Physical characterization of Euterpe precatoria Mart. seeds and the influence of ultrasound on seedling emergence

The irregular and slow seedling emergence of Euterpe precatoria Mart. is a challenge in seedling production. Therefore, this study aimed to characterize the physical aspects of the seeds and evaluate the potential of ultrasound to stimulate emergence. The seeds were treated using a total of 36 treatments (frequencies of 1 and 3 MHz; intensities of 0.5, 1.0, 1.5, and 2.0 W/cm², and times of 3, 5, 7, and 9 minutes) in a completely randomized research design. Morphological characteristics, viability, moisture content, and 1,000-seed weight were evaluated. The variables analyzed included emergence, speed index, and mean emergence time. Overall, the seeds had rounded shapes, with an average length of 15.09±0.24 mm, width of 12.45±0.83 mm, area of 144.34±4.02 mm2, perimeter of 48.32±1.78 mm, circularity of 0.79±0.03 and roundness of 0.84±0.08. The viability was 97.00%, moisture content of 16.05% and weight of one thousand seeds of 923.55 g, characterizing them as large. The 1MHz-1.0W/cm² treatment at 5 and 7 minutes reached 86.00±5.29% and 93.00±1.00% emergence, respectively, with high-speed indexes of 0.58±0.02 and 0.61±0.01 seeds/day, respectively. In addition, low average emergence times of 37.55±1.07 and 38.51±0.67 days after 5 and 7 minutes of ultrasound treatment were obtained respectively. It is concluded that the use of ultrasound is promising to accelerate the emergence of Euterpe precataria Mart. seedlings, representing a green sustainable alternative for forest nurseries and restoration projects in the Amazon.