No abstract

Germination test for papaya seeds demands thirty days to obtain the results, which is a long period for decision-making. Thus, rapid tests become essential tools to evaluate seed viability, and the tetrazolium test is an alternative for this purpose. Hence, this study aimed to establish the adequate procedure to apply this test, in order to reduce the time of evaluation of papaya seeds. For that, four tetrazolium solution concentrations (0.05, 0.1, 0.5 and 1%) and three staining times (3, 6 and 9 hours) were tested at temperatures of 35 and 40 ºC. The experimental design was completely randomized in 4 × 3 + 1 factorial scheme (concentrations × staining times + one control = germination test). It was found that the tetrazolium test allows to evaluate the physiological quality of papaya seeds, thus reducing the time for decision-making. For the test, we recommend using the concentrations of 0.1% for 9 hours or 1% for 6 hours of staining, at temperature of 40 ºC.

Water availability and temperature are among the main abiotic factors that influence seed germination and vigor, since they act directly on biochemical and physiological processes, which result in the production of the primary root. The objective of this study was to verify the effects of stress on germination and vigor of H. impetiginosus (‘ipê-roxo’) seeds under different temperatures and osmotic agents. The experimental design was completely randomized, in a 6 x 2 factorial scheme (osmotic potentials x temperatures) with four replicates of 25 seeds for each osmotic agent. In order to simulate water stress, polyethylene glycol (PEG 6000) and mannitol solutions were used and distilled water was used as control. Osmotic potentials of 0, -0.2, -0.4, -0.6, -0.8 and -1.0 MPa were evaluated at temperatures of 25 and 30 °C, under 8 h photoperiod. The variables analyzed were: germination, germination speed index, shoot length, root length, and total dry matter of seedlings. Simulated water stress affected seed germination and seed vigor of H. impetiginosus at both temperatures and osmotic agents from -0.6 MPa.

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 Ceará). 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.

Seeds are one of the main inputs used in agriculture, and their quality is directly related to the success of the field crop. Thus, seed companies increasingly need to obtain fast and reliable seed quality results, making it easier to make decisions regarding the use of seed batches. In this sense, the objective was to evaluate the CO2 measurement efficiency in the classification of S. bicolor seed vigor. For this, six batches of cv. Ponta Negra seeds were used, from different national producers. The physiological quality of the seeds was evaluated by means of the following tests: germination, first germination count, germination speed index, accelerated aging, total dry matter of seedlings, electrical conductivity and respiratory activity. The experimental design was completely randomized, with four replications. The Pearson correlation coefficient between the respiratory activity and the germination and vigor tests was determined. The respiratory activity test on S. bicolor seeds was shown to be promising for the identification of differences in vigor between seed batches.