Dissertação
Qualidade fisiológica de sementes de soja sob estresse em pós-semeadura em solo seco
Fecha
2021-08-27Autor
Santos, Cassiano Vasconcelos dos
Institución
Resumen
Seeding in dry soil is the practice of placing the seed in the soil with low humidity before
precipitation occurs, in this way, the seeds are stored in the soil, exposed to hydric and
thermal stress, pests attack and diseases, while waiting for moisture conditions to begin the
germination process. The use of quality seeds is a very important practice for the production
system, because there is an increase in the germination percentage, normal seedlings and
vigor. Therefore, this study aims to evaluate the effects of seeding in dry soil and exposure to
stress periods on the physiological quality of soybean seeds. Thus, two different experiments
were carried out. The first experiment, aimed to evaluate the effects that drought periods after
seeding in dry soil have on the physiological quality of seeds and the action of soil vegetation
coverage as a possible stress reliever. To simulate periods of hydric stress, two seed batch
remained in the soil without irrigation for 0, 4, 8, 12 and 16 days, after seeding in the pots,
these pots had or not a ground cover with black oat straw. The assessment were made from
emergence to the beginning of the reproductive stage of crop. Vigor effects provide greater
emergency and faster establishment in sowing conditions under hydric stress and they are
more expressive in the early stages of germination and establishment, and less obvious as the
phenological stages progress. Storage in dry soil within 4 days does not affect emergency,
which is reduced from 8 to 16 days of storage with equal intensity. Vegetation coverage of the
soil enables greater emergency and initial growth in relation to the bare ground, improving the
establishment and plant stand. The second experiment had goal to evaluate effects of
temperature and period in days that the seeds were stored in dry soil under their physiological
quality and the consequences on the germination process and post-germination development
in soybean seeds. Seeds were sown in trays and stored for periods of 0, 7, 14 and 21 days in
the soil without moisture and placed in a BOD germinator with controlled temperature of 15,
25 and 35 ºC. After storage, the dry soil was irrigated, raising its moisture to 60% of its
retention capacity and keep the BODs at 25 ºC and constant light during germination. Five
days after irrigation, emergency, seedling classifications as normal, abnormal and dead, length
and dry mass were evaluated. In addition, digitalization was performed using images of the
seedlings for further analysis. Seeding in dry soil for up to 21 days of storage at a temperature
of 35 ºC does not affect the physiological quality of soybean seeds, it was also observed that
storage at lower temperatures can result in more heterogeneous results and be harmful to seed
performance.