Some Germination Responses of Lechuguilla (Agave lecheguilla torr.)

Seeds were obtained from plants within three Mexican and two Texas populations of lechuguilla. Preliminary studies indicated no dormancy mech- anisms were involved and that germination was light insensitive. Various popula- tions were then tested to determine germination response to constant temperature, pH, and osmotic potential. Lechuguilla germinated readily over a wide range of each condition tested. High temperature pre-treatment at 60?C for 7 days did not significantly affect viability. The optimum constant temperature for germination is between 25?C and 300C, with limits occurring near 10TC and 400C. Seeds germi- nated well under water stresses up to -5.0 atm, and, of the pH's tested, germinated best at the moderately acid 6.15. A sharp decline in percent germination occurred at the moderately basic pH values of 7.30 and 7.85. Seed weights differed significantly between Texas and Mexico populations sampled, but no correlation appeared between seed weight and viability. No marked ecotypic variability of germination response was noted. Intra-population variability of germination response was high under extreme conditions. Lechuguilla is a century plant commonly found throughout the Chihuahuan Desert of southwestern North America. Its range (Fig. 1) extends from southern New Mexico (330N) to the Mexican state of Hidalgo (200N). It is perhaps the best plant indicator species of the Chihuahuan Desert (Bailey, 1905; Benson and Darrow 1954), which is noteworthy for its paucity of widespread endemic specie-. With a few exceptions, such as in El Paso County, Texas, and Big Bend Na- tional Park, Texas (Gehlbach 1967), lechuguilla appears restricted to light colored and highly calcareous, limestone-derived soils. Typical of century plants, flowering occurs only once, at the end of the plant's life cycle. Lechuguilla produces large numbers of cap- sules along a spike-like panicle, with each capsule producing up to several hundred seeds. In spite of this production of large numbers of seeds, seedlings are rare under field conditions. The species appears to