Effect of light on germination of seven species of cacti from the Zapotitlan valley in Puebla, Mexico

Seed germination of seven species of cacti from Zapotitlan Valley, Puebla, Mexico, were compared at four different light treatments (red light, far-red light, white light and darkness) at a constant temperature of 25 degrees C, and at two light treatments (white light and darkness) at two fluctuating temperatures (15-30 degrees C and 20-30 degrees C). Results allowed us to divide the studied species into two groups: positive photoblastic and indifferent to light. Positive photoblastics were barrel cacti and indifferent to light species were columnar cacti. Although barrel cacti had a light requirement for germination, they germinated in far-red light. Probable relationships among life-form, species distribution and light requirements for germination are discussed. (C) 1997 Academic Press Limited.