Abstract
Seedling emergence patterns of Protea susannae, Leucadendron coniferum, Protea obtusifolia, and Leucadendron meridianum were investigated in the field. Possible factors contributing to these patterns were investigated in laboratory experiments. In the field all species had less complete, more intermittent emergence in colluvial sands (poorer water-retention properties) than in the adjacent limestone (greater water retention) soil type. Protea susannae had the highest emergence percentage in both soils. In the colluvial sands both Protea spp. showed less scattered emergence than the Leucadendron spp. In the laboratory, imbibed seeds of all species lost less water after a drying treatment when planted in limestone soil than in colluvial sands, indicating that the former soil acts as a better buffer. Protea susannae showed superior ability to imbibe, and to retain water after drying, in both soils. These results corroborated the field emergence patterns. Imbibed seeds of each of the Protea spp. (higher pericarp to embryo ratios) retained more water than the Leucadendron spp. (lower ratios) after subsequent drying in air, suggesting that the thicker pericarps help minimise water loss. Germination success following wetting–drying cycles (on filter paper in Petri dishes) led to higher percent germination of P. susannae than L. coniferum seeds, further helping explain the field emergence patterns. Key words: field seedling emergence, germination ecology, seed morphology, seed wetting–drying, soil moisture properties, South African fynbos Proteaceae.
Published Version
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