Seed germination ofStenocereus thurberi(Cactaceae) under different solar irradiation levels

Germination ofStenocereus thurberiseeds was evaluated under different conditions of solar irradiation and humidity. Seed germination increased under higher humidity and low solar irradiation which provided cooler temperatures and higher water availability. Seedlings were also greener and more turgid under these conditions. Increased solar irradiation reduced seed germination and decreased seedling size and water content. The results of this study support the importance of natural shelter systems in the arid zones in providing better conditions forS. thurberiseed germination and seedling establishment, particularly in the desert of Baja California.