Embryo Development and Germination of Cycas Seeds

in Journal of the American Society for Horticultural Science
Authors:
Bijan DehganHorticultural Systematics Laboratory, Department of Ornamental Horticulture, University of Florida, Gainesville, FL 32611

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Bart SchutzmanHorticultural Systematics Laboratory, Department of Ornamental Horticulture, University of Florida, Gainesville, FL 32611

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Abstract

Germination of Cycas revoluta seed is slow and erratic when planted immediately after collection, and most lose viability in a few months. In a 2 × 4 × 4 factorial experiment, seeds were stored at 5° and 22°C for 24 weeks and subsequently treated with H2SO4 (18 M) for 0, 1, 2, or 3 hr followed by GA3 (1000 ppm) for 0, 24, 48, or 72 hr. Morphophysiological complex dormancy contributes to the lengthy germination process. Removal of the fleshy, water-repellant sarcotesta (containing inhibitors), scarification of the thick water-impermeable sclerotesta, and maturation of the embryo, which is in very early stages of development at the time of seed abscission, all enhance germination. At 5°, 92% of the seeds survived, but only 42% of the seeds stored at 22° were viable after 24 weeks, the result of desiccation. Under all but 72 hr of GA3 exposure time, response surface shapes lead to the expectation that germination will be better without H2SO4 or with higher levels of H2SO4 than with intermediate levels. The response to GA3 at any given exposure to H2SO4 is similar in both cold- and warm-stored seeds: for a given GA, level, one optimum H2SO4 exposure gives the best germination percentage, peak value (PV), or germination value (GV). Optimal GV results when seeds are stored at 5° for 24 weeks to allow embryo maturation followed by removal of the sarcotesta, 1 hr of H2SO4 exposure, and 36 hr of GA3 exposure.

Contributor Notes

Professor.

Graduate student.

Received for publication 15 Mar. 1988. Florida Agricultural Experiment Station Journal Series no. 8851. We thank R.C. Littell for statistical analysis, T. Nance for technical assistance, and Fairchild Tropical Garden for seeds of several species of Cycas. The cost of publishing this paper was defrayed in part by the payment of page charges. Under postal regulations, this paper therefore must be hereby marked advertisement solely to indicate this fact.

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