Seed germination of three species of Bignoniaceae trees under water stress

Seed germination and seedling development are strongly influenced by water availability and temperature, therefore, knowledge of the tolerance limits against these factors can generate subsidies to improve the multiplication and conservation strategies of native tree species. This study evaluates the effects of water stress on the germination of Tabebuia roseoalba, Handroanthus chrysotrichus, and H. impetiginosus seeds at two temperatures. Germination was performed on paper rolls moistened with polyethylene glycol (PEG 6000) solutions for the osmotic potentials of 0 (water); -0.05; -0.10; -0.15; -0.20; -0.30; -0.40; -0.60; -0.80 and -1.00 MPa. Germination tests were conducted at 25 and 30 degrees C, under 8 h photoperiod. Statistical analyses for each studied species followed a randomized complete block design, in a 2 x 10 split-plot scheme (plots - two temperatures and subplots - ten water potentials). The percentage of germination and normal seedlings, as well as the germination speed and synchronization indexes, were evaluated. The germination of T. roseoalba, H. chrysotrichus, and H. impetiginosus seeds decreased with increasing water deficit and at higher rates when associated with higher temperatures. The results demonstrate that the species sensitivity to water deficits induced by PEG 6000, increases with rising temperatures. T. roseoalba and H. chrysotrichus exhibited a germination tolerance range between -0.80 and -1.00 MPa. Furthermore, H. impetiginosus is more sensitive and displayed a tolerance range between -0.60 and -0.80 MPa.