Showing papers in "Botanical Journal of the Linnean Society in 1990"
TL;DR: The literature on heavy metals in bryophytes is reviewed, including mechanisms of metal uptake, retention, toxicity and tolerance and interspecies differences in particular are discussed, including the development of extreme tolerance encountered in certain taxa.
Abstract: The literature on heavy metals in bryophytes is reviewed, including mechanisms of metal uptake, retention, toxicity and tolerance. Interspecies differences in particular are discussed, including the development of extreme tolerance encountered in certain taxa. The use of bryophytes in monitoring heavy metal deposition is considered and comparisons are made with direct deposition measurements.
275 citations
TL;DR: This paper considers a separate aspect of moss growth and production from the perspective of broad macroclimatic patterns, finding that moss populations are dynamic, highly active entities and can tell us not only about the mosses themselves but also about the systems in which they live.
Abstract: Three basic questions arc addressed in this paper. Each of them considers a separate aspect of moss growth and production. A common theme throughout is that moss populations are dynamic, highly active entities. The study of these dynamics can tell us not only about the mosses themselves but also about the systems in which they live. The following conclusions are reached. (1) Moss populations are organized into complex canopies, some having at least 6000 leaves cm“‘. Drought-tolerant mosses may achieve high rates of growth when moist, but generally are dry and inactive a large percentage of lime. (2) For the ectohydric, drought-tolerant moss, Hylocomium splendens, growth is highly variable over its North American boreal range and can be related to precipitation and continentality. However, for the endohydric, less drought-tolerant moss, Polytrichum strictum, growth is more constant over its North American range and is not as distinctly related to broad macroclimatic patterns. It may have nutrient limited growth, whereas Hylocomium splendens may have climatically limited growth. (3) (a) In mires, calcium, magnesium, sodium and hydrogen ions are important chemical factors that are closely correlated to mire type. Available amounts of nitrate, ammonium, phosphorus and total organic nitrogen in surface waters do not correlate with mire type; likewise, they do not increase across the bog-rich fen gradient. Extreme-rich fens and bogs have about the same concentrations of these components, but water-flow differences may modify the total nutrient input during a season in fens, (b) Moss production in extreme-rich fens is similar to, or somewhat less than, in bogs and poor fens. However, decomposition is much greater in extreme-rich fens. Peat accumulation may, therefore, be greater in bogs and poor fens than in extreme-rich fens, (c) Net production on bog hummocks is about half that of hollows, whereas in poor fens and rich fens, production on hummocks is greater than or equal to that in the hollows. Decomposition in poor fens and bogs is much less on hummocks, while there are few differences between height extremes in rich fens. Hummocks appear to be maintained in bogs due to low decomposition rates, while in rich fens they are maintained by relatively high production, (d) Production rates of Sphagnum species are generally similar to or higher than those of brown mosses. Different species of Sphagnum dominate different parts of the chemical and topographic gradients in bogs while different brown moss species dominate parts of comparable gradients in rich fens.
187 citations
TL;DR: A summary is given of recent laboratory work on the internal redistribution of elements in Rhytidiadelphus squarrosus and of field experiments involving fertilizer addition to Pseudoscleropodium purum; their significance is assessed.
Abstract: Direct information on nutrient cycling through bryophytes is limited and often incomplete. Evidence bearing on the sources and pathways by which nutrient elements are acquired (e.g. aerial deposition, throughfall and substratum) and lost (e.g. leaching and decomposition) is critically discussed. The need to distinguish between the extracellular and intracellular location of elements is emphasized. The involvement of microorganisms and the problems of accurately measuring decomposition are considered. A summary is given of recent laboratory work on the internal redistribution of elements in Rhytidiadelphus squarrosus and of field experiments involving fertilizer addition to Pseudoscleropodium purum; their significance is assessed.
177 citations
TL;DR: Hypodermal Casparian bands were found in roots of hydrophytic, mesophytic and xerophytic species and in members of primitive as well as advanced families, suggesting that this feature has been retained by many species in this group.
Abstract: PERUMALLA, C. J., PETERSON, C. A. & ENSTONE, D. E., 1990. A survey of angiosperm species to detect hypodermal Casparian bands. I. Roots with a uniseriate hypodermis and epidermis. Roots of 181 species from 53 families were surveyed to determine the frequency of Casparian bands in hypodermal layers. For six species, inconclusive data were obtained. The roots of the remaining 175 species were divided into three categories on the basis of this survey. In the first, a hypodermis is absent (12 species): no wall modifications were observed in the outer cortex and this region was permeable to the apoplastic dye Cellufluor. In the second, a hypodermis is present, but a hypodermal Casparian band is absent (seven species). In roots of six species, no wall modifications were detected in the hypodermis; the one remaining species had lignified phi thickenings which were permeable to Cellufluor. In the third, both a hypodermis and a hypodermal Casparian band are present (156 species). These Casparian bands consisted of suberin deposits throughout the width of the anticlinal walls of the hypodermis. The tangential walls of the hypodermis were also suberized, indicating that suberin lamellae were probably also present. Hypodermal Casparian bands were found in roots of hydrophytic, mesophytic and xerophytic species and in members of primitive as well as advanced families. The widespread occurrence of these bands (in 89% of the species surveyed) suggests that they were present in the type ancestral to the flowering plants and that this feature has been retained by many species in this group. The epidermal cell walls of the majority of species examined were suberized but were permeable to Cellufluor.
173 citations
TL;DR: Most bryophytes, including species of well-illuminated habitats, function in effect as shade plants, with low chlorophyll a/b ratios, and become light-saturated at relatively low irradiance.
Abstract: In the main features of their carbon metabolism and physiological responses, bryophytes behave as normal C:) plants. However, their small size and frequent poikilohydric habit have important effects on the context in which these characteristics are expressed, and on their environmental physiology. Many are tolerant of drying out to low water contents (c. 5–10%, of dry weight). Photosynthesis declines rapidly with water loss, and resumes with greater or lesser delay on remoistening. The rate and completeness of recovery depend on the intensity and duration of desiccation, and on drought-hardening (perhaps largely related to protection of cell components from oxidative damage) which lakes place as the bryophyte dries. Most bryophytes, including species of well-illuminated habitats, function in effect as shade plants, with low chlorophyll a/b ratios, and become light-saturated at relatively low irradiance. Boundary-layer resistance is critically important in determining water loss from bryophytes in many situations. The time for which a poikilohydric species can photosynthesize after rain is determined by storage capacity and rate of water loss, both strongly influenced by growth-form. In sheltered habitats with extensive bryophyte cover water loss is largely determined by radiation balance, and may be very slow in deeply shaded places. Bryophyte growth-forms must represent an adaptive balance between water economy and needs for light capture and carbon and mineral nutrient acquisition.
160 citations
TL;DR: Bryophytes are involved in a variety of competitive, parasitic, symbiotic, mutualistic and as yet unspecifiable interactions with vascular plants, algae, fungi, lichens, cyanobactcria and autotrophic and heterotrophic bacteria, in only very few cases have these interactions been analysed functionally.
Abstract: Bryophytes live in microhabitats determined by the physical environment, usually modified by the vascular plant vegetation, and seemingly in ‘ecological isolation’ from other plants.
However, bryophytes are involved in a variety of competitive, parasitic, symbiotic, mutualistic and as yet unspecifiable interactions with vascular plants, algae, fungi, lichens, cyanobactcria and autotrophic and heterotrophic bacteria. In only very few cases have these interactions been analysed functionally. Yet, such information may be essential for a better understanding of (1) such aspects of bryophyte ecology as mineral nutrition, carbon economy, herbivory, and growth and development of the gametophyte, and (2) the ecological role of bryophytes in terrestrial ecosystems.
143 citations
TL;DR: In this paper, a comparison between the range of strategies displayed by bryophytes and that already described for vascular plants is made, and some of the implications of these strategy theories for the role of Beryophytes in the structure and dynamics of plant communities.
Abstract: In this paper reference will be made to three widely recurrent types of functional specialization. These correspond to (1) strategies* apparent in the established (adult) phase of the life history, (2) strategies of the regenerative (juvenile) phase and (3) strategies of growth response to seasonal variation in temperature and moisture supply. In each case a comparison will be drawn between the range of strategies displayed by bryophytes and that already described for vascular plants. Reference will be made also to some of the implications of these strategy theories for the role of bryophytes in the structure and dynamics of plant communities.
109 citations
TL;DR: The facility for vegetative reproduction and reproduction by spores was compared in four common mosses by observations on naturally occurring spores, sporclings and juvenile shoots combined with experimental field plantings, showing contrasting life-history strategies shown by the four species.
Abstract: The facility for vegetative reproduction and reproduction by spores was compared in four common mosses by observations on naturally occurring spores, sporclings and juvenile shoots combined with experimental field plantings. In Polytrichum alpestre no evidence of spore germination in the field was obtained, but shoots were formed by regeneration from shoot fragments. Spore germination leading to shoot development, and ultimately to sporophyte production, occurred freely in Funaria hygrometrica. Atrichum undulatum and Bryum argenteum gave intermediate results in that regeneration occurred freely from shoot fragments, and while many spores germinated the sporelings normally failed to develop. There was strong evidence that experimentally planted spores occasionally gave rise to shoot production in both the latter species, however, and shoots commonly developed on protonema planted in the field. The results are discussed in relation to the contrasting life-history strategies shown by the four species.
81 citations
TL;DR: In this paper, a review of the literature on bryophyte communities is presented, particularly those involving niche breadth and overlap, and special attention is given to niche diversification in Sphagnum, Splachnaceae, and ephemeral Bryophytes.
Abstract: Classical niche theory, particularly in terms of competitive exclusion, does not appear to apply as well to bryophytes as to other organisms. Bryophyte communities, as well as those of other plants and of animals, can be thought of in terms of individual species each utilizing particular portions of various resource or habitat continua. Quantitative studies carried out since 1981, particularly those involving niche breadth and overlap, are reviewed. Special attention is given to niche diversification in Sphagnum, Splachnaceae, bryophyte communities in streams, and to ephemeral bryophyte communities. Some bryophyte communities appear to have equilibrium characteristics and to contain species with relatively narrow niche breadths and with no or only partial niche overlap. In many habitats, however, bryophyte communites have non-equilibrium characteristics and diversification of species in microhabitats is opportunistic. Do any bryophyte communities persist long enough for complete saturation by species which have realized niches determined by competitive interactions? Recent studies indicate that this is the case for at least some Sphagnum communities, but that it is the exception not the rule for bryophytes.
81 citations
TL;DR: HUSAIN et al. as mentioned in this paper performed a micromorphological study of some representative genera in the tribe Saturejeae (Lamiaceae) and showed that the structure of the nutlet surface and leaf indumentum can provide useful additional character combinations in delimiting these closely related genera.
Abstract: HUSAIN, S. Z., MARIN, P. D., SILIC, C., QAISER, M. & PETCOVIC, B., 1990. A micromorphological study of some representative genera in the tribe Saturejeae (Lamiaceae). The Old World genera in the tribe Saturejeae are usually distributed either in Europe and North Africa or in the temperate parts of Asia. The centres of distribution of investigated genera are mainly in the Mediterranean region. In taxonomic revisions very little reference is made to micromorphological characters, in particular, to nutlets and leaf indumentum, in spite of the stability of these characters. Scanning electron microscopy of nutlet surface and patterns of leaf indumentum show a wide range of variation, not only among genera, but also at lower levels of classification. In view of this, nutlet surface and leaf indumentum structure, as seen with the SEM, of representative species of eight genera in the tribe Saturejeae provides useful additional character combinations in delimiting these closely related genera. This study also supports Boissier's delimitation of sections Micromeria and Pseudomelissa.
71 citations
TL;DR: The occurrence of the Spondias-type in Canarium, a member of the sister group Burseraceae, suggests that this type is plesiomorphic in the Anacardiaceae, and the presence ofThe Anacardium- type in Blepharocarya and Orthopterygium Qulianiaceae further supports the inclusion of these taxa in the ANACardiaceae.
Abstract: Pericarp structure is surveyed in 29 genera. Homologous regions termed exocarp, mesocarp and endocarp are established. While exocarp and mesocarp structure show some uniformity, there are two very distinct types of endocarp, designated the Anacardium-type and the Spondias-type. The distribution of these indicates that the current division of the family into five tribes is artificial. The occurrence of the Spondias-type in Canarium, a member of the sister group Burseraceae, suggests that this type is plesiomorphic in the Anacardiaceae. In addition, the presence of the Anacardium-type in Blepharocarya (Blepharocaryaceae) and Orthopterygium Qulianiaceae) further supports the inclusion of these taxa in the Anacardiaceae.
TL;DR: The neobasic number, n= 120, appears to have arisen through various combinations and permutations of these, theoretically 2401 routes; only a relatively few of these routes exist today, suggesting that extreme selection has been exerted against the majority, and further suggesting that Ophioglossum represents an evolutionary dead end through repeated cycles of polyploidy and is possibly at the verge of extinction.
Abstract: Cytological observations on eleven species of Ophioglossum revealed low gametic (n) chromosome numbers of 30, 34 and 60 in populations of O.eliminatum, contrasting with an earlier report of n= 90 in the same species. The rest of the species is based on n=120.Cytologically studied species of Ophioglossum exhibit a range of chromosome numbers from n = 30 in O.eliminatum to n=720 in O.reticulatum. The weighted highest common factor (HGF) from all the reported chromosome numbers in twelve species was found to be 30. This number is proposed as the palaeobasic chromosome number for the genuS. Reported chromosome numbers which are not multiples of 30 were subjected to sequential analysis, yielding three distinct ultimate base numbers, 4, 5 and 6, which can produce n= 30 in seven different ways. The neobasic number, n= 120, appears to have arisen through various combinations and permutations of these, theoretically 2401 routes; only a relatively few of these routes exist today, suggesting that extreme selection has been exerted against the majority, and further suggesting that Ophioglossum represents an evolutionary dead end through repeated cycles of polyploidy and is possibly at the verge of extinction. The stoichiometric model of evolution, which derives the various chromosome numbers possessed by the twelve species from the basic and ultimate basic chromosome numbers, is used to explain chromosomal evolution in the genus.
TL;DR: It is suggested that mangosteen is an allopolypoid derivative of these species which arose as a female from a single hybridization event in cultivation, and which has since reproduced asexually.
Abstract: RICHARDS, A. J., 1990. Studies in Garcinia, dioecious tropical fruit trees: the origin of the mangosteen (G. mangostana L.). Mangosteen does not grow in the wild state. Plants are said to be invariable, and almost all are female. Mangosteen (2n=?88–90), an obligate agamosperm, has only two close relatives, G. hombroniana (2n= 48) and G. malaccensis (2n=?42) which are facultative agamosperms. For the 13 main characters by which they differ, mangosteen takes an intermediate morphological position for five characters, and resembles each of the other species for four of the remainder. It is suggested that mangosteen is an allopolypoid derivative of these species which arose as a female from a single hybridization event in cultivation, and which has since reproduced asexually. To overcome difficulties in propagation and establishment that mangosteen presents, attempts should be made to graft and hybridize mangosteen with its presumptive parents.
TL;DR: It is considered that facultative agamospermy renders the genus Garcinia particularly suitable for the development of new types of fruit, as well as unusual phenomena, which are discussed in the context of the lifestyle of a tropical forest tree.
Abstract: RICHARDS, A. J., 1990. Studies in Garcinia, dioecious tropical forest trees: agamospermy. In Garcinia, agamospermy is known or suspected for ten species. Most are facultative agamosperms, with males occurring, but males are probably lacking in G. mangostana. In G. mangostana and G. hombroniana, adventitious embryony occurs autonomously, and haploid parthenogenesis may also occur rarely. In G. parvifolia, it is reported previously that gametophytic agamospermy occurs, and adventitious embryos are suppressed. Autonomous endospermy is found in G. mangostana and G. parvifolia. In G. hombroniana, endosperm probably only develops after PEN fertilization. In G. hombroniana, some proembryos are formed precociously, and further proembryo formation is inhibited by sexual embryos. Asexual proembryos tend to occur in large ovules in small ovaries, and sexual embryos tend to occur in small ovules in large ovaries. It is considered that facultative agamospermy renders the genus Garcinia particularly suitable for the development of new types of fruit. Agamospermy in a dioecious genus, adventitious embryony in the absence of fertilization and/or pseudogamy, and the co-occurrence of gametophytic and sporophytic agamospermies in the same genus are unusual phenomena, which are discussed in the context of the lifestyle of a tropical forest tree. For G. hombroniana, n= 24, and for G. cowa, n= 26 are reported.
TL;DR: The approaches which have been used and results obtained from monitoring bryophytes in urban and industrial habitats are described, illustrating the increasing interest in low cost methods for monitoring contamination.
Abstract: The widespread distribution of bryophytes and the tolerance of many species to certain contaminants has led to their use for monitoring purposes. Early this century, changes in the distribution of mosses in urban habitats indicated deteriorating air quality; alterations in species composition in rivers has reflected changing water quality. The main focus in the past 10 to 20 years has been on measuring levels of contaminants in both terrestrial and aquatic bryophytes. Concentrations of metals, organic chemicals, radionuclides and derivatives of acidic gases have been widely reported in species from contaminated and background areas. More rarely, physiological and biochemical parameters are monitored. This paper describes the approaches which have been used and results obtained from monitoring bryophytes in urban and industrial habitats. Data are reviewed from a range of countries illustrating the increasing interest in low cost methods for monitoring contamination.
TL;DR: Microscopical investigations on the detached cells of the stigma after compatible and incompatible pollinations, suggest that the incompatibility response is probably controlled by these cells.
Abstract: JOHANSEN, B., 1990. Incompatibility in Dendrobium (Orchidaceae). A unique self-incompatibility system in Dendrobium is demonstrated by more than 1700 pollination experiments. The majority (72%) of the 61 species that were self-pollinated showed self-sterility. In contrast with many other orchid genera Dendrobium showed high incompatibility in interspecific pollinations. Self-and interspecific incompatibility is expressed by flower abscission and not by inhibition of pollen germination or pollen tube growth. The incompatibility system is gametophytic and complementary, and it is likely that the auxin content in the pollinia triggers the incompatibility reaction. Microscopical investigations on the detached cells of the stigma (here called eleutherocytes) after compatible and incompatible pollinations, suggest that the incompatibility response is probably controlled by these cells.
TL;DR: The data support the conclusion that the ‘Cotuleae’ is an unnatural assemblage: Cotula, Leptinella, Nananthea and Soliva appear to form one close-knit group, and Dimorphocoma, Elachanthus and Isoetopsis another, while the remaining genera are highly diverse.
Abstract: Ontogeny in Cotula australis, Leptinella dioica and L.pyrethrifolia confirms the presence of layers derived from the endosperm, testa and pericarp surrounding the embryo in mature cypselae in Asteraceae. The structure of mature cypselae of 24 species, representing all 12 genera that have been assigned to the ‘Cotuleae’, is reported. Several characters that appear to be relatively constant within genera or groups of genera are identified as providing information on affinities above the generic level. The data support the conclusion that the ‘Cotuleae’ is an unnatural assemblage: Cotula, Leptinella, Nananthea and Soliva appear to form one close-knit group, and Dimorphocoma, Elachanthus and Isoetopsis another, while the remaining genera are highly diverse. The first group appear to be good members of the Anthemideae. Evidence is provided to support the placement of the second group in the Astereae near Minuria. Cypsela characters support the placement of Plagiocheilus near Solenogyne.
TL;DR: It can be stated that phytomass of epiphytic bryophytes in equatorial latitudes increases from the tropical lowlands to the foreslline by gradients of factors such as precipitation, humidity, temperature and desiccation, or combinations of these.
Abstract: Knowledge about bryophyte production and phytomass in the tropics is poor and has been derived principally from studies of epiphytic bryophytes. Such work has been undertaken in Transvaal, Tanzania, Venezuela, Peru and Borneo. Except for the studies in Peru and Borneo, the vegetation types studied and the methods used have been too variable to allow many comparisons or generalizations to be made. However, in general it can be stated that phytomass of epiphytic bryophytes in equatorial latitudes increases from the tropical lowlands to the foreslline. This striking phenomenon has been hypothetically explained by gradients of factors such as precipitation, humidity, temperature and desiccation, or combinations of these. Recent experiments on the gas exchange of tropical-montane bryophytes have revealed that the rate of net assimilation decreases dramatically above 25oC and that high temperature combined with low light intensities, as realized in the tropical lowland forest, results in high rates of respiration and insufficient net photosynthesis. Experiments with temperate bryophytes show the same results. If can be assumed that tropical lowland species have special physiological adaptations to survive these unfavourable conditions, such as a specialized phytochrome system or effective storage of photosynthetic products. Additional factors could include the relatively high nutrient supply provided by abundant precipitation in tropical montane forests, and damage to cells by strong desiccation in the tropical lowlands.
TL;DR: Shoot extracts on starch-wafer substrate appeared to be more acceptable than intact shoots suggesting that the cell wall provides the barrier to free consumption, and the form and location of a possible feeding deterrent is discussed.
Abstract: Observations in the held suggest that moss shoots are seldom freely consumed by either vertebrate or invertebrate herbivores, but damage to immature capsules by slugs is abundant. Palatability of the mosses Mnium hornum, Brachythecium rutabulum and Funaria hygrometrica to the generalist herbivores, Arion subfuscus and A. rufus was investigated by offering the slugs four stages in the moss life cycle; protonema, leafy shoot, immature capsule and mature capsule. The slugs showed a preference for immature capsules and protonemata in all moss species tested. Consumption of shoots of M. hornum and B. rutabulum was negligible even after seven days starvation, but some shoots of F. hygrometrica were eaten in every overnight trial performed. Shoot extracts on starch-wafer substrate appeared to be more acceptable than intact shoots suggesting that the cell wall provides the barrier to free consumption. The form and location of a possible feeding deterrent is discussed.
TL;DR: It is unfortunate, therefore, that the emphasis has shifted away from bryophyte autecological studies at important northern sites where increasing human impact is threatening this fragile biome type.
Abstract: Bryophytes attain maximum relative importance in terms of biomass and production in the tundra biome. They contribute an average of 30% to the vegetation cover across a broad range of tundra sites, but often reach 100% cover in wetter and more protected situations. Figures for bryophyte phytomass span several orders of magnitude depending on severity of habitat conditions. Very high standing crops reflect organic matter accumulation due to low decomposition rates at the wettest sites. Initial annual loss rates are commonly below 10% in bryophyteâdominated habitats throughout the tundra. Bryophyte production ranges from less than 1 g mâ2 yrâ1 in polar desert, to more than 1000gmâ2yrâl at wetter sites in the subâAntarctic where a long growing season prevails. However, many published values for tundra bryophyte production are based on suspect methodology and cannot be accurately compared between sites. The new generation of lightweight fieldâportable equipment for measuring gas exchange and microclimatic variables provides the potential for improving our knowledge of bryophyte productivity in relation to environmental factors in the tundra biome. It is unfortunate, therefore, that the emphasis has shifted away from bryophyte autecological studies at important northern sites where increasing human impact is threatening this fragile biome type.
TL;DR: Cultivation experiments indicate that protonema and shoots of Splachnum sphaericum have a greater tolerance for concentrated dung liquid than the control species Physcomitrium pyrij'orme, Funaria hygrometrica and Pohlia nutans.
Abstract: The Splachnaceae is the only moss family in which entomophily has been observed. There are three kinds of adaptation for entomophily: (1) adaptations to substrates of animal origin, (2) morphological adaptations and (3) chemical adaptations.
Species of Sptachnum and the entomophilous species of Tayloria are restricted to the dung of herbivorous mammals. Species of Tetraplodon grow on skeletal remains, on antlers, on stomach pellets of predatory birds, or on dung, which contains both bone and hair. The entomophilous species Aplodon wormskioldii grows on corpses, on caribou (reindeer) dung, bones and antlers, on owl pellets, or on enriched gravel.
Cultivation experiments indicate that protonema and shoots of Splachnum sphaericum have a greater tolerance for concentrated dung liquid than the control species Physcomitrium pyrij'orme, Funaria hygrometrica and Pohlia nutans. Tetraplodon mnioides, A. wormskioldii and Splachnum vasculosum have higher nitrogen contents in their tissues than do other arctic bryophytcs and the levels of nitrogen, phosphorus and calcium in the plant tissues of T. mnioides and A. wormskioldii reflect those of their substrata. The adaptation to grow on osmotically concentrated substrates confers a selective advantage upon these species.
Morphological adaptations of the sporophyte are the enlarged, coloured neck (hypophysis), the coloured upper region of the seta, and the hygroscopic movements of the urn wall and peristome which help the spores to leave the urn. The small, thin-walled spores are dispersed in clumps on the hairs of visiting flies.
Chemical adaptations are the odours produced and released by the sporophyles. Several volatile compounds have been found in the urn and hypophysis of entomophilous species, volatile octane derivatives and organic acids such as acetic, propionic and butyric acids particularly in the hypophysis. Volatile compounds may be released through the many stomata of the hypophysis. The seta, the gametophyte and the substratum do not contain these compounds. Flies which are attracted to and visit species of Splachnum in Europe and North America include Scatophaga furcala, (Scatophagidae), Pyrellia cyanicolor, Myospila metida (Muscidae) and Delia platura (Anthomyidae). The most common visitors to Tetraplodon mnioides are Delia platura and species of the Muscidae. Scatophagids have been found to benefit from a possible increase in copulatory success after visiting these plants.
Entomophilly in the Splachnaceae can be regarded as chemical mimicry. Other organisms that mimic faecal/carrion odours to attract flies to disperse the spores include the macrofungus Phallus impudkus. Some species in the angiospcrm families Ramcsiaccae and Araceae, which arc pollinated by flies, produce odours resembling those found in the Splachnaceae.
TL;DR: A preliminary cladistic analysis was undertaken to evaluate the relationships between families of the superorder Lamiiflorae sensu Dahlgren, and several family interrelationships could not be resolved, although several groups were common to all three cladograms.
Abstract: LU AN-MING, 1990. A preliminary cladistic study of the families of the superorder Lamiiflorae. A preliminary cladistic analysis was undertaken to evaluate the relationships between families of the superorder Lamiiflorae sensu Dahlgren. Several character complexes were surveyed, and ultimately 29 informative characters were used for the study. Three families, Clethraceae, Oleaceae and Solanaceae were selected for outgroup comparison and polarization of the characters. A data matrix was constructed for the 23 ingroup families. The data matrix was analysed with the cladistic parsimony program Hennig86. Three equally parsimonious cladograms were found. Many family interrelationships could not be resolved, although several groups were common to all three cladograms, as shown by a strict consensus tree. The Retziaceae emerged as the sister group to the remaining families. About half of those appeared in a large polytomy in the consensus tree. There was also one possibly monophyletic complex of families involving the Lamiales with the families Verbenaceae, Lamiaceae, Phrymaceae and Callitrichaceae as well as the three isolated families Trapellaceae, Hippuridaceae, and Hydrostachyaceae. Within this complex, Verbenaceae and Lamiaceae came out as sister groups, as did Callitrichaceae and Hydrostachyaceae, with Hippuridaceae as sister group to them. However, the results must be regarded as tentative.
TL;DR: The ‘wet’ stigma and binucleate pollen suggest that Garcinia arose from hermaphrodite plants with a gametophytic self-incompatibility system and is considered as ‘steady state’ strategists.
Abstract: RICHARDS, A. J., 1990. Studies in Garcinia, dioecious tropical forest trees: the phenology, pollination biology and fertilization of G. hombroniana Pierre. Garcinia hombroniana is a facultative agamosperm which is pollinated by Trigona bees. Nectar is restricted to the large discoid stigma (or pistillode in male flowers), which also captures and hydrates pollen. The ‘wet’ stigma and binucleate pollen suggest that Garcinia arose from hermaphrodite plants with a gametophytic self-incompatibility system.
On stigmas, nectar is secreted early on three or four successive days. On male pistillodes, nectar is secreted when anthers dehisce, on the second morning after anthesis. Pollen is most viable when freshly collected, but some viability remains four days after collection. Pollen germinates within 24 h of hydration. Similar results to pollinations are obtained by germinating pollen in 1 % sucrose.
Garcinia hombroniana flowers principally from January to June. Cultivated females are considered as ‘big bang’ strategists. Male flowers are considered as ‘steady state’ strategists.
TL;DR: Patterns of leaf exudate compounds separated by two-dimensional thin-layer chromatography and revealed by staining with Fast Blue B have been obtained for all but one of the Aloe species in Reynolds' Group 19 and Series Arborescentes.
Abstract: As an aid to taxonomic discussions, patterns of leaf exudate compounds separated by two-dimensional thin-layer chromatography and revealed by staining with Fast Blue B have been obtained for all but one of the Aloe species in Reynolds' Group 19 and Series Arborescentes
TL;DR: The effects of nitrogen and sulphur pollutants on Sphagnum species are used to make broad generalizations as to how other bryophyte species might respond to these pollutants and to explain known effects of atmospheric pollution on bryphyte communities.
Abstract: The responses of Sphagnum species to atmospheric pollution by sulphur and nitrogen oxides are reviewed. An explanation of the tolerance of sulphur dioxide in Sphagnum cuspidatum is provided. This involves an exclusion mechanism by the oxidation of bisulphite ions to less toxic sulphate ions catalysed by the presence of iron and possibly other metals on the cell wall cation-exchange sites. Tolerance is influenced by changing the iron content of the plants. A similar mechanism may account for sulphur dioxide tolerance in Sphagnum recurvum.
Evidence for a close coupling of nitrate assimilation with the atmospheric nitrogen supply in ombrotrophic Sphagnum species in unpolluted regions is reviewed, and this coupling is shown to be lost in polluted environments with high atmospheric nitrogen supply. The potential effects of a supra-optimal atmospheric nitrogen supply to Sphagnum species on the ecology of mires is discussed.
The effects of nitrogen and sulphur pollutants on Sphagnum species are used to make broad generalizations as to how other bryophyte species might respond to these pollutants and to explain known effects of atmospheric pollution on bryophyte communities.
TL;DR: Water relations of bryophytes must be understood along at least four dimensions: hydration/dehydration frequency; hydration duration; dehydration duration; degree of water loss; and biomass-dependent functions such that large colonies of b Bryophytes may maintain hydration longer than smaller colonies.
Abstract: Water relations of bryophytes must be understood along at least four dimensions: hydration/dehydration frequency; hydration duration; dehydration duration; degree of water loss. All these are biomass-dependent functions such that large colonies of bryophytes may maintain hydration longer than smaller colonies. The spread of a bryophyte colony allows lateral movement of capillary water; contiguous clones will thus allow lateral conduction of that water. In contrast, separated tufts or cushions may store water but will contribute very little to its transfer over the surface of the phorophyte.
Many of the tropical rainforests of New Guinea have a larger mass of epiphytic bryophytes than any temperate forest. The primary effect of disturbance in these forests is a reduction in bryomass, presumably due to desiccation because of increased insolation and wind movement. The reduction of bryomass will decrease water and mineral retention in the bryophyte clones; and the reduction in the size of those clones will reduce their contiguity and thus interfere with bryophyte-mediatcd water and mineral transfer. Disturbance may alter bryophyte species frequency but, under present agricultural and forestry practices in New Guinea, I have seen no evidence of significant loss of bryophyte species.
TL;DR: Embryological features suggest that Bretschneidera is distinct from any of the taxonomically related families but resembles both Hippocastanaceae and Sapindaceae (Sapindales) more closely than Moringaceae or Capparaceae (Capparales) which have been considered alternative allies, supporting most of the modern taxonomic treatments that place Bretsnidera as a separate family in Sapindales.
Abstract: TOBE, H. & PENG, C.-I, 1990. The embryology and taxonomic relationships of Bretschneidera (Bretschneideraceae). We present the first report on the embryology of Bretschneidera, the only genus of Bretschneideraceae (which are one of 15 glucosinolate-producing families), to clarify its relationships. Embryologically Bretschneidera is characterized by the following features: ovule campylotropous, bitegmic and crassinucellate; outer integument thick, multiplicative and vascularized; embryo sac formation of the Allium type; seed exalbuminous; seed coat ‘exotestal’ with a palisade of columellar, thick-walled exotestal cells; mesotesta thick with the inner half aerenchymatous. These features suggest that Bretschneidera is distinct from any of the taxonomically related families but resembles both Hippocastanaceae and Sapindaceae (Sapindales) more closely than Moringaceae or Capparaceae (Capparales) which have been considered alternative allies, supporting most of the modern taxonomic treatments that place Bretschneidera as a separate family in Sapindales.
TL;DR: Observations in natural and experimental situations suggest that the window of Diascia section Racemosae is used as an orientation cue by oil-collecting bees.
Abstract: The Diascia (Scrophulariaceae) window: an orientation cue for oil-collecting beeS. Flowers of Diascia section Racemosae are characterized by an unusual translucent ‘window’ at the base of the upper corolla lip which is bright yellow with maroon flecks and varies from a nearly flat to a deeply cone-shaped depression. The inner epidermal cells of the window are also variable in shape ranging from lenticular to long papillate. In contrast to the surrounding corolla which strongly reflects ultraviolet light, the window tissue is strongly ultraviolet absorptive due to the presence of ultraviolet absorbing flavonoids in the epidermal cellS. Observations in natural and experimental situations suggest that the window is used as an orientation cue by oil-collecting bees.
TL;DR: An analysis of the geographical distribution of the closest relatives of these five taxa leads to hypotheses on their geographical origin, which suggest that P. rhoeas originates from the eastern border of the Mediterranean, where it might have differentiated only under human influence.
Abstract: KADEREIT, J. W., 1990. Some suggestions on the geographical origin of the central, west and north European synanthropic species of Papaver L. Papaver rhoeas, P. dubium subsp. dubium and subsp. lecoqii, P. argemone subsp. argemone and P. hybridum are considered to be introduced in central, western and northern Europe. An analysis of the geographical distribution of the closest relatives of these five taxa leads to hypotheses on their geographical origin. It is suggested that P. rhoeas originates from the eastern border of the Mediterranean, where it might have differentiated only under human influence. The origin of P. dubium subsp. lecoqii is suggested to lie in S.E. Europe or west Anatolia, and that of subsp. dubium in S.E. central Europe. Papaver argemone subsp. argemone might have differentiated from two related subspecies in west Anatolia. No suggestions can be made with respect to P. hybridum, which is taxonomically isolated. The assumptions necessary for hypotheses on the geographical origin of synanthropically widespread taxa are briefly discussed.
TL;DR: None of the members of section Solanum appears to be a weed of significant agronomic importance in this area, except in a few localized areas.
Abstract: Material of Solanum section Solanum from India and Pakistan is assignable to three species: a diploid, S. americanum; a tetraploid, S. villosum; and a hexaploid, S. nigrum. These species are distinguished by slight but consistent differences and a key is included to facilitate their identification. None of the members of section Solanum appears to be a weed of significant agronomic importance in this area, except in a few localized areas.