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 a nd cultivated populations of the columnar cactus Stenocereus stellatus to a nalyse the effect of domestication on their seed behaviour and dormancy mec hanisms. Experiments on germination capacity were tested on constant (25 de greesC) and fluctuating temperature (20/35 degreesC; 18/6 h) under white li ght and darkness, and adding five different concentrations of gibberellic a cid (GA(3)) in darkness at 25 degreesC. Cultivated individuals had signific antly heavier seeds (1.12 +/- 0.04 mg) than wild individuals (0.80 +/- 0.02 mg). Germination percentage in all populations was generally higher at con stant temperature but cultivated plants had significantly higher seed germi nation than the wild ones in both temperature treatments. All seeds increas ed their germination percentage with storage age in both constant and fluct uating temperature. All seeds were positive photoblastic, and addition of G A(3) did not promote germination in darkness. The results suggest that huma n selection has favoured seedling vigour and a greater germination capacity in cultivated variants. (C) 2001 Academic Press.