The germination response of bambara groundnut (Vigna subterranea (L.) Verdc.) to temperature

The germination response of a bambara groundnut landrace from Zimbabwe to a range of constant temperatures was examined using a thermal gradient plate . A gamma distribution adequately described the progress of germination bet ween 16.8 degrees C and 43.4 degrees C for the bambara groundnut landrace u sed in this study. The response of germination rate (expressed as the recip rocal of time to 50% germination) between 16.8 degrees C and 39.5 degrees C followed the typical pattern previously observed for many other species. T he germination data from each temperature regime, where percentage germinat ion was at least 50%, were combined to model the distribution of germinatio n. The results confirmed that the spread of germination across all temperat ure regimes could be described using a gamma distribution. However, an addi tional factor in the germination response of this bambara groundnut landrac e is that final fractional germination declined rapidly at temperatures abo ve and below the optimum far germination rate. Less than 50% of seeds germi nated at temperatures below 16.7 degrees C and above 39.5 degrees C. It app ears therefore, that crop establishment of bambara groundnut in the field m ust depend on sail temperature as temperature affects not only the timing a nd spread of germination but also the fraction of the seed population that finally germinates.