This is part of a study project on Leucospermum seed germination ecophysiology conducted at the Conservation Biology Unit of the National Botanical Institute, kirstenbosch, Cape Town.
Desiccation as the active principle in heat-stimulated seed germination of Leucospermum R. Br. (Proteaceae) in fynbos*
Article first published online: 28 APR 2006
Volume 125, Issue 2, pages 397–403, October 1993
How to Cite
BRITS, G. J., CALITZ, F. J., BROWN, N. A. C. and MANNING, J. C. (1993), Desiccation as the active principle in heat-stimulated seed germination of Leucospermum R. Br. (Proteaceae) in fynbos. New Phytologist, 125: 397–403. doi: 10.1111/j.1469-8137.1993.tb03892.x
- Issue published online: 28 APR 2006
- Article first published online: 28 APR 2006
- (Received 13 December 1992; accepted 2 June 1993)
- seed dormancy;
A new seed biological phenomenon in the myrmecochorous, fire-recruiting fynbos species Leucospermum cordifolium (Salisb. ex Knight) Fourcade is reported. This is the extensive breaking, following desiccation treatment, of the seed testa which in intact, soil-stored seeds imposes dormancy on the embryo by means of oxygen exclusion. In this study the pericarps of L. cordifolium seeds were removed and seeds with intact exotestas were selected stereomicroscopically. Samples of seeds were placed in nylon bags and suspended over (cone.) H2SO4 or dried silica gel. A third series of seeds were exposed for varying periods to 40 °C, cooled and immersed in water before performing breakage tests on both the exo- and endotesta. All treatments resulted in extensive breaking of the exo- as well as the endotesta of seeds. The two ‘cool’ desiccating treatments both caused more effective breaking than heat treatments. This indicates strongly that the breakage phenomena are desiccation effects and not caused directly by heat intensity. Rehydration in air before wetting seeds completely prevented breakage effects in all treatments in the endotesta, but not in the exotesta. This further supports the conclusion that endotesta breakage is a function of desiccation plus wetting and not of heat per se. The results suggest that in nature desiccation by fire could break the exotesta and the endotesta as well, if fire is followed soon by rain. These effects amount to effective scarification of the seed and thus suggest a positive correlation, in nature, between heat intensity of fire and emergent seedling numbers.