The ecosystem and evolutionary contexts of allelopathy

Plants can release chemicals into the environment that suppress the growth and establishment of other plants in their vicinity, a process known as ‘allelopathy’. However, chemicals with allelopathic functions have other ecological roles, such as plant defense, nutrient chelation, and regulation of soil biota in ways that affect decomposition and soil fertility. These ecosystem-scale roles of allelopathic chemicals can augment, attenuate or modify their community-scale functions. In this review we explore allelopathy in the context of ecosystem properties, and through its role in exotic invasions consider how evolution might affect the intensity and importance of allelopathic interactions

Potent endogenous allelopathic compounds in Lepidium sativum seed exudate: effects on epidermal cell growth in Amaranthus caudatus seedlings

Many plants exude allelochemicals – compounds that affect the growth of neighbouring plants. This study reports further studies of the reported effect of cress (Lepidium sativum) seed(ling) exudates on seedling growth in Amaranthus caudatus and Lactuca sativa. In the presence of live cress seedlings, both species grew longer hypocotyls and shorter roots than cress-free controls. The effects of cress seedlings were allelopathic and not due to competition for resources. Amaranthus seedlings grown in the presence of cress allelochemical(s) had longer, thinner hypocotyls and shorter, thicker roots – effects previously attributed to lepidimoide. The active principle was more abundant in cress seed exudate than in seedling (root) exudates. It was present in non-imbibed seeds and releasable from heat-killed seeds. Release from live seeds was biphasic, starting rapidly but then continuing gradually for 24 h. The active principle was generated by aseptic cress tissue and was not a microbial digestion product or seed-treatment chemical. Crude seed exudate affected hypocotyl and root growth at ∼25 and ∼450 μg ml(−1) respectively. The exudate slightly (28%) increased epidermal cell number along the length of the Amaranthus hypocotyl but increased total hypocotyl elongation by 129%; it resulted in a 26% smaller hypocotyl circumference but a 55% greater epidermal cell number counted round the circumference. Therefore, the effect of the allelochemical(s) on organ morphology was imposed primarily by regulation of cell expansion, not cell division. It is concluded that cress seeds exude endogenous substances, probably including lepidimoide, that principally regulate cell expansion in receiver plants

Effects of an allelochemical in Phaeodactylum tricornutum filtrate on Heterosigma akashiwo : morphological, physiological and growth effects

© The Author(s), 2017. This is the author's version of the work. It is posted here under a nonexclusive, irrevocable, paid-up, worldwide license granted to WHOI. It is made available for personal use, not for redistribution. The definitive version was published in Chemosphere 186 (2017): 527-534, doi:10.1016/j.chemosphere.2017.08.024.The effects of an allelochemical extracted from the culture filtrate of diatom Phaeodactylum tricornutum on the raphidophyte Heterosigma akashiwo were investigated using a series of morphological, physiological and biochemical characters. Growth experiments showed that H. akashiwo was significantly inhibited immediately after exposure to the allelochemical, with many cells rapidly dying and lysing based on microscopic observation. The effects of the allelochemical on the surviving cells were explored using Scanning Electron Microscopy (SEM) and Flow cytometry (FCM), the latter by examination of a suite of physiological parameters (membrane integrity, esterase activity, chlorophyll-a content, membrane potential). The results demonstrate that the membrane of H. akashiwo was attacked by the allelochemical directly, causing cell membrane breakage and loss of integrity. Esterase activity was the most sensitive indicator of the impacts of the allelochemical. Membrane potential and chlorophyll-a content both showed significant decreases following exposure of the Heterosigma cells to high concentrations of the allelochemical for 5 and 6 days. Both were affected, but the membrane potential response was more gradual compared to other effects. The cell size of H. akashiwo did not change compared with the control group. The surviving cells were able to continue to grow and in a few days, re-establish a successful culture, even in the presence of residual allelochemical, suggesting either development of cellular resistance, or the degradation of the chemical.The authors wish to thank the National Programme on Global Change and Air-Sea Interaction (Grant No. GASI-03-01-02-01); the National Key Research and Development Program [Grant No. 2016YFC1402101]; the assessment of nanomaterials on biological and ecological effects in the coastal area (Grant No. 201505034)

Differential Suitability of 12 Great Lakes Tree Species for \u3ci\u3ePapilio Canadensis\u3c/i\u3e (Lepidoptera: Papilionidae) Larval Survival and Growth

Differential nutritional suitabilities of the 12 potential host plants of Papilio canadensis in the Great Lakes region of North America were determined with gravimetric techniques for penultimate and final larval instars. While leaf water content and leaf nitrogen content explain some of the variation, allelochemicals in different plants are likely to be involved in differential larval growth performances as well as mortal- ity of neonate larvae on tuliptree and spicebush. Oviposition tests using 3-choice arenas with quaking aspen, paper birch, and balsam poplar showed no strong host preferences. Factors affecting patterns of Papilio host use in the Great Lakes region are discussed

Compensatory Feeding and Growth Responses of \u3ci\u3ePapilio Glaucus\u3c/i\u3e (Lepidoptera: Papilionidae) Larvae Reared in Darkness.

The goal was to determine the potential impact of photoperiod on feeding behavior and larval growth rates. Larvae from six different families of the eastern swallowtail butterfly, Papilio glaucus L. (Lepidoptera: Papilionidae) were placed into 3 different photoperiod regimes (long days at 18:6 h, short days at 12:12 h, and total darkness at 0:24 h, all at 27°C) as neonate first instars and reared to pupation. The initial 11 days reflected very slow growth of the larvae in darkness (only half the weight of the long day larvae). No differences in survival at 4 days or 11 days or until pupation were evident between any treatments. Average time to pupation ( = total larval duration) was statistically identical between the treatments. However, despite their slow start during the first two instars, the larvae in complete darkness were able to increase their growth rates in the final 3 instars to such magnitude that they grew to the same final pupal size as those in the long day (and bigger than those in the short day) treatments. Such compensatory feeding and growth as a result of photoperiod has not previously been reported. Potential additional causes for such behavioral/physiological compensatory growth rates in caterpillars of other species are discussed

Mathematical Modeling of Allelopathy. III. A Model for Curve-Fitting Allelochemical Dose Responses

Bioassay techniques are often used to study the effects of allelochemicals on plant processes, and it is generally observed that the processes are stimulated at low allelochemical concentrations and inhibited as the concentrations increase. A simple empirical model is presented to analyze this type of response. The stimulation-inhibition properties of allelochemical-dose responses can be described by the parameters in the model. The indices, p% reductions, are calculated to assess the allelochemical effects. The model is compared with experimental data for the response of lettuce seedling growth to Centaurepensin, the olfactory response of weevil larvae to α-terpineol, and the responses of annual ryegrass (Lolium multiflorum Lam.), creeping red fescue (Festuca rubra L., cv. Ensylva), Kentucky bluegrass (Poa pratensis L., cv. Kenblue), perennial ryegrass (L. perenne L., cv. Manhattan), and Rebel tall fescue (F. arundinacea Schreb) seedling growth to leachates of Rebel and Kentucky 31 tall fescue. The results show that the model gives a good description to observations and can be used to fit a wide range of dose responses. Assessments of the effects of leachates of Rebel and Kentucky 31 tall fescue clearly differentiate the properties of the allelopathic sources and the relative sensitivities of indicators such as the length of root and leaf. allelopathyallelochemicalsmathematical modellingstimulationdose-response relationshipinverted U-shape response

Intra and interspecific competition via allelopathy among native and non-native plants

Invasive non- native species success often is attributed to their competitive superiority, potentially through allelochemical inhibition (allelopathy) of native species, as suggested by the novel weapons hypothesis. However, it is also possible that non- native species are able to be successful through decreased intraspecific competition. Decreased intraspecific competition could be attributed to a lack of genetic variation creating less variable allelopathic effects. I predict that if non- native species follow the novel weapons hypothesis, their allelochemicals will restrict more biomass and give them a competitive edge compared to native species. Additionally, I predict that if non- native species have lower intraspecific genetic variation, non- native species will have less variation of allelopathic effects than natives. Furthermore, if non- native plant invasion is driven by allelopathy, I expect greater inhibitory effects of non- native than native plants. I conducted a greenhouse experiment to compare the competitive allelopathy of the non- native and native plants. This experiment involved assessing the restricted growth of non- native and native plant pairs (shrub or tree) in both intra- and inter-specific competition, with allelochemical extracts applied. Additionally, I conducted a laboratory bioassay experiment to evaluate the variability of allelopathic effects on model seed germination and growth using field- collected non- native and native leaf samples. My results showed little evidence that non- native invasive plants in Western New York possess particular novel or stronger allelopathic effects compared to native plants. Allelopathic effects did not vary based on invasive status, and non- native allelochemicals did not inhibit model seeds more than native allelochemicals. These findings suggest that native allelochemicals could be just as prominent as those from non- native species

The Effect of Accumulation of Leaf Litters and Allelochemicals in the Soil to the Sustainability of the Newly Introduced Crop Plants

Indonesia is the second-largest vanilla production and the third-largest cocoa production in the world, but it sustained for a short period. The unsustainability of these crops is speculated to occur because of the change in leaf litter accumulation which affected the sustainability of soil organic carbon that plays an important role in maintaining soil health and fertility. To find out methods that could improve the sustainability of the production, a literature review was conducted. The articles, related to the sustainability of vanilla and cacao production, were collected using Google Scholar, Wiley Online Library, ResearchGate, and Google Chrome browser. Keywords were employed to find the articles includingsoil organic carbon, cocoa plantation, vanilla, leaf litter, and allelochemical. This current article review foundthat introducing crop by clearing of previously existing vegetation could severely reduce the rate of leaf litter accumulation.  Consequently, in a prolonged period, the soil organic carbon and soil fertility are very low and are unable to support the healthy growth and production of the crops.  To restore production, the plantation then is returned to more traditional agroforestry such as replanting shading trees and addition of mulch. However, in the higher density of canopy, the crop production is low attributed partly to the decreasing soil pH which increases the impact of allelochemical. This review concluded that the sustainability of leaf litter accumulation is crucial to maintain soil health, but mitigation is required to reduce the impact of allelochemical accumulation.

Algal polyunsaturated fatty acids and effects on plankton ecology and other organisms

A review and discussion of the effects of algal polyunsaturated fatty acids (PUFAs) on phytoplankton and zooplankton ecology and their effects on other animal systems. Topics discussed also include the relationship of cyanobacterial classification to PUFA occurrence, lipid concentrations occurring in the aqueous environment, the general effect of microalgae on zooplankton, and how algal PUFAs may be exerting their inhibitory and toxic effects