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 between 16.8 degrees C and 43.4 degrees C for the bambara groundnut landrace used in this study. The response of germination rate (expressed as the reciprocal 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. The germination data from each temperature regime, where percentage germination was at least 50%, were combined to model the distribution of germination. The results confirmed that the spread of germination across all temperature regimes could be described using a gamma distribution. However, an additional factor in the germination response of this bambara groundnut landrace is that final fractional germination declined rapidly at temperatures above and below the optimum far germination rate. Less than 50% of seeds germinated at temperatures below 16.7 degrees C and above 39.5 degrees C. It appears therefore, that crop establishment of bambara groundnut in the field must depend on sail temperature as temperature affects not only the timing and spread of germination but also the fraction of the seed population that finally germinates.