Magnesium supplementation alleviates drought damage during vegetative stage of soybean plants.

Our working hypothesis was that magnesium (Mg) supplementation modulates plant performance under low water availability and improves drought tolerance in soybean genotypes. Plants of Bônus 8579, M8808 and TMG1180 genotypes were grown under field conditions and subjected to three water stress treatments (control, moderate and severe stress) and three Mg levels [0.9 (low), 1.3 (adequate) and 1.7 cmolc dm-³ (supplementation)]. After 28 days of drought imposition, the growth parameters, osmotic potential, relative water content, leaf succulence, Mg content and photosynthetic pigments were assessed. In general, drought drastically decreased the growth in all genotypes, and the reductions were intensified from moderate to severe stress. Under adequate Mg supply, TMG1180 was the most drought-tolerant genotype among the soybean plants, but Mg supplementation did not improve its tolerance. Conversely, although the M8808 genotype displayed inexpressive responses to drought under adequate Mg, the Mg-supplemented plants were found to have surprisingly better growth performance under stress compared to Bônus 8579 and TMG1180, irrespective of drought regime. The improved growth of high Mg-treated M8808-stressed plants correlated with low osmotic potential and increased relative water content, as well as shoot Mg accumulation, resulting in increased photosynthetic pigments and culminating in the highest drought tolerance. The results clearly indicate that Mg supplementation is a potential tool for alleviating water stress in M8808 soybean plants. Our findings suggest that the enhanced Mg-induced plant acclimation resulted from increased water content in plant tissues and strategic regulation of Mg content and photosynthetic pigments.

Bioherbicidal potential of plant species with allelopathic effects on the weed Bidens bipinnata L.

Plant species with allelopathic effects against weeds have emerged as a potential strategy for the development of ecologically friendly bioherbicides. In this study, the allelopathic effects of the plant species Dipteryx lacunifera Ducke, Ricinus communis L., Piper tuberculatum Jacq., and Jatropha gossypiifolia L. on the weed Bidens bipinnata L. were investigated. In vitro bioassays revealed that aqueous extracts of selected plant species were able to inhibit seed germination and seedling growth of B. bipinnata, highlighting the strongest allelopathic effect evidenced by R. communis. The phytotoxicity of the aqueous extracts was evaluated in pot experiments, which indicated that the foliar application of R. communis and P. tuberculatum extracts on B. bipinnata plants caused yellowing of leaves, affecting the chlorophyll content and reducing growth. The discrimination of the plant extracts by attenuated total reflectance Fourier transform mid-infrared (ATR FT-MIR) spectroscopy combined with principal component analysis (PCA) indicated the presence of allelochemical compounds, such as phenolics and terpenoids, which may be associated with allelopathic activity. Overall, this study provides valuable information about the substantial allelopathic inhibitory effects of the plant species R. communis and P. tuberculatum on the weed B. bipinnata, which may be used for the development of eco-friendly bioherbicides.

Wastewater from swine farming in the growth and nutrition of Khaya senegalensis (DESR. ) A Juss seedlings / Água residuária da suinocultura no crescimento e nutrição de mudas de khaya senegalensis (DESR. ) a juss

This study evaluated the use of wastewater from swine farming in the growth and nutritional balance of Khaya senegalensis (Desr.) A. Juss. (African mahogany) seedlings. The experiment was setup in a shade house on the Professor Cinobelina Elvas Campus of the Federal University of Piauí, in Bom Jesus, in the State of Piauí, Brazil. The experimental design was completely randomised, with five concentrations of swine farm wastewater (SFW) (0, 25, 50, 75 and 100%) added to the irrigation water. The growth and nutritional balance of the seedlings were evaluated 100 days after sowing, by measuring shoot height (H), stem diameter (SD), number of leaves (NL), total chlorophyll (TC), leaf area (LA), shoot dry weight (SDW) and root dry weight (RDW), and by calculating the total dry weight (TDW), leaf (LBA), stem (SBA), and root (RBA) biomass allocation, Dickson Quality Index (DQI) and average Nutritional Balance Index (NBIm). It was found that K. senegalensis seedlings responded to the SFW, showing the best results for growth and nutritional balance at concentrations of around 50%.

Este trabalho foi realizado com o objetivo de avaliar a utilização da água residuária da suinocultura no crescimento e no balanço nutricional de mudas de Khaya senegalensis (Desr.) A. Juss. (mogno-africano). O experimento foi instalado no Campus Profa. Cinobelina Elvas, Universidade Federal do Piauí, em Bom Jesus, PI, dentro de uma casa de sombra. O experimento foi implantado em delineamento inteiramentecasualizado, com cinco concentrações de água residuária de suinocultura (ARS) (0; 25; 50; 75 e 100%) na água de irrigação. O crescimento e balanço nutricional das mudas foram avaliados aos 100 dias após a semeadura, com a mensuração da altura da parte aérea (H), diâmetro do coleto (DC), número de folhas (NF), clorofila total (CT), área foliar (AF), massa seca da parte aérea (MSPA) e do sistema radicular (MSR) e calculadas a massa seca total (MST), as alocações de biomassa foliar (ABF), caule (ABC), raízes (ABR), o Índice de Qualidade de Dickson (IQD) e Índice de Balanço Nutricional médio (IBNm). Constatou-se que a as mudas de K. senegalensis responderam à ARS, apresentando os melhores resultados de crescimento e equilíbrio nutricional em concentrações em torno de 50%.