J Integr Plant Biol. ›› 1991, Vol. 33 ›› Issue (5): -.

• Research Articles •    

Vascular Bundle Distribution Within Broad Bean Seed Coat and the Structure of Unloading Region

Wang Xin-ding   

Abstract: Cytological observations were made on developing seed coat of broad bean (Vicia faba L.) by use of light and electron microscopy. Attention was focused on vascular distribution. The seeds were attached by the funiculus to tile large vascular bundles of pericarp of broad bean. The vascular bundle passed through hilum and two layers of palisade, entered the pa- renchyma of seed coat, then diverged in to two routes. One was a complete vascular bundle composed of both'phloem and xylem elements, it stretched down through seed raphe, then upward and terminated near the radical. The other was a two-recurrent-vascular-bundle with only phloem constitutents, they extended forward detoured the micropyle and extended downward, but did not join with the upward complete vascular bundle. The recurrent vascular bundles branched out many small short branches. The obvious difference between phloem of recurrent vascular bundle and of complete vascular bundle was that the companion ceils of the former did not normally modify to transfer ceils, but connected to the adjoining parenchyma cells through abundant plasmodesmata. It is deduced from the structural analysis that the symplastic route may play an important role, particularly in the region of recurrent vascular bundle, in the course of importing assimilates unloading in seed coat and transporting to the embryo.

Key words: Broad bean, Seed coat, Distribution of vascular, Unloading, Plasmodes-Mata

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