木瓜種子構造與特性之探討

Study on Structure and Characteristics of Papaya (Carica papaya L.) Seeds

本研究利用4批木瓜（Carica papaya L.）種子，包括台農2號、日陞種及兩批採自台農2號果實中的種子為材料，以立體光學顯微鏡及掃描式電子顯微鏡進行種子構造觀察及其特性調查。木瓜種子為雙子葉有胚乳種子，除去假種皮後發現，種子呈橢圓球形，表面具有多條網狀構造的單脊狀突起（single-ridge）及一條雙脊狀突起（double-ridge），4批種子之平均長度與厚度分別為6.12及4.05mm；平均百粒重為1.64g，其中種皮佔47%。種皮由內、外種皮所構成，其厚度約為1mm。胚乳最外層為糊粉層（aleurone layer），胚則呈軸心飯匙形（axile spatulate type）於胚乳中，兩片子葉厚約0.3mm。沿雙脊狀突起縱切，子葉與切面的角度並不一致，呈平行、垂直及斜角等三種角度，分別為30.2、22.3及47.5%。

Four lots of papaya seeds including cultivars Tainung 2 and Sunrise and seeds from commercial fruits of Tainung 2 were used to study the structure and characteristics by stereo light micrscopy and scanning electron microscopy. The papaya seeds are dicotyledonous in nature with endosperm. After removing the sarcotesta, the seeds are obong in shape with an avesge length of 6.12mm and width of 4.05 mm. The average 100-seed weight 1.64g, and 47% of which is contributed by the seed coat. The surface of the seeds is characterized by many reticular-structured single-ridges and one reticular-structured double-ridge. The seed coat, about 1 mm in thickness, is composed of testa and tegmen. The outmost layer of the endosperm is aleurone layer. The embryo, located within the endosperm, is of axile spatulate type, For each lot investigated, about 10% of the seeds contained shrunken or even 30 endosperm and embryo. The thickness of two coteioncions is0.3 mm. Longitudinal section along the double-ridge revealed ununiform angle between the cut surfact and cotyledons. 30.2, 22.3 and 47.5% of the seeds showed parallel, perpendicular, and oblique angles, respectively.