Some Factors Affecting the Germination of Seed of the Saguaro Cactus (Carnegiea Gigantea)

A lcorn , S tanley M. (U. S. Dept. of Agric., Tucson, Ariz.), and E dwin B. K urtz , J r . Some factors affecting the germination of seed of the saguaro cactus (Carnegiea gigantea). Amer. Jour. Bot. 46(7): 526–529. 1959.—Germination of saguaro cactus seeds is stimulated by red light (approx. 6550 A) or daylight and far‐red light (approx. 7350 A) counteracts this effect. About 0.1% germinate in continuous darkness. A single exposure to red light was most effective when the seeds were imbibed 24 hr., but maximum germination resulted from multiple exposures to red light during a 72‐hr. imbibition period. The optimum temperature for germination was 25°C.; no germination occurred at 15°C. and only slight germination at 35°C. Imbibition of light‐treated seeds in 0.05 to 0.2% KNO 3 increased germination. Germination of seeds in either light or dark was increased by imbibing the seeds in 500 to 1000 p.p.m. gibberellic acid.