Effects of silicon on growth processes and adaptive potential of barley plants under optimal soil watering and flooding

Barley (Hordeum vulgare L.) was grown in pots with brown loess soil and highly soluble amorphous silicon dioxide as the source of monosilicic acid to examine its influence on plant growth and adaptive potential under optimal soil watering and flooding. The adaptive potential of plants was estimated by the concentration of the thiobarbituric acid reactive substances (TBARs) as well as superoxide dismutase (SOD), guaiacol peroxidase (GPX) and ascorbate peroxidase (AsP) activities. Application of amorphous silica to the soil increased the Si content in barley shoots and roots and stimulated their growth and biomass production under optimal soil watering. Soil flooding suppressed the growth both of the (−Si)- and (+Si)-plants. The intensity of oxidative destruction estimated by the concentration of TBARs was lower in the roots and leaves of the (+Si)-plants. Soil flooding induced SOD activity in the roots and in the leaves of the (−Si;+flooding) and (+Si;+flooding)-plants, but no significant differences were observed due to the Si treatment. GPX activity in the roots of (+Si)-plants was higher than in the (−Si)-ones under optimal soil watering, but under soil flooding no differences between (+Si)- and (−Si)-treatments were observed. AsP activity was not influenced by Si treatment neither under optimal soil watering nor under flooding. Thus, application of Si stimulates growth processes of barley shoots and roots under optimal soil watering and decreases intensity of oxidative destruction under soil flooding without significant changes in the activities of antioxidant enzymes.     

Effects of ultraviolet-B irradiation on plants during mild water stress.

Cucumber ( Cucumis sativus L. cv. Delikatess) and radish ( Raphanus sativus L. cv. Saxa Treib) were grown in a factorial design under two ultraviolet-B (UV–B) irradiances and three levels of water stress. On a weighted, daily dose basis the UV–B radiation treatments were equivalent to ambient levels during the beginning of the growing season (controls) and those predicted for an 11.6% ozone depletion during the summer solstice at 49°N latitude. Water stress was achieved by varying the frequency of watering. The combination of UV–B radiation and water stress resulted in large species differences in the pattern of stomatal resistances. This study indicated that Cucumis is one of the most sensitive crop species to UV–B radiation yet identified and that the primary effect of UV–B radiation in this species is a decrease in the leaf diffusive resistance to water vapor. This, therefore, may result in reductions in growth via increased water stress.     

The ecology-genetic consequences of chronic irradiation for the populations of the plants and animals

The modem presentations are considered in the review about the consequences for the genotype of animals and of plants of the chronic action of factors of low intensity. Inoffer is spoken about possible dug the chronic irradiation in small doses in microevolution events.     

Effects of extracorporeal blood irradiation on the lymphocyte population in chronic lymphadenosis

The surface markers of lymphocytes were detected in 18 patients with chronic lymphatic leukemia (CLL), with 9 of them being treated by means of extracorporeal blood irradiation (ECIB) and 9 of them being without any treatment. We found that B-lymphocytes were eliminated by ECIB to a higher degree than it can be recognized by the decrease of lymphocytes. As to their percentage B-cells with ME-receptors or EAC-receptors respectively were partially diminished to a higher degree than the total population of B-cells. Moreover, the pathological Ig-type could be shown to be affected predominantly. The changes of marker profiles and absolute values achieved by ECIB revealed an approach of values in treated patients to those of untreated patients. The investigations make it clear that the determination of lymphocyte subpopulation can be used not only for diagnosis and differential diagnosis of lymphatic system diseases, also for evaluating therapy effects.     

Effects of chronic irradiation on age-related biochemical changes in mice

Some of the biochemical indices relevant to the "free radical theory" of aging have been assessed in mice subjected to chronic low-dose whole-body irradiation. Radiation exposure results in enhanced accumulation of the lipofuscins in brain, heart, and intestine. In these animals, the degree of lipoperoxidation in liver was greatly increased, as were the free activities of acid phosphatase and cathespin, indicating damage to lysosomal membranes. The activity of SOD in brain and liver 20,000g post-mitochondrial supernatants was lower in the irradiated mice. All these changes arising from chronic whole-body irradiation are similar to those observed during aging and are effectively prevented by dietary supplementation with BHT. These observations lend considerable support to the "free radical theory" of aging.     

Evolutionary rates in the adaptive radiation of beetles on plants

Herbivorous insects and other small consumers are often specialized both in use of particular host taxa and in use of particular host tissues. Such consumers also often seem to show consistent differences in the rates of evolution of these two dimensions of host use, implying common processes, but this has been little studied. Here we quantify these rates of change in host use evolution in a major radiation of herbivorous insects, the Chrysomeloidea, whose diversity has been attributed to their use of flowering plants. We find a significant difference in the rates of evolutionary change in these two dimensions of host use, with host taxon associations most labile. There are apparently similar differences in rates of host use evolution in other parasite groups, suggesting the generality of this pattern. Divergences in parasite form associated with use of different host tissues may facilitate resource partitioning among successive adaptive radiations on particular host taxa.     

Constraints on the evolution of adaptive phenotypic plasticity in plants

The high potential fitness benefit of phenotypic plasticity tempts us to expect phenotypic plasticity as a frequent adaptation to environmental heterogeneity. Examples of proven adaptive plasticity in plants, however, are scarce and most plastic responses actually may be 'passive' rather than adaptive. This suggests that frequently requirements for the evolution of adaptive plasticity are not met or that such evolution is impeded by constraints. Here we outline requirements and potential constraints for the evolution of adaptive phenotypic plasticity, identify open questions, and propose new research approaches. Important open questions concern the genetic background of plasticity, genetic variation in plasticity, selection for plasticity in natural habitats, and the nature and occurrence of costs and limits of plasticity. Especially promising tools to address these questions are selection gradient analysis, meta-analysis of studies on genotype-by-environment interactions, QTL analysis, cDNA-microarray scanning and quantitative PCR to quantify gene expression, and two-dimensional gel electrophoresis to quantify protein expression. Studying plasticity along the pathway from gene expression to the phenotype and its relationship with fitness will help us to better understand why adaptive plasticity is not more universal, and to more realistically predict the evolution of plastic responses to environmental change.     

干旱-复水对两种石斛属植物叶水势的影响

石斛属植物多附着在其他植物体或岩石上,水分获取困难,其特殊的水分利用策略是其生存和发展的重要保证.为弄清石斛属植物对干旱胁迫的适应能力和机制,该文选用3年生金钗石斛和铁皮石斛,通过盆栽控水进行干旱胁迫和复水处理,探讨在不同干旱历时和干旱后复水条件下两种石斛的叶水势变化情况.结果表明:随着干旱时间的延长,两种石斛叶水势均...     

Effects of chronic irradiation upon a self-incompatible clone ofLycopersicum peruvianum

Summary Flovering plants from a self-incompatible clone ofLycopersicum peruvianum were exposed during 90 days to different dose-rates of gamma-rays ranging from 2 to 17 rad perhour. Irradiation was continuous, except for a daily interruption of 7 hours.Whereas irradiation at dose-rates higher than 7.50 rad per hour seriously inhibited bud formation and floral development, chronic exposure at dose-rates ranging from 3 to 7 rad/hour increased the number of seeds per plant. This stimulation is not due to a higher number of seeds per fruit but to a very significant rise in the number of fruits per plant. As irradiation treatment did not significantly increase the number of flowers per plant and did not appear to stimulate pollen tube germination in the styles, it is concluded that the recorded increase in fruit-setting essentially resulted from a radio-induced inhibition of the processes which control floral abscission in the absence of cross-pollination.Three plants with reduced self-incompatibility and one completely parthenocarpic individual were observed in theM ₂ progeny but no evidence was obtained that irradiation could induce a permanent type of self-compatibility inL. peruvianum.

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Zusammenfassung Blühende Pflanzen eines selbstunverträglichen Klons vonLycopersicum peruvianum wurden 90 Tage hindurch verschiedenen Dosen von Gammastrahlen ausgesetzt (2 bis 17 rad/h). Die Bestrahlungsdauer betrug täglich seiben Stunden.Während Bestrahlungen in Dosierungen von mehr als 7,5 rad/h die Knospenbildung und Blütenentwicklung stark hemmten, steigerte eine Dauerbestrahlung mit 3 bis 7 rad/h die Samenzahl je Pflanze. Diese Erscheinung beruht nicht auf einer Zunahme der Samenzahl der einzelnen Früchte, sondern auf einer hochsignifikanten Steigerung der Fruchtzahl der einzelnen Pflanzen. Da durch die Behandlung die Blütenzahl nicht signifikant zunimmt und das Einwachsen des Pollens in den Griffel nicht gefördert wird, ist anzunehmen, daß die festgestellte Zunahme des Fruchtansatzes im wesentlichen auf eine strahleninduzierte Hemmung des Blütenverlustes bei Ausbleiben der Fremdbefruchtung zurückzuführen ist.Drei Pflanzen mit herabgesetzter Selbstunverträglichkeit und ein vollständig parthenokarpes Exemplar wurden in derM ₂-Generation angetroffen; es wurde kein Grund für die Annahme gefunden, die Bestrahlung könne eine erbliche Selbstverträglichkeit beiLycopersicum peruvianum hervorrufen.

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This publication is contribution no. 368 of the Euratom Biology Division.     

Effects of chronic gamma irradiation on reproduction in the earthworm Eisenia fetida (Oligochaeta)

Eisenia fetida were exposed continuously to (60)Co gamma radiation during two generations (F(0) and F(1)). Adult F(0) reproduction capacity (i.e., number of cocoons produced, hatchability and number of F(1) hatchlings) in controls and at five dose rates (0.18, 1.7, 4, 11 and 43 mGy/h) was measured over a 13-week exposure period. Survival, growth and sexual maturation of F(1) hatchlings were observed for 11 weeks. F(1) adults were exposed for a further 13 weeks to determine their reproduction capacity. There was no radiation-induced effect on the cocoon production rate in either F(0) or F(1). For F(0), hatchability of cocoons produced during the first 4 weeks was reduced to 60% at 43 mGy/h (98% in controls), and none of the cocoons produced at 5-13 weeks hatched. At 11 mGy/h the cocoon hatchability was reduced to 25% at 9-13 weeks. In addition, the number of hatchlings per hatched cocoon was reduced at 11 and 43 mGy/h. Correspondingly, at these dose rates, the total number of F(1) hatchlings per adult F(0) was significantly lower than in the control. This number was also reduced at 4 mGy/h, but the effect was of borderline significance. For adult F(1), the hatchability of cocoons at 11 mGy/h was reduced to 45-69% during the 13-week exposure period. The number of hatchlings (F(2)) per cocoon and the total number of F(2) individuals produced was also reduced. However, and in contrast to the results observed for F(0), hatchability increased with time, suggesting a possible acclimatization or adaptation of the F(1) individuals. In conclusion, chronic irradiation reduced the reproduction capacity of E. fetida, but extensive exposure periods (13 weeks) were needed for these effects to be expressed. The lowest dose rates at which an effect was observed were 4 mGy/h in F(0) and 11 mGy/h in F(1).     

Effects of 3,4-dihydroxybenzoic acid on root membrane potential in micropropagated tobacco plants

In order to understand the mechanism of action of the phenolic compound 3,4-dihydroxybenzoic acid, we tested its effect on tobacco root membrane potential. Tobacco root segments, excised from micropropagated plants grown in liquid media, were perfused with 0.1–5 mM 3,4-dihydroxybenzoic acid. Activity on the plasma membrane potential was compared with that obtained after perfusion with 0.05 mM indole-3-acetic acid, 0.05 mM kinetin and 0.05 mM gibberellic acid. Possible interactions between 3,4-dihydroxybenzoic acid and plant growth regulators were evaluated by the means of successive applications. When applied to tobacco root segments, 3,4-dihydroxybenzoic acid elicited a transient membrane depolarization. The membrane depolarization induced by 3,4-dihydroxybenzoic acid was followed by a repolarization phase, as for auxin applications. In roots preconditioned with the other growth regulators, the activity of 3,4-dihydroxybenzoic acid on membrane potential was non-specifically affected. In roots preconditioned with 3,4-dihydroxybenzoic acid, indole-3-acetic acid activity on cell membrane was altered, suggesting a specific reciprocal interaction. This revised version was published online in June 2006 with corrections to the Cover Date.     

Effects of chronic gamma irradiation on the activity of adenylate cyclase in rat lung tissue]

Different phase changes were observed in adenylate cyclase (AC) activity of pulmonary tissue plasma membranes under chronic gamma-irradiation of rats at a dose-rate of 12.9 cGy/day. Comparison of AC basal activity with the data reported earlier on changes in ornithine decarboxylase activity under similar radiation conditions showed unidirectional changes which indicated that cAMP-dependent processes were possibly involved in radiation modification of ornithine decarboxylase.     

Maximising adaptive potential in translocated populations of clonal saltmarsh plants: a case study on Wilsonia backhousei, Convolvulaceae

We investigated the implications of clonality for translocation of Wilsonia backhousei, a threatened, outbreeding, saltmarsh plant with tidally-dispersed fruit. Eight microsatellite loci were used to characterise samples from three estuaries in New South Wales, Australia, and to determine the size and distribution of genetically distinct individuals (genets). Within-population diversity was compared to the presence or absence of seed production using the t test. Ordinal logistic regression was used to investigate the relative influence on seed yield of soil characteristics (soil moisture, salinity, pH) and the number of clonal lineages within a 5 and 10 m radius. Principal coordinate analysis, analysis of molecular variance and Bayesian analysis were used to investigate the extent of gene flow within and among the three estuaries. We found individual genets could cover extensive areas (up to 225 m²) and apparently large populations could consist of only a few individuals. Populations that failed to produce seed had significantly less genetic diversity than populations that produced seed (P = 0.001). Seed yield showed a significant positive response to both increasing soil moisture content (P = 0.003) and increasing genetic diversity in a 5 m radius (P = 0.003). Gene flow was found to occur chiefly within estuaries though occasional longer-distance gene transfer was evident. To maximise adaptive potential in translocated populations of W. backhousei, we recommend sourcing propagules from multiple populations and planting representatives of the different populations in close proximity to facilitate sexual reproduction. These findings are likely to be applicable to other outbreeding clonal saltmarsh plants with tidally-dispersed fruit or seed.     

Determining the adaptive potential of maternal stress

Ecological and medical researchers are investing great effort to determine the role of Maternally‐Derived Stress (MDS) as an inducer of phenotypic plasticity in offspring. Many researchers have interpreted phenotypic responses as unavoidable negative outcomes (e.g., small birth weight, high anxiety); however, a biased underestimate of the adaptive potential of MDS‐induced effects is possible if they are not viewed within an ecologically relevant or a life‐history optimization framework. We review the ecological and environmental drivers of MDS, how MDS signals are transferred to offspring, and what responses MDS induces. Results from four free‐living vertebrate systems reveals that although MDS induces seemingly negative investment trade‐offs in offspring, these phenotypic adjustments can be adaptive if they better match the offspring to future environments; however, responses can prove maladaptive if they unreliably predict (i.e., are mismatched to) future environments. Furthermore, MDS‐induced adjustments that may prove maladaptive for individual offspring can still prove adaptive to mothers by reducing current reproductive investment, and benefitting lifetime reproductive success. We suggest that to properly determine the adaptive potential of MDS, researchers must take a broader integrated life‐history perspective, appreciate both the immediate and longer term environmental context, and examine lifetime offspring and maternal fitness.     

Effects of solar ultraviolet radiation on the potential efficiency of photosystem II in leaves of tropical plants

The effects of solar ultraviolet (UV)-B and UV-A radiation on the potential efficiency of photosystem II (PSII) in leaves of tropical plants were investigated in Panama (9°N). Shade-grown tree seedlings or detached sun leaves from the outer crown of mature trees were exposed for short periods (up to 75 min) to direct sunlight filtered through plastic or glass filters that absorbed either UV-B or UV-A+B radiation, or transmitted the complete solar spectrum. Persistent changes in potential PSII efficiency were monitored by means of the dark-adapted ratio of variable to maximum chlorophyll a fluorescence. In leaves of shade-grown tree seedlings, exposure to the complete solar spectrum resulted in a strong decrease in potential PSII efficiency, probably involving protein damage. A substantially smaller decline in the dark-adapted ratio of variable to maximum chlorophyll a fluorescence was observed when UV-B irradiation was excluded. The loss in PSII efficiency was further reduced by excluding both UV-B and UV-A light. The photoinactivation of PSII was reversible under shade conditions, but restoration of nearly full activity required at least 10 d. Repeated exposure to direct sunlight induced an increase in the pool size of xanthophyll cycle pigments and in the content of UV-absorbing vacuolar compounds. In sun leaves of mature trees, which contained high levels of UV-absorbing compounds, effects of UV-B on PSII efficiency were observed in several cases and varied with developmental age and acclimation state of the leaves. The results show that natural UV-B and UV-A radiation in the tropics may significantly contribute to photoinhibition of PSII during sun exposure in situ, particularly in shade leaves exposed to full sunlight.