(Picture = Echinocactus platyacanthus)
Introduction
Seeds of three columnar cacti species: Pachycereus hollianus, Neobuxbaumia tetetzo, and Cephalocereus chrysacanthus were gathered fresh. Seeds of four barrel cacti: Ferocactus robustus, Ferocactus flavovirens, Ferocactus recurvus, and Echinocactus platyacanthus were also gathered fresh. Seeds were gathered from at least 10 plants per species. The seeds were germinated at different temperatures and the results were tabulated for each species.
Details
Some seeds were germinated at single (constant) temperatures: 10C, 15C, 20C, 25C, 30, C, 35C, or 40C. Other seeds experienced alternating temperatures: 0/10C, 5/20C, 10/25C, 15/30C, and 20/35C. So, there were many temperatures and many regimens. All of the species yielded different results. Some species had high germination rates and others had lower. Most germinated better at warmer temperatures, etc. None germinated at the lowest temperature.
For instance, the barrel cacti did not germinate until temperatures reached 15C. In contrast, all of the columnar cacti germinated at some level at 10C. All of the columnar cacti had germination percentages better than the barrel cacti, at any temperature. Most of the species reached maximum germination in the 20-30C range, as might be expected for warm, arid-land plant species.
The authors speculated that the various germination rates at the various temperatures might represent ecological adaptations to germination in the shade under shrubs or rocks, etc. Or, perhaps they may represent responses to winter and summer temperatures when rainfall varies.
Additional Reading: Cactus Seed Responses to Temperature