The clonal structure of dandelion coenopopulations under conditions of radioactive contamination in the Urals

The diversification of rare and unique morphs of some ferment systems and the clonal structure of dandelion coenopopulations, growing in radioactive contaminated drained watershed and flood-land ecosystems in the Ural region was studied. Drained watershed and flood-land dandelion coenopopulations significantly differed in the number of rare and of unique morphs and in the clonal structure. In the gradient of contamination in the drained watershed coenopopulations (zone of East-Urals radioactive trace) the share of rare morphs in most ferments systems increased, while the number of clones decreased. In two flood-land coenopopulations of the Techa River essential differences in the enzyme structure were observed, but these peculiarities were not connected with the level of radioactive contamination.     

The phospholipid composition of the liver in root voles living under different radioecological conditions

The effect of the increased natural radiation background (within some areas in Komi Republic) and man-caused radioactive contamination in the Chernobyl NPP accident zone on the composition of liver phospholipids in Microtus oeconomus inhabiting these areas was studied. The significant changes in the liver lipid composition in rodents inhabiting both the Chernobyl accident zone and the areas with the increased natural radiation background were found. The maximal changes in the liver phospholipid composition were revealed during the first year after the accident. The reverse dependence between the phosphatidyl choline/phosphatidyl ethanolamine ratio and the ratio between the sum of more readily oxidizable phospholipids and the sum of more poorly oxidizable ones was found. However, the slope of corresponding curves significantly depends on the radioactive state in the area of the population inhabitance. The conclusion about high sensitivity of the lipid composition of hepatocytes in Microtus oeconomus both to the impact of the man-caused radioactive contamination and the increased level of the natural radioactivity was drawn.     

Time-dependent changes of the physiological status of Bromus inermis Leyss. seeds from chronic low-level radiation exposure areas

The seed progeny of smooth brome (Bromus inermis Leyss.) were evaluated over a year for their viability, mutation rate, resistance to radiation and antioxidant status in response to chronic radiation exposure. Bromus inermis is found in the Eastern Ural Radioactive Trace (EURT) area and the background territories (surrounding territories that are used as controls as they only have natural background radiation). The absorbed doses by smooth brome from the EURT area were 1.5–18.5 times higher compared to background locations for parent plants and 1.1–11.6 times higher for the seed embryos. There are predictable and asynchronous changes in the survival of shoots and root growth rate between background populations and chronically irradiated samples. The provocative dose of 250 Gy is more damaging in the winter months, than in the summer and autumn. The frequency of anomalies in shoots varied in different months, with the biggest rate of mutation recorded in physiologically harsher period (autumn–winter). There is no correlation between resulting survival rate of shoots and their resistance to radiation. The intense activity of the antioxidant systems (estimated by the content of low molecular weight antioxidants) allowed faster growth of the shoots and reduced the number of abnormalities seen in development.     

Viability selection at three early life stages of the tropical tree,Platypodium elegans (Fabaceae,Papilionoideae)

Given the enormous number and high mortality of fertilized ovules in plants, it is possible that selection during the earliest stages of the life cycle plays an important role in shaping the genetic composition of plant populations. Previous research involving selection component analyses found strong evidence for viability selection in annual plant species. Yet despite this evidence, few attempts have been made to identify the magnitude and timing of viability selection as well as the mechanisms responsible for mortality among genotypes. Platypodium elegans, a Neotropical tree with high rates of early fruit mortality, represents an opportunity to study viability selection at a level of discernment not previously possible. Microsatellite markers were used to analyze the genetic composition of aborted embryos, as well as mature seeds and seedlings of the same cohort. While selection resulted in an overall decrease in self-fertilized progeny across each life stage, the greatest change in the genetic composition of progeny occurred between mature seeds and established seedlings. This suggested that inbreeding depression, and not late-acting self-incompatibility, was responsible for early selection. An investigation of the mature seed stage revealed that self-fertilized seeds weigh significantly less than outcrossed seeds. The result of this early selection conceals the mixed-mating system and high levels of inbreeding depression in Platypodium elegans, resulting in an apparently outcrossed adult population that does not differ significantly from Hardy-Weinberg expectations.     

The cytogenetic consequences of chronic irradiation in rodent populations inhabiting the Eastern Urals Radioactive Trace zone

In bone marrow cells of rodents (Apodemus (Sylvaemus) uralensis Pall., 1811, Apodemus agrarius Pall., 1771) inhabiting the Eastern Urals Radioactive Trace (EURT) zone (Kyshtym radiation accident 1957) and adjacent areas of Urals, the chromosome instability and 90Sr accumulation in bones were investigated. Intensive mutagenic process in both species from impact plots (the soil pollution by 90Sr 2322-16690 kBq/m2) was found. Significant positive correlation of aberrant cells frequencies and 90Sr was shown. Possible causes of the lack of resistance to long-term mutagenic factor (over 100 generations since 50 years from the accident) such as migration of animals and specific configuration of the EURT zone (narrow extended territory with sharply falling gradient of radionuclide pollution), which considerably decrease the probability that certain changes will be fixed and inherited in a series of generations of rodents, are discussed.     

Adaptation of small mammals to radiocontaminated environment: Oxidative metabolism and radioresistance

Differences in radioresistance and oxidative metabolism parameters in rodents of different ecological specialization in the East Ural radioactive trace (EURT) area are shown. Northern mole voles (radiosensitive species) exhibit a pronounced resistance to chronic exposure to radiation, living in a series of generations in a radioactive environment, whereas pigmy wood mice (radioresistant species) are less resistant in the EURT area due to their migration activity. Thus, under the EURT area conditions, northern mole voles realize the genotypic radioadaptation, whereas pigmy wood mice realize the physiological radioadaptation, the key role in which is played by the ecological and physiological characteristics and the lifestyle of animals.     

Radiation dose rates estimation and allozyme variability in the population of the northern red-backed vole (Clethrionomys rutilus) from the East-Ural Radioactive Trace

The paper estimates the external (due to radionuclides accumulated in the soil) and internal (due to incorporated radionuclides) exposure of rodents that live in the head of the East Urals Radioactive Trace (EURT). It is shown that in the last decades the dose rates were lower than the values that lead to a doubling the number of mutations in the allozyme loci in mammals. The variability of the eight allozyme loci in populations of northern red-backed voles from the EURT zone and their neighboring plots, as well as the territories of the Urals and Trans-Urals with background levels of radioactive contamination, are analyzed. No differences in the pattern and frequency of allozymes that would distinguish the EURT samples from a number of other populations of the Urals, were found. In the control sample “Sysert’,” “unique” for the Ural populations of northern red-backed voles, alleles of the loci Got and Sod were marked, conspecific to a closely related species-the bank vole. This fact can be regarded as evidence of recent cross-species hybridization.     

Analysis of microsatellite DNA in rodents from Eastern Urals Radioactive Trace zone and contiguous territories

The variability of four microsatellite loci of rodents, caught from the head part of Eastern Urals Radioactive Trace (EURT), along with the rodents inhabiting contiguous zone with background radiation level and distant reference territory, was analyzed for the first time. Differences in the parameters of genetic diversity between northern red-backed voles from the EURT zone and from the reference population were detected. An increase in some indices of genetic diversity in animals from a contiguous to the EURT zone was found; this is probably associated with animal migration and configuration of the area of pollution. A transfer of radiation-induced effects to the contiguous territories and a decrease in the possibility of fixation of adaptations in a series of generations of mobile rodent species in the area of local radioactive pollution are consequences of migrations. The results of the study make it possible to recommend microsatellite markers for the analysis of radiation-induced effects in rodents as model objects of radioecological monitoring.     

The dispersal unit of Dacrycarpus dacrydioides (A. Rich.) de Laubenfels (Podocarpaceae) and the significance of the fleshy receptacle

FOUNTAIN, D. W., HOLDSWORTH, J. M. & OUTRED, H. A., 1989. The dispersal unit of Dacrycarpus dacrydioides (A. Rich.) de Laubenfels (Podocarpaceae) and the significance of the fleshy receptacle. Dacrycarpus dacrydioides (formerly Podocarpus dacrydioides ) is an arborescent gymnosperm endemic to New Zealand. The high water content (43%) and sensitivity of viability towards desiccation, suggest the seeds are of the 'recalcitrant' type. The 'fruits' comprising a seed borne on a fleshy receptacle arc shed in large numbers. The development of the seed precedes the full development of succulence in the receptacle and at maturity the seed has a high relative water content (RWC) relative to the receptacle. Within the maturing reproductive unit, the receptacle buffers the seed against the effects of water stress. After shedding, seeds are rapidly desiccated in moving air, and viability is impaired below approximately 80"' RWC and abolished at 34", seed RWC. The presence of the receptacle during drying confers resistance to desiccation-associated damage. Five phases of desiccation sensitivity are distinguished in recognition of the protective role of the receptacle. It is suggested that the advantages associated with prolonging seed viability may have contributed to the evolutionary development of succulence in the reproductive unit. This might be considered as a selection pressure in a manner similar to the proposal that such fleshy structures are associated with seed dispersal by birds.     

Fecundity, phenology, and seed dormancy of F1 wild-crop hybrids in Sunflower (Helianthus annuus, Asteraceae)

Crop-to-wild hybridization has the potential to introduce beneficial traits into wild populations. Gene flow from genetically engineered crops, in particular, can transfer genes coding for traits such as resistance to herbicides, insect herbivores, disease, and environmental stress into wild plants. Cultivated sunflower (Helianthus annuus) hybridizes spontaneously with wild/weedy populations (also H. annuus), but little is known about the relative fitness of F1 hybrids. In order to assess the ease with which crop-to-wild introgression can proceed, we compared characteristics of F1 wild-crop progeny with those of purely wild genotypes. Two nontransgenic, cultivated varieties were crossed with wild plants from three different regions-Texas, Kansas, and North Dakota. Seed burial experiments in the region of origin showed that wild-crop seeds had somewhat higher germination rates (less dormancy) than wild seeds from Kansas and North Dakota, while no differences were seen in seeds from Texas. Progeny from each type of cross were grown in outdoor pots in Ohio and in a weedy field in Kansas to quantify lifetime fecundity and flowering phenology. Flowering periods of hybrid and wild progeny overlapped considerably, especially in plants from North Dakota and Texas, suggesting that these hybrids are very likely to backcross with wild plants. In general, hybrid plants had fewer branches, flower heads, and seeds than wild plants, but in two crosses the fecundity of hybrids was not significantly different from that of purely wild plants. In Ohio, wild-crop hybrids from North Dakota appeared to be resistant to a rust that infected 53% of the purely wild progeny, indicating a possible benefit of "traditional" crop genes. In summary, our results suggest that F1 wild-crop hybrids had lower fitness than wild genotypes, especially when grown under favorable conditions, but the F1 barrier to the introgression of crop genes is quite permeable.     

Desiccation-induced ROS accumulation and lipid catabolism in recalcitrant <Emphasis Type="Italic">Madhuca latifolia</Emphasis> seeds

Loss of viability in desiccation-sensitive seeds of Madhuca latifolia (Roxb.) J. F. Macbr., an important multipurpose tropical tree, was correlated with seed water content (WC). WC declined from 0.59 to 0.19 g g^?1 fresh mass, 35 days after harvest from mother plant, at ambient conditions (temperature 25 ± 2 °C, relative humidity 50 ± 2%). The desiccation-induced reduction in viability was related with an accumulation of reactive oxygen species (ROS) that promoted lipid peroxidation associated loss of membrane integrity. Conducted study revealed 1.6–19 folds rise in lipid peroxidized products in desiccated M. latifolia seeds, and was found to be linked inversely with WC and germination percentage. Additionally, increased activities (7 and 13 folds) of lipid hydrolyzing enzymes; lipase (EC 3.1.1.3) and lipoxygenase (EC 1.13.11.12) respectively, were discernible in desiccating M. latifolia seeds. In summary, increased ROS, lipid oxidation, lipase and lipoxygenase were strongly correlated with viability loss in desiccating M. latifolia seeds.     

Seed limitation of woody plants in Neotropical savannas

The failure of seeds to arrive at all suitable sites (seed limitation) greatly affects plant distribution and abundance. In contrast to tropical forests, the degree of seed limitation in Neotropical savannas is unclear because empirical studies at the community level are scarce. We estimated seed limitation of 23 woody species from annual seed rain measurements along a tree density gradient in the savannas of Central Brazil. These savannas differ in tree density and canopy cover, from closed to open savannas, and are located along shallow topographic gradients. We also studied post-dispersal seed predation and removal of 17 representative woody species, and seed viability loss over time of 12 common woody species under dry-storage conditions. Annual seed rain was lower in open (410 seeds/m²) than in closed savannas (773 seeds/m²). Average seed limitation across woody species was higher than 80% along the tree density gradient. More than 60% of seeds of the studied woody species were predated or removed within 30–45 days in all savannah types. Seeds of most common woody species (66%) lost their viability in less than 12 months of dry storage. This study shows that Neotropical savannah woody plants are strongly seed-limited because of low and poor distribution of seeds among sites, post-dispersal seed removal, and short seed longevity. The high seed limitation of tree species in Neotropical savannas, particularly in open savannas, also may contribute to maintain their relatively low tree densities and help to explain the spatial variation of tree abundance along topographic gradients.     

Variability of enzyme systems in the coenopopulation of Taraxacum officinale s.l. from the zone of East-Ural- radioactive trace

Levels of soil contamination with 90Sr and 137Cs radionuclides on the plots within the zone of Eastern-Ural radioactive trace exceed values of the global level 4-240 times. We have carried out allozyme analysis of apomict species Taraxacum officinale s.l. from this zone. Zimogrammes were interpreted as allozyme phenotypes. In condition of chronic irradiation the plants had increased phenogenetic variability of majority enzymes systems and high frequency of rare morphs. Thus, in plant coenopopoulations situated in radioactive-polluted zone, genomic recombination processes show higher intensity. High enzymatic variability provides the material for natural selection and increase the adaptive potential of coenopopulations.     

Do pollen donors with fastest-growing pollen tubes sire the best offspring in an anemophilous tree, Betula pendula (Betulaceae)?

The relationship between pollen and progeny performance has been a subject of many studies but the evidence for pollen-tube growth rate as an indicator of progeny fitness is equivocal. We used an anemophilous tree, Betula pendula, to examine the relationship between pollen-tube growth rate and seed and seedling performance. We crossed nine maternal plants with pollen from six pollen donors in a clonal B. pendula seed orchard, measured the pollen-tube growth rates for every cross, and analyzed the performance of the resulting seeds and seedlings. The only significant positive correlation was found between pollen-tube growth rate and seed mass when we controlled for seed number per inflorescence. Using seed mass as a covariate, we found that only maternal parent had a significant effect on the number of seeds per inflorescence, the percentage of germinable and embryonic seeds, and early seedling growth. Both maternal and paternal parents had significant effects on seedling height after 85 d of growth. These results are in concordance with the general view that maternal effects are usually most apparent in seed characters and during early plant growth. This study does not provide strong evidence for the theory of pollen-tube growth rate as an indicator of progeny quality.     

Seed mass,genotype, and density effects on growth and yield of Oenothera biennis L.

Summary Seed mass and genotypic effects on the growth and reproduction of Oenothera biennis L. over a gradient of intraspecific density were examined in a greenhouse experiment. By using genetically identical seeds from five parental genotypes we were able to examine independently the effects of seed mass and genotype on seedling and adult performance. Seedling size was significantly correlated with seed mass for the first five weeks but had no effect on adult size or reproductive output. In contrast, genotype differences became increasingly apparent with time. In particular, there were striking differences in reproductive output among genotypes. Plants grown from two of the genotypes consistently produced more, but lighter, seeds and a greater proportion flowered at high density than the other three genotypes. In all five genotypes, seed number was much more variable than seed mass across the density gradient. Initial seed mass accounted for a significant proportion of the variation in progeny seed mass, and mean seed mass produced in the greenhouse was positively correlated with mean seed mass of the parent (in the field). This result, together with the observed constancy of seed mass within a genotype across the density gradient, indicates the differences in reproductive output among these genotypes are genetically determined.     

Dynamics of Neotyphodium endophyte infection in ageing seed pools: incidence of differential viability loss of endophyte,infected seed and non-infected seed

Symbiotic associations between grasses and vertically transmitted endophytic fungi are widespread in nature. Within grass populations, changes in the frequency of infected plants are driven by influence of the endophyte on the fitness of their hosts and by the efficiency of endophyte transmission from parent plants to their offspring. During the seed stage, the endophyte might influence the fitness of its host by affecting the rate of seed viability loss, whereas the efficiency of endophyte transmission is affected by losses of viability of the fungus within viable seeds. We assessed the viability losses of Lolium multiflorum seeds with high and low level of infection of the endophyte Neotyphodium occultans, as well as the loss of viability of the fungus itself, under accelerated seed ageing and under field conditions. Starting with high endophyte-infected accessions of L. multiflorum, we produced their low endophyte-infected counterparts by treating seeds with a fungicide, and subsequently multiplying seeds in adjacent plots allowing pollen exchange. In our accelerated ageing experiments, which included three accessions, high endophyte-infected seeds lost viability significantly faster than their low endophyte-infected counterpart, for only one accession. High endophyte-infected seeds of this particular accession absorbed more water than low endophyte-infected seeds. In contrast, the endophyte lost viability within live seeds of all three accessions, as the proportions of viable seeds producing infected seedlings decreased over time. In our field experiment, which included only one accession, high endophyte-infected seed lost viability significantly but only slightly faster than low endophyte-infected seed. In contrast, the loss of viability of the endophyte was substantial as the proportions of viable seeds producing infected seedlings decreased greatly over time. Moving the seeds from the air to the soil surface (simulating seed dispersion off the spikes) decreased substantially the rate of seed viability loss, but increased the rate of endophyte viability loss. Our experiments suggest that, in ageing seed pools, endophyte viability loss and differential seed mortality determine decreases in the proportions of endophyte-infected seeds in L. multiflorum. Endophyte viability loss within live seeds contributes substantially more to infection frequency changes than differential viability losses of infected and non-infected seeds.     

Outbreeding Depression Caused by Intraspecific Hybridization Between Local and Nonlocal Genotypes in Abies sachalinensis

To evaluate the effects of intraspecific hybridization of local and nonlocal genotypes on growth traits of progeny in Abies sachalinensis, we performed reciprocal crossing between nonlocal trees in a high‐elevation zone (1,100–1,200 m asl) and local trees in a low‐elevation zone (530 m asl) in Hokkaido, northern Japan, in 1979 and established a common garden experiment using local × local (female × male ), local × nonlocal , nonlocal × local , and nonlocal × nonlocal progeny in the low‐elevation zone in 1986. Survival, height, diameter at breast height (dbh), needle nitrogen content, specific leaf area (SLA), and needle area per shoot diameter (NA) of 25‐year‐old progeny were measured in 2005. The survival rate was consistently high (>85% on average). Reductions in height and dbh were apparent in F1 hybrids compared with local × local progeny. Furthermore, outbreeding depression was significant in height growth of nonlocal × local F1 hybrids and in dbh of both F1 hybrids. Reductions in growth traits may be related to morphological needle traits, such as the low values of SLA and NA. Elevation guidelines for A. sachalinensis seed zones are discussed to ensure the long‐term viability of both restored and native populations.     

Protein repair L-isoaspartyl methyltransferase in plants. Phylogenetic distribution and the accumulation of substrate proteins in aged barley seeds.

Protein L-isoaspartate (D-aspartate) O-methyltransferases (MTs; EC 2.1.1.77) can initiate the conversion of detrimental L-isoaspartyl residues in spontaneously damaged proteins to normal L-aspartyl residues. We detected this enzyme in 45 species from 23 families representing most of the divisions of the plant kingdom. MT activity is often localized in seeds, suggesting that it has a role in their maturation, quiescence, and germination. The relationship among MT activity, the accumulation of abnormal protein L-isoaspartyl residues, and seed viability was explored in barley (Hordeum vulgare cultivar Himalaya) seeds, which contain high levels of MT. Natural aging of barley seeds for 17 years resulted in a significant reduction in MT activity and in seed viability, coupled with increased levels of "unrepaired" L-isoaspartyl residues. In seeds heated to accelerate aging, we found no reduction of MT activity, but we did observe decreased seed viability and the accumulation of isoaspartyl residues. Among populations of accelerated aged seed, those possessing the highest levels of L-isoaspartyl-containing proteins had the lowest germination percentages. These results suggest that the MT present in seeds cannot efficiently repair all spontaneously damaged proteins containing altered aspartyl residues, and their accumulation during aging may contribute to the loss of seed viability.     

Transgenerational consequences of plant responses to herbivory: an adaptive maternal effect?

Herbivory has many effects on plants, ranging from shifts in primary processes such as photosynthesis, growth, and phenology to effects on defense against subsequent herbivores and other species interactions. In this study, I investigated the effects of herbivory on seed and seedling characteristics of several families of wild radish (Raphanus raphanistrum) to test the hypothesis that herbivory may affect the quality of offspring and the resistance of offspring to plant parasites. Transgenerational effects of herbivory may represent adaptive maternal effects or factors that constrain or amplify natural selection on progeny. Caterpillar (Pieris rapae) herbivory to greenhouse-grown plants caused plants in some families to produce smaller seeds and those in other families to produce larger seeds compared with undamaged controls. Seed mass was positively associated with probability of emergence in the field. The number of setose trichomes, a putative plant defense, was higher in the progeny of damaged plants in some families and lower in the progeny of damaged plants in other families. In a field experiment, plant families varied in their resistance to several herbivores and pathogens as well as in growth rate and time to flowering. Seeds from damaged parent plants were more likely to become infested with a plant virus. Although herbivory on maternal plants did not directly affect interactions of offspring with other plant parasites, seed mass influenced plant resistance to several attackers. Thus, herbivory affected seed characters, which mediated interactions between plants and their parasites. Finally, irrespective of seed mass, herbivory on maternal plants influenced components of progeny fitness, which was dependent on plant family. Natural selection may act on plant responses to herbivory that affect seedling-parasite interactions and, ultimately, fitness.     

Latitudinal variation in seeds characteristics of Acer platanoides and A. pseudoplatanus

Climate change will likely affect population dynamics of numerous plant species by modifying several aspects of the life cycle. Because plant regeneration from seeds may be particularly vulnerable, here we assess the possible effects of climate change on seed characteristics and present an integrated analysis of seven seed traits (nutrient concentrations, samara mass, seed mass, wing length, seed viability, germination percentage, and seedling biomass) of Acer platanoides and A. pseudoplatanus seeds collected along a wide latitudinal gradient from Italy to Norway. Seed traits were analyzed in relation to the environmental conditions experienced by the mother trees along the latitudinal gradient. We found that seed traits of A. platanoides were more influenced by the climatic conditions than those of A. pseudoplatanus. Additionally, seed viability, germination percentage, and seedling biomass of A. platanoides were strongly related to the seed mass and nutrient concentration. While A. platanoides seeds were more influenced by the environmental conditions (generally negatively affected by rising temperatures), compared to A. pseudoplatanus, A. platanoides still showed higher germination percentage and seedling biomass than A. pseudoplatanus. Thus, further research on subsequent life-history stages of both species is needed. The variation in seed quality observed along the climatic gradient highlights the importance of studying the possible impact of climate change on seed production and species demography.