Major Plant Groups Research Articles

ON CLADISTIC RELATIONSHIPS IN GREEN PLANTS

SummaryInterrelationships of major groups of green algae and land plants are currently hypothesized in cladograms by various authors. A summary cladogram is given and controversial points such as the precise sister group of the land plants are indicated. Sequence data from 5S ribosomal RNA are more homoplasious than morphological data and hence less useful for inferring phylogeny. Traditional textbook classifications contain several paraphyletic taxa and are frequently uninformative with respect to interrelationships/phylogeny. A cladistic classification with monophyletic taxa is advocated. It is superior for teaching purposes and provides natural taxa that are meaningful for biology in general.

Biological monitoring of environmental contaminants (plants)

DNA amounts (C-value and genome size) are much-used biodiversity characters. A workshop held at Kew in 1997 identified major gaps in our knowledge of plant DNA amounts, recommending targets for new work to fill them. Murray reviewed non-angiosperm plants noting that representation of pteridophyte species (approx. 0.42%) was poor, while locating C-value data for them was very difficult. The workshop confirmed the need to make data for other groups besides angiosperms accessible for reference purposes. This paper pools DNA C-values for 48 pteridophyte species from eight original sources into one reference source, and fulfils a key workshop recommendation for this group. Comparing these data shows that nuclear 1C-values in pteridophytes vary approx. 1000-fold, from 0.055 pg in Selaginella species to about 55 pg in Ophioglossum petiolatum. Genome size estimates for 25 pteridophytes vary approx. 200-fold from 0.055 to 10.7 pg, and the mean genome sizes in diploids and polyploids (5.15 and 4.59 pg, respectively) are not significantly different. Wider comparisons show that ranges of genome sizes in the major groups of land plants are very different. Those in bryophytes and pteridophytes are narrow compared with those in gymnosperms and angiosperms. The data indicate that the origin of land plants possibly involved a first major increase in genome size in the evolution of vascular plants, while a second such increase occurred later in gymnosperms. C-values for pteridophytes remain very few, but conversely opportunities for new work on them are many.

Vegetative and Fertile Structures of Cyathotheca ventilaria from the Upper Pennsylvanian of the Appalachian Basin

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.

VEGETATIVE AND FERTILE STRUCTURES OF CYATHOTHECA VENTILARIA FROM THE UPPER PENNSYLVANIAN OF THE APPALACHIAN BASIN

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.

Changes in Diets of Wapiti during a Hunting Season

Changes in Diets of Wapiti during a Hunting Season

Protamines in plant sperm

Sperm protamines have been isolated from representatives of three major plant groups: algae ( Chara corallina), bryophytes ( Marchantia polymorpha), and ferns ( Marsilea vestitia). We previously reported the complete displacement of histones by protamines in Marchantia (Reynolds W F & Wolfe, S L, Exp cell res 116 (1978) 269 [8]). Marchantia protamines appear as four components on acid-urea gels, whereas Chara and Marsilea protamines comigrate as a single band with a mobility comparable to salmon protamine. The amino acid compositions of the plant protamines show these to be arginine-rich, highly basic (35–42%) proteins which display overall similarity in amino acid composition (84–91%). The molecular weights of Chara and Marsilea protamines are approx. 4 700 – 5 300 D.

Patterns in vascular land plant diversification

Statistical analyses indicate that the Phanerozoic history of vascular land plants (tracheophytes) may be interpreted in terms of the successive radiations of four major plant groups, each characterized by a common morphological and/or reproductive grade. Following initial invasion of the land, the diversification of each group coincides with a decline in species numbers of the previously dominant group. Analyses indicate that each group is initially characterized by a high rate of appearance of new species but short species durations. However, within a group through time, new species appear less frequently but species durations increase. Parallels between the diversification patterns observed for tracheophytes and those previously noted for marine invertebrates1 suggest there are generalized patterns in the evolution of higher taxa.

Methods of production of new varieties

A review is given of the methods in general use in the breeding of crops belonging to the major groups of crop plants and an assessment is given of the important factors that determine their efficiency, especially gene-environment interaction in the early segregating generations. Variations of the standard techniques including generating homozygotes through single seed descent, cytological production of homozygous diploids, multiplication of advanced segregating bulk populations without selection, and the production of F 1 hybrid varieties in inbreeding crops, are outlined and assessed. The importance of production-scale testing to supplement data from plot trials, and its relevance to the organization of plant breeding and to the successful identification of superior selections, are considered.

On the Evolution of Complex Life Cycles in Plants: A Review and an Ecological Perspective

Complex life cycles and alternation of generations are characteristic of many plants, a diploid sporophyte typically alternating with a haploid gametophyte. The prominence of each generation varies greatly among taxa. Purely phylogenetic or morphogenetic explanations of these differences are unsatisfying, as are those based solely on population fitness. Existing adaptational explanations seek selective advantages in diploidy and in sexual reproduction, but these explanations leave much to be explained-i.e., the existence of asexuality and of haploid organisms. Much of the existing variation in life cycles can be explained by selection on reproductive rates to meet the ecological problems of dispersal, colonization, niche preemption and exploitation, and mate competition. Placement of complex life cycles of plants in an ecological framework will, I hope, encourage specific studies exploring possible adaptive aspects and limitations on the evolution of life cycles in plants with different life histories. A prominent feature of most textbook introductions to various major groups of plants is the description of reputedly typical life cycles of selected forms. Attention is focused on the alternation of haploid and diploid phases (or generations) of the cycle, the relative dominance of one phase or another, the timing of meiosis and fertilization, the occurrence of asexual reproduction, and which phase is the dispersal or resting stage. Most of the available published literature on plant life cycles is directed toward elucidating developmental, morphological or physiological and, finally, phylogenetic patterns. A rather small number of papers (see below) addresses the possible selective advantages or disadvantages of reproducing sexually or asexually, of being haploid or diploid, or of having more than one morphological generation. Here, I use the word generation to refer to both the alternating diploid and haploid entities and to any intervening, asexually produced, progenies. So far as I can determine, virtually nothing has been written on the ecology (aside from genetics) of complex life cycles in plants. Several botanical reviewers have claimed that all of the ideas summarized here regarding the ecology and evolution of plant life cycles are old hat. They should be, perhaps, but no one has shown me evidence that they are. This review is presented in hopes of stimulating discussion and research that include an ecological perspective. I begin by summarizing some apparently classic life cycles of selected plants (broadly defined to include fungi, but excluding prokaryotes). There follows a review of available hypotheses attempting to explain the evolution of such cycles in plants and a critique of these hypotheses. Finally, I review some of the liter

Early angiosperm reproduction: An introductory report

The phylogeny of angiosperms presented by various authors is based principally upon our knowledge of modern plants. The fossil history of flowering plants has had little influence upon current concepts of primitive features of the flower. Several reproductive characters of non-angiospermous plants demonstrate the diversity of flower-like characters common to some extinct major groups of plants. Various Lower and Middle Cretaceous angiosperm reproductive structures illustrate the nature of the early receptacles, carpels and perianth parts. Pteridosperms (seed ferns), which bore separate clusters of ovules and microsporangia are considered a likely ancestral source of the angiosperms. Probable radiations of both diclinous (unisexual), mainly wind-pollinated, and monoclinous (bisexual), mainly insect-pollinated, lines are suggested for the ancestral flowering plants. The primitive flower types are thought to be quite simple with subsequent elaboration and other modifications of the flower, resulting from the adaptive ecological strategies of reproductive mechanisms through time. Insects have played a major role in floral evolution but not to the exclusion of ancient wind-pollinated forms. There have been major and minor shifts of the reproductive ecology in various groups of angiosperms so that the diverse flowers and fruits seen today are the product of reticulate patterns of evolution.

Chemotaxonomy of Some Paleozoic Vascular Plants. Part III. Cluster Configurations and Their Bearing on Taxonomic Relationships

Chemical data are given forSciadophyton, Eogaspesiea,Lepidodendropsis, Triphyllopteris, Chlidanophyton andDrepanophycus. The participation of these taxa within clustering analysis is shown to generate a cluster referable tentatively to the lycopods. Introgression of clusters representative of some major plant groups (e.g., zosterophyllophytes with the lycopods, and the trimerophytes with the progymnosperms) may reflect fortuitous statistical relationships referable to different states of preservation orbona fide phylogenetic trends. Weighting of the data is shown to result in the greater resolution of clusters, while sample size (presently 34 taxa) demonstrates a considerable effect on statistical relationships. Thermolytic alterations of extant plant materials, when incorporated within fossil plant ordination diagrams, are shown to provide internal monitors allowing for a more precise evaluation of taxonomic-chemical relationships.

Evaluation of Biological Control of Nuisance Aquatic Vegetation by Grass Carp

Grass carp introductions at Red Haw Lake, Iowa resulted in a decrease of aquatic macrophytes from 2,438 g/m2 in 1973 to 211 g/m2 in 1976, with species of Potamogeton, Elodea, Ceratophyllum, and Najas all controlled effectively by grass carp. During 1974-1976 mean nitrites, nitrates, biological oxygen demand, and turbidity showed significant decreases, while alkalinity increased significantly from a mean of 115 mg/liter in 1974 to 132 mg/liter in 1976. Mean concentrations of organic and inorganic phosphates gradually increased during the investigation, but were not statistically different. Average primary production was nearly identical in 1974-1975 at about 2 g carbon/m2/day, but decreased significantly to 1.35 g carbon/m2/day in 1976. Growth of stocked grass carp was rapidly increasing from a mean weight of 380 g in July, 1973 to 6,847 g by October, 1976. Body condition ranged from 1.05-2.02 with average condition over 1.37 in October and 1.25-1.30 in January-February. Greatest population biomass was estimated in 1975 at 61 kg/hectare. Grass carp consumed all major plant groups at the lake with greatest selection for Najas and Potamogeton. Movement, behavior, and activity as determined by ultrasonic telemetry showed grass carp inbabited all areas of the lake, but overall there was a preference for sballow areas of the main lake with lesser selection for embayments. Most of the time grass carp were sedentary near weed beds with more rapid and extended movement in midwater. Normal swimming speed in midwater was 0.12-0.35 m/s with maximum speed of 1.46 m/s. Homing tendency was shown in two of nine tagged fish. There was similarity in nocturnal and diurnal activity. Reduction in vegetation biomass by 91% in four years increased the opportunity for anglers to fish from shore. During the investigation popularity of shoreline fishing increased by 241% with catch success remaining greater than 0.70 fish per hour.

Photosynthesis and respiration of some tropical marine plants

This paper presents mean values of light saturated net photosynthesis (Pn) and dark respiration (R) rates of 91 species of tropical marine plants studied in Cuba and Hawaii. All the major taxonomic groups of macroscopic marine plants studied are not significantly different from the “productivity” point of view, with total mean “Pn” and “R” rates of 7.2 and 1.4 mg O 2 g(dry) −1 h −1, respectively. More than half of the green, brown and red algae studied have “Pn” rates lower than 7.2 mg O 2 g(dry) −1 h −1, but for seagrasses, only 20% is included in the above-mentioned range. Amongst each taxonomic group there are more productive species. Species whose Pn/R ratios are higher than 15 include the following: Lyngbya majuscula, Cladophoropsis luxurians, Microdictyon setchellianum, Ulva reticulata, Dictyota linearis, Lobophora variegata, Turbinaria turbinata and Galaxaura apiculata. They can be considered to be the most “productive”, although sometimes they are not the most abundant.

Chemotaxonomy of Some Paleozoic Vascular Plants. Part II: Chemical Characterization of Major Plant Groups

Chemical data are given forCooksonia, Rhynia, Zosterophyllum, Pseudosporochnus, Gosslingia,Crenaticaulis, Leclercqia, Tetraxylopteris, Oocampsa, andArchaeopteris, thus extending principal component analysis of multi-state and discrete characters to 27 Paleozoic plant taxa. Ordination patterns of these data suggest that while overlapping of major plant groups occurs, rhyniophytes, zosterophyllophytes, trimerophytes and other supra-generic taxa may be chemically characterized. The effects of heat (thermolysis) on organic constituents is shown to severely alter chemical profiles of plant taxa and is discussed as a thermometric tool. Taxonomic distancemeasures between plant groupings are suggested to be the result of both preand post-fossilization phenomena.

FLORAL EVOLUTION IN THE HAMAMELIDIDAE. I. GENERAL ASSESSMENT OF THE PROBABLE PHYLOGENY AND TAXONOMIC POSITION OF THE GROUP

SUMMARY After the publication of an emended version of the Anthocorm Theory and the introduction of the concept of the holomonandron and its meromonandrial derivatives, a number of major groups are re-interpreted as far as their floral morphology and phylogeny are concerned. The present paper is the first of a series dealing with the subclassis of the Hamamelididae. The “Amentiferae” appear to exhibit various trends of floral evolution, but the androecia sometimes remained primitive. Generally speaking, the structures conventionally called “flowers” represent modified gonoclads (or sometimes monogona) which function as reproductive units. These functional reproductive units (or anthoids) are usually coaxially arranged in so-called inflorescences (“catkins”) or “part-inflorescences” (“dichasia”, “cymes”, etc.), but as far as can be ascertained these names are utterly misleading. A characteristic trait of the group is that, in contrast to nearly all other major groups of dicots, the anthocorms hardly, if ever, evolved into a brachyblastic holanthocormous flower. The Juglandales, Hamamelidales and Urticales exhibit similar trends of anthocorm evolution, and apparently hang together. Neither euanthous forms, nor groups with primitive (macro- and leptoblastic) anthocormoids specialised (reduced, oligomerised) in a different way (such as Chloranthacecae, Piperales, some Laurales), can be derived from, or considered prototypic to, hamamelidid taxa. A common phylogenetic origin of the Hamamelididae with other major groups of Flowering Plants can only be visualised as a descent of both from a common group of progenitors with primitive (i.e., polymerous and macroblastic) anthocorms, and chances are that this ancestral group was still hemi- or pre- angiospermous. Within the hamamelidid assembly early specialisations caused a divergent evolution resulting in an early (presumably Mid-Cretaceous) separation of the casuarinalean, juglandalean, urticalean, betulalean/fagalean and hamameli-dalean groups. These conclusions will serve as a basis for the discussions in other papers of these series.

Plants in the Laboratory. A Manual and Text for Studies of the Culture, Development, Reproduction, Cytology, Genetics, Collections, and Identification of the Major Plant Groups.William J. Koch

<i>Plants in the Laboratory. A Manual and Text for Studies of the Culture, Development, Reproduction, Cytology, Genetics, Collections, and Identification of the Major Plant Groups.</i>William J. Koch

Potential of opal phytoliths for use in paleoecological reconstruction

Opal phytoliths, inorganic biogenetic plant particles of microscopic size, were investigated to determine the level at which their varied morphology is taxonomically significant. Extraction methods for the isolation of these particles from living plants and from soils were developed to provide maximum preservation of morphological features while remaining simple, rapid, and inexpensive. Extracts were made and microscopically viewed from 30 live specimens, of which 16 were systematically typed in order to develop taxonomic guidelines for their identification in soils. Clear taxonomic differentiation was noted between and within major plant groups with considerable indication that more detailed investigation will yield finer subdivisions. Since opal phytoliths are reported to be a particularly durable fossil found in deposits as far back as Tertiary Age, it appears that opal phytolith analysis can provide paleobotanical information comparable to palynological data in many areas where pollen is absent. When used in conjunction with pollen where present, they should serve to confirm pollen data as well as provide additional botanical data not available in pollen studies.

Directional Cell Division in Shoot Apices

Comparative cytohistological studies were made of shoot tips of Equisetum hyemale, Picea abies, and Prunus Persica, as examples from three major taxonomic groups of plants: lower vascular plants, gymnosperms, and angiosperms. The purpose of this study was to find out more specifically what factors determine the formation of apical histogenic layers. Obviously the plane of mitotic division in the cells at the upper surface of shoot apices determines the presence or absence of apical cell-layer formation. The hypothesis proposed is that the plane of mitotic division-positioning of metaphase chromosome plates-in cells in the surface region in shoot apices is determined by: 1) size of cells relative to shape and size of apical dome; 2) size of cells and space in cells relative to size of their nuclei and the freedom of their nuclei from wall pressure; and 3) location of cells and their shape and availability of space across a particular plane in cells in which metaphase plates can be accommodated. The hypothesis would explain the general predominance, or presence, of histogenic layers in shoot apices of angiosperms and relative paucity or lack of them in shoot apices of gymnosperms and lower plants.

Mineral elements in temperate crop and pasture plants. II. Calcium

Twenty-five annual crop and pasture plant varieties from 21 species were grown on a lateritic gravelly sand at Gidgegannup in Western Australia. Plant tops were sampled at three stages during the growing season and at maturity. This paper presents data for calcium contents of the tops. Calcium concentrations varied widely among species, and to a smaller extent with age and among plant parts at maturity. Species rankings varied only slightly among harvests. Herbs and all legumes except lupins maintained high calcium concentrations throughout the growing season. By contrast, the concentrations in grasses, and even more markedly in the cereals, were low in the young plants and declined further as the season progressed. Concentrations in lupins were intermediate in the first two harvests, but fell precipitously towards maturity to levels similar to those in grasses. Despite low overall levels in the mature plant, seeds of lupins were generally higher in calcium concentration than other legume seeds and several times as high as cereal grains. Calcium concentrations of plant tops correlated reasonably well with published data on cation exchange capacities (CEC) of roots when taken over the whole range of species, but within major plant groups the correlation was poor. It is suggested that, rather than signifying a causal relationship between root CEC and calcium concentration in the tops, the results may merely indicate that dicotyledonous plants tend to have high calcium concentrations and CEC values while monocotyledonous plants have low. It is also suggested that if any such causal relationship does exist, its origins are more likely to lie in the CEC properties of the tops than in those of the roots.

Histochemical &amp; Biochemical Differences Between Lignin-Like Materials in Phleum pratense L.

Although differences in lignins among major plant groups are known (23), the extent of variations found within one plant is not well understood (3). Histochemical tests for lignin with phloroglucinol and with Maule reagents do not always give identical patterns of lignification (3, 10, 24). Since similar discrepancies were observed in Phleum pratense L., the lignin in different parts of the timothy plant at various developmental stages was compared by histochemical and biochemical tests. Differences can be detected among the lignins of the elongated first internode, the upper internodes or sheaths, and the blade. These are related in part to the type of lignified cells. The results indicate that a satisfactory definition of lignin is still needed, that the detection of the extent of lignification may depend on the analytical method used, and the factors controlling lignification may vary in different tissues or even in the same tissue at various stages of development.