Abstract

Background: This study compares seed germination and seedling growth parameters of native Senegalia catechu with its closely related invasive Leucaena leucocephala in Nepal. For the comparison of seed germination percentage (GP), mean germination time (MGT), and Timson’s index (TI), the seeds of both species were incubated under different light (photoperiod and dark), tiperatures (30/20ºC and 25/15ºC) and water stress conditions (−0.1, −0.25, −0.5, −0.75, and −1 MPa). The seedling iergence from different soil depths was also evaluated. The relative growth rate (RGR), root mass fraction (RMF), sti mass fraction, leaf mass fraction (LMF), and root-to-shoot ratio (RSR) of seedlings were also measured. Results: The seed length and mass of invasive L. leucocephala were higher than that of native S. catechu. The GP of S. catechu was higher at high tiperature and photoperiod comparing to L. leucocephala. There was no difference in GP between two species under other light and tiperature conditions. The MGT of S. catechu was shorter than that of L. leucocephala at both tiperatures. Senegalia catechu exhibited higher TI than L. leucocephala, particularly at high tiperatures. Water stress above −0.5 MPa reduced the GP and TI of both species and it was more pronounced in S. catechu than L. leucocephala. The seedling iergence percentage of L. leucocephala was higher than that of S. catechu. Both species exhibited comparable RGR and biomass allocations (RMF, LMF, and RSR). However, L. leucocephala had always greater values of shoot height, root length, leaf number and seedling biomass compared to S. catechu. Conclusions: Larger seeds may not always lead to higher seed GP. Some, but not all, seed germination and seedling growth traits can be useful to characterize invasive alien plant species. Invasiveness of L. leucocephala could be attributed to relatively high tolerance of seed germination to water stress, capacity to germinate from deeper soil, and larger seedling size compared to the confamilial native species.