Question

有英语(生物专业)的高手帮忙翻译一下，不胜感激！！！

About 12 months earlier, the pollen grain germinated, producing a pollen tube that slowly digested its way through the tissues of the nucellus toward the developing megagametophyte.About a year after pollination, the generative cell of the four-celled male gametophyte undergoes division, giving rise to two kinds of cells—a sterile cell (stalk cell) and a spermatogenous cell (body cell). Subsequently, the spermatogenous cell divides, producing two sperm. The male gametophyte, or germinating pollen grain, is now mature. Recall that seed plants do not form antheridia.

Some 15 months after pollination, the pollen tube reaches the egg cell of an archegonium, where it discharges much of its cytoplasm and both of its sperm into the egg cytoplasm (Figure 20-26). One sperm nucleus unites with the egg nucleus, and the other degenerates. Commonly, the eggs of all archegonia are fertilized and begin to develop into embryos (the phenomenon of polyembryony). Only one embryo usually develops fully, but about3 to4 percent of three seedlings upon germination.

During early embryogeny, four tiers of cells are produced near the lower end of the archegonium. Each of the four cells of the uppermost tier (that is, the tier farthest form the micropylar end of the ovule) begins to form an embryo. Simultaneously the four cells of the tier below the embryo, the suspensor cells, elongate greatly and force the four developing embtyos through the wall of the archegonium and into the female gametophyte. Thus, a second type of polyembryony is found in the pine life cycle. Once again, however, usually only one of the embryos develops fully. During embryogeny, the integument develops into a seed coat.

The conifer seed is a remarkable structure, for it consists of a combination of two different diploid sporophytic generations—the seed coat (and remnants of the nucellus) and the embryo—and one haploid gametophytic generation (Figure 20-27). The gametophyte serves as a food reserve or nutritive tissue. The embryo consists of a hypocotyls-root axis, with a rootcap and apical meristem at one end and an apical meristem and several (generally eight) cotyledons, or seed leaves, at the other. The integument consists of three layers, of which the middle layer becomes hard and serves as the seed coat.

Answer 1

大约 12 年之前，花粉谷粒发芽,产生慢慢地经过向发展中的 megagametophyte 的 nucellus 的薄的纱织品消化了它的方法的花粉管。在授粉后大约一年, 四个中生殖细胞-细胞男性的配偶体接受区分, 引起细胞的二个类型-一个不毛的细胞 (茎细胞) 和一个 spermatogenous 细胞 (身体细胞). 后来, spermatogenous 细胞分歧, 产生二个精液。 男性的配偶体, 或发芽花粉谷粒, 是现在成熟的。 取消哪一种子厂不形成 antheridia。

在授粉后 15 月，花粉管到达它放电许多的它的细胞质和它的两个精液进入蛋细胞质 (图 20-26) 的造卵器的蛋细胞。 一个精液核心以蛋核心联合，而且另一个退化。 普遍，所有 archegonia 的蛋被施肥而且开始进入胚胎 (polyembryony 的现象) 之内发展。 只有一个胚胎通常完全发展, 但是在发芽之上的大约 3-4% 三个苗木。

在早的胚形成期间，细胞的四列在造卵器的下端的附近被生产。 每个在四个细胞中最上列 (哪一是, 列最远形成 ovule 的 micropylar 结束) 开始形成一个胚胎。 同时地列的这四个细胞在胚胎,suspensor 细胞, 下面延长很大而且强迫穿过造卵器的墙壁四发展中的 embtyos 和进入女性的配偶体之内。 因此， polyembryony 的第二类型在松树生命周期中被发现。 再一次，然而, 通常，胚胎的只有一个完全发展。 在胚形成期间，外壳进入一件种子外套之内发展。

松类种子是显着的结构，因为它有一个二不同的双重 sporophytic 的组合世代-种子外套 (和 nucellus 的剩余) 和胚胎-和一 haploid gametophytic 世代 (图 20-27). 配偶体视为食物预备品或有营养的薄纱织品。 胚胎有胚桥-根轴, 藉由 rootcap 和顶上的分裂组织在一端和一个顶上的分裂组织和一些 (通常八) 子叶或种子树叶, 在另一个。外壳有三层，其中中央的层变成很难而且视为种子外面复盖。