in many Paleocene floras but have not been linked previously to Nordenskioldia. Anatomical details of infructescence axes are identical to those of distinctive long and short shoot systems that cooccur with Nordenskioldia, and neither the infructescence axes nor shoots have vessels in the secondary xylem. Comparison of the floras at Almont, Melville, and Monarch with those at other Paleogene localities in Asia, Europe, and North America provides association evidence supporting earlier conclusions that the Nordenskioldia plant bore simple, entire‐ to crenatemargined leaves with actinodromous venation. Such leaves have been previously assigned to extant genera such as Cercidiphyllum, Cocculus, and Populus but are treated here as Zizyphoides flabella (Newberry) comb. nov. Based on the combined morphological and anatomical details now available, the Nordenskioldia plant is assigned to the Trochodendrales as an extinct genus most closely related to extant Trochodendron.
ORIGIN AND ACTIVITY OF SUCCESSIVE CAMBIA IN CYCAS (CYCADALES)
Authors: Terrazas Teresa
Published: January 2018

Observations of the vascular tissue of Cycas shoots have provided supporting evidence that the first vascular cambium as well as subsequent successive cambia are simultaneously active. The establishment of the second cambium occurs during the seedling stage, and differentiates mainly within the cortical cells. However, cambial activity also occurs within phloem parenchyma cells of the first vascular cylinder. Tracheids in the first and the successive vascular cylinders are generally of the same length; however, there is a trend toward increasing length within the successive cylinders, possibly because the successive cambia are long‐lived.
CHLOROPLAST DNA EVIDENCE FOR GENOME DIFFERENTIATION IN WILD POTATOES (SOLANUM SECT. PETOTA: SOLANACEAE)
Authors: Spooner David M. , Sytsma Kenneth J. , Conti Elena
Published: January 2018

Chloroplast DNA restriction site analysis has been used to test Hawkes's phylogenetic interpretations of the genomic data in Solanum sect. Petota. Hawkes hypothesized a diploid (2n = 24) origin of the tuber‐bearing members of this group (subsection Potatoe) in Mexico and Central America (as a B genome) with later migrations and evolution to an A genome in South America, later followed by a return migration of the A genome to Mexico and Central America with A × B hybridizations and polyploidizations to produce ser. Longipedicellata (4x) and Demissa (6x). Our results provide partial support for this hypothesis by demonstrating the paraphyletic and primitive nature of the B genome species group, and the monophyletic and derived nature of all A genome and A × B genome species, including S. verrucosum, a hypothesized A genome progenitor of ser. Demissa. Thus, the Mexican and Central American polyploid species must have obtained their cytoplasm from the A genome. However, our results question the Stellata/Rotata hypothesis of Hawkes and the taxonomic placement of S. chomatophilum in ser. Conicibaccata.
NONRANDOM MATING IN WILD RADISH: VARIATION IN POLLEN DONOR SUCCESS AND EFFECTS OF MULTIPLE PATERNITY AMONG ONE‐ TO SIX‐DONOR POLLINATIONS
Authors: Marshall Diane L.
Published: January 2018

Nonrandom mating in plants may involve differential success of self‐ vs. outcross pollen, of pollen from relatives vs. nonrelatives, and of pollen from several compatible donors. Of these, the last is least understood. Wild radish plants were crossed with six pollen donors in all possible combinations to investigate differences in pollen donor performance and to compare multiply sired fruits with different numbers and identities of fathers. Pollen donors differed in number of seeds sired, position of seeds sired within fruits, and mass of seeds sired. Performance in single pollination was not a good predictor of performance in mixed pollination. Performance in two‐donor pollinations was a better predictor of the outcome of multidonor pollinations. Multiply sired fruits were selectively filled, but not all multiply sired fruits were equal. Both the number and identity of donors affected fruit filling. These results and others with wild radish suggest that variation in pollen donor ability to sire seeds is relatively common in wild radish. Since wild radish plants in the field typically receive pollen from several donors, there may be considerable opportunity for selection at this stage of the life cycle in wild radish.
DIFFERENTIAL POLLEN‐TUBE GROWTH RATES AND NONRANDOM FERTILIZATION IN HIBISCUS MOSCHEUTOS (MALVACEAE)
Authors: Snow Allison A. , Spira Timothy P.
Published: January 2018

The prevalence of nonrandom fertilization due to postpollination events has rarely been studied in natural populations, despite important implications for outcrossing rates, mate choice, and plant fitness. Nonrandom paternity within fruits can be caused by both unequal fertilization and unequal embryo abortion. Using self‐compatible Hibiscus moscheutos, we studied the potential for nonrandom fertilization by comparing growth rates of pollen‐tubes from different donors. The branched style of Hibiscus allowed within‐flower comparisons between pollen donors. Relative pollen‐tube growth rates were determined by applying pollen from pairs of donors to different stigmas on adjacent stylar branches. We then measured the number of callose plugs per tube in cross‐sectional transects across the style after 3 hr. We demonstrate that rates of callose plug formation can be used as a sensitive indicator of relative pollen‐tube growth rate. Differences between pollen donors were common and repeatable. Self‐pollen‐tubes grew slower than outcross pollen‐tubes in some crosses and faster in others. Allozyme variation in glucose phosphate isomerase was used to show that individuals with fast‐growing pollen‐tubes sired a disproportionate number of seeds following mixed pollinations (up to 72%). Since seed abortion was negligible, we conclude that variation in pollen‐tube growth rates leads to nonrandom paternity within fruits.
THE GENOME ORIGIN OF TETRAPLOID SPECIES OF LEYMUS (POACEAE: TRITICEAE) INFERRED FROM VARIATION IN REPEATED NUCLEOTIDE SEQUENCES
Authors: Zhang g‐Bin , Dvořák Jan
Published: January 2018

To investigate the origin of the tetraploid species of Leymus Hochst., we examined variation in 26 repeated nucleotide sequence families isolated from four species of Triticeae. The genome relationships were determined by calculating repeated nucleotide sequence identity (RSI) between species. RSI is the ratio of the number of diagnostic bands (DBs) and diagnostic hybridization intensities (DIs) in Southern blots of a diploid taxon encountered in a polyploid species divided by the total number of the DBs and DIs of the diploid taxon (DB is a band in Southern blot observed in a single diploid taxon, and DI is the intensity of hybridization higher by at least one order of magnitude in a diploid taxon than in any other diploid taxon). The RSIs of Psathyrostachys Nevski with Leymus ranged from 0.92 to 0.95, which confirmed that the N genome of Psathyrostachys was involved in the phylogeny of Leymus. Since RSIs of other genera of Triticeae with Leymus varied from 0.00 to 0.17, it is unlikely that any of them contributed the second pair of Leymus genomes. RSIs were also calculated between Leymus and the lineage of Lophopyrum Löve‐Thinopyrum Löve or the lineage of Lophopyrum‐Thinopyrum‐Pseudoroegneria (Nevski) Löve‐Agropyron Gaertn. The RSIs were close to zero, which made it unlikely that the second pair of Leymus genomes originated from even an extinct species in these major lineages of Triticeae. Several lines of evidence were obtained that indicated that the second pair of Leymus genomes is also from Psalhyrostachys. The genomes of tetraploid species of Leymus were designated N1N1N2N2, rather than JJNN as proposed by other workers.
CHANGES IN HYDRAULIC CONDUCTIVITY AND ANATOMY CAUSED BY DRYING AND REWETTING ROOTS OF AGAVE DESERTI (AGAVACEAE)
Authors: North Gretchen B. , Nobel Park S.
Published: January 2018

Concurrent determinations of changes in hydraulic conductivity and tissue anatomy were made for roots of Agave deserti excised during drying and following rewetting in soil. At 30 d of drought, hydraulic conductivity had declined less than twofold for older nodal roots, tenfold for young nodal roots, and more than 20‐fold for lateral roots (“rain roots” occurring as branches on the nodal roots). These decreases were consistent with increases in cortical lacunae caused by cell shrinkage and collapse. Similarly, reduction of lacunae in response to rewetting after 7 d of drought corresponded to levels of recovery in hydraulic conductivity, with young nodal roots showing full recovery, lateral roots returning to only 21 % of initial conductivity, and older nodal roots changing only slightly. Increases in suberization in the exodermis, endodermis, and cortex adjacent to the endodermis in response to drying coincided with decreases in hydraulic conductivity. Measurements of axial hydraulic conductance per unit length before and after pressurization indicated that embolism caused reductions in axial conductance of 98% for lateral roots, 35% for young nodal roots, and 20% for older nodal roots at 7 d of drought. Embolism, cortical lacunae, and increasing suberization caused hydraulic conductivity to decline during drought in the three root types, thereby helping limit water loss to dry soil; the recovery in hydraulic conductivity for young nodal roots after rewetting would allow them to take up water readily once soil moisture is replenished.
ADAPTATIONS FOR A TWO‐PHASE SEED DISPERSAL SYSTEM INVOLVING VERTEBRATES AND ANTS IN A HEMIEPIPHYTIC FIG (FICUS MICROCARPA: MORACEAE)
Authors: Kaufmann Sandra , McKey Doyle B. , Hossaert‐McKey Martine , Horvitz Carol C.
Published: January 2018

Figs (Ficus spp., Moraceae) are considered a classic example of plants with fleshy fruits adapted for seed dispersal by vertebrates, usually mammals or birds. Partially covering the endocarp of each individual drupelet of F. microcarpa is a fleshy, discrete lipid‐containing exocarp that suggests adaptation for seed dispersal by ants. This structure is highly attractive to ants. F. microcarpa drupelets from which the fleshy exocarp was experimentally removed were much less likely to be transported by ants than those with this structure intact. The exocarps retained their attractiveness to ants and were not visibly altered following passage of the entire fruit through the gut of a frugivorous bird, the Indian Hill Mynah (Gracula religiosa). Germination percentage was not significantly affected by gut passage or exocarp removal. These results suggest that F. microcarpa has a two‐stage seed dispersal system, in which primary dispersal by vertebrates is followed by secondary dispersal by ants. Dispersal aided by ants may be of significance in the biology of this exotic hemiepiphyte in southern Florida, where it is naturalized and appears to be spreading.
POPULATION VARIATION, OUTCROSSING, AND COLONIZATION OF DISTURBED AREAS BY CALAMAGROSTIS CANADENSIS: EVIDENCE FROM ALLOZYME ANALYSIS
Authors: MacDonald S. Ellen , Lieffers Victor J.
Published: January 2018

Calamagrostis canadensis (a rhizomatous grass) exists in temperate forest sites of different successional age. It can rapidly colonize disturbed sites to form dense swards. We examined allozyme variation in: four populations (mature forest, intermediate aged forest, forest cutblock, wetland); nine small plots (2 m × 4 m) within the cutblock; and progeny of several families from three populations; in order to assess the mode of colonization of disturbed areas and the effect of successional changes on population genetic structure. All four populations showed equal and extensive genetic variation (1.5 to 1.7 alleles per locus [K], 41.7% to 50% polymorphic loci [PPL], Hst = 0.155 to 0.208) and were not genetically differentiated (Gst = 0.0193, 1 = 0.986 to 0.997). The cutblock subpopulations also showed considerable genetic variation (K = 1.6 to 1.8, PPL = 50% to 58.3%, Hst = 0.151 to 0.278) and no microdifferentiation (Gst = 0.034, I = 0.967 to 0.997). We found 14 different genotypes among the 30 individuals sampled from the cutblock as a whole (based on five polymorphic loci). The cutblock subpopulations had from nine to 14 different genotypes each (same five loci, 18 individuals per subpopulation). Seed produced was primarily outcrossed (multilocus estimate 0.888 to 0.900). We concluded that disturbed sites are colonized primarily by sexually produced seedlings. Potential genetic drift and natural selection, which occur during subsequent successional changes, do not result in reduced genetic variation or population differentiation.
OCCURRENCE, TYPE, AND LOCATION OF CALCIUM OXALATE CRYSTALS IN LEAVES AND STEMS OF 16 SPECIES OF POISONOUS PLANTS
Authors: Doaigey Abdullah R.
Published: January 2018

Crystals in 16 species of poisonous plants growing naturally in Saudi Arabia were studied with light microscopy. Three types of crystals were observed: druses, prismatics, and crystal sand. Raphides and styloids were not observed in any of the species studied. Druses occur more frequently in the leaf midrib and in the cortex and pith of the stem. In contrast, crystal sand and prismatic crystals are rare and occur in the leaf, intercostal lamina, and in the vascular tissues. The preliminary results show the absence of the three types of calcium oxalate crystals in the stem and leaf of seven species: Ammi majus L., Anagallis arvensis L., Calotropis procera Ait., Citrullus colocynthis (L.) Schard, Euphorbia peplis L., Hyoscyamus muticus L., and Solarium nigrum L., and the presence of druses, prismatic crystals, and crystal sand either in the leaf and stem or in the leaves or stems of nine species: Anabasis articulata (Forssk.) Moq. in DC., Chenopodium album L., Convolvulus arvensis L., Datura stramonium L., Nerium oleander L., Ricinus communis L., Rumex nervosus Vahl., Pergularia tomentosa L., and Withania somnifera (L.) Dun. in DC. These observations indicate that there is no apparent relationship between the distribution of calcium oxalate crystals and the toxic organs of the plants, and supports the view that the presence of calcium oxalate crystals may not be related to plant toxicity.
VARIATION IN STRUCTURE AMONG FRUITS OF MALOIDEAE (ROSACEAE)
Authors: Rohrer Joseph R. , Robertson Kenneth R. , Phipps James B.
Published: January 2018

Fruits of Rosaceae subfamily Maloideae are known as pomes, a fruit type unique to the Maloideae. Using light microscopy we examined the pomes of 173 species, broadly representing the taxonomic diversity of the subfamily. Significant variation occurs among pomes in retention, orientation, and texture of calyx lobes on the distal end of the fruit; density and distribution of sclereids in the flesh; heterogeneity among flesh parenchyma cells; carpel number and number of ovules per carpel; degree of connation among the carpels and adnation between ovary and hypanthium; and texture of the core. Phenetic clustering closely links congeneric fruits. Sorbus is a notable exception; fruits of the compound‐leaved species form a cluster unrelated to fruits of the simple‐leaved species. Fruits of Malus are also heteromorphic. Division of the Maloideae into two tribes, Crataegeae and Sorbeae, based largely on texture of the core is not substantiated. We hypothesize that the ancestral pome had five carpels, minimal connation of carpels, minimal adnation of ovaries to the hypanthium, two ovules per carpel, and a leathery core. Various adaptations for frugivore dispersal of the seeds partially explain trends in pome evolution.
A NEW JURASSIC ISOETITES (ISOETALES) FROM THE WALLOWA TERRANE IN HELLS CANYON, OREGON AND IDAHO
Authors: Ash Sidney R. , Pigg Kathleen B.
Published: January 2018

A new species of the quillwort Isoetites, I. rolandii sp. nov. Ash and Pigg, is described from the Middle Jurassic Coon Hollow Formation in the Wallowa terrane in Hells Canyon, Oregon and Idaho. The new species is based on coalified impressions and mold‐casts of an isoetaceous corm with narrow, elongate leaves, and isolated masses of leaves that have been studied using light microscopy. Plants are about 10 cm in maximum height and consist of cormose plant bases from 1.5 to 2.5 cm wide and 0.6 cm high bearing incomplete microphyllous leaves up to 8.4 cm long and 3.0 mm wide, that taper to about 2.0 mm wide distally. Associated casts of sporophyll bases and sporangia contain spherical structures about 440 μm in diameter that may represent megaspores. Based on the occurrence of complete plants, some specimens of I. rolandii are thought to have been preserved in situ. The new Isoetites provides the first floristic evidence for the occurrence of an aquatic or semiaquatic paleoenvironment in the Wallowa terrane. It is also the first documented occurrence of Isoetes‐like plants in the Jurassic of western North America.
DEVELOPMENTAL STUDY OF BRANCHED RHIZOPHORES IN THREE SELAGINELLA SPECIES
Authors: Imaichi Ryoko , Kato Masahiro
Published: January 2018

A morphogenetic investigation was made of the rhizophore of three large‐sized tropical Selaginella species. The rhizophores of Selaginella delicatula, S. caudata, and S. plana arise exogenously at the points of branching of the main stems. In S. delicatula they are initiated at the junction of the second youngest branching. The rhizophore apical meristem has a tetrahedral apical cell and is capless. The rhizophores are usually three or four times dichotomously branched in S. delicatula and S. plana and four or five times in S. caudata. In S. delicatula, dichotomous branching of the rhizophore involves formation of two new apical cells subsequent to loss of an original apical cell. A pair of roots is formed endogenously from inner cells below the dermal layer at the apex of ultimate rhizophore branches. The finding that the rhizophore is an autonomously branched, leafless, and capless axis leads us to argue that Selaginella rhizophores, like lepidodendrid rhizomorphs, are fundamental axial organs that coordinate with the stem and root.
CONE AND OVULE DEVELOPMENT IN SCIADOPITYS (TAXODIACEAE‐CONIFERALES)
Authors: Takaso T. , Tomlinson P. B.
Published: January 2018

Ontogeny of seed cones of Sciadopitys, with special reference to the ovule‐supporting structure, is studied in material collected in Japan and Massachusetts. Cones are initiated as lateral or terminal structures in summer and complete the formation of most organs before winter. Bract development is well advanced before ovule‐supporting structures are initiated. Continued cone development involves the formation of a narrow ridge of tissue in the axil of each fertile bract. This ridge develops a series of nine (but up to 12) apical lobes in centrifugal order, each of which is the primordium of a future tooth on the ovuliferous scale. Ovules are initiated as outgrowths of the adaxial surface of each lobe so that there is a one‐to‐one ratio between lobes and ovules. Intercalary extension of the ovuliferous scale itself (distally) and the common base of the bract and ovuliferous scale (proximally) greatly extends the complex. The ovuliferous scale eventually exceeds the subtending bract and its apex becomes recurved. Bracts each have a single trace, but each ovuliferous scale has a pair of traces that proliferate distally to irrigate ovule and scale lobe. Intercalary growth results in recurvature of the ovule trace. The organization of the cone is directly comparable with certain Permian fossils. Sciadopitys also seems unique within the Taxodiaceae in its centrifugal development of the ovule‐supporting complex.
IMMUNOFLUORESCENT LOCALIZATION OF MICROTUBULES THROUGHOUT THE CELL CYCLE IN THE GREEN ALGA MOUGEOTIA (ZYGNEMATACEAE)
Authors: Galway M. E. , Hardham A. R.
Published: January 2018

Indirect immunofluorescence microscopy was used to survey the three‐dimensional distribution of microtubules throughout the cell cycle in the green alga Mougeotia. The network of microtubules present in the cortex of the cells at interphase gradually disappeared before mitosis. A band of cortical microtubules reminiscent of the preprophase band of higher plants surrounded the nuclei of some preprophase cells undergoing cortical microtubule disassembly. Longitudinally oriented bundles of microtubules appeared at the future spindle poles on either side of the nuclei in prophase. These bundles disappeared gradually as the spindle microtubule arrays formed. New spindles had broad poles but these became quite pointed before anaphase. Interzonal microtubules appearing at anaphase persisted until the end of nuclear migration, by which time they were concentrated into narrow bundles on either side of the centripetally forming crosswalls. During decondensation of the chromosomes and early nuclear migration, the spindle poles persisted as sites of microtubule concentration. New arrays of microtubules radiated from these microtubule centers into the cytoplasm ahead of the migrating nuclei. After cytokinesis, reinstatement of cortical microtubules was best observed in regions of the cells remote from the nuclei and associated microtubules. In contrast to higher plants, the first detectable cortical microtubules were short and already oriented transverse to the long axes of the cells.
GENDER VARIATION AND SEXUAL DIFFERENCES IN REPRODUCTIVE CHARACTERS AND SEED PRODUCTION IN GYNODIOECIOUS GERANIUM MACULATUM
Authors: Ågren Jon , Willson Mary F.
Published: January 2018

Variation in sex expression, flowering pattern, and seed production was studied in the self‐compatible perennial herb Geranium maculatum in Illinois and Indiana. In a survey of eight populations, female (male‐sterile) plants were found in seven (frequencies ranging from 0.5% to 24.3% [median 4.2%]), and intermediate plants (with partly reduced male function) were found in all populations. Gender variation and sexual differences in reproductive characters were studied in detail in two populations. One population consisted of 5% female, 27% intermediate, and 68% hermaphrodite plants; the other consisted of 1% female, 20% intermediate, and 79% hermaphrodite plants. Females produced smaller flowers and began flowering earlier than hermaphrodites. Intermediates produced flowers of an intermediate size and began flowering as early as females. Females and hermaphrodites did not differ in flower number, vegetative size, flowering frequency, survival, or seed size. However, females produced 1.6 times more seeds than hermaphrodites. Intermediates produced 1.3–1.6 times more seeds than hermaphrodites. Some between‐year variation in sex expression was observed. Hand‐pollination with outcross pollen produced two to four times as many seeds as hand‐pollination with self‐pollen. A lower outcrossing rate in hermaphrodites than in females may at least partly explain the lower seed set in hermaphrodites. The higher seed production of females, and possibly the high fecundity of the intermediates, should contribute to the maintenance of this sexual polymorphism.