Diversity of resident plant communities could weaken their allelopathic resistance against alien and native invaders

Elton’s classic diversity-invasibility hypothesis posits that diversity of resident communities increases resistance against invaders. We tested whether the diversity-invasibility relationsip might be mediated by allelopathic effects of the resident species. In a large germination experiment, we exposed seeds of six alien and six native test species to leachates of one, three, six or twelve species. The leachates tended to slightly delay germination, and almost all single-species leachates reduced the proportion of germinated seeds. Nevertheless, the overall effect of the plant leachate mixtures on the proportion of germinated seeds was not significant. This was because a higher diversity of the leachates increased the proportion of germinated seeds, particularly for native test species. Among the six alien test species, it was only the most invasive one that benefited from increased diversity of the leachates, just like the natives did. Overall, our findings suggest that allelopathy of diverse communities does not provide resistance but could actually facilitate the germination of invaders.

Horizontal orientation facilitates pollinator attraction and rain avoidance in radially symmetrical flowers

PremiseFloral angle, such as upward, horizontal, and downward orientation are known to evolve under both biotic and abiotic agents to enhance pollination success in zoophilious plants. Adaptive significance of horizontal orientation in radially symmetrical (actinomorphic) flowers under biotic and abiotic selection pressures were largely unknown, although those in bilaterally symmetrical flowers have been well studied.MethodsUsing experimentally angle changed flowers, we examined the effects of flower angle on pollinator behaviors, pollination success and rain avoidance in a population of insect-pollinated Platycodon grandiflorus. We further investigated the frequency and amount of precipitation in the flowering season and pollen damage by water in this species. Main results: Horizontally oriented flowers received more visitations and pollen grains on the stigma in male and/or female phases than downward and/or upward oriented flowers and avoided pollen damage by rainfall compared to upward oriented flowers. The pollen germination experiment showed that approximately 30% of pollen grains burst in distilled water, thus pollen damage by rainfall was potentially serious in P. garndiflorus.ConclusionIn this study, our field experiments revealed that upward flowers cannot avoid damage from rainfall during the flowering period whereas both upward and downward flowers suffered from pollinator limitation in female success. Thus, horizontal flower orientation is suggested to be adaptive in this insect-pollinated actinomorphic species which blooms in the rainy season.

Allelopathic and competitive interactions between native and alien plants

The novel-weapons and homeland-security hypotheses are based on the idea that aliens and natives are not adapted to each other’s allelochemicals as they did not co-evolve. However, as only a few studies have tested this, it remains unclear how important co-evolutionary history is in determining the strength of allelopathic interactions between aliens and natives. Here, we tested for potential pairwise allelopathic effects on each other of five alien and five native herbaceous species in China. We did a germination experiment and a competition experiment. In the germination experiment, we tested whether aqueous extracts of the ten study species had allelopathic effects on each other’s seed germination. In the competition experiment, we tested whether the alien and native species differed in their competitive effects and responses, and whether these were changed by the presence of activated carbon—a presumed allelopathy neutralizer– in the soil. Plant extracts had negative allelopathic effects on seed germination. This was particularly the case for extracts from the native species. Moreover, aqueous extracts had slightly stronger negative effects on germination of the aliens than on germination of the natives. In the competition experiment, on the other hand, the natives suffered more from competition than the alien species did, but we could not relate this to allelopathy. Alien plants had negative competitive and allelopathic effects on native plants, but the reverse was also true. These alien-native interactions, however, were not consistently stronger or weaker than native-native or alien-alien interactions.

Rapid continental spread of a salt-tolerant plant along the European road network

The spread of alien species with the expansion of road networks and increasing traffic is a well-known phenomenon globally. Besides their corridor effects, road maintenance practices, such as the use of de-icing salts during winter facilitate the spread of halophyte (salt tolerant) species along roads. A good example is Plantago coronopus, a mainly coastal halophyte which has started spreading inland from the Atlantic and Mediterranean coastal habitats, recently reaching even Central European countries (e.g. Hungary). Here we studied the spread of this halophyte and tried to identify factors explaining its successful dispersion along roads, while also comparing native and non-native roadside occurrences with regard to altitude of the localities, size of roadside populations and frequency of roadside occurrences. We completed a comprehensive literature review and collected more than 200 reports of occurrence from roadsides spanning a total of 38 years. During systematic sampling the frequency of the species along roads was significantly higher in the Mediterranean (native area), than along Hungarian (non-native area) roads, however the average number of individuals at the sampling localities were very similar, and no significant difference could be detected. Using a germination experiment, we demonstrate that although the species is able to germinate even at high salt concentrations, salt is not required for germination. Indeed salt significantly decreases germination probability of the seeds. The successful spread of the species could most likely be explained by its remarkably high seed production, or some special characteristics (e.g. seed dimorphism) and its ability to adapt to a wide range of environmental conditions. Considering the recent and rapid eastward spread of P. coronopus, occurrences in other countries where it has not been reported yet can be predicted in coming years.

The sediment akinete bank links past and future blooms of Nostocales in a shallow lake

In this paper we analyzed how well the akinete bank in the sediments from a shallow lake reflected past blooms of planktonic Nostocales (cyanobacteria), the akinete bank’s potential for reflecting future blooms and whether different nutrient scenarios affect germination and recruitment using a laboratory experiment. Most species found in the plankton were also found in the akinete bank and in the germination experiment. Based on their shape, the most abundant viable akinetes in the sediments potentially corresponded to some of the species forming intense blooms in previous years, and coincided with the most abundant species in a 3-week germination experiment. The effects of nutrients on germination and recruitment were only observed in the early phase of the life cycle (Day 7), where nitrogen-sufficient conditions enhanced germination, while phosphorus concentration had a positive effect on the number of heterocytes. Combined approaches of morphological analysis and experimental germination seem a good method for assessing the past diversity of Nostocales and allowing predictions of the diversity of potential future blooms in shallow lakes and as a tool for water quality management, especially in water bodies lacking information on previous cyanobacteria blooms.

Enhanced Selective Removal of Cd(II) by an Amino-Functional Water-Retaining Agent Incorporating Nano Hydrous Manganese Oxide

An amino-functionalized water-retaining agent (PPM40-NH2) and a water-retaining agent lacking functionalization (PPM40) were prepared to investigate their selective Cd(II) removal properties. The affinity for Cd(II) was increased after introducing the amino functional group. The SFCd/Ca of PPM40-NH2 was 3–7 fold higher than that of PPM40 although the CCa was 100–1000 times higher than that of CCd. The chelating effect of –COOH and –NH2 in PPM40-NH2 corresponded well with the selective adsorption of Cd(II), as confirmed by simulations. A seed germination experiment demonstrated that PPM40-NH2 could act as a filter of heavy metals to supply “clean” water for the roots of the pakchoi plant. The leaching experiment indicated that PPM40-NH2 is an efficient in situ fixation agent for the remediation of agricultural soil contaminated with Cd(II) in the presence of high concentrations of Ca(II) salts.

Seed-borne pathogenic fungi on some soybean varieties

Soesanto L, Hartono ARR, Mugiastuti E, Widarta H. 2020. Seed-borne pathogenic fungi on some soybean varieties. Biodiversitas 21: 4010-4015. The present study was conducted to detect and identify seed-borne pathogenic fungi in some soybean varieties and their effect on seed germination. Experiment was performed in a completely random design with eight treatments and four replicates. Eight soybean varieties i.e., Malabar, Kaba, Dering, Detam I, Sinabung, Dena, Gepak Kuning, and Slamet were selected for the investigation. Seed borne fungi were isolated using blotter test and agar plate techniques. The variables observed were morphological/cultural characteristics, microscopic features of fungi, and percentage of seed germination. A total of eight fungi namely Aspergillus flavus Link, Aspergillus niger van Tieghem, Cladosporium oxysporum Berk. & M.A. Curtis, Colletotrichum dematium (Pers. et Fr.) Grove f.sp. truncate (Schw.) Arx, Curvularia pallescens Boedijn, Fusarium solani (Mart.) Sacc., Melanospora zamiae Corda, and Nigrospora sp. Mason were isolated from different varieties of soybean seeds. The highest seed germination was found to be 80.5% in Daring and Detam I varieties, respectively, and the lowest 53% was recorded in Dena variety.

Analyses of Hybrid Viability across a Hybrid Zone between Two Alnus Species Using Microsatellites and cpDNA Markers

Diploid Alnus glutinosa s. str. and autotetraploid A. rohlenae form a narrow hybrid zone in a study area in southern Serbia, which results in triploid hybrid formation. The vast majority of previous studies have been focused on studies of maternal plants, but the offspring resulting from their crossing have not been much studied. Here, we use the variability of microsatellites and chloroplast DNA between these species and their putative hybrids to create an overall picture of the development of the hybrid zone and its predicted type. To elucidate the gene transfer within both species, the origins of individual ploidies and especially the role of triploid hybrids, a germination experiment was carried out linked with a flow cytometry study of the resulting seedlings. The tension zone model seems to offer the most adequate explanation of our observations, with selection against triploid hybrids and the spatial positioning of the hybrid zone. Despite selection against them, the triploid hybrids play an important role in the exchange of genes between the two species and therefore serve as a bridge for introgression. The presence of fertile triploids is essential for enriching the haplotype diversity between these species and for the development of new genetic lineages.

Does the substrate affect the germination of soybean seeds treated with phytosanitary products?

ABSTRACT The use of an appropriate method that accurately expresses physiological seed quality and minimizes possible phytotoxicity by chemical products in laboratory testing with soybean seeds is relevant. The objective of this work was to evaluate the influence and infer the method adequacy for the representative evaluation of physiological quality of soybean seeds treated with phytosanitary products. Two experiments were carried out in a completely randomized design, with trial 1 in a 9×5 factorial scheme involving nine seed treatments, including fungicides and insecticides, and solutions with five osmotic potentials (0, -0.25, -0.5, -0.75 and -1.0 MPa) for wetting a paper substrate in a germination experiment, with evaluation of the normal seedlings at five and eight days after sowing. The second experiment consisted of a 9×7 factorial, with nine seed treatments and seven methods for germination evaluation at 5 days (between paper - BP, between sand - BS, between paper with water restriction - BPWR, between paper with preconditioning - BPC, sand between paper - SBP and vermiculite between paper - VBP). Treatments with insecticides affect seedling germination and evaluation, with greater phytotoxicity in relation to fungicides. Methods with readily available water led to greater phytotoxicity than methods with low water availability. For soybean germination evaluation of seeds treated with phytosanitary products, the BPC, SBP and VBP methods were optimal.