Sporobolus Poibetii (R. et S.) Hitch. e Oenothera Sinuata L. Nella Selva di San Rossore

Summary

The author describes a Sporobolus Poiretii (R. et S.) Hitchc. and Oenothera sinuata L. stand in the «Selva» (forest) of S. Rossore (near Pisa).

Earlier reports of these two adventive and perhaps naturalized species are mentioned.

The author discussues the critical and complex sistematic definition, nomenclature and sinonimy of Sporobolus Poiretii in connection with the nearly related species Sporobolus indicus R. Br.

The author prospects at the end how both Sp. Poiretii and Oe. sinuata can be inserted in the «Nuova Flora Analitica» of Italy, by Adriano Fiori.     

Evaluation of elemental allelopathy in Acroptilon repens (L.) DC. (Russian Knapweed)

Although Acroptilon repens (L.) DC. (Russian knapweed) is known to concentrate zinc (Zn) in upper soil layers, the question of whether the elevated Zn has an allelopathic effect on restoration species has not been addressed. Experiments were conducted to investigate whether soils collected from within infestations of A. repens (high-Zn) inhibit the germination or growth and development of desirable restoration species, compared to soils collected adjacent to an A. repens infestation (low-Zn). Four bioassay species [Sporobolus airoides (Torrey) Torrey (alkali sacaton), Pseudoroegneria spicata (Pursh) A. Love (bluebunch wheatgrass), Psathyrostachys juncea (Fischer) Nevski (Russian wildrye) and A. repens] were germinated in a growth chamber and grown in a greenhouse in both soils and received treatments for the alleviation of Zn toxicity (P, Fe, Fe-oxide, and soil mixing) to isolate the effects of elevated soil Zn on plant performance. Percent germination, total plant biomass, tiller and stem number, inflorescence number, and tissue metal levels were compared among soil types and treatments for each species. There was no evidence from any of the indicators measured that high-Zn soils reduced plant performance, compared to low-Zn soils. Tissue Zn levels barely approached the lower range of phytotoxic levels established for native grasses. Older plants with longer exposure times may accumulate higher Zn concentrations. S. airoides and A. repens both had higher biomass in the high-Zn soil, most likely due to increased macronutrient (N and P) availability. As the Zn levels in the soils used in this study were much higher than any levels previously reported in soils associated with A. repens, it is unlikely that the elevation of soil Zn by A. repens will hinder germination or growth and development of desirable grasses during establishment.     

Some studies on field distribution and seed germination ofSuaeda fruticosa andSporobolus arabicus with reference to salinity and sodicity of the medium

Summary Vegetation of two wasteland sites near Dera Chahl, 30 km from Lahore, was studied quantitatively. Soil samples obtained from the two sites were analysed.Suaeda fruticosa (L.) Forssk. was a dominant species on saline and sodic soil whereas soil underSporobolus arabicus Boiss. was saline and non-sodic. Seed germination studies show thatSporobolus arabicus is relatively more affected by Nasalinity than by Ca-salinity. This species tolerates salinity to some extent but is sensitive to sodicity.Suaeda fruticosa is relatively more tolerant to salinity and sodicity thanSporobolus arabicus and is capable of growing on saline and sodic soils.     

Assessment of veld conditions with multivariate techniques in mixed bushveld,South Africa

The species composition of the herbaceous layer was surveyed in eight plant communities with a small-quadrat method. Ordination techniques were applied to these data to identify relative homogenous grazing areas, assess the veld condition of each unit and to identify indicator species, based on a grazing gradient. Five relative homogenous grazing areas were identified and should be treated as such for management purposes. The veld in the Nylsvlei Nature Reserve was generally in a good condition due to the low stocking densities of game (≈0.29 animals ha^?1) which have been maintained for many years. Nine indicator species, i.e. Cynodon dactylon, Digitaria eriantha, Ischaemum afrum, Leersia hexandra, Oryza longistaminata, Setaria sphacelata, Sporobolus ioclados, Sporobolus pyramidalis, and forbs, were identified which may be used for future monitoring of veld condition in the different vegetation units.     

CHROMOSOME NUMBERS OF SOME EAST AFRICAN GRASSES

Chromosome numbers of 133 collections of grasses belonging to 51 genera and 105 species are reported here for material from East Africa. These include first counts for 5 genera and 51 species. The basic chromsome number of x = 6 has been found in Sporobolus; x = 10 in Loudetia and x = 13 in Pentaschistis have been confirmed. It is pointed out that chromosomes of Eragrostis vary considerably in size. The genera Harpachne, Commelinidium, Acritochaete, Pseudechinolaena and Exotheca, which are cytologically examined for the first time, have chromosomes with the socalled “panicoid” features, viz., chromosomes with small size and x = 9 or 10.     

Chemical quality of the burnt and non-burnt grass layer in the Nylsvlei Nature Reserve,South Africa

The forage quality of the herbaceous layer in burnt and non-burnt plant communities was determined seasonally to serve as a baseline for managing the food supply. The near-infrared reflectance spectroscopy method and wet chemical analyses were applied to analyse the grass samples. Differences in forage quality were found between plant communities. The Sporobolus ioclados–Acacia tortilis Savanna had the highest forage quality throughout the year. Plant communities on the lithosols had a low forage quality. The highest total calcium and total phosphorus concentrations were found in the Eragrostis pallens–Burkea africana Savanna, total potassium in the plant communities on the lithosols, and total sodium in the Sporobolus ioclados–Acacia tortilis Savanna and floodplain. The most optimum Ca:P ratio was found in the Eragrostis pallens–Burkea africana Savanna when burnt and non-burnt. In non-burnt areas the highest K:Na ratio was found in the Sporobolus ioclados–Acacia tortilis Savanna. Burning increased the forage quality in some plant communities. In general, only percentage in vitro organic matter digestibility differed significantly between burnt and non-burnt plant communities. The forage quality did not increase significantly in plant communities on lithosols and on vertisols. Mineral ratios did not differ between newly burnt plant communities. A low protein and mineral content in the winter forage should be countered with supplementary feeding or burning of grass to improve the condition of animals.     

Suberized bundle sheaths in grasses (Poaceae) of different photosynthetic types I. Anatomy,ultrastructure and histochemistry

Summary We investigated the histochemistry and ultrastructure of the cell walls of mestome sheaths and parenchymatous bundle sheaths of ten species of grasses. The species surveyed included representatives from all the major photosynthetic types: C₃-Bromus tectorum, Phalaris arundinacea; C₄/NAD-ME-Eragrostis cilianensis, Panicum capillare; C₄/NAD-ME/PCK-Bouteloua curtipendula; C₄/PCK-Chloris gayana, Sporobolus elongatus; C₄/NADP-ME-Echinochloa crus-galli, Setaria glauca, Themeda triandra. All vein orders (designated here as major, minor and transverse) from mature leaves of each species were tested histochemically for lipids and phenols, and the majority of species were also examined with the electron microscope. A suberized lamella was detected ultrastructurally in at least some walls of major vein bundle sheath cells of all species examined. These lamellae were also present in some cells associated with the minor veins of the C₃ species and in the minor and transverse veins of the C₄/NADP-ME species. Histochemical tests for lipids and phenols consistently failed to differentiate this layer. Based on these tests, none of the vein orders in any species showed evidence of a Casparian band. In all suberized bundle sheaths, the compound middle lamella between cells with suberin lamellae is modified by the presence of phenols. These did not, however, confer resistance to acid digestion to the cell layer, in contrast to cell layers with Casparian bands. Therefore, although the mestome sheath has some features in common with the root endodermis (i.e. cells with a suberized lamella and thick, cellulosic walls which may be further modified), we could find no substantive anatomical or ultrastructural evidence for the presence of a Casparian band in any of the grass leaves investigated. The significance of these observations is discussed in the context of apoplastic permeability of these walls.     

Ecological studies on sporobolus virginicus (L.) kunth with particular reference to salinity and inundation

Sporobolus virginicus is shown to occupy low-lying areas on the shores of Lake St. Lucia, where it is subjected to periodic inundation and widely varying salinities. Whilst seeds are not permanently affected by storage under waterlogged saline conditions, young plants are markedly influenced by both inundation and salinity. Older plants are more tolerant of these conditions.     

Waterlogging responses of Sporobolus virginicus (L.) Kunth.

Summary Flooding responses in Sporobolus virginicus (L.) Kunth., a perennial C₄ grass, propagated from plants collected on the fringes of a mangrove swamp, were examined in a glasshouse study over 42 days. Flooding significantly reduced soil redox potential, induced adventitious root development, shifted resource allocation from below- to above-ground components without affecting total biomass accumulation and significantly decreased below-ground/above-ground biomass ratios. Although soil waterlogging significantly increased alcohol dehydrogenase activity (ADH) after 30 h, significant increase in central air space by 45–50% of the cross-sectional stem area eliminated root hypoxia, and ADH activity decreased to levels equivalent to drained controls after 42 days. In addition, flooded plants exhibited significantly higher carbon dioxide assimilation rates but similar relative growth rates (RGR) to drained controls. The results indicate that S. virginicus responds to water-logging by a combination of metabolic, morphological and anatomical mechanisms, which may account for its widespread distribution in coastal lagoons, estuaries and marshes.     

Competition between co-dominant plants of the Serengeti plains depends on competitor identity,water, and urine

Kyllinga nervosa (Steud.) and Sporobolus kentrophyllus (K. Schum.) are co-dominant plants of the Serengeti short-grass plains, Tanzania. The plains are characterized by seasonal and sporadic rainfall and currently support in excess of 1.5 million migratory ungulates. The interactive effect of simulated bovine urine and water availability were tested on the competitive interactions of these species in the laboratory. Sporobolus kentrophyllus was a superior competitor to K. nervosa over the tested treatment levels with respect to growth and reproductive effort. Sporobolus kentrophyllus exhibited rapid growth in response to urine addition, leading to a significant species × urine interaction while reduced growth by K. nervosa in response to low water availability explained the significant species × water interaction and is likely explained by K. nervosa's shallow root system. Kyllinga nervosa, however, appears to be more tolerant of low nitrogen conditions based on its similar growth with and without the urine treatment. The effect of intraspecific competition on total biomass was similar for S. kentrophyllus and K. nervosa. Competition resulted in increased size differences (asymmetry) for K. nervosa and for the interspecific competition treatments compared to the size differences observed for plants grown individually (in absence of competition).Total reproductive biomass was reduced most by competition with S. kentrophyllus, irrespective of target species. The water treatment did not influence reproduction while the urine treatment significantly increased reproductive biomass and interacted with target species, competitor species, and yielded a three-way urine × target × competitor species interaction.Results suggest that codominance of these two species in the Serengeti is regulated by water availability, nitrogen input from grazers, and local neighbor identity.     

The role of alien plants in the natural coastal vegetation in central-northern Spain

Alien plants in coastal habitats and their influence on natural vegetation are studied. After 5 years working on this subject in the Basque Country and surrounding areas, a number of results from the coastal ecosystems are presented. These ecosystems are one of the most threatened and affected by the invasion of alien plants, especially shore dunes, saltmarshes and cliffs. These kinds of habitats, especially the dunes, experience significant pressure from human activities which favours the expansion of some of these species: Arctotheca calendula, Sporobolus indicus and Oenothera spp. The presence and abundance of these invasive plants and others such as Baccharis halimifolia, Cortaderia selloana, Spartina patens and Carpobrotus edulis in the plant communities in an area between the French border and the western part of the region of Cantabria have been studied. The degree of invasion of each plant in each syntaxonomic unit has been analysed.     

Research note: Amorphochlora amoebiformis gen. et comb. nov. (Chlorarachniophyceae)

A chlorarachniophycean alga, Lotharella amoebiformis, which has been classified in the genus Lotharella is placed into a new genus Amorphochlora gen. nov., based on its phylogenetic position, which has been clarified by the recently accumulated molecular phylogenetic information, and the morphological difference between the vegetative cells of the Lotharella species. Following this taxonomic treatment, a new combination Amorphochlora amoebiformis comb. nov., is proposed.     

Sulphydryl and Disulphide Levels in Protein Fractions from Hydrated and Dry Leaves of Resurrection Plants

Significant changes in sulphydryl (‘SH’) and disulphide(‘SS’) levels during air-drying in leaves of ‘resurrection’plants (whose protoplasm survives dehydration) stemmed mainlyfrom protein turnover effects. No significant changes were foundin the SH, SS levels in leaves of the desiccation sensitivespecies Sporobolus pyramidalis following air-drying. The three tolerant species studied differed in the directionof change. Some data were consistent with Levitt's SH, SS hypothesis:increases in protein-SS levels in Sporobolus stapfianus (desiccationtolerant) were consistent with a stabilization of new proteinby SS bonds; lower reactivity of protein-SH in the tolerantspecies Talbotia elegans (which on the other hand has decreasedprotein-SS) is consistent with a second mechanism of decreasingprotein denaturation proposed in Levitt's hypothesis. Evidence of some conversion of SH to SS in the soluble proteinsof Xerophyta viscosa (a tolerant species) would on Levitt'shypothesis indicate an injurious process. Some degree of proteindenaturation might be indicated by partial inactivation of thesoluble enzyme ribulose bisphosphate carboxylase in this species,and loss of some soluble isoenzymes (peroxidase and alkalinephosphatase). An apparent lack of SH conversion to SS in thesensitive species Sporobolus pyramidalis was not consistentwith the SH, SS hypothesis. Resurrection plants, Sporobolus pyramidalis, Sporobolus stapfianus, Talbotia elegans, Xerophyta viscosa, drought resistance, desiccation tolerance, protein turnover, sulphydryl groups     

VA MYCORRHIZAE IN STRAND VEGETATION OF HAWAII: EVIDENCE FOR LONG-DISTANCE CODISPERSAL OF PLANTS AND FUNGI

Vesicular-arbuscular mycorrhizal fungi (VAMF) were a nearly constant component of the coastal strand of the Hawaiian Islands, occurring in beach sand, driftline debris, in roots of 23 of 31 species of vascular plants examined, and in association with rhizomes of two native species, Sporobolus virginicus and Jacquemontia sandwicensis. Mycorrhizae were most frequent and intensity of VAM development was greatest in endemic plants, less in indigenous species, and least in alien species. Spores of VAMF were produced in abundance between the rhizome and the leaf sheaths of Sporobolus. Roots of two strand species, including roots of Sporobolus that were immersed in seawater for 7 days, functioned as inocula of VAMF in pot-culture studies. The close association between propagules of VAMF and vegetative fragments of indigenous plants found in the present study suggests a mechanism of codispersal that appears to ensure the maintenance of the symbiosis in nutrient-deficient sites where it is most beneficial. The codispersal of fungus and plant may explain the high frequency of mycotrophy in strand species in the tropical Pacific.     

Infection of Glaucocystis nostochinearum (Glaucophyta) by Lagenidium sp. (Oomycota) and its hyperparasite Pythiella sp. (Oomycota)

The glaucophyte Glaucocystis nostochinearum has to our knowledge been observed to be infected by a parasite for the first time. It was found in samples taken from the northernmost freshwater pond in Germany (on the island of Sylt). The fungal parasite was identified as the oomycete Lagenidium sp. which itself was parasitised by another oomycete, Pythiella sp.     

CHROMOSOME NUMBERS IN WESTERN GRASSES

Chromosome numbers are reported for 221 collections from eleven western states. These records represent 85 species included in 48 genera. Counts for the following species are here presented for the first time: Melica spectabilis, Blepharidachne kingii, Eragrostis obtusijlora, Hilaria rigida, Redfieldia flexuosa, and Sporobolus interruptus. The record for Redfieldia is also the first for that genus. In addition, numbers which differ from those in the literature are recorded for ten species, in three cases two different numbers for the same taxon. Cytological evidence is also presented indicating that Hilaria jamesii and H. rigida have hybridized and that the F₁ has backcrossed to both parents.     

Ecology of two geographically restricted Astragalus species (Fabaceae), A. bibullatus and A. tennesseensis, of the eastern United States

Astragalus bibullatus is endemic to limestone glades in the Central Basin of Tennessee, and except for one population in Illinois,A. tennesseensis is endemic to limestone glades in the Central Basin and in the Moulton Valley of Alabama. However,A. tennesseensis has been extirpated from four counties in Illinois, from its only known site in Indiana, from one county in Tennessee, and from one county in Alabama.Astragalus bibullatus is closely related to the geographically wide-spread Great Plains taxonA. crassicarpus var.crassicarpus (sectionSarcocarpi), whereasA tennesseensis is the only taxon in sectionTennesseensis. Both species are shallow-rooted, hemicryptophyte perennials without vegetative reproduction, have no effective means of seed dispersal, form long-lived seed banks, have similar life cycle phenologies, are intolerant of heavy shade, and have moderate amounts of genetic diversity. Much. additional information is available on the autecology ofA. tennesseensis. Its primary habitat is the transition zone between open glades and glade woods, where physical environmental factors are intermediate between those of the adjacent zones. Seedling-juvenile survival is low. Plants flower first in their second to fifth year and only a few times before dying, are self-incompatible, respond to drought by shedding leaves and by accumulating large amounts of proline, and compete poorly. Populations exhibit high fluctuations in number of individuals and have high turnover rates. A greenhouse study ofA bibullatus andA crassicarpus var.crassicarpus did not identify any difference in responses of these species to light or soil moisture that could account for the great differences in geographic ranges. Thus, historical factors were also considered to explain the narrow endemism ofA. bibullatus. Finally, we present previously unpublished data on the effect of light level and of competition with the cedar glade dominantSporobolus vaginiflorus in several watering regimes on growth ofA. tennesseensis. The role of these factors in restriction of this species to its transition zone microhabitat is discussed.     

The cytology of the genus Briza L. (Gramineae)

Meiosis has been studied in five European and four South American species of Briza. The various species have different chiasma frequencies and different patterns of chiasma localisation. Population studies show that there are significant differences in mean plant chiasma frequency between populations of B. maxima whereas B. media and B. spicata do not show interpopulation differences. B. media is shown to have diploid and autotetraploid races and the distribution of these chromosome races in Europe has been plotted. The South American species studied are all bivalent forming tetraploids and would therefore appear to have an allopolyploid origin. Interchange heterozygosity has been found in B. media and B. elatior, different populations of B. media have been shown to be heterozygous for different interchanges. These topics are discussed in relation to the regulation of recombination.     

BIOSYSTEMATICS OF RUELLIA TUBEROSA L. (ACANTHACEAE)

Ruellia tuberosa is a wide-ranging tropical, perennial herb that has been designated the type species for the large genus Ruellia. To clarify interspecific relationships, the R. tuberosa species complex, including R. nudiflora, R. malacosperma, and R. lorentziana, and R. tuberosa, has been proposed as the redefined and restricted genus Ruellia. All other Ruellia species would be transferred to segregate genera. Biosystematic investigations that included artificial hybridization experiments, herbarium comparisons, chromatographic analyses, and cytological studies demonstrated that R. tuberosa is genetically related to a number of North American temperate taxa and to certain other tropical species. The narrow definition of Ruellia cannot be supported from the biosystematic evidence at hand. Morphological comparisons suggest that R. tuberosa may be a primitive component in a broadened generic concept.