紅楠異儲型種子微細構造的研究

Ultrastructural Study on the Recalcitrant Seeds of Machilus thunbergii Sieb. & Zucc

紅楠種子屬於不耐旱種子，其新鮮成熟種子內的胚芽已具四至六片初生葉。子葉含油細胞與黏液分泌細胞，然而胚主軸只有油細胞。胚芽與胚根頂端分生組織的細胞含大的細胞核與小液胞，細胞質緻密含各種胞器，色素體具澱粉粒與少量油滴。成熟種子經乾燥儲存後，頂端分生組織細胞之微細構造受到破壞（液胞化與細胞膜脫離等），且隨著貯存濕度之降低與貯存時間之延長而更為明顯，且其萌芽率也隨之降低。

The recalcitrant (desiccation sensitive) seeds of Machilus thunbergii were histochemically and ultrastructurally investigated by using light and electron microscopy. The embryo of mature seed has 4-6 subopposite primary leaves in the plumule. We found two types of idioblastic secretory cells (oil cells and mucilage cells) in the cotyledons, but observed only the oil cells in the embryonic axes. Cells in shoot and radicle meristem of the fresh mature embryo have a large nucleus and small vacuoles. The cytoplasm is dense with organelles, and the plastids contain some starch grains and few oil droplets. Under 75% relative humidity storage condition, the desiccation processes set off the subcellular damages (vacuolation, withdrawal of plasmalemma) of the mature seeds. Such processes intensified with time and ultimately resulted in the loss of viability.