Structurally preserved sphenophytes from the Triassic of Antarctica: reproductive remains of Spaciinodum

Permineralized cones found organically attached to Spaciinodum collinsonii stems are described from the early Middle Triassic silicified flora from the Fremouw Formation of Antarctica, and the species diagnosis is emended to include the reproductive specimens. The apical cones are organized into internodal and leaf-bearing nodal regions. Nodal septations span the central pith and cortex, and thin fimbrils subdivide the internodal areas into smaller chambers. The vascular system consists of 31-33 continuous bundles that do not alternate in position between successive nodes and internodes. Simple sporangia are associated with the cortical chambers and occur in one whorl on the axis. Spores are small, lack elaters, and have no discernible ultrastructure preserved, and they are interpreted to be immature. The Antarctic cones are different in structure from typical cones of modern and fossil members of Equisetales; however, they share similarities with some morphologically aberrant cones of extant Equisetum and several Late Paleozoic and Mesozoic compression-impression fossils. Spaciinodum is now the most complete anatomically described Mesozoic sphenophyte.     

STEMS AND LEAVES OF CUNNINGHAMIOSTROBUS GOEDERTII FROM THE OLIGOCENE OF WASHINGTON

This report is based on nine specimens of fossil conifer stems and leaves from the Early Oligocene Jansen Creek Member of the Makah Formation. They were collected along the northern shore of the Olympic Peninsula of Washington. The fossils are preserved as siliceous permineralizations and were exposed in surface view along rock fractures. Details of leaf morphology and epidermal construction appear on fracture surfaces of certain specimens while the cellular construction of the leaves and twigs is visible in thin sections. Leaves are dorsiventrally flattened, attached to twigs that contain up to four growth increments of secondary xylem, up to 2.3 cm long, 3.5 mm wide, and have parallel margins with minute teeth. The leaves are about 0.5 mm thick and have a central vascular strand surrounded by transfusion tissue. A large resin canal occurs abaxial to the vascular strand, and generally two additional resin canals occur in the mesophyll near each leaf margin. Leaves are mostly hypostomatic, with sunken stomata in two longitudinal bands, one to each side of the midline of the leaf and each containing eight to 13 longitudinal rows of stomata. Several unusual anatomical features in the stems also occur in the peduncle and cone axis of seed cones described as Cunninghamiostrobus goedertii, which occurs at the same locality. Thus, the leafy twigs belong to the same species as produced the cones. The cones, leaves, and shoots of this Tertiary conifer are similar to those of modern Cunninghamia but differ from the living species in several respects.     

Leafy branches of Gangamopteris from the Gzhelian–Asselian of westernmost Gondwana

The first reconstructions of glossopterids interpreted this Gondwanan group as arborescent, deciduous plants, with leaves and reproductive structures inserted on short shoots, which were arranged on long branches. The leaves are its most abundant organ in the fossil record, but they are mainly found isolated. The arrangement of the leaves as terminal whorls or tight spirals has been the most accepted phyllotaxis hypothesis. The few examples of leaf impressions preserved in connection with axes correspond mainly to leaves of Glossopteris Brongniart, and mostly without clear evidence of the type of insertion. Several specimens of Gangamopteris McCoy leaves attached to axes from the Bajo de Véliz Formation (Latest Carboniferous–Earliest Cisuralian) facilitate reconstruction of the foliar arrangement of the genus, to date known mostly from isolated leaves. The available evidence from the new specimens confirms a variation from well-spaced to dense helical insertion of the leaves without forming true whorls, and discards the early notion that they were mainly clustered apically on short shoots in a similar manner to the extant Ginkgoales.     

Pleuromeia discovered from the Middle Triassic Linjia Formation of Benxi,Northeast China

A new species Pleuromeia shaolinii Zhang et Wang n. sp. was established under the family Pleuromeiaceae, based on eight specimens of stems and leaves, cones, rhizophores, and adventitious roots that were recently collected from the Middle Triassic Linjia Formation in Benxi, Northeast China. P. shaolinii n. sp. is similar to the type species P. sternbergii, in the morphology of the stem and rhizophore, but differs from it by the transversely rounded sporophylls organized in a heterosporous cone, and the two conspicuous triangular scars present on both sides of the vascular bundle scar. The Linjia flora, an only reliable Middle Triassic flora in Northeast China, was discovered 40 years ago. Although the Linjia Formation can be compared with the Middle Triassic Ermaying Formation from another area of the North China plate, its age was questionable due to the absence of the Early to Middle Triassic index fossil Pleuromeia. Based on the flora similarity, the zircon dating, lithologic characteristics, presence of a disconformity, and the occurrence of the Middle Triassic–Early Cretaceous insect fossil Sogdoblatta, the age of the Linjia Formation can be confirmed as Middle Triassic. The new species not only supplements our knowledge in biology and taxonomy of Pleuromeia, but also supports the Middle Triassic age assignment of the Linjia flora.     

Changes in photosynthesis, antioxidant enzymes and lipid peroxidation in soybean seedlings exposed to UV-B radiation and/or Cd

Aims

With a high growth rate and biomass production, bamboos are frequently used for industrial applications and recently have proven to be useful for wastewater treatment. Bamboos are considered as Si accumulators and there is increasing evidence that silicon may alleviate abiotic stresses such as metal toxicity. The aim of this study was to investigate the extent of metal concentrations and possible correlations with Si concentrations in plants.

Methods

This study presents, for the first time, reference values for silicon (Si), copper (Cu) and zinc (Zn) concentrations in stems and leaves of various bamboo species grown under the natural pedo-climatic conditions of the island of Réunion (Indian Ocean).

Results

A broad range of silicon concentrations, from 0 (inferior to detection limit) to 183 mg g^?1 dry matter (DM), were found in stems and leaves. Mean leaf Cu and Zn concentrations were low, i.e. 5.1 mg kg^?1 DM and 15.7 mg kg^?1 DM, respectively. Silicon, Cu and Zn concentrations increased over the following gradient: stem base?<?stem tip?<?leaves. Significant differences in Si, Cu and Zn contents (except Zn in the stem) were noted between bamboo species, particularly between monopodial and sympodial bamboo species, which differ in their rhizome morphology. Sympodial bamboos accumulated more Si and Cu than monopodial bamboos, in both stems and leaves, whereas sympodial bamboos accumulated less Zn in leaves than monopodial bamboos.

Conclusions

The findings of this study suggest that a genotypic character may be responsible for Si, Cu and Zn accumulation in bamboo.     

More evidence for a slender growth habit in Mesozoic cycadophytes

From the Pekin Formation (Upper Triassic) of the Deep River basin in central North Carolina, U.S.A., originate remains of a slender cycadeoidalean (bennettitalean) stem with leaves of a type combining features of the form genera Otozamites and Zamites. The plant, placed in the new genus and species Ischnophyton iconicum, is additional evidence that the common growth habit of Triassic and Jurassic cycadophytes was one involving a slender stem, without closely spaced, persistent leaf bases.     

SCIADOPITOPHYLLUM CANADENSE GEN. ET SP. NOV.: A NEW CONIFER FROM WESTERN ALBERTA

A new Sciadopitys-like conifer is described on the basis of compression fossils of shoots and leaves found at the Smokey Tower locality in western Alberta. The specimens consist of long, strap-like leaves attached in apparent whorls and subtended by groups of scale leaves. Other scale leaves are borne in loose spirals on the shoots between whorls. These specimens represent the first record of Sciadopitys-like foliage from western North America. Comparisons are made with extant and extinct species of the genus Sciadopitys (Siebold and Zuccarini, 1841) and with the widely distributed fossil genus Sciadopitytes (Goeppert and Menge, 1883).     

STRUCTURALLY PRESERVED SPHENOPHYTES FROM THE TRIASSIC OF ANTARCTICA: VEGETATIVE REMAINS OF SPACIINODUM,GEN. NOV.

Sphenophyte remains of Early-Middle Triassic age are described from silicified peat collected in the Transantarctic Mountains of Antarctica. The new sphenophyte, Spaciinodum collinsonii sp. nov., is represented by ribbed, jointed stems with characteristic pith and carinal canals. Stems are relatively small, ranging from 1.8–3.0 mm in diameter, lack secondary tissues, and are characterized by vallecular canals that are restricted to nodal regions. The internodal vascular system consists of 12–18 collateral bundles which alternate between successive internodes. A complete vascular ring is present in the nodal region and is surrounded by a continuous double endodermis. Xylem is endarch and composed of elements ranging from annular to reticulate. The Antarctic sphenophyte is compared with other Gondwana fossil articulates and extant Equisetum. Superficial stomata suggest affinities with modern Equisetum subgenus Equisetum; however, some anatomical differences preclude assignment with living species.     

Growth and leaf production in the tropical palm Euterpe edulis: Light conditions versus developmental constraints

We studied developmental and environmental constraints on leaf dynamics, morphology and physiology in the monopodial tropical palm of the Atlantic Forest biome, Euterpe edulis. Plastic responses to light environments in terms of photosynthesis, leaf size, leaf life span, patterns of biomass allocation and growth were analysed. Plants were grown during 14 months in a shade house under four different growth irradiances. Plants of Euterpe edulis were able to adjust leaf demography and biomass allocation in the different light treatments. Leaf life span increased by 100 days with decreasing light levels while the rate of leaf production decreased, consistent with lower electron transport rates. At low light levels, adjustments in biomass allocation to leaf components allowed E. edulis to reduce self-shading and increase light interception. At high light plants allocated more biomass to roots, and the plants exhibited small leaf sizes when leaves were compared using an explicit ontogenetic analysis. Ontogeny constrained the maximum size that each consecutive leaf could achieve, while growth irradiance determined the rate of leaf production and other leaf traits. Consequently, there were both, developmental constraints and environmental determinants influencing leaf demography and morphology in E. edulis. The findings of this ecophysiological and demographic study are relevant to palms growing under natural conditions and help to explain the success of E. edulis in the forest understory and its absence from large gap openings. Our results not only confirm that E. edulis is a shade tolerant species, but also show that palms are able to acclimate to different growing condition as well as trees.     

SHOOT VASCULAR SYSTEM AND PHYLLOTAXIS OF CASUARINA (CASUARINACEAE)

In species of Casuarina with multileaved whorls, each stem vascular bundle divides radially into two at the site of a leaf trace separation, and the same two bundles rejoin acropetally to where the trace supplies a leaf. Such divisions are divisions of a single vascular bundle, and the rejoining of bundles forms a single bundle. Proposals that the extant primary vascular systems of dicotyledons may have been derived as in conifers are incorrect in so far as Casuarina is concerned, or the system has evolved beyond that so far proposed for dicotyledons. Reasons are offered, however, for considering that fernlike leaf gaps are not present. Leaf traces supply leaves at the first nodes distal to their origins. The ways by which an increase or decrease of stem bundles occur are described. Phyllotactic patterns range from helical (rare) to whorled. In the embryo, where leaves occur decussately, of certain species with multileaved whorls, and in the shoot apices of species with tetramerous whorls, slight differences in the levels of leaf attachments and the bending of leaf traces indicate the probable evolution of extant whorled phyllotaxies from one or more helical arrangements. Stages in the evolution are suggested. The leaves in most species with multileaved whorls are in true whorls. The original periderm of branchlets lies internally to the internodal traces and chlorenchyma, but is otherwise external to the vascular system. It is concluded that each leaf originates at its level of separation from the axis despite several structural features suggesting that the leaf bases have become congenitally adnate to the stem.     

Chenia zanderi C.Feng & J.Kou (Pottiaceae,Musci), a new species from Yunnan,China

A new species, Chenia zanderi C.Feng & J.Kou, from Xishan Forest Park in Yunnan Province, China is described and illustrated. Particularly distinctive features of the new species are the fragile stems and leaves fragile along their insertions, narrow leaves usually constricted near the middle, broadly rounded leaf apices with a long apiculus, large distal laminal cells with numerous solid and bifurcate papillae, a narrow groove on the distal ventral surface of the costa, and absence of a costal stereid band. A key for the species recognised in Chenia R.H.Zander is also provided.     

New Sphenophyllum plant from the Upper Devonian of Zhejiang Province,China

Sphenophyllum was an important and long-surviving sphenopsid genus in the Paleozoic floras, with a worldwide distribution. A new species, Sphenophyllum changxingense sp. nov., is described from the Upper Devonian Wutong Formation of Changxing County, Zhejiang Province, China. This plant is characterized by two orders of slender axes and wedge-shaped leaves borne in whorls. The axes bear short spines and show longitudinal ridges and furrows on surface. Three to eight isophyllous leaves, with one, two, or no second-order axes, are attached at each node of first-order axes. Leaves bear spines and show a bilobate morphology; the two leaf lobes divide distally to form several marginal segments, each segment with a leaf vein. Sphenophyllum changxingense represents an early and primitive species within the genus, in light of the absence of heterophylly and specialized hook-like leaves. Like some Carboniferous and Permian species, it appears to have formed dense mats with mutually supportive axes. This plant adds to the known diversity of early sphenopsids in the Late Devonian.     

Effect of Leaf Detachment on Chlorophyll Fluorescence during Chilling Experiments

The effect of leaf detachment on chlorophyll fluorescence was analyzed for Zea mays, Cucumis sativus, Phaseolus vulgaris, and Echinochloa crus-galli. Results clearly indicate that detachment hastens the decrease in chlorophyll fluorescence during the course of chilling experiments. For maize and bean, the activity of photosystem II of chloroplasts isolated from detached leaves is lower than that of chloroplasts isolated from attached leaves. There are also large differences in ionic loss between detached and attached leaves of barnyard grass which could correlate with changes in leaf water status. The detached leaves lost some 50% of their total ionic content. Finally, detachment alters the ranking of the species with regard to their chilling tolerance.     

Field growth characteristics of two aquatic carnivorous plants,Aldrovanda vesiculosa andUtricularia australis

Basic growth characteristics of two species of free-floating submerged carnivorous plants, the very rare and stenotopicAldrovanda vesiculosa and the very common and eurytopicUtricularia australis, were investigated in a 10/11-day field growth experiment within three nylon enclosures at two artificialAldrovanda sites in the T?eboň region, S Bohemia, Czech Republic, at the peak of a growing season. Growth ofAldrovanda was best at a meso-eutrophic site (biomass doubling time,T ₂, 8.4–10.7 days, mean growth of new leaf whorls 0.96 whorls days^?1, 1.6 developed branches per shoot) and slower at an oligo-mesotrophic site (T ₂ 17.2–21.5 days, growth of whorls 1.01 whorls days^?1, 0.1–0.5 branches per shoot). Growth ofUtricularia was similar at both sites (T ₂ 19.8–33.2 days or 9.1–16.8 days, growth of whorls 3.1 or 2.7 whorls days^?1, 1.5–2.1 or 0.8–1.4 developed branches per shoot at the former or latter site, respectively). Throughout the experiment, both species at the meso-eutrophic site allocated relatively more biomass to the production and growth of branches, than to that of new whorls. The results show thatAldrovanda, although usually considered as competitively weaker, can grow faster during the growing season peak thanUtricularia due to frequent branching and the subsequent rapid growth and separation of daughter shoots. Very rapid growth of rootless aquatic carnivorous plants in nutrient-poor habitats allows the consideration of ecophysiological adaptations that enable the plants to gain limiting mineral nutrients. These adaptations include carnivory, efficient nutrient reutilization from senescent shoots, and very high affinity for mineral nutrient uptake from water. Comparison of growth rates of rare and stenotopicA. vesiculosa and very common and eurytopicU. australis shows that differences in their rarity do not seem to be based on differences of growth rate.     

毛竹的无性系生长与立竹密度和叶龄结构的关系

毛竹为单轴型散生竹,属典型的无性系植物,原产我国亚热带地区。由于其个体高大、生长迅速、产量高、材质好、分布广,长期以来,一直是我国最为重要的经济竹种。本文应用无性系生长生理整合的理论,从种群统计学的角度,探讨了毛竹林立竹密度与叶龄结构对其无性系生长潜力的影响。结果表明：由于毛竹叶的生活期为两年,１龄新叶的光合能力比２龄老叶高,每样地的出笋数、活笋数与带１龄新叶的立竹数呈正相关,而与带２龄老叶的立竹数相关性不显著。另外,竹笋的死亡率是非密度制约的。本研究结果合理地解释了常见的毛竹林产量大小年交替变化的现象。     

A new species of Verbesina (Asteraceae: Heliantheae) from northeastern Mexico

Verbesina lanulosa is described as a new species from the Mexican state of Nuevo Leon. This species is compared with V. chihuahuensis and V. suberosa, and mainly differs by its leaf shape, petiole form, and pubescence of the stems, leaves, and inflorescences. An illustration is included.     

Differential Induction of Endoproteinases during Senescence of Attached and Detached Barley Leaves

Endoproteinase activities and species were compared during dark-induced senescence of attached and detached primary barley leaves by isoelectric focusing and polyacrylamide gel electrophoresis of cell-free extracts. Neither of the two major endoproteinases (EP1 and EP2) changed in amounts during senescence of attached leaves, nor did new endoproteinases appear. In contrast, during senescence of detached leaves, both EP1 and EP2 activities increased and four new species of endoproteinases appeared. Proteolytic activity was evenly distributed throughout attached leaves, but activity in the detached leaf increased sharply from the tip to the base with the four new higher molecular weight species of proteinases present only in the bottom half of the leaf nearest the cut end. Thus a wound response may be superimposed on the processes of senescence in detached leaves. Cycloheximide and kinetin both inhibited the increase of EP1, EP2, and the induction of the four new endoproteinases; chloramphenicol had no effect. Indications are that both the increases in activity and the induction of new species of proteinases were the result of activity of cytoplasmic ribosomes.

Hydrolysis of total protein and ribulose-1,5-bisphosphate carboxylase protein in vivo was somewhat faster in detached than attached leaves. The difference, however, was much less than would be expected from the great increase in proteolytic activity in detached leaves.

     

“Lycostrobus” chinleana,an equisetalean cone from the Upper Triassic of the southwestern United States and its phylogenetic implications

Detailed study of the cone Lycostrobus chinleana Daugherty shows that the fossil was incorrectly attributed to the Lycopodiales by the author and to the quillworts by Retallack and that it actually should be assigned to the Equisetales. The cone, which occurs in the Upper Triassic Chinle Formation at several localities in the southwestern United States, is ∼2.5 cm wide and nearly 6 cm long and consists of a stout axis bearing whorls of peltate sporangiophores. Each sporangiophore is composed of a slender stalk and a hexagonal disk, which typically bears a single, generally long, lanceolate, forward-directed leaf-like umbo tip on the outer surface and several recurrent sporangia on the inner surface. Small round to oval trilete spores occur in the sporangia. Since the leaf-like umbo tip is similar to the sterile leaves found in certain calamite cones and the recurrent sporangia are equisetalean-like, it appears that the cone may represent a intermediate stage between Calamites and modern Equisetum. According to this hypothesis, the nonbracteate Equisetum cone could have developed from a bracteate calamite cone, through reduction and fusion of the bracts and the sporangiophores, rather than by the loss of whorls of bracts of the Calamites cone as suggested earlier by others. As a result of this study the cone is assigned to the new Equisetalean genus Equicalastrobus and redescribed under the name E. chinleana (Daugherty) Grauvogel-Stamm and Ash, n. comb.     

Growth-unit structure in trees: effects of branch category and position on Nothofagus nervosa, N. obliqua and their hybrids (Nothofagaceae)

In plants with rhythmic growth, a branch segment extended in one event is known as growth unit (GU). GU structure, resulting from the resources allocated to stem length, volume and mass, and to leaf area and mass, is relevant for understanding branch functioning in the context of plant development. This study compares GU structure between main branches and short branches positioned at low and high positions on nursery-grown trees of three closely related genetic entities: Nothofagus nervosa, N. obliqua and natural hybrids between these species. GUs of short branches, compared to those of main branches, had lower length, diameter and number of leaves, and higher specific leaf area (SLA), stem density and proportional mass in leaves than in stems. GUs at high position on the trees had a higher proportion of their mass in stem than in leaves and a lower SLA than those at low position. Stem density was higher for N. nervosa and the hybrid trees than for N. obliqua. Most other GU traits did not differ statistically between the considered genetic entities. The three genetic entities exhibited distinct patterns of variation in leaf size with leaf position along main-branch GUs. The individual tree had a significant effect on most variables. GU structure would have a major ontogenetic component and would play a relevant role in the architecture of Nothofagus species and their adaptation to different environmental conditions.     

林下引入耐阴树种功能性状特征及其与生长的关系

植物功能性状之间的协调性揭示了其适应特定生境的主要策略,而植物早期生长与功能性状可能具有很大关联性。为探讨林下引入耐阴树种的根、茎、叶功能性状协调性及其与生长的关系,研究了杉木人工林林下引入5种常绿阔叶树种（洒金叶珊瑚、杨桐、蚊母树、栀子和海桐）的生长率（树高和地径相对增长率）以及27个根茎叶形态、生理性状指标。结果表明：（1）由主成分分析（Principal component analysis,PCA）可知耐阴树种种间根茎功能性状关联更紧密。此外,种间根、茎性状的变异系数均小于叶面积;（2）耐阴树种种间和种内关键性状与生长率网络关联性差异较大。在种间水平上,生长率与大部分叶性状显著正相关,与根茎性状多为显著负相关;在种内水平上,关键性状与生长率关系网更加复杂;（3）树高相对增长率是种间和种内关系网中心性最高的生长率指标。种间中心性最高的性状指标是叶面积;叶、茎生物量占比和根干物质含量是种内中心性最高的性状指标。但只有叶面积与树高相对增长率在种间和种内均显著正相关,因此,叶面积更适合作为指示林下耐阴树种生长率变化的性状。总体上,耐阴树种叶性状对生长率的调控要强于根茎性状,其中引入较大叶面积的常绿阔叶树种可能更有利于杉木纯林的人促更新和高效复层林的构建。