Sara Monaliza Costa Carvalho

Teste de condutividade elétrica na avaliação da qualidade fisiológica de sementes de coentro

Os testes de germinacao e de vigor sao componentes essenciais do processo de controle de qualidade das empresas produtoras de sementes. Diante disso, nesta pesquisa o objetivo foi estudar a metodologia do teste de condutividade eletrica, verificando sua eficiencia na identificacao de diferentes niveis de vigor de lotes de sementes de coentro. Para tanto, utilizaram-se quatro cultivares (Portugues, Super Verdao, Tabocas e Verdao), cada uma representada por quatro lotes de sementes, que inicialmente foram submetidas as avaliacoes do grau de umidade, germinacao, primeira contagem de germinacao e emergencia de plântulas. O teste de condutividade eletrica foi realizado com 25 e 50 sementes embebidas em 50 e 75 mL de agua destilada, a 25 oC, por 2, 8 e 24 horas. O teste de condutividade eletrica e eficiente para a avaliacao do potencial fisiologico de sementes de coentro quando conduzido com 50 sementes imersas em 50 mL de agua destilada, a 25 oC, apos duas horas de embebicao.

Water Stress Affect Germination, Seed Vigor and Seedlings Growth of Bidens subalternans

The beggartick (Bidens subalternans L.) is one of the main weeds present in agricultural crops, capable of adapting to different environmental conditions. The water stress caused by water deficiency can affect the germination of weed seeds and, consequently, their capacity to colonize the agroecosystem. Knowledge of germination under water stress can be important to obtain an adequate management of the species in the agricultural systems. The objective of this study was to determine the effects of water stress on the germination process and vigor of two batches of Bidens subalternans seeds under different osmotic agents. It was completely randomized experimental design was used, with four replicates of 25 seeds. The treatments were arranged in factorial 6 × 2, with the first factor corresponding six levels of osmotic potentials (0.0, -0.2, -0.4, -0.6, -0.8 and -1.0 MPa) and the second the batches (Pernambuco and Ceara). For the simulation of the water stress, the test of germination was installed in substrate paper blotting, moistened with solutions of polyethylene glycol (PEG 6000) and mannitol. The analyzed variables were germination, germination speed index, length and seedling dry mass. Water stress reduced germination, seed vigor and growth of seedlings in all batches of B. subalternans. Seeds of B. subalternans presented greater tolerance to stress induced by mannitol than to PEG-6000 in terms of germination and germination speed index. Regardless of the osmotic agent used for stress induction, B. subalternans seeds did not tolerate water stress higher than -0.4 MPa.