Estresse hídrico e térmico na germinação de sementes de Leucaena leucocephala (Lam.) de Wit

Abstract

Leucaena leucocephala (Lam.) de Wit (Fabaceae) is an arboreal species of wide use in the world, mainly for feeding ruminants in semiarid climate regions. Given its relevance, the aim of this study was to evaluate the effects of water and thermal stress on the germination and vigor of L. leucocephala seeds. The experiment was installed in 3 x 4 factorial arrangement, considering the water potential (0.0, -0.3 and -0.6 MPa) and temperature (25, 30, 35 and 40 °C) factors on the seeds germination performance. The variables evaluated were: germination, abnormal seedlings, first germination count, germination speed index and seedling performance (length and dry mass weight of root and aerial part). The reduction of the water potential from -0.3 MPa reduced the germination and seed vigor, indicating that the tolerance of the species to water stress in the germination phase is low. The temperature range of 25-30 °C is ideal for germination and seedlings initial growth, but the seeds continue to germinate under a temperature elevation to 35 °C. The L. leucocephala seeds are poorly tolerant to water and thermal stresses and, consequently, the germinative capacity and vigor are reduced with decreasing water potential from -0.3 MPa and temperatures above 30 °C.