Planktonic Fauna of Small Reservoirs in the Komi Republic

One hundred and eight species and forms of planktonic organisms have been revealed in three small reservoirs in the Komi Republic (the northeast of European Russia). Species that were not previously known for the water bodies of the Vychegda River Basin (Limnosida frontosa) and the Republic of Komi (Lecane mira, Macrochaetus subquadratus, Filinia longiseta limnetica, and Rhynchotalona falcata) have been found. It has been established that the richness of the planktonic fauna depends on the age of the water body: the maximum number of species is found in the oldest reservoir, namely, the Kazhim Reservoir. The planktonic communities of artificial reservoirs are distinguished by a low level of similarity of faunas both with each other and in comparison with the natural lakes of the region. The fauna distribution in the old reservoirs is uneven. The relatively large fauna richness of planktonic communities in the littoral zones is due to the water-level regime in the reservoirs.     

Phytoalexins of woody plants

Summary Phytoalexins accumulated in selected woody plants in response to microbial attack or stress are reviewed and listed with respect to their chemical structure and probable biogenetic origin. The host-pathogen systems from which they have been isolated are described. The review also considers the antimicrobial activity of the phytoalexins to the causal pathogens and other microorganisms.     

Triacontanol-supported micropropagation of woody plants

 The effectiveness of triacontanol in the micropropagation of two woody, economically important fruit plant species was investigated. Triacontanol was added to the routine multiplication and rooting media of apple (Malus domestica cv. JTE-E4) and sour cherry (Cerasus fruticosa cv. Probocskai) rootstocks at concentrations of 2, 5, 10 and 20 μg/l. It was found to increase the number of shoots and the fresh weight of apple in the multiplication phase and to enhance root number and chlorophyll content in the rooting phase. The addition of indole-3-butyric acid (IBA) to the media further improved the effect of triacontanol. A less pronounced effect could be seen in the multiplication phase of sour cherry, although there was an enhancement of shoot proliferation. In the rooting phase, however, the application of triacontanol caused a significant increase in the number of roots per plant, and this effect was further improved when triacontanol was combined with 0.5 mg indole-3-butyric acid/l. Received: 29 March 2000 / Revision received: 1 September 2000 / Accepted: 4 September 2000     

Atlas of foliar surface features in woody plants,IX. Betulaceae of eastern United States

Scanning electron microscopy was used to examine foliar surface features such as cuticular patterns, epicuticular wax, and trichome types in species ofAlnus, Betula, Carpinus, Corylus, andOstrya. Six trichome types are recognized in this survey, four non-glandular (acicular, filiform, aduncate, subulate) and two glandular (stipitate gland and peltate scale). The distribution of these trichomes among the genera supports the recognition of two tribes, Betuleae (Alnus andBetula) and Coryleae (Carpinus, Corylus, andOstrya). Trichome morphology can be an important supportive taxonomic character in determining evolutionary relationships.     

Methanogenic activity of woody plants

Methane production in trunks of living and dead trees was demonstrated. Forest trees are one of sources for this gas emission into the atmosphere. Quantitative evaluation of the methagenic activity of living wood and that digested by xylotrophic fungi is presented.     

Genetic engineering of forest woody plants

The present state of genetic engineering (GE) of forest woody plants is considered with special reference to the materials of the International Conference "Wood, Breeding, Biotechnology and Industrial Expectations" held in France in June, 2001. Main tree species subjected to GE are listed, aims of constructing transgenic plants discussed, and methods described. Major achievements in the field are considered along with the problems associated with the employment of GE in the breeding of forest woody plants.     

Differentiation of the ray system in woody plants

The regulation of vascular ray differentiation has received limited attention, despite the fact that vascular rays constitute an important part of the secondary body of plants. In this paper we review developmental aspects of the ray system and suggest a general hypothesis for the regulation of ray differentiation and evolution. In studies of ray differentiation, two basic factors should be taken into consideration: 1) the normal gradual increase in ray size in relation to age, distance from the pith, and distance from the young leaves; and 2) the influence of wound effects on the size, structure, and spacing of rays. The relationships between the rate of cambial activity and secondary xylem differentiation are not clearly understood. There are contrasting results on the relationships between ray number and rate of radial growth. The rate of radial growth (= rate of cambial activity) is not the regulating mechanism of ray characteristics. Bünning (1952, 1965) proposed that rays are distributed regularly in the tissue, as the outcome of an inhibitory influence expressed by them. However, Bünning’s hypothesis contradicts a basic feature of the vascular ray system, namely, fusion of rays. Detailed histological studies of the secondary xylem revealed that proximity to and contact with rays plays a major role in the survival of fusiform initials in the cambium (Bannan, 1951, 1953). Such evidence led Ziegler (1964) to suggest that since the cambium is supplied predominantly via the rays, this is an effective feedback regulative system for an equidistant arrangement of the rays. The hypothesis that rays are induced and controlled by a radial signal flow seems to be the best explanation for the structure and spacing of rays. The formation of a polycentric ray—a special case of “ray” initiation inside a vascular ray—supports the idea that radial signal flow occurs within the rays (Lev-Yadun & Aloni, 1991a). This idea is also supported by findings fromQuercus species in which aggregate rays in the xylem disperse naturally in branch junctions and, following partial girdling, leave a longitudinal narrow bridge of cambium and bark as a result of enhanced axial signal flow (of auxin and other growth regulators) (Lev-Yadun & Aloni, 1991b). The longitudinally elongated shape of rays is their response to axial signal flows (mainly the polar auxin flow). Two methods have been used to study the evolution of the ray system: 1) statistical studies of the relationships between vessel and ray characteristics in many species, when vessel characteristics were the evolutionary standard, and 2) comparison of ray characteristics in fossils originating from several geological eras. We suggest that evolution of the ray system reflects changes in the relations between radial and axial signal flows.     

'Convergent' traits of mediterranean woody plants belong to pre-mediterranean lineages

The evergreen-sclerophyllous vegetation associated to the mediterranean-type ecosystems shares common characteristics that have been explained invoking an evolutionary convergence driven by the mediterranean climate. Mediterranean climate originated in the Quaternary but the plant 'convergent' characteristics are also present in tropical-like lineages that evolved along the Tertiary, before the mediterranean climate appeared. Because evergreen-sclerophyllous vegetation was broadly distributed across the world in the Tertiary, current trait similarities among the mediterranean taxa may be due to historical and phylogenetical constraints and not to evolutionary convergence. We tested historical and phylogenetical vs. convergence hypotheses to explain present ecological attributes found in woody plant species in mediterranean areas. Multivariate analyses were performed on the matrix of genera × life-history reproductive characteristics in three mediterranean-type ecosystems and a tropical system as an outgroup, the Mexical shrubland. These analyses indicate that character syndromes in mediterranean plants may largely be explained in relation to the age of the lineage (Tertiary vs. Quaternary). We also found that the similarities shown among mediterranean vegetations are due to Tertiary (pre-mediterranean-) and not to Quaternary (true mediterranean-) taxa. Furthermore, the similarities among mediterranean taxa are due to phylogenetical inertia because similarities in the character syndromes disappear when common genera are excluded from the analysis. © 2003 The Linnean Society of London , Biological Journal of the Linnean Society , 2003, 78, 415–427.     

Gas-resistance of the woody plants of West Siberia

A resistant of the woody plants in West Siberia to toxic substances (sulfur dioxide, hydrocarbons, and carbon black) is studied by the reaction of the pigment complex, change of acidity of the leaf blade, activity of oxidative enzymes, moisture regime, and degree of damage of the leaf blade. The data of the study can be used in the landscaping of the sanitary protective zones of enterprises.     

Invasive belowground mutualists of woody plants

Most plants require mutualistic associations to survive, which can be an important limitation on their ability to become invasive. There are four strategies that permit plants to become invasive without being limited by a lack of mutualists. One is to not be dependent on mutualists. The other three strategies are to form novel mutualisms, form associations with cosmopolitan species, or co-invade with mutualists from their native range. Historically there has been a bias to study mutualisms from a plant perspective, with little consideration of soil biota as invasive species in their own right. Here we address this by reviewing the literature on belowground invasive mutualists of woody plants. We focus on woody invaders as ecosystem-transforming plants that frequently have a high dependence on belowground mutualists. We found that co-invasions are common, with many ectomycorrhizal plant species and N-fixing species co-invading with their mutualists. Other groups, such as arbuscular mycorrhizal plants, tend to associate with cosmopolitan fungal species or to form novel associations in their exotic range. Only limited evidence exists of direct negative effects of co-invading mutualists on native mutualist communities, and effects on native plants appear to be largely driven by altered environmental conditions rather than direct interactions. Mutualists that introduce novel ecosystem functions have effects greater than would be predicted based solely on their biomass. Focusing on the belowground aspects of plant invasions provides novel insights into the impacts, processes and management of invasions of both soil organisms and woody plant species.     

Acclimation and adaptive responses of woody plants to environmental stresses

The predominant emphasis on harmful effects of environmental stresses on growth of woody plants has obscured some very beneficial effects of such stresses. Slowly increasing stresses may induce physiological adjustment that protects plants from the growth inhibition and/or injury that follow when environmental stresses are abruptly imposed. In addition, short exposures of woody plants to extreme environmental conditions at critical times in their development often improve growth. Furthermore, maintaining harvested seedlings and plant products at very low temperatures extends their longevity. Drought tolerance: Seedlings previously exposed to water stress often undergo less inhibition of growth and other processes following transplanting than do seedlings not previously exposed to such stress. Controlled wetting and drying cycles often promote early budset, dormancy, and drought tolerance. In many species increased drought tolerance following such cycles is associated with osmotic adjustment that involves accumulation of osmotically active substances. Maintenance of leaf turgor often is linked to osmotic adjustment. A reduction in osmotic volume at full turgor also results in reduced osmotic potential, even in the absence of solute accumulation. Changes in tissue elasticity may be important for turgor maintenance and drought tolerance of plants that do not adjust osmotically. Water deficits and nutrient deficiencies promote greater relative allocation of photosynthate to root growth, ultimately resulting in plants that have higher root:shoot ratios and greater capacity to absorb water and minerals relative to the shoots that must be supported. At the molecular level, plants respond to water stress by synthesis of certain new proteins and increased levels of synthesis of some proteins produced under well-watered conditions. Evidence has been obtained for enhanced synthesis under water stress of water-channel proteins and other proteins that may protect membranes and other important macromolecules from damage and denaturation as cells dehydrate. Flood tolerance: Both artificial and natural flooding sometimes benefit woody plants. Flooding of orchard soils has been an essential management practice for centuries to increase fruit yields and improve fruit quality. Also, annual advances and recessions of floods are crucial for maintaining valuable riparian forests. Intermittent flooding protects bottomland forests by increasing groundwater supplies, transporting sediments necessary for creating favorable seedbeds, and regulating decomposition of organic matter. Major adaptations for flood tolerance of some woody plants include high capacity for producing adventitious roots that compensate physiologically for decay of original roots under soil anaerobiosis, facilitation of oxygen uptake through stomata and newly formed lenticels, and metabolic adjustments. Halophytes can adapt to saline water by salt tolerance, salt avoidance, or both. Cold hardiness: Environmental stresses that inhibit plant growth, including low temperature, drought, short days, and combinations of these, induce cold hardening and hardiness in many species. Cold hardiness develops in two stages: at temperatures between 10° and 20°C in the autumn, when carbohydrates and lipids accumulate; and at subsequent freezing temperatures. The sum of many biochemical processes determines the degree of cold tolerance. Some of these processes are hormone dependent and induced by short days; others that are linked to activity of enzyme systems are temperature dependent. Short days are important for development of cold hardiness in species that set buds or respond strongly to photoperiod. Nursery managers often expose tree seedlings to moderate water stress at or near the end of the growing season. This accelerates budset, induces early dormancy, and increases cold hardiness. Pollution tolerance: Absorption of gaseous air pollutants varies with resistance to flow along the pollutant’s diffusion path. Hence, the amount of pollutant absorbed by leaves depends on stomatal aperture, stomatal size, and stomatal frequency. Pollution tolerance is increased when drought, dry air, or flooding of soil close stomatal pores. Heat tolerance: Exposure to sublethal high temperature can increase the thermotolerance of plants. Potential mechanisms of response include synthesis of heat-shock proteins and isoprene and antioxidant production to protect the photosynthetic apparatus and cellular metabolism. Breaking of dormancy: Seed dormancy can be broken by cold or heat. Embryo dormancy is broken by prolonged exposure of most seeds to temperatures of 1° to 15°C. The efficiency of treatment depends on interactions between temperature and seed moisture content. Germination can be postponed by partially dehydrating seeds or altering the temperature during seed stratification. Seed-coat dormancy can be broken by fires that rupture seed coats or melt seedcoat waxes, hence promoting water uptake. Seeds with both embryo dormancy and seed-coat dormancy may require exposure to both high and low temperatures to break dormancy. Exposure to smoke itself can also serve as a germination cue in breaking seed dormancy in some species. Bud dormancy of temperate-zone trees is broken by winter cold. The specific chilling requirement varies widely with species and genotype, type of bud (e.g., vegetative or floral bud), depth of dormancy, temperature, duration of chilling, stage of plant development, and daylength. Interruption of a cold regime by high temperature may negate the effect of sustained chilling or breaking of bud dormancy. Near-lethal heat stress may release buds from both endodormancy and ecodormancy. Pollen shedding: Dehiscence of anthers and release of pollen result from dehydration of walls of anther sacs. Both seasonal and diurnal pollen shedding are commonly associated with shrinkage and rupture of anther walls by low relative humidity. Pollen shedding typically is maximal near midday (low relative humidity) and low at night (high relative humidity). Pollen shedding is low or negligible during rainy periods. Seed dispersal: Gymnosperm cones typically dehydrate before opening. The cones open and shed seeds because of differential shrinkage between the adaxial and abaxial tissues of cone scales. Once opened, cones may close and reopen with changes in relative humidity. Both dehydration and heat are necessary for seed dispersal from serotinous (late-to-open) cones. Seeds are stored in serotinous cones because resinous bonds of scales prevent cone opening. After fire melts the resinous material, the cone scales can open on drying. Fires also stimulate germination of seeds of some species. Some heath plants require fire to open their serotinous follicles and shed seeds. Fire destroys the resin at the valves of follicles, and the valves then reflex to release the seeds. Following fire the follicles of some species require alternate wetting and drying for efficient seed dispersal. Stimulation of reproductive growth: Vegetative and reproductive growth of woody plants are negatively correlated. A heavy crop of fruits, cones, and seeds is associated with reduced vegetative growth in the same or following year (or even years). Subjecting trees to drought during early stages of fruit development to inhibit vegetative growth, followed by normal irrigation, sometimes favors reproductive growth. Short periods of drought at critical times not only induce formation of flower buds but also break dormancy of flower buds in some species. Water deficits may induce flowering directly or by inhibiting shoot flushing, thereby limiting the capacity of young leaves to inhibit floral induction. Postharvest water stress often results in abundant return bloom over that in well-irrigated plants. Fruit yields of some species are not reduced or are increased by withholding irrigation during the period of shoot elongation. In several species, osmotic adjustment occurs during deficit irrigation. In other species, increased fruit growth by imposed drought is not associated largely with osmotic adjustment and maintenance of leaf turgor. Seedling storage: Tree seedlings typically are stored at temperatures just above or below freezing. Growth and survival of cold-stored seedlings depend on such factors as: date of lifting from the nursery; species and genotype; storage temperature, humidity, and illumination; duration of storage; and handling of planting stock after storage. Seedlings to be stored over winter should be lifted from the nursery as late as possible. Dehydration of seedlings before, during, and after storage adversely affects growth of outplanted seedlings. Long-term storage of seedlings may result in depletion of stored carbohydrates by respiration and decrease of root growth potential. Although many seedlings are stored in darkness, a daily photoperiod during cold storage may stimulate subsequent growth and increase survival of outplanted seedlings. For some species, rapid thawing may decrease respiratory consumption of carbohydrates (over slowly thawed seedlings) and decrease development of molds. Pollen storage: Preservation of pollen is necessary for insurance against poor flowering years, for gene conservation, and for physiological and biochemical studies. Storage temperature and pollen moisture content largely determine longevity of stored pollen. Pollen can be stored successfully for many years in deep freezers at temperatures near −15°C or in liquid nitrogen (−196°C). Cryopreservation of pollen with a high moisture content is difficult because ice crystals may destroy the cells. Pollens of many species do not survive at temperatures below −40°C if their moisture contents exceed 20–30%. Pollen generally is air dried, vacuum dried, or freeze dried before it is stored. To preserve the germination capacity of stored pollen, rehydration at high humidity often is necessary. Seed storage: Seeds are routinely stored to provide a seed supply during years of poor seed production, to maintain genetic diversity, and to breed plants. For a long time, seeds were classified as either orthodox (relatively long-lived, with capacity for dehydration to very low moisture contents without losing viability) or recalcitrant (short-lived and requiring a high moisture content for retention of viability). More recently, some seeds have been reclassified as suborthodox or intermediate because they retain viability when carefully dried. True orthodox seeds are preserved much more easily than are nonorthodox seeds. Orthodox seeds can be stored for a long time at temperatures between 2° and −20°C, with temperatures below −5°C preferable. Some orthodox seeds have been stored at superlow temperatures, although temperatures of −40°, −70°, or −196°C have not been appreciably better than −20°C for storage of seeds of a number of species. Only relatively short-term storage protocols have been developed for nonorthodox seeds. These treatments typically extend seed viability to as much as a year. The methods often require cryopreservation of excised embryos. Responses to cryopreservation of nonorthodox seeds or embryos vary with species and genotype, rate of drying, use of cryoprotectants, rates of freezing and thawing, and rate of rehydration. Fruit storage: Storing fruits at low temperatures above freezing, increasing the CO₂ concentration, and lowering the O₂ concentration of fruit storage delays senescence of fruits and prolongs their life. Fruits continue to senesce and decay while in storage and become increasingly susceptible to diseases. Both temperate-zone and tropical fruits may develop chilling injury characterized by lesions, internal discoloration, greater susceptibility to decay, and shortened storage life. Chilling injury can be controlled by chemicals, temperature conditioning, and intermittent warming during storage. Stored fruits may become increasingly susceptible to disease organisms. Fruit diseases can be controlled by cold, which inhibits growth of microorganisms and maintains host resistance. Exposure of fruits to high CO₂ and low O₂ during storage directly suppresses disease-causing fungi. Pathogens also can be controlled by exposing fruits to heat before, during, and after storage. Scald that often develops during low-temperature storage can be controlled by chemicals and by heat treatments.     

Springtail (Collembola) communities in floodplains of the taiga zone of the Komi Republic

The species composition and structure of collembolan communities in floodplain soils were analyzed; a total of 65 species were found. The highest springtail species diversity was revealed in soils of birch-aspen forests. Collembolan communities in meadow soils were the most similar to those in the aspen forests of the second and third age classes. Prevalence of edaphic and hemiedaphic species is characteristic of soils of birch-aspen forests.     

Stem turnover strategy of multiple-stemmed woody plants

We have investigated stem turnover strategy for Lindera umbellata, an understory shrub that sprouts from its rootstock under natural conditions to replace constituent stems, on the basis of the hypothesis that the multiple-stemmed form of woody species is an adaptation enabling efficient reproduction in high-stress environments. We tested the hypothesis that the timing of stem replacement maximizes sexual reproduction for the shrub. We developed a model for the time of optimum replacement of a stem by a daughter stem which maximizes the sexual reproduction of a shrub and tested the model using L. umbellata growing in the field. From the model, the optimum time of replacement of a stem with a daughter stem is when cumulative sexual reproduction per unit time for the stem is maximum. In practice, this will be the last age (t _opt) at which annual sexual reproduction in a stem can potentially exceed cumulative sexual reproduction per unit time for the stem. Half of the stems died at almost t _opt and had sexually mature daughter stems at that time. Other stems, however, died at times more remote from t _opt when daughter stems were sexually immature. It is thought that normal replacement of the latter stems was prevented by accidents such as breakage. We conclude that clumps of L. umbellata achieve efficient sexual reproduction by stem replacement at the optimum time, although accidents can, to some extent, determine when the stem actually dies.     

Induction of somatic embryogenesis in woody plants

Somatic embryogenesis, the in vitro developmental program by which somatic cells are reprogrammed to undergo cellular and molecular changes that make them competent to produce somatic embryos, has been achieved with many woody plants. The program involves the stages of competence acquisition, induction and expression of the morphogenic pathway by the cultured cells and tissues. The ability to express the program in cultured cells/tissues is regulated by many factors, including genotype, explant type and age and culture conditions. In many woody plants, somatic embryogenesis was achieved with mature, immature explants or both. Juvenile tissues as immature and mature zygotic embryos are regarded best explants to establish embryogenic cultures in woody plants and potential to obtain the cultures decline with increasing maturity of the explant.     

Atlas of foliar surface features in woody plants,V. fraxinus (Oleaceae) of eastern North America

Scanning electron microscopy of foliar surfaces of the seven species ofFraxinus native in eastern North America confirms the importance of cuticular patterns (smooth, striated, striate-papillose, and coronulate) as useful taxonomic character states. There are there trichome types (acicular hairs ornamented with micro-striae or-papillae, peltate glands, and scales) which are found in nearly all species and which vary only in density. No differences in surface features are found by which determination can be made of either sex or ploidy level inF. americana. Hybridization betweenF. americana andF. pennsylvanica is considered to be rare in nature and is not a probable cause for the overlap of character states and concomitant difficulty of identification based upon gross morphological features. Likewise, the putative hybrid origins ofF. biltmoreana andF. profunda are not supported by micro-morphological features. Illustrations are given for all species.     

Leaf-out phenology of temperate woody plants: from trees to ecosystems

Leafing-out of woody plants begins the growing season in temperate forests and is one of the most important drivers of ecosystem processes. There is substantial variation in the timing of leaf-out, both within and among species, but the leaf development of almost all temperate tree and shrub species is highly sensitive to temperature. As a result, leaf-out times of temperate forests are valuable for observing the effects of climate change. Analysis of phenology data from around the world indicates that leaf-out is generally earlier in warmer years than in cooler years and that the onset of leaf-out has advanced in many locations. Changes in the timing of leaf-out will affect carbon sequestration, plant-animal interactions, and other essential ecosystem processes. The development of remote sensing methods has expanded the scope of leaf-out monitoring from the level of an individual plant or forest to an entire region. Meanwhile, historical data have informed modeling and experimental studies addressing questions about leaf-out timing. For most species, onset of leaf-out will continue to advance, although advancement may be slowed for some species because of unmet chilling requirements. More information is needed to reduce the uncertainty in predicting the timing of future spring onset.     

Perennation in woody fruit plants and its relationship to carbohydrate turnover

Carbohydrates constitute the principal reserves in temperate woody fruit plants and are depleted during winter, particularly around the time of bud-break before new growth makes good the losses. Movement of reserves between underground and aerial parts occurs during winter. All perennial parts show alternate depletion and replenishment but root extremities may undergo irreversible depletion and die. Interconversions between soluble carbohydrates and polysaccharides indicate a balance between degradation and synthesis. High growth potential is associated with high starch/starch + sugar ratio.