Biochemical changes in squash hybrid seeds at different stages of maturation

This study aimed to evaluate the biochemical changes of squash hybrid seeds obtained from fruits harvested at different maturity dates (15, 30, 45, 60 and 75 days after anthesis - DAA). In every stage, thirty fruits were harvested; fifteen fruits had their seeds extracted immediately and the other fifteen fruits were stored for twenty days in plastic boxes and, after this period, the seeds were extracted. After seed processing and drying, the following determinations were made: seed moisture content, germination, first count, electrophoretic profile analysis of heat-resistant proteins (Late Embryogenesis Abundant - LEA) and activity of antioxidant enzymes (peroxidase and ascorbate peroxidase). Seeds from fruits harvested at 30 DAA showed high concentration of antioxidant enzymes and low concentration of LEA proteins, demonstrating that the seeds were immature and that the desiccation possibly caused damage in their cell membranes. Thus, there was an increased activity of antioxidant enzymes by the accumulation of reactive oxygen species (ROS), leading the seeds not to resist the oxidative damage. The reduction in seed germination was caused possibly by the high concentration of antioxidant enzymes and low concentration of LEA proteins.