BIOMETRICS OF FRUITS AND SEEDS AND EMERGENCE POTENTIAL OF LEUCAENA LEUCOCEPHALA (LAM.) DE WIT. SEEDLINGS

Abstract

Leucaena was introduced into Brazil for timber production and the restoration of degraded areas and has become an aggressive invasive species, impacting ecosystems and hindering the regeneration of native flora. Invasive species have characteristics that make them strong competitors, such as large production of small, easily dispersed seeds, rapid growth, high germination rates, and high adaptability to adverse environments. Therefore, this study aimed to characterize fruits and seeds and investigate the emergence potential of leucaena seedlings at different positions and sowing depths. In a sample of 200 fruits and seeds, fruit length (CFR, cm), width (LFR, cm), thickness (EFR, cm), and weight (PFR, g) were determined, as well as number of seeds per fruit (NSFR). Subsequently, length (CS, cm), width (LS, cm), thickness (ES, cm), and thousand-seed weight (PMS, g) were measured. The experiment was conducted at the Universidade Estadual da Paraíba, in Catolé do Rocha, PB, in a completely randomized design, in a 3 x 6 factorial scheme, with 4 replicates of 25 seeds with the hilum facing down (HB), sideways (HL) and upwards (HC), at depths of 0.5; 1.0; 1.5; 2.0; 2.5 and 3.0. The following were evaluated: first emergence count (PCE, %), emergence percentage (E, %), emergence speed index (IVE), root length (CR, cm) and shoot length (CPA, cm), root/shoot ratio (RR/PA), root dry mass (MSR, g), shoot dry mass (MSPA, g) and total dry mass (MST, g). There was no fit to the polynomial models tested for the HB and HL positions. In the HC position, the highest E (82%) was observed at the greatest sowing depth (3.0 cm). There was no significant interaction between position and sowing depth for PCE, IVE, CR, CPA, MSR, MSPA, RR/PA, and MST. Furthermore, there was no fit to the polynomial models for MSPA and MST of leucaena seedlings. The highest values for PCE (38%), IVE (4.4), CR (9.6 cm), MSR (0.58 g), and RR/PA (0.40) were obtained at a depth of 0.5 cm. Conversely, the highest CPA (6.7 cm) was observed at a depth of 3.0 cm. Leucaena produces fruits with a large number of small, light seeds, and its emergence is favored by sowing at shallower depths, which demonstrates the competitive potential of this invasive species in exploiting environments with limited resources, typical of the semiarid Northeast.