Brits G J, Calitz F J, Brown N A C, Manning J C
Fynbos Research Unit, Vegetable and Ornamental Plant Institute, Private Bag, Elsenburg 7607, South Africa.
Agrimetrics Institute, Private Bag X5013, Stellenbosch 7600.
New Phytol. 1993 Oct;125(2):397-403. doi: 10.1111/j.1469-8137.1993.tb03892.x.
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.) H SO 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.
报道了蚁播、需火的南非开普植物区系物种心叶银宝树（Leucospermum cordifolium (Salisb. ex Knight) Fourcade）中一种新的种子生物学现象。这一现象是，经干燥处理后，种子种皮大量破裂，而在完整的、贮藏于土壤中的种子中，种皮通过排除氧气使胚处于休眠状态。在本研究中，去除了心叶银宝树种子的果皮，并在体视显微镜下挑选出外种皮完整的种子。将种子样本置于尼龙袋中，悬挂在（锥形）浓硫酸上方或置于干燥硅胶上。第三组种子在不同时间段暴露于40℃，冷却后浸入水中，然后对外种皮和内种皮进行破裂测试。所有处理均导致种子的外种皮和内种皮大量破裂。两种“冷”干燥处理比热处理导致的破裂更有效。这有力地表明，破裂现象是干燥效应，而非直接由热强度引起。在完全浸湿种子之前先在空气中复水，完全防止了所有处理中内种皮的破裂效应，但外种皮未受影响。这进一步支持了内种皮破裂是干燥加浸湿的作用而非热本身作用的结论。结果表明，在自然环境中，如果火灾后很快下雨，火灾造成的干燥可能会使外种皮和内种皮都破裂。这些效应相当于对种子进行了有效的擦伤处理，因此表明在自然环境中，火灾的热强度与出土幼苗数量之间存在正相关。
