金钱松雌球花的形态构造及大孢子和雌配子体的形成

金钱松雌球花着生于树冠上部5a以上短枝顶端。成熟雌球花中央为1球花轴,其上螺旋着生苞鳞和珠鳞,珠鳞上着生2倒生胚珠,胚珠单珠被,珠心喙较厚,珠被唇顶部和内侧壁表皮为乳头状细胞,珠被中具溶生树脂道,珠被和珠鳞表皮下数层细胞将发育成种子的种翅和硬壳。花芽中胚珠原基出现至雌配子体卵细胞形成需5个月。1月胚珠原基出现。3月形成大孢子母细胞期的幼胚珠。3月下旬～4月上旬大孢子母细胞减数分裂形成大孢子。4月中旬雌球花迅速增长为胚乳游离核期。5月胚乳细胞壁形成,颈卵器原始细胞出现并发育为颈细胞、腹沟细胞和卵细胞,雌配子体成熟。

The Morphology and Structure of Female Cone and the Formation of Megaspore and Female Gametophyte in Golden Larch

The characteristics of the morphology and structure of feminine strobilus and the formation process from flower bud stage to egg cell of female gametophyte in Pseudolarix kaempferi are mainly reported. The female cone is borne on the top of spur shoot which is more than five years in higher branches of the crown. The mature feminine strobilus is composed of a centeral axis bearing ovuliferous scales and bracts spirally, with two anatropous ovules on the ovuliferous scale. The ovule with relatively thick nucellar beak has single integument in which lysigenous resin ducts are present. The epidermic cells of the upper part of integument lip and the wall of micropyle ditch are papillose. Several-layer tissue under the epidermis of integument and ovuliferous scale will develop into seed wing and the part of hardened shell. It takes five months from the appearance of ovule initial in flower bud to the formation of egg cell in female gametophyte. The ovule initial occurs in January and young ovule where meg-asporocyte is produced makes its appearance in March. Megasporocyte undertakes meiosis to form megaspore in late March to early April. Female cone elongates rapidly in middle April and at this time endosperm is in free nuclear stage. When the cell walls of endosperm are formed in May, the initial cell of archegonium begins to appear and develop into neck canal cell, ventral canal cell and egg cell progressively, thus far the develop ment of female gametophyte finishes.