Conservação ex situ e tolerância à dessecação em sementes de Lecythis pisonis cambess
Nenhuma Miniatura disponível
Data
2024-02-23
Autores
Araujo, Caroline Palacio de
Título da Revista
ISSN da Revista
Título de Volume
Editor
Universidade Federal do Espírito Santo
Resumo
Plants are sessile life forms, which makes them more susceptible to environmental temperature variations, especially during their reproduction and adaptation. Germination is a sensitive and crucial stage in the life cycle of seed-producing plants and occurs within temperature ranges suitable for the species. The objective of this study was to investigate fixed temperatures and thermal shocks at different exposure times on the physiology of seeds and initial growth of L. pisonis seedlings. Vigor, emergence, seedling growth, chlorophyll fluorescence, chlorophyll a and b index, maximum PS II quantum yield, oxidative stress enzymes, lipid peroxidation, hydrogen peroxide, and DNA methylation in seedlings were evaluated. In experiment 1, L. pisonis seeds exposed to thermal shock 30-45 °C (20 h/4 h) showed high seedling emergence (88%), vigor, and an efficient antioxidant system, with increased activity of SOD, CAT, and APX enzymes. This same treatment showed high concentrations of H2O2, indicating that it may have acted as a signaling molecule favoring seedling emergence. It was also observed in experiment 1 that fixed temperatures of 40, 45, and 50 °C led to loss of seed viability, and that high temperatures for long periods caused decreased vigor, seed deterioration, damage to the photosynthetic apparatus (PS II), and formation of seedlings with absent root systems. In experiment 2, it was observed that the treatment 30-45 °C (21 h/3 h) achieved high percentages of emergence (84%) and vigor in a short period of time (23 days), corroborating with the results of experiment 1. This treatment also provided high activity of SOD, CAT, and APX, evidencing an efficient antioxidant system. In experiment 2, it was observed that the quality of seedlings was affected in the thermal shock 30-45 °C when exposed at a temperature of 45 °C for 5, 6, and 7 hours. It is concluded from this study that L. pisonis seeds do not tolerate long exposure to high temperatures, however, they express greater vigor and seedling emergence when subjected to short periods of time under these conditions. Thermal shock 30-45 °C at exposure times 20 h/4 h and 21 h/3 h are suggested as optimal for the emergence of L. pisonis seedlings.
Descrição
Palavras-chave
Choque térmico , Estresse oxidativo , Vigor de sementes , Enzimas antioxidantes , Fluorescência da clorofila