Operation Allelopathy: An Experiment Investigating an Alternative to Synthetic Agrochemicals

Synthetic herbicides represent a serious problem in modern agriculture because they are not biodegradable and can accumulate in the soil and in the groundwater, a situation that allows them to enter the trophic chain and ultimately leads to human exposure. Allelopathic chemicals offer an effective alternative to the synthetic compounds. The aim of this experiment is to highlight the differences between chemical and biological control of diseases in crops and to demonstrate the use of natural fungicides and herbicides as alternatives to synthetic chemicals. The experiment involves an evaluation by students of the potential of plant extracts as an alternative to synthetic agrochemicals to identify new ecological farming techniques that could be applied in agriculture. In an effort to encourage 1800 students in high school (14 to 16 years old) to have an interest in science, technology, and innovation, the third edition of the Summer Science Campus was organized by the Spanish Foundation for Science and Technology and the Ministry of Education, Culture, and Sports with support from the foundation Obra Social “la Caixa”

Carbon assimilation, isotope discrimination, proline and lipid peroxidation contribution to barley (Hordeum vulgare) salinity tolerance

Barley (Hordeum vulgare L.) exhibits great adaptability to salt tolerance in marginal environments because of its great genetic diversity. Differences in main biochemical, physiological, and molecular processes, which could explain the different tolerance to soil salinity of 16 barley varieties, were examined during a two-year field experiment. The study was conducted in a saline soil with an electrical conductivity ranging from 7.3 to 11.5 dS/m. During the experiment, a number of different physiological and biochemical characteristics were evaluated when barley was at the two-to three-nodes growing stage (BBCH code 32–33). The results indicated that there were significant (p < 0.001) effects due to varieties for tolerance to salinity. Carbon isotopes discrimination was higher by 11.8% to 16.0% in salt tolerant varieties than that in the sensitive ones. Additionally, in the tolerant varieties, assimilation rates of CO2 and proline concentration were 200% and up to 67% higher than the sensitive varieties, respectively. However, in sensitive varieties, hydrogen peroxide and lipid peroxidation were enhanced, indicating an increased lipid peroxidation. The expression of the genes Hsdr4, HvA1, and HvTX1 did not differ among barley varieties tested. This study suggests that the increased carbon isotopes discrimination, increased proline concentration (play an osmolyte source role), and decreased lipid peroxidation are traits that are associated with barley tolerance to soil salinity. Moreover, our findings that proline improves salt tolerance by up-regulating stress-protective enzymes and reducing oxidation of lipid membranes will encourage our hypothesis that there are specific mechanisms that can be co-related with the salt sensitivity or the tolerance of barley. Therefore, further research is needed to ensure the tolerance mechanisms that exclude NaCl in salt tolerant barley varieties and diminish accumulation of lipid peroxides through adaptive plant responses. © 2021 by the authors. Licensee MDPI, Basel, Switzerland

Influência de cultivares de arroz e épocas da adubação nitrogenada nas relações de interferência da cultura com cultivar simulador de infestação de arroz-vermelho Influence of rice cultivars and nitrogen fertilizer timing on the interference relationships between the crop and cultivar simulating red rice infestation

O objetivo deste trabalho foi avaliar os efeitos de cultivares de arroz irrigado e de épocas de adubação nitrogenada durante o ciclo da cultura sobre a habilidade competitiva do cereal em relação ao cultivar EEA 406, usado como simulador da planta daninha arrozvermelho. Para isso, conduziu-se experimento em campo, na estação de crescimento 2001/02. Os tratamentos, dispostos em esquema fatorial, constaram de cultivares de arroz (BRS-38 Ligeirinho, IRGA 417 e BR-IRGA 409), épocas de aplicação do nitrogênio (N) (100% do N na semeadura, 50% do N na semeadura mais 50% no início da diferenciação da panícula (IDP), 100% no IDP e testemunha sem o adubo) e populações do cultivar simulador do arroz-vermelho. Para relacionar as perdas de produtividade de grãos de arroz com populações do cultivar simulador, utilizou-se o modelo de regressão da hipérbole retangular, ajustado de modo independente para os fatores estudados. Verificou-se que a época de aplicação do N influenciou na habilidade competitiva dos cultivares de arroz. Cultivares de ciclo muito curto e curto apresentaram maior habilidade competitiva com o cultivar simulador, quando a adubação foi realizada na semeadura, enquanto o cultivar de ciclo médio se beneficiou do fracionamento da adubação na semeadura e no IDP.<br>The objective of this study was to evaluate the effects of flooded rice cultivars and timings of nitrogen fertilizer application during the crop cycle on the competitive ability of this cereal in relation to EEA 406 cultivar, used as a mimicker of red rice. Thus, a field experiment was carried out during the 2001/02 growing season. The treatments were arranged in a factorial design,comprising the rice cultivars (BRS-38 Ligeirinho, IRGA 417, and BR-IRGA 409), nitrogen (N) application timings (100% at sowing, 50% at sowing plus 50% at the beginning of panicle differentiation (BPD), 100% at BPD, and check without fertilizer), and densities of the mimicker cultivar. In order to relate rice grain yield losses to densities of the mimicker cultivar, a retangular hyperbolic regression model was applied, independently adjusted for the factors tested. It was verified that N application timing influenced the competitive ability of rice cultivars. Very early and early maturity rice cultivars showed greater competitive ability with mimicker genotype when N fertilizer was applied at sowing time, whereas medium maturity cultivar took more advantage with N fertilizer fractioning at sowing and BPD

Physiological and biochemical parameters: new tools to screen barley root exudates allelopathic potential (*Hordeum vulgare* L. subsp. *vulgare*

peer reviewedMorphological markers/traits are often used in the detection of allelopathic stress, but optical signals including chlorophyll a fluorescence emission could be useful in developing new screening techniques. In this context, the allelopathic effect of barley (Hordeum vulgare subsp. vulgare) root exudates (three modern varieties and three landraces) were assessed on the morphological (root and shoot length, biomass accumulation), physiological (Fv/Fm and F0), and biochemical (chlorophyll and protein contents) variables of great brome (Bromus diandrus Roth., syn. Bromus rigidus Roth. subsp. gussonii Parl.). All the measured traits were affected when great brome was grown in a soil substrate in which barley plants had previously developed for 30 days before being removed. The response of receiver plants was affected by treatment with activated charcoal, dependent on barley genotype and on the nature of the growing substrate. The inhibitory effect was lower with the addition of the activated charcoal suggesting the release of putative allelochemicals from barley roots into the soil. The barley landraces were more toxic than modern varieties and their effect was more pronounced in sandy substrate than in silty clay sand substrate. In our investigation, the chlorophyll content and Fv/Fm were the most correlated variables with barley allelopathic potential. These two parameters might be considered as effective tools to quantify susceptibility to allelochemical inhibitors in higher plants