长豇豆种皮和种脐的发育

SEED COAT AND HILUM DEVELOPMENT IN VIGNA SESQUIPEDALIS FRUWIRTH

长豇豆的胚珠具内外两层珠被,内珠被在种子发育早期退化消失,种皮仅由外珠被发育而成。外珠被的外表皮细胞径向伸长,外壁和径向壁增厚,形成约占成熟种皮厚度一半的栅栏层;亚表皮细胞发育为骨状石细胞层。第三层细胞类似于亚表皮层但细胞壁增厚不明显,其内方的多层薄壁细胞形成海绵组织。种脐具两层栅栏细胞,外栅栏层及其以外部分由珠柄组织发育而来,内栅栏层由表皮细胞发育而成。脐中央的少数细胞退化形成脐缝,脐缝内方的薄壁细胞发育成管胞群。本文还对脐缝和管胞群的作用以及豆科种子的吸水机制进行了讨论。

The ovule of Vigna sesquipedalis Fruwirth has two integuments. The inner integument has crushed during early stage of seed development,so the seed coat develops from the outer integument only. The outer epidermal cells of the outer integument elongate radially to form a palisade layer, outer and radial walls thicken. The length of the palisade layer is about 1/2 of the thickness of the mature seed coat. The hypodermal cells form the osteosclereid layer. The cells of third layer are somewhat similar to hypodermal cells,but their walls are thinner than the later. The parenchyma cells become spongy tissue. There are two palisade layers in the hilum region. The outer layer differentiates from funicular tissue,and the inner one from outer epidermis of ottter integument. The cells in the centre of hilum degenerate and form hilar fissure. The parenchyma cells inside hilum differentiate to form the tracheid bar. The functions of tracheid bar and hilar fissure are discussed.