Front Range Seed Analysts
1994 Seed Forum Volume 8 Number 3
CRAZY CUPHEA
by Annette Logan
Cuphea is a large genus of new world plants in the f amily Lythraceae. The flower is showy and the seeds are very oily. C. ignea is bred and sold for its ornamental attributes and it is the only Cuphea with a published seed testing method (ISTA: TP H20 20-30). No AOSA rules exist for any Cuphea. The other Cuphea species have attracted the attention of oilseed breeders. The ails have high percentages of unsaturated fatty acids thus making the oil a high quality nutritional oil. For the past 10 years, breeders have been trying to overcome problems of shattering and dormancy to make the seed commercially acceptable.
With these notes, I want to explain some morphologic features of Cuphea that make it so fascinating and different. Cuphea's seedcoat is a strange variation on the usual mucilaginous seed coat. The outer layer of cells contain coiled up spiral hairs which are extruded with as little time as 10-20 minutes of imbibition. The hairs are sticky, spiral, long, elastic, and generally serve to cement the seed to the germination substrate. The hairs have fooled more than one analyst into mistaking them for fungal hyphae! The middle layer is dark and leathery. The inside layer is thin and transparent like cellophane. Though these features seem like barriers, water uptake is rapid. When cutting seeds for TZ tests, water squirts out as the seed coat is punctured. Some species have a prominent raphe on one side. This raphe is a convenient marker for a longitudinal cut through the radicle/hypocotyl axis.
To produce plants for seed increases in breeding programs, three researchers report using an excised embryo technique. My own experience with embryo excision shows little correlation with a tetrazolium test. Some of my viability tests are still in progress. I will address this more thoroughly in a future article.
References:
Graham, S. A. 1988. Revision of Cuphea section Heterodon (Lythraceae) . Syst. Bot. Mono. 20:1-168.
Kaliangile, I. and 0. F. Grabe. 1988. Seed Maturation in Cuphea. J. Seed Tech. 12(2):107-113.
Knapp, S. J., and L. A. Tagliani, 1990: Genetic variation for seed dormancy in Cuphea lamiuligaria and C. lanceolata. Euphytica. 47:65-70.
Thompson, A. E. 1984. Cuphea- A Potential New Crop. HortScience. 19(3):352-354.