Low frequency ultrasound as an enhancer for the germination process of Stizolobium pruriens

Mucuna (Stizolobium pruriens) is widely used in agriculture as a green allowance and in crop rotation, due to its ability to fix nitrogen and recover degraded areas; without embargo, there is a slow and uneven germination. This study used some classical methods, together with the use of low-frequency ultrasound to accelerate and homogenize the germination and emergence of the seeds. The experiment was carried out at the Plant Tissue Cultivation Laboratory of the Ilha Solteira Campus, São Paulo, Brazil. The design used was a completely randomized one, with five replications, in a 3x6 factorial scheme, the factors being: three pre-treatments for latency break: mechanical scarification, thermal scarification, and without scarification with six levels of ultrasound exposure: 0, 1, 2, 3, 5, 8 min, totaling 18 treatments. For eight days the germination and the initial stages of the seedlings were controlled. The method without scarification subjected to 4.5 min of ultrasound can become an excellent alternative, since it presented greater germination vigor, while 3.14 min of exposure to ultrasound were enough to improve the emergence speed, regardless of the method used in the preparation of seeds. In conclusion, only with the use of low-frequency ultrasound, it is possible to improve both the germination speed index and the germination vigor, without the need for additional treatments.