Gibson A, Bachelard E P
Department of Forestry, Australian National University, GPO Box 4, Canberra, ACT 2601, Australia.
Tree Physiol. 1988 Dec;4(4):389-99. doi: 10.1093/treephys/4.4.389.
Before Eucalyptus sieberi L. Johnson seeds germinate, the protein reserves in a small group of cells in the collet are mobilized and the cells swell sufficiently to break the seed coat allowing further water uptake. If the seedling is desiccated at this stage, the embryo remains viable and when the seed is rewetted reserves are mobilized in the cells immediately behind those which expanded initially. Mobilization of reserves and subsequent cell elongation occur sequentially along the hypocotyl after successive dry periods until the reserves are exhausted. Early in the sequence, the distal end of the hypocotyl extends and is positively geotropic, whereas at the end of the sequence the proximal end of the hypocotyl extends and is negatively geotropic, raising the cotyledons rapidly. If the radicle is destroyed or unable to elongate, it is replaced by two adventitious roots, one below the petiole of each cotyledon. Indole acetic acid and sucrose can substitute for the cotyledons in the production of adventitious roots.
在西氏桉（Eucalyptus sieberi L. Johnson）种子萌发前，根颈处一小群细胞中的蛋白质储备被调动起来，细胞充分膨胀以冲破种皮，从而允许进一步吸收水分。如果幼苗在此阶段干燥，胚仍保持活力，当种子再次湿润时，储备物质会在最初膨胀的细胞后面的细胞中立即被调动起来。在连续干旱期后，储备物质的调动和随后的细胞伸长沿着下胚轴依次发生，直到储备物质耗尽。在这个序列的早期，下胚轴的远端伸长并呈正向地性，而在序列的末尾，下胚轴的近端伸长并呈负向地性，迅速将子叶抬起。如果胚根被破坏或无法伸长，它会被两条不定根取代，每条子叶叶柄下方各有一条。吲哚乙酸和蔗糖在不定根的产生中可以替代子叶。
