Valorization of Cladophora glomerata Biomass and Obtained Bioproducts into Biostimulants of Plant Growth and as Sorbents (Biosorbents) of Metal Ions.

The aim of this study was to propose a complete approach for macroalgae biomass valorization into products useful for sustainable agriculture and environmental protection. In the first stage, the effects of macroalgal extracts and ZnO NPs (zinc oxide nanoparticles) on the germination and growth of radish were examined. Macroalgal extract was produced from freshwater macroalga, i.e., Cladophora glomerata by ultrasound assisted extraction (UAE). The extract was used to biosynthesize zinc oxide nanoparticles. In germination tests, extracts and solutions of ZnO NPs were applied on paper substrate before sowing. In the second stage, sorption properties of macroalga, post-extraction residue, and ZnO NPs to absorb Cr(III) ions were examined. In the germination tests, the highest values of hypocotyl length (the edible part of radish), i.e., 3.3 and 2.6 cm were obtained for 60 and 80% extract (among the tested concentrations 20, 40, 60, 80, and 100%) and 10 and 50 mg/L NPs, respectively. The highest sorption capacity of Cr(III) ions (344.8 mg/g) was obtained by both macroalga and post-extraction residue at a pH of 5 and initial Cr(III) ions concentration of 200 mg/L. This study proves that macroalgae and products based on them can be applied in both sustainable agriculture and wastewater treatment.

Identification of Maize Kernel Vigor under Different Accelerated Aging Times Using Hyperspectral Imaging.

Seed aging during storage is irreversible, and a rapid, accurate detection method for seed vigor detection during seed aging is of great importance for seed companies and farmers. In this study, an artificial accelerated aging treatment was used to simulate the maize kernel aging process, and hyperspectral imaging at the spectral range of 874⁻1734 nm was applied as a rapid and accurate technique to identify seed vigor under different accelerated aging time regimes. Hyperspectral images of two varieties of maize processed with eight different aging duration times (0, 12, 24, 36, 48, 72, 96 and 120 h) were acquired. Principal component analysis (PCA) was used to conduct a qualitative analysis on maize kernels under different accelerated aging time conditions. Second-order derivatization was applied to select characteristic wavelengths. Classification models (support vector machine-SVM) based on full spectra and optimal wavelengths were built. The results showed that misclassification in unprocessed maize kernels was rare, while some misclassification occurred in maize kernels after the short aging times of 12 and 24 h. On the whole, classification accuracies of maize kernels after relatively short aging times (0, 12 and 24 h) were higher, ranging from 61% to 100%. Maize kernels with longer aging time (36, 48, 72, 96, 120 h) had lower classification accuracies. According to the results of confusion matrixes of SVM models, the eight categories of each maize variety could be divided into three groups: Group 1 (0 h), Group 2 (12 and 24 h) and Group 3 (36, 48, 72, 96, 120 h). Maize kernels from different categories within one group were more likely to be misclassified with each other, and maize kernels within different groups had fewer misclassified samples. Germination test was conducted to verify the classification models, the results showed that the significant differences of maize kernel vigor revealed by standard germination tests generally matched with the classification accuracies of the SVM models. Hyperspectral imaging analysis for two varieties of maize kernels showed similar results, indicating the possibility of using hyperspectral imaging technique combined with chemometric methods to evaluate seed vigor and seed aging degree.

Decline in RNA integrity of dry-stored soybean seeds correlates with loss of germination potential.

This study investigates the relationship between germination ability and damage to RNA in soybean seeds (cv 'Williams 82') stored dry at 5 °C for 1-27 years. Total germination of 14 age cohorts harvested between 2015 and 1989 ranged from 100% to 3%. Germination decline followed classic seed viability kinetics, with symptomatic seed aging beginning after 17 years of storage. RNA integrity was assessed in dry seeds by electrophoresis of total RNA, followed by calculation of the RNA integrity number (RIN, Agilent Bioanalyzer software), which evaluates RNA fragment size distributions. Analysis of RNA extracted from cotyledons, embryonic axes, plumules, and seed coats across the range of age cohorts showed consistent RNA degradation: older seeds had over-representation of small RNAs compared with younger seeds, which had nearly a 2:1 ratio of 25S and 18S rRNAs. RIN values for cotyledons and embryonic axes from the same seed were correlated. Decline in RIN tracked reduced germination, with a pronounced decrease in RIN after 17 years of storage. This led to a high correlation between the mean RIN of cotyledon RNA and the total germination percentage (R2=0.91, P<0.0001). Despite this relationship, germinable and non-germinable seeds within cohorts could not be distinguished unless the RIN was <3.5, indicating substantial deterioration. Our work demonstrates that seed RNA incurs damage over time, observable in fragment size distributions. Under the experimental conditions used here, RIN appears to be a promising surrogate for germination tests used to monitor viability of stored seeds.

Ecotoxicological evaluation of an aqueous phytoextract of Melia azedarach L.

Melia azedarach L. is a Meliaceae that has shown important insecticidal activities. However, few researchers have extensively studied the toxicology of aqueous extracts of M. azedarach (MAE). Therefore, the main objective of this study was to characterize the phyto-eco-toxicological profile of MAE. First, a botanical and phytochemical characterization of MAE was performed using a histological, and metabolomic multi-analytical approach. Second, the toxicological effects on pollinating insects (Apis mellifera ligustica) and soil collembola (Folsomia candida) were evaluated. In addition, acute toxicity was evaluated in zebrafish (Danio rerio) to assess effects on aquatic fauna, and toxicity was determined in human neuroblastoma (SH-SY5Y) and fibroblast (FB-21) cell models. Finally, phytotoxic effects on germination of Cucumis sativus L., Brassica rapa L. and Sorghum vulgare L. were considered. Metabolomic analyses revealed the presence of not only limonoids but also numerous alkaloids, flavonoids and terpenoids in MAE. Histological analyses allowed us to better localize the areas of leaf deposition of the identified secondary metabolites. Regarding the ecotoxicological data, no significant toxicity was observed in bees and collembola at all doses tested. In contrast, severe cardiac abnormalities were observed in zebrafish embryos at concentrations as low as 25 µg/mL. In addition, MAE showed toxicity at 1.6 µg/mL and 6.25 µg/mL in FB-21 and SH-SY5Y cells, respectively. Finally, MAE inhibited seed germination with inhibitory concentrations starting from 5.50 µg/mL in B. rapa, 20 µg/mL in S. vulgare, and 31 µg/mL in C. sativus. Although M. azedarach extracts are considered valuable natural insecticides, their ecological impact cannot be underestimated. Even the use of an environmentally friendly solvent (an aqueous solution), for the first time, is not without side effects. Therefore, the data collected in this study show the importance of evaluating the dosages, modes of administration and production methods of M. azedarach phytoextracts in agricultural settings.

Effect of Biochar Type, Concentration and Washing Conditions on the Germination Parameters of Three Model Crops.

Biochar has been recognized as a promising and efficient material for soil amendment. However, its effects on seed germination are variable due to its alkaline pH and/or the presence of phytotoxic substances. In this study, two types of biochar (B1 and B2) were mixed with soil at different concentrations (0%, 5%, 10%, 25%, 50% and 100%, w:w), and both the solid and liquid fractions of these mixtures were tested on the germination of basil, lettuce and tomato seeds. Furthermore, solid fractions subjected to a pre-washing treatment (B1W and B2W) were also investigated for their effects on seed germination. Three germination parameters were then measured: seed germination number (GN), radicle length (RL) and germination index (GI). Biochar B2W at 10% increased both RL and GI in basil by 50% and 70%, respectively, while B1 at 25% increased these parameters in tomato by 25%. No effects or negative effects were recorded for lettuce. Liquid fractions (L1 and L2) generally hampered seed germination, suggesting the presence of potentially water-soluble phytotoxic compounds in biochar. These results point to biochar as a suitable component for germination substrates and highlight that germination tests are critical to select the best performing biochar according to the target crop.

The Effect of Organic Mulching and Irrigation on the Weed Species Composition and the Soil Weed Seed Bank of Tomato.

Mulching is a management technique to control weeds in organic and integrated tomato production. Our experiment was designed to investigate the impact of organic mulch combined with irrigation on the weed species composition and weed seed bank of open-field tomato. For three consecutive years (2016-2018), treatment of microplots included mulch only, irrigation only, mulch and irrigation combined, and the untreated control. Marginal microplots (bordered by the surrounding mown grassland) were distinguished from inner microplots to check margin effect. We collected soil samples from different depths and let the weed seeds germinate in a greenhouse. Germinated weed seedlings were counted and identified. The number of weeds, and time needed for weeding was reduced by mulching, temperature, sampling date, and the succession of the study years. Irrigation, on the other hand, had no effect on weeding time. Margin effect and year had the highest influence on weed species composition. Regarding seed bank, year and mulching had the highest influence. The importance of other variables remained low, with mulching being the strongest explained variable. Regardless of treatments, weed composition of the study area was transformed during the three-year study.

The mycorrhizal relationship of multinucleate rhizoctonias from non-orchids with Microtis (Orchidaceae).

Multinucleate rhizoctonias isolated from the roots of non-orchid plants were used in symbiotic germination tests with seed of 18 orchid species from 10 genera. The rhizoctonias only stimulated germination of Microtis. Investigation of the natural mycosymbionts of adult Microtis failed to yield fungi similar to the original multinucleate rhizoctonias: 27 Microtis plants collected at seven sites in the Sydney region yielded 26 binucleate rhizoctonias tentatively identified as Tulasnella calospora (Boudier) Juel and one very slow growing multinucleate rhizoctonia tentatively identified as Sebacina vermifera Oberwinkler. Fungi closely resembling the original multinucleate rhizoctonias were isolated by baiting the soil with subterranean clover (Trifolium subterraneum L.) plants at three of the seven Microtis sites.

Frugivory and seed dispersal by birds in Cereus jamacaru DC. ssp. jamacaru (Cactaceae) in the Caatinga of Northeastern Brazil / Frugivoria e dispersão de sementes por aves em Cereus jamacaru DC. ssp. jamacaru (Cactaceae) na Caatinga, uma floresta seca no Nordeste do Brasil

Studies of the dispersal modes of plants aid our understanding of the dynamics of resource and its availability for dispersal agents. The present work sought to characterize the fruiting patterns of the native Caatinga (dryland) cactus Cereus jamacaru, identify its principal dispersers, and evaluate the effects of seed passage through digestive tract of dispersers on its germination. Cereus jamacaru present an annual fruiting pattern and fruiting peaks occurred during June/2009 and February/2010. A total of 135 visits by nine species of resident Caatinga bird species were recorded. The most frequent visiting bird species were Paroaria dominicana and Euphonia chlorotica. Length of bird visits varied from 15 seconds to 4 minutes and seeds removed by birds travelled 10.6 ± 11.2 m until dispersers make the first landing perch, in some cases more than 40 meters away. Germination tests show birds had a high quantity of viable seeds of C. jamacaru in its feces. Seeds that passed through the digestive tract of birds showed a similar germinability of the seeds of the control group. However, the seeds dispersed by birds showed lowest mean germination time related to the control group seeds. This study highlights the potential role of birds as seed dispersers of C. jamacaru, swallowing the whole seeds and defecating intact seeds, accelerating the germination process and transporting seeds away from the mother plant.

Estudos do modo de dispersão das espécies vegetais permitem o entendimento da dinâmica dos recursos e sua disponibilidade para os dispersores. O objetivo deste trabalho foi caracterizar o padrão de frutificação de Cereus jamacaru, uma espécie nativa da Caatinga, identificar os seus principais dispersores e avaliar o efeito da passagem das sementes pelo trato digestivo destes animais sobre sua germinação. Cereus jamacaru apresentou um padrão de frutificação anual, com pico de frutificação nos meses de Junho/2009 e Fevereiro/2010. No total foram registradas 135 visitas de nove espécies de aves frugívoras da Caatinga, sendo os dispersores mais frequentes Paroaria dominicana e Euphonia chlorotica. O tempo de duração das visitas foi curto, variando de 15 segundos a 4 minutos, e a distância média dos voos pós-alimentação foi 10,6 ± 11,2 m da planta-mãe, podendo também alcançar distâncias superiores a 40 metros. Os resultados dos testes de germinação mostraram que as aves apresentam uma alta quantidade de sementes viáveis de C. jamacaru em suas fezes. As sementes que passaram pelo trato digestivo das aves mostraram germinabilidade semelhante aquelas do grupo controle. No entanto, as sementes dispersadas pelas aves apresentaram um menor tempo médio necessário para germinação. Esse estudo destaca o papel das aves como potenciais dispersores de C. jamacaru, eliminando sementes intactas, acelerando o processo de germinação e carregando as sementes para longe da planta mãe.