Seed germination of wild and cultivated Stenocereus stellatus (Cactaceae) from the Tehuacan-Cuicatlan Valley, Central Mexico

Germination rate and percentage, and seed weight were compared among wild and cultivated populations of the columnar cactus Stenocereus stellatus to analyse the effect of domestication on their seed behaviour and dormancy mechanisms. Experiments on germination capacity were tested on constant (25 degreesC) and fluctuating temperature (20/35 degreesC; 18/6 h) under white light and darkness, and adding five different concentrations of gibberellic acid (GA(3)) in darkness at 25 degreesC. Cultivated individuals had significantly heavier seeds (1.12 +/- 0.04 mg) than wild individuals (0.80 +/- 0.02 mg). Germination percentage in all populations was generally higher at constant temperature but cultivated plants had significantly higher seed germination than the wild ones in both temperature treatments. All seeds increased their germination percentage with storage age in both constant and fluctuating temperature. All seeds were positive photoblastic, and addition of GA(3) did not promote germination in darkness. The results suggest that human selection has favoured seedling vigour and a greater germination capacity in cultivated variants. (C) 2001 Academic Press.