Weeds negatively influence agricultural production. However, those losses depend on weed specie, its time of emergence, and period of interference on agricultural crops. Synthetic herbicides are commonly used to control these plants species; however, they may cause damage to the environment, human beings and animals health, and this problem justify the need to develop alternative bioherbicides. To evaluate the allelopathic potential of Ricinus communis (Castor bean) and light spectrum variation on the emergence and growth of Cyperus rotundus L., a trial was carried out in a protected environment with 15% of brightness reduction at the Center for Agricultural and Environmental Sciences at the Paraíba State University. Four aqueous extract concentrations of R. communis leaves were tested (0, 5, 10, and 15%) and four light spectrums variations (white, purple, blue, and red lights). Variables such as emergence, length, dry matter accumulation and growth rates of shoots and root of C. rotundus seedlings were assessed. Data were analyzed by normality test, analysis of variance, polynomial regression, and averages test. Soot and root emergence, length, and dry matter accumulation of C. rotundus seedlings were reduced due to the allelopathy caused by R. communis aqueous extract leaves (15% concentration) and under purple or red light spectrum radiation.

Moringa oleifera é uma planta de usos múltiplos, seja utilizada como alimentação humana (flores, folhas, frutos e sementes) e animal (produção de forragem), tratamento de água para consumo humano, indústria de cosméticos e medicinal, combustível e produção de papel. É considerada uma espécie arbórea exótica que se adaptou às condições edafoclimáticas do semiárido do nordeste brasileiro, embora a ocorrência de déficit hídrico reduza o crescimento, limite o desenvolvimento e comprometa a fisiologia da planta. O silício é um agente mitigador do déficit hídrico. Objetivou-se com o presente estudo, avaliar o efeito das doses de silício na indução à tolerância da Moringa oleífera ao estresse hídrico, sobre o crescimento vegetativo. O estudo foi desenvolvido em parceria com o Centro de Ciências Agrárias e Ambientais da Universidade Estadual da Paraíba, localizado no município de Lagoa Seca – PB. O experimento foi instalado em delineamento de blocos ao acaso, em parcelas subdivididas em esquema fatorial duplo 5x5, sendo cinco lâminas de irrigação (25, 50, 75, 100 e 125% da Evapotranspiração da cultura) e cinco de doses de dióxido de silício (0, 3, 6, 9 e 12 g de dióxido de silício por planta), totalizando 25 tratamentos com quatro repetições, com 100 unidades experimentais as quais eram constituídas de três plantas úteis. Nas parcelas ficaram as lâminas de irrigação e nas sub-parcelas ficaram as de doses de dióxido de silício. As lâminas de irrigação exerceram influência significativa em todas as variáveis de crescimento estudadas.

Global climate changes have intensified water stress in arid and semi-arid regions, reducing plant growth and yield. In this scenario, the present study aimed to evaluate the mitigating action of salicylic acid and methionine in cowpea cultivars under water restriction conditions. An experiment was conducted in a completely randomized design with treatments set up in a 2 × 5 factorial arrangement corresponding to two cowpea cultivars (BRS Novaera and BRS Pajeú) and five treatments of water replenishment, salicylic acid, and methionine. After eight days, water stress decreased the Ψw, leaf area, and fresh mass and increased the total soluble sugars and catalase activity in the two cultivars. After sixteen days, water stress increased the activity of the superoxide dismutase and ascorbate peroxidase enzymes and decreased the total soluble sugars content and catalase activity of BRS Pajeú plants. This stress response was intensified in the BRS Pajeú plants sprayed with salicylic acid and the BRS Novaera plants with salicylic acid or methionine. BRS Pajeú is more tolerant to water stress than BRS Novaera; therefore, the regulations induced by the isolated application of salicylic acid and methionine were more intense in BRS Novaera, stimulating the tolerance mechanism of this cultivar to water stress.

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