Piven N M, Barredo-Pool F A, Borges-Argáez I C, Herrera-Alamillo M A, Mayo-Mosqueda A, Herrera-Herrera J L, Robert M L
Centro de Investigación Científica de Yucatán, Calle 43, No. 130, Col. Chuburná de Hidalgo, CP 97200, Mérida, Yucatán, México.
Am J Bot. 2001 Nov;88(11):1966-76.
The pathways of micro- and megagametophyte development in Agave fourcroydes (henequén) and A. angustifolia were studied. We used histology and light microscopy to observe anther ontogeny and ovary differentiation in relation to flower bud size. Both species have the same sexual reproductive strategies and gametophyte development that may be divided into three phases: (1) premeiotic, which includes the establishment of the megaspore mother cell and the pollen mother cell; (2) meiotic, the formation of mature microspores and functional megaspores; (3) postmeiotic, which encompasses the development of mature pollen grains and the formation of the embryo sac. A successive type microsporogenesis was found in both species with formation of T-shaped tetrads and binuclear pollen grains. In vitro germination tests revealed very low pollen fertility. The female gametophyte is formed from two micropylar megaspore cells after the first meiotic division (bisporic type). Male and female gametogenesis occur asynchronously with microsporogenesis finishing before macrosporogenesis. The results so far show that the formation of male and female gametophytes in henequén is affected at different stages and that these alterations might be responsible for the low fertility shown by this species.
对剑麻（龙舌兰麻）和狭叶龙舌兰的小孢子体和大孢子体发育途径进行了研究。我们使用组织学和光学显微镜观察了与花芽大小相关的花药个体发育和子房分化。这两个物种具有相同的有性生殖策略和配子体发育过程，可分为三个阶段：（1）减数分裂前阶段，包括大孢子母细胞和花粉母细胞的建立；（2）减数分裂阶段，形成成熟的小孢子和功能大孢子；（3）减数分裂后阶段，包括成熟花粉粒的发育和胚囊的形成。在这两个物种中均发现了连续型小孢子发生，形成了T形四分体和双核花粉粒。体外萌发试验显示花粉育性极低。雌配子体由第一次减数分裂后的两个珠孔大孢子细胞形成（双孢子类型）。雄配子发生和雌配子发生异步进行，小孢子发生在大孢子发生之前完成。目前的结果表明，龙舌兰麻中雄配子体和雌配子体的形成在不同阶段受到影响，这些变化可能是该物种育性低的原因。
