Potential phytotoxic and shading effects of invasive Fallopia (Polygonaceae) taxa on the germination of dominant native species

Two species of the genus Fallopia (F. sachalinensis, F. japonica, Polygonaceae) native to Asia, and their hybrid (F. ×bohemica), belong to the most noxious plant invaders in Europe. They impact highly on invaded plant communities, resulting in extremely poor native species richness. The low number of native species in invaded communities points to the possible existence of mechanisms suppressing their germination. In this study we assessed, under laboratory conditions, whether there are phytotoxic effects of the three Fallopia congeners on seed germination of three target species: two native species commonly growing in habitats that are often invaded by Fallopia taxa (Urtica dioica, Calamagrostis epigejos), and Lepidium sativum, a species commonly used in allelopathic bioassays as a control. Since Fallopia taxa form dense stands with high cover, we included varying light conditions as an additional factor, to simulate the effects of shading by leaf canopy on germination. The effects of aqueous extracts (2.5%, 5.0%, and 0% as a control) from dry leaves and rhizomes of the Fallopia congeners on germination of the target species were thus studied under two light regimes, simulating full daylight (white light) and light filtered through canopy (green light), and in dark as a control regime. Rhizome extracts did not affect germination. Light treatments yielded inconclusive results, indicating that poor germination and establishment of species in invaded stands is unlikely to be caused by shading alone. However, we found a pronounced phytotoxic effect of leaf extracts of Fallopia taxa, more so at 5.0% than 2.5% extract concentration. Fallopia sachalinensis exerted the largest negative effect on the germination of Urtica dioica, F. ×bohemica on that of C. epigejos, and F. japonica had invariably the lowest inhibitory effect on all test species. The weak phytotoxic effect of F. japonica corresponds to the results of previous studies that found this species to be generally a weaker competitor than its two congeners. Although these results do not necessarily provide direct evidence for allelopathic effects in the field, we demonstrate the potential phytotoxic effect of invasive Fallopia taxa on the germination of native species. This suggests that allelopathy may play a role in the impact of Fallopia invasion on species diversity of invaded communities

Potential phytotoxic and shading effects of invasive Fallopia (Polygonaceae) taxa on the germination of dominant native species

Two species of the genus Fallopia (F. sachalinensis, F. japonica, Polygonaceae) native to Asia, and their hybrid (F. ×bohemica), belong to the most noxious plant invaders in Europe. They impact highly on invaded plant communities, resulting in extremely poor native species richness. The low number of native species in invaded communities points to the possible existence of mechanisms suppressing their germination. In this study we assessed, under laboratory conditions, whether there are phytotoxic effects of the three Fallopia congeners on seed germination of three target species: two native species commonly growing in habitats that are often invaded by Fallopia taxa (Urtica dioica, Calamagrostis epigejos), and Lepidium sativum, a species commonly used in allelopathic bioassays as a control. Since Fallopia taxa form dense stands with high cover, we included varying light conditions as an additional factor, to simulate the effects of shading by leaf canopy on germination. The effects of aqueous extracts (2.5%, 5.0%, and 0% as a control) from dry leaves and rhizomes of the Fallopia congeners on germination of the target species were thus studied under two light regimes, simulating full daylight (white light) and light filtered through canopy (green light), and in dark as a control regime. Rhizome extracts did not affect germination. Light treatments yielded inconclusive results, indicating that poor germination and establishment of species in invaded stands is unlikely to be caused by shading alone. However, we found a pronounced phytotoxic effect of leaf extracts of Fallopia taxa, more so at 5.0% than 2.5% extract concentration. Fallopia sachalinensis exerted the largest negative effect on the germination of Urtica dioica, F. ×bohemica on that of C. epigejos, and F. japonica had invariably the lowest inhibitory effect on all test species. The weak phytotoxic effect of F. japonica corresponds to the results of previous studies that found this species to be generally a weaker competitor than its two congeners. Although these results do not necessarily provide direct evidence for allelopathic effects in the field, we demonstrate the potential phytotoxic effect of invasive Fallopia taxa on the germination of native species. This suggests that allelopathy may play a role in the impact of Fallopia invasion on species diversity of invaded communities

Plant propagation by seedage, cuttage, layerage and separation

Caption title.Digitized 2006 AES MoU

Laboratory and field evaluations of propolis as a plant protective agent : a thesis submitted in partial fulfilment of the requirement for the degree of Master of Horticultural Science at Massey University

Propolis is a plant derived resinous substance with known antibiotic properties. Laboratory and field trials were carried out in 1989/90 to evaluate propolis for control of insects and diseases in horticultural systems. Field trials were carried out in the organic block of Levin Horticultural Research Station. Ether extracts of propolis in agar (10, 100 1 000 and 10 000 ppm) were screened against 20 plant pathogenic fungi. Radial mycelial growth from fungal plugs were measured daily. Propolis inhibited the growth of all fungi tested although the sensitivity of fungi to propolis varied. The EC50 was between 100 and 10 000 ppm for all species with complete inhibition at 10 000 ppm in 16 species. Propolis collected from different geographic locations had different activity. There was less antifungal activity in water extracts than in ether extracts of propolis. Ethanol, surfactant and ethanol extracts of propolis were sprayed on cucumber plants weekly in a glasshouse. Weekly estimates of powdery mildew cover (Erysiphe cichoracearum) for 5 weeks were analysed. Foliar spray applications of 1% propolis extract reduced powdery mildew cover from 84.5% in the untreated plants to 33.4% in the treated ones. Eight treatments were tested on a 10 day spray calendar on zuccinis. Assessment for powdery mildew cover was made on four occassions. The number of harvested fruit from each plant were recorded. A 1% ethanol extract of propolis reduced powdery mildew only until the second assessment, 39% vs. 60% cover in the controls. The fruit number was not affected by treatments. Late blight of tomatoes (Phytophthora infestans) in the field was not affected by foliar sprays of 1% propolis extract. Radish seeds treated with a seed dressing of 36% propolis extract were not protected against (Pythium ultimum) in agar petri plate trials Laboratory screening of propolis against light brown apple moth (Epiphyas postvittana) and green peach aphid (Myzus persicae) did not indicate sufficient activity to be used in crop protection. In conclusion propolis showed some antifungal activity in laboratory trials. Successful applications in the field using the methods evaluated here however would require concentrations of raw propolis that are both impractical and uneconomic. The potential for use of propolis in plant protection is likely to come from further chemical analysis, with identification of active components and their possible synthesis. Key words: propolis, fungicide, insecticide, Phytophthora infestans, late blight of tomatoes, Erysiphe cichoracearum, powdery mildew of cucurbits, Pythium ultimum, damping off, light brown apple moth (Epiphyas postvittana), green peach aphid (Myzus persicae)

Wood Anatomy of Gnetales in a Functional, Ecological, and Evolutionary Context

New scanning electron microscope (SEM) and light microscope data and illustrations are presented in order to compare hydraulic adaptations of non-gnetalean conifers and angiosperms to relevant wood features of Gnetales. Gnetales have essentially all of the adaptations of both groups, yet have not competed well, despite predating angiosperms in origin and radiation. Angiosperms may be advantaged more by life cycle abbreviation and by heterochronic possibilities than by wood features. Wood features of Gnetales that relate to conduction (torus-margo differentiation of tracheid pit membranes, distribution of tori within the wood, perforation plate simplification, growth rings, vesturing, helical thickenings, and axial parenchyma) are reviewed in the light of recent work that demonstrates the physiological significance of these features in angiosperms. The various xylary adaptations of Ephedra, Gnetum, and Welwitschia are analyzed in terms of conductive efficiency versus conductive safety, and in turn, compared to the habitats of the three genera, respectively: Ephedra and Welwitschia survive in rather extreme habitats, whereas Gnetum competes in mesic forest by what may be minor shifts among basically similar niches. Gnetales have essentially all of the wood anatomical advantages of angiosperms, except for ability to shift degrees of wood anatomical juvenilism or adulthood—an important angiosperm advantage. The relatively lengthy life cycle of Gnetales, requiring female gametophyte formation prior to embryo formation (vs. simultaneous endosperm and embryo development in angiosperms) and the related requirement for at least several years\u27 growth prior to seed formation are probably the prime reasons for lack of gnetalean success. Wood features should be interpreted as adapted to the present-day ecology of a woody species, and ideas that evolutionary flexibility to shift into more seasonal conditions is hindered by rigid wood formulas (which actually can change rather rapidly) should be questioned. Wood evolution of Gnetales, like that of angiosperms, can be regarded as a series of shifts in the trade-offs between conductive efficiency and conductive safety

The effect of two ectomycorrhizal fungi, Paxillus involutus and Suillus tomentosus, and of Bacillus subtilis on Fusarium damping-off in jack pine seedlings

On a testé l'effet de deux espèces de champignons ectomycorhiziens, le Paxillus involutus et le Suillus tomentosus, et une lignée de la bactérie Bacillus subtilis sur le Fusarium moniliforme, agent pathogène de la fonte des semis du pin gris (Pinus banksiana). Le P. involutus et B. subtilis ont tous les deux inhibé la croissance in vitro du F moniliforme. Les filtrats de culture de P. involutus et de B. subtilis ont été toxiques pour le F moniliforme, mais la formation de chlamydospores par le F moniliforme a été observée. Une meilleure survie des plantules a été observée lorsqu'elles étaient co-inoculées avec le P. involutus et le B. subtilis plutôt qu'avec le F moniliforme seulement. Le S. tomentosus n'a pas inhibé la croissance in vitro du F. moniliforme ni accru la survie des plantules de pin gris en présence de F moniliforme. Ce dernier a réduit la formation d'ectomycorhizes sur le pin gris par le P. involutus et le S. tomentosus. Le nombre d’unités formatrices de colonies du F. monoliforme a été significativement réduit quand les plantules ont été inoculées avec le P. involotus ou le B. subtilis seul ou en combinaison. D’autre part, le S. tomentosus n’a pas réduit le nombre d’unités formatrices de colonies du F. monoliforme. La suppression de la croissance du F. monoliforme par le P. involutus et le B. subtilis a entraîné la production de composés antifongiques.Two species of ectomycorrhizal fungi, Paxillus involutus and Suillus tomentosus, and a bacterial strain of Bacillus subtilis, were tested against Fusarium moniliforme, the causal agent of damping-off in jack pine (Pinus banksiana) seedlings. Both P. involutus and B. subtilis inhibited in vitro growth of F moniliforme. The culture filtrates of P. involutus and B. subtilis were toxic to F moniliforme, but chlamydospore formation of F moniliforme was observed. Greater jack pine seedling survival was observed when co-inoculated with P. involutus and B. subtilis than with F moniliforme alone. S. tomentosus neither inhibited in vitro growth of F moniliforme nor increased survival of jack pine seedlings against F moniliforme. F moniliforme reduced ectomycorrhiza formation on jack pine seedlings by P. involutus and S. tomentosus. The number of colony forming units of F moniliforme was significantly reduced when seedlings were inoculated with P. involutus and B. subtilis alone or in combination. S. tomentosus, on the other hand, did not reduce the number of colony forming units of F moniliforme. The suppression of F moniliforme growth by P. involutus and B. subtilis involved production of antifungal compounds