Water stress on germination and vigor of 'mofumbo' (Combretum leprosum Mart.) seeds at different temperatures

Combretum leprosum Mart., commonly known as 'mofumbo', is used for medicinal purposes, recovery of degraded areas and apiculture. The objective of this study was to evaluate the effect of water stress on the germination and vigor of C. leprosum seeds as function of different temperatures. To compose the treatments, the substrate used was paper roll moistened with polyethylene glycol solutions (PEG 6000), at the following levels of osmotic potential: 0.0; -0.1; -0.2; -0.2; -0.4; and -0.5 MPa, and placed in chamber at constant temperatures of 25, 30 and 35 and alternating temperature of 20-30 degrees C, forming a 6 x 4 factorial. The seeds were submitted to the following evaluations: germination percentage, germination speed index, root length, shoot length, root dry matter, shoot dry matter. There was a significant interaction for all variables, with a negative effect as the osmotic potentials decreased. Thus, C. leprosum showed high sensitivity to low osmotic potentials, showing a steeper decrease from the potential of -0.2 MPa for all evaluated temperatures. Initial germination and development of C. leprosum seedlings was negatively affected by low osmotic potentials, with a tolerance limit of -0.4 MPa. Temperatures of 25 and 35 degrees C accentuate the negative effect of the low osmotic potential of water on the germination and early development of C. leprosum seedlings.